Patent Publication Number: US-2013239652-A1

Title: Variable frequency impact test

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 12/916,776, entitled “Synthetic Materials for PDC Cutter Testing or for Testing other Superhard Materials” and filed on Nov. 1, 2010, which claims priority to U.S. Provisional Patent Application No. 61/288,143, entitled “Method and Apparatus for Testing Superhard Material Performance,” filed Dec. 18, 2009, the disclosures of which are incorporated by reference herein. 
     The present application is related to U.S. patent application Ser. No. 12/916,815, entitled “Synthetic Materials for PDC Cutter Testing or for Testing other Superhard Materials” and filed on Nov. 1, 2010, and U.S. patent application Ser. No. 12/914,847, entitled “Synthetic Materials for PDC Cotter Testing or for Testing other Superhard Materials” and filed on Nov. 1, 2010, the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a method and apparatus for testing PDC cutters or other superhard components; and more particularly, to a method and apparatus for testing the abrasive wear resistance and/or the impact resistance of PDC cutters or other superhard components. 
     BACKGROUND 
       FIG. 1  shows a superhard component  100  that is insertable within a downhole tool (not shown) in accordance with an exemplary embodiment of the invention. One example of a superhard component  100  is a cutting element  100 , or cutter, for rock bits. The cutting element  100  typically includes a substrate  110  having a contact face  115  and a cutting table  120 . The cutting table  120  is fabricated using an ultra hard layer which is bonded to the contact face  115  by a sintering process. The substrate  110  is generally made from tungsten carbide-cobalt, or tungsten carbide, while the cutting table  120  is formed using a polycrystalline ultra hard material layer, such as polycrystalline diamond (“PCD”), polycrystalline cubic boron nitride (“PCBN”), or tungsten carbide mixed with diamond crystals (impregnated segments). These cutting elements  100  are fabricated according to processes and materials known to persons having ordinary skill in the art. The cutting element  100  is referred to as a polycrystalline diamond compact (“PDC”) cutter when PCD is used to form the cutting table  120 . PDC cutters are known for their toughness and durability, which allow them to be an effective cutting insert in demanding applications. Although one type of superhard component  100  has been described, other types of superhard components  100  can be utilized. 
     Common problems associated with these cutters  100  include chipping, spalling, partial fracturing, cracking, and/or flaking of the cutting table  120 . These problems result in the early failure of the cutting table  120 . Typically, high magnitude stresses generated on the cutting table  120  at the region where the cutting table  120  makes contact with earthen formations during drilling can cause these problems. These problems increase the cost of drilling due to costs associated with repair, production downtime, and labor costs. For these reasons, testing methods have been developed to ascertain the abrasion resistance and/or impact resistance of cutters  100  so that improved cutter longevity is achieved and the problems mentioned above are substantially reduced. 
     Superhard components  100 , which include PDC cutters  100 , have been tested for abrasive wear resistance through the use of two conventional testing methods. Early in the development of PDC materials, the abrasive wear resistance was tested using a conventional granite log test, which is described in further detail with respect to  FIG. 2 . However, as the PDC cutters  100  became more wear resistant and too much time and conventional target cylinders  250  ( FIG. 2 ) were required to complete the conventional granite log test, the conventional vertical turret lathe (“VTL”) test which is described in further detail with respect to  FIG. 3 , replaced the conventional granite log test for testing abrasive wear resistance. 
       FIG. 2  shows a lathe  200  for testing abrasive wear resistance of a superhard component  100  using a conventional granite log test. Although one exemplary apparatus configuration for the lathe  200  is provided, other apparatus configurations can be used without departing from the scope and spirit of the exemplary embodiment. Referring to  FIG. 2 , the lathe  200  includes a chuck  210 , a tailstock  220 , and a tool post  230  positioned between the chuck  210  and the tailstock  220 . A conventional target cylinder  250  has a first end  252 , a second end  254 , and a sidewall  258  extending from the first end  252  to the second end  254 . According to the conventional granite log test, sidewall  258  is an exposed surface  259  which makes contact with the superhard component  100  during the test. The first end  252  is coupled to the chuck  210 , while the second end  254  is coupled to the tailstock  220 . The chuck  210  is configured to rotate, thereby causing the conventional target cylinder  250  to also rotate along a central axis  256  of the conventional target cylinder  250 . The tailstock  220  is configured to hold the second end  254  in place while the conventional target cylinder  250  rotates. The conventional target cylinder  250  is fabricated from a single uniform material which is typically a natural rock type, such as granite, or concrete. Other single uniform rock types have been used for the conventional target cylinder  250 , which includes, but is not limited to, Jackfork sandstone, Indiana limestone, Berea sandstone, Carthage marble, Champlain black marble, Berkley granite, Sierra white granite, Texas pink granite, and Georgia gray granite. The conventional target cylinder  250  has a compressive strength of about 25,000 pounds per square inch (“psi”) or less and an abrasiveness of about 6 CAI or less when natural rock types are used. These conventional target cylinders  250  fabricated from natural rock types are costly to acquire, shape, ship, and handle. The conventional target cylinder  250  has a compressive strength of about 12,000 psi or less and an abrasiveness of about 2 CAI or less when concrete is used. 
     The PDC cutter  100  is fitted to the lathe&#39;s tool post  230  so that the PDC cutter&#39;s cutting table  120  makes contact with the conventional target cylinder&#39;s exposed surface  259  and drawn back and forth across the exposed surface  259 . The tool post  230  has an inward feed rate on the conventional target cylinder  250 . The abrasive wear resistance for the PDC cutter  100  is determined as a wear ratio, which is defined as the volume of conventional target cylinder  250  that is removed to the volume of the PDC cutter&#39;s cutting table  120  that is removed. This wear ratio can be referred to as a grinding ratio (“G-Ratio”). Common values of the G-Ratio range from about 1,000,000/1 to 15,000,000/1 depending on the abrasiveness of the conventional target cylinder and the PDC cutter. Alternatively, instead of measuring volume of rock removed, the distance that the PDC cutter  100  travels across the conventional target cylinder  250  can be measured and used to quantity the abrasive wear resistance for the PDC cutter  100 . Common values of the travelling distance range from about 15,000 feet to about 160,000 feet depending on the abrasiveness of the conventional target cylinder and the PDC cutter. Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the conventional granite log test. Operation and construction of the lathe  200  is known to people having ordinary skill in the art. Descriptions of this type of test is found in the Eaton, B. A., Bower, Jr., A. B., and Martis, J. A. “Manufactured Diamond Cutters Used In Drilling Bits.”  Journal of Petroleum Technology,  May 1975, 543-551. Society of Petroleum Engineers paper 5074-PA, which was published in the Journal of Petroleum Technology in May 1975, and also found in Maurer, William C.,  Advanced Drilling Techniques,  Chapter 22, The Petroleum Publishing Company, 1980, pp. 541-591, which is incorporated by reference herein. 
     As previously mentioned, this conventional granite log test was adequate during the initial stages of PDC cutter  100  development. However, PDC cutters  100  have become more resistant to abrasive wear as the technology for PDC cutters  100  improved. Current technology PDC cutters  100  are capable of cutting through many conventional target cylinders  250  without ever developing any appreciable and measurable wear flat; thereby, making the conventional granite log test method inefficient and too costly for measuring the abrasive wear resistance of superhard components  100 . 
       FIG. 3  shows a vertical turret lathe  300  for testing abrasive wear resistance of a superhard component  100  using a conventional vertical turret lathe (“VTL”) test. Although one exemplary apparatus configuration for the VTL  300  is provided, other apparatus configurations can be used without departing from the scope and spirit of the exemplary embodiment. The vertical turret lathe  300  includes a rotating table  310  and a tool holder  320  positioned above the rotating table  310 . A conventional target cylinder  350  has a first end  352 , a second end  354 , and a sidewall  358  extending from the first end  352  to the second end  354 . According to the conventional VTL test, second end  354  is an exposed surface  359  which makes contact with a superhard component&#39;s cutting table  120  during the test. The conventional target cylinder  350  is typically about thirty inches to about sixty inches in diameter, but can be smaller or larger depending upon the testing requirements. The conventional target cylinder  350  is typically larger in diameter than the conventional target cylinder  250  ( FIG. 2 ). 
     The first end  352  is mounted on the lower rotating table  310  of the VTL  300 , thereby having the exposed surface  359  face the tool holder  320 . The PDC cutter  100  is mounted in the tool holder  320  above the conventional target cylinder&#39;s exposed surface  359  and makes contact with the exposed surface  359 . The conventional target cylinder  350  is rotated via the rotating table  310  as the tool holder  320  cycles the PDC cutter  100  from the center of the conventional target cylinder&#39;s exposed surface  359  out to its edge and back again to the center of the conventional target cylinder&#39;s exposed surface  359 . The tool holder  320  has a predetermined downward feed rate. 
     The VTL  300  is generally a larger machine when compared to the lathe  200  ( FIG. 2 ) used for the conventional granite log test. The conventional VTL test allows for larger depths of cut to be made in the conventional target cylinder  350  and for the use of a larger conventional target cylinder  350  when compared to the depths of cut made and the size of the conventional target cylinder  250  ( FIG. 2 ) used in the conventional granite log test. The capability of having larger depths of cut allows for higher loads to be placed on the PDC cutter  100 . Additionally, the larger conventional target cylinder  350  provides for a greater rock volume for the PDC cutter  100  to act on and hence a longer duration for conducting the test on the same conventional target cylinder  350 . Thus, fewer conventional target cylinders  350  are used when performing the conventional VTL test when compared to the number of conventional target cylinders  250  ( FIG. 2 ) that are used in the conventional granite log test. The conventional target cylinder  350  is typically fabricated entirely from granite; however, the conventional target cylinder can be fabricated entirely from another single uniform natural material that includes, but is not limited to, Jackfork sandstone, Indiana limestone, Berea sandstone, Carthage marble, Champlain black marble, Berkley granite, Sierra white granite, Texas pink granite, and Georgia gray granite, or concrete. The conventional target cylinder  350  has a compressive strength of about 25,000 psi or less and an abrasiveness of about 6 CAI or less when natural rock types are used. As previously mentioned, these conventional target cylinders  350  fabricated from natural rock types are costly to acquire, shape, ship, and handle. The conventional target cylinder  350  has a compressive strength of about 12,000 psi or less and an abrasiveness of about 2 CAI or less when concrete is used. The abrasive wear resistance for the PDC cutter  100  is determined as a wear ratio, which is defined as the volume of conventional target cylinder  350  that is removed to the volume of the PDC cutter  100  that is removed. This wear ratio can be referred to as a grinding ratio (“G-Ratio”). Common values of the G-Ratio range from about 1,000,000/1 to about 15,000,000/1 depending on the abrasiveness of the conventional target cylinder and the PDC cutter. Alternatively, instead of measuring volume of rock removed, the distance that the PDC cutter  100  travels across the conventional target cylinder  350  can be measured and used to quantity the abrasive wear resistance for the PDC cutter  100 . Common values of the travelling distance range from about 15,000 feet to about 160,000 feet depending one the abrasiveness of the conventional target cylinder and the PDC cutter. 
     Referring back to  FIGS. 2 and 3 , the conventional target cylinders  250  and  350  have limitations due to the material compositions used in fabricating the conventional target cylinders  250  and  350 , which is either a natural material or concrete. When using a natural material, the material must be mined and shaped before the natural material becomes suitable for use as a conventional target cylinder  250  and  350 . Additionally, certain provisions are to be made when using these natural materials due to their variability in properties. For instance, once a natural material is selected for use as the conventional target cylinder  250  and  350 , additional natural material must be selected from the same mine to avoid expensive recalibration of the test. The same natural material from a different mine is likely to have different properties and thus result in testing discrepancies. Further, shipping costs, limited supplies of natural material, and natural variations ail increase the cost and ability to obtain repeatable test results. 
     Concrete, however, has some advantages over natural material when fabricating the conventional target cylinders  250  and  350 . Concrete is widely available and relatively inexpensive when compared to natural materials. Concrete is fabricated using local materials hence reducing transportation costs. Although concrete has some advantages over natural materials, concrete also has several disadvantages. According to one disadvantage, concrete has a much lower compressive strength when compared to rock strength found in the field. Conventional concrete has a typical compressive strength of about three kilo-pounds per square inch (“kpsi”), while some specialty concretes can reach about twelve to kpsi. However, rock strength found in the field typically ranges in compressive strength from about twenty kpsi to about sixty kpsi. Thus, the tests performed using concrete-formed conventional target cylinders  250  and  350  are not indicative of field results. According to another disadvantage, fabricating concrete is a much longer time consuming process. Concrete is typically cured for about twenty-eight days so that its specified strength is reliably reached. As known to people having ordinary skill in the art, a long fabrication duration for preparing the conventional target cylinder  250  and  350  becomes very expensive due to loss of time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and aspects of the invention are best understood with reference to the following description of certain exemplary embodiments, when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows a superhard component that is insertable within a downhole tool in accordance with an exemplary embodiment of the invention; 
         FIG. 2  shows a lathe for testing abrasive wear resistance of a superhard component using a conventional granite log test; 
         FIG. 3  shows a vertical turret lathe for testing abrasive wear resistance of a superhard component using a conventional vertical turret lathe test; 
         FIG. 4  shows a top perspective view of a target cylinder in accordance with an exemplary embodiment of the invention; 
         FIG. 5  shows a top perspective view of a casting form used for forming the target cylinder of  FIG. 4  according to an exemplary embodiment of the invention; 
         FIG. 6  shows a top perspective view of a target cylinder in accordance with an alternative exemplary embodiment of the invention; 
         FIG. 7  shows a top perspective view of a target cylinder in accordance with a second alternative exemplary embodiment of the invention; 
         FIG. 8  shows a top perspective view of a target cylinder in accordance, with a third alternative exemplary embodiment of the invention; 
         FIG. 9  shows a top perspective view of a target cylinder in accordance with a fourth alternative exemplary embodiment of the invention; 
         FIG. 10  shows a side perspective view of a target cylinder in accordance with a fifth alternative exemplary embodiment of the invention; 
         FIG. 11  shows a side perspective view of a target cylinder in accordance with a sixth alternative exemplary embodiment of the invention; and 
         FIG. 12  shows a top perspective view of a target cylinder in accordance with a seventh exemplary embodiment of the invention. 
     
    
    
     The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. 
     BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present invention is directed to a method and apparatus for testing the abrasive wear resistance and/or the impact resistance of superhard components. Although the description of exemplary embodiments is provided below in conjunction with a PDC cutter, alternate embodiments of the invention may be applicable to other types of superhard components including, but not limited to, PCBN cutter or other superhard components known or not yet known to persons having ordinary skill in the art. 
     The invention is better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings, wherein like parts of each of the figures are identified by like reference characters, and which are briefly described as follows.  FIG. 4  shows a top perspective view of a target cylinder  400  in accordance with an exemplary embodiment of the invention. Referring to  FIG. 4 , the target cylinder  400  is cylindrically shaped and includes a first end  410 , a second end  420 , and a sidewall  430  extending from the first end  410  to the second end  420 . According to this exemplary embodiment, the second end  420  is also referred to as an exposed portion  422  of the target cylinder  400  because the second end  420  is subjected to contact with the superhard component  100  ( FIG. 1 ) when the testing is performed using the VTL test. The exposed portion  422  is substantially planar. Although the target cylinder  400  is cylindrically shaped, the target cylinder  400  can be any other geometric or non-geometric shape without departing from the scope and spirit of the exemplary embodiment. The target cylinder  400  has a diameter  402  of approximately three feet and a height  404  of approximately four inches. However, in alternate exemplary embodiments, the diameter  402  can range from about four inches to about ten feet without departing from the scope and spirit of the exemplary embodiment. Additionally, in alternate exemplary embodiments, the height  404  can range from about one inch to about twenty feet without departing from the scope and spirit of the exemplary embodiment. Although the target cylinder  400  is dimensioned for use in the conventional VTL test, the target cylinder  400  can be dimensioned for use in the conventional granite log test, as previously described above. 
     The target cylinder  400  is fabricated using a synthetic material  440 .  FIG. 5  shows a top perspective view of a casting form  500  used for forming the target cylinder  400  according to an exemplary embodiment of the invention. Referring to  FIG. 5 , the casting form  500  includes a base  505  and a sidewall  507  extending substantially perpendicular from the base  505 . The base  505  and the sidewall  507  collectively form a cavity  509  therein. The cavity is shaped into a negative shape of the target cylinder  400  ( FIG. 4 ), which is a cylindrical shape. However, the cavity  509  is shaped into other shapes including, but not limited to, the negative shapes of a wheel for use on a grinding wheel (not shown), or other geometric or non-geometric forms according to other exemplary embodiments. Thus, in other exemplary embodiments, the target cylinder  400  ( FIG. 4 ) can be dimensioned and shaped into a wheel for use in a grinding wheel, a square-shaped cylinder, an oval-shaped cylinder, a triangular-shaped cylinder, or any other shape. The cavity  509  is filled with the aggregate material  510  and the cementing agent  320 , and thereafter processed, according to methods known to people having ordinary skill in the art and which is briefly described below, to convert the aggregate material  510  and the cementing agent  520  into the synthetic material  440  ( FIG. 4 ). The synthetic material  440  ( FIG. 4 ) is formed from the aggregate material  510  and the cementing agent  520 , which bonds the aggregate material  510  to one another. 
     Referring to  FIGS. 4 and 5 , according to some exemplary embodiments, the cementing agent  520  is mixed together with the aggregate material  510 , placed into the casting form  500 , and processed to form the resulting synthetic material  440 . According to other exemplary embodiments, the cementing agent  520  is coated onto and/or around the aggregate material  510 , placed into the casting form  500 , and processed to form the resulting synthetic material  440 . After the synthetic material  440  is formed, the casting form  500  is removed. Once the casting form  500  is removed, the exposed portion  422  is made smooth and substantially planar. According to some exemplary embodiments, the casting form  500  is destroyed, while in other exemplary embodiments, the casting form  500  is removable and reusable. 
     The aggregate material  510  includes, but is not limited to, blast media and foundry casting media. Blast media includes, but is not limited to, silica sand, garnet, silicon carbide, aluminum oxide, zircon sand, and other blast media types known to people having ordinary skill in the art. These aggregate materials  510  are widely available for industrial applications and have controlled hardness and particle size. The cementing agent  520  includes, but is not limited to, sodium silicate which is also referred to as water glass, a plastic resin, a multi-part epoxy resin, clay based ceramic particles for forming ceramic bonds within the resulting synthetic material  440 , known compounds for producing a vitrified bond within the resulting synthetic material  440 , and an abrasive cement. According to some exemplary embodiments, the cementing agent  520  is a strong and fast curing material, wherein the curing time ranges from almost instantly to up to about five days. In other exemplary embodiments, the curing time can range from almost instantly to about fifteen days. By using cementing-agents  520  that are strong and last curing, synthetic materials  440  are fabricated with a controlled compressive strength and with the required efficiency. Alternatively, the synthetic material  440  is fabricated using other synthetic manufactured materials, such as Corian®, Zodiaq®, Silestone®, Ceracem®, Sikacrete®, Condensil®, and aluminum oxide according to some exemplary embodiments. According to some exemplary embodiments, the other synthetic manufactured materials form the synthetic material  440  by laminating slabs of these other synthetic manufactured materials together and shaping them into a desired shape. 
     According to one example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example silica sand, with sodium silicate to form a mixture  530 . The sodium silicate is coated onto the aggregate material  510  according to some exemplary embodiments. The mixture  530  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. The mixture  530  is then cured by applying carbon dioxide to the mixture  530 . During the curing process, the mixture  530  is solidified to form the synthetic material  440  in the negative shape of the cavity  509 . The curing process occurs in less than about an hour; however, the length of time can be greater or less in other exemplary embodiments. The following chemical reaction takes place during the curing process: 
       Na 2 SiO 3 +CO 2 →Na 2 CO 3 +SiO 2  
 
     Based upon the reaction provided above, the sodium silicate forms a silicon oxide during the curing reaction while also facilitates bonding the aggregate material  510  to one another. Silicon oxide is the most abrasive component of sedimentary rocks. The silicon oxide content is increased as the reaction proceeds forward, thereby increasing the abrasiveness of the resulting synthetic material  440 . According to some exemplary embodiments, the reaction occurs at about room temperature and at about atmospheric pressure; however, the temperature and/or the pressure can be altered in different exemplary embodiments. 
     According to another example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example silicon oxide, with plastic resin to form a mixture  530 . The plastic resin is coated onto the aggregate material  510  according to some exemplary embodiments. The mixture  330  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. The casting form  500 , along with the mixture  530 , is then placed in an oven (not shown) where the mixture  530  is cured at a proper temperature. According to some exemplary embodiments, the proper temperature ranges from about 200° F. to about 300° F.; however, the temperature can be higher or lower in other exemplary embodiments. When subjected to the proper temperature, the plastic resin melts and bonds the aggregate material  510  together into a single piece which forms the negative shape of the cavity  509 . The curing process occurs in about two hours; however, the length of time can be greater or less in other exemplary embodiments. According to some exemplary embodiments, the process occurs at about atmospheric pressure; however, the pressure can be altered in different exemplary embodiments. 
     According to another example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example silica sand, with a multi-part epoxy resin to form a mixture  530 . The multi-part epoxy resin typically consists of two parts, an epoxy resin and a hardener, which when placed in contact with one another initiates a reaction which bonds the aggregate material  510  together. According to one example, the multi-part epoxy resin includes phenolic resin and hexamine catalyst. In some exemplary embodiments, the multi-part epoxy resin includes more than two parts. The mixture  530  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. Within the casting form  500 , the reaction occurs when each of the components of the multi-part epoxy resin contact one another; thereby resulting in bonding the aggregate material  510  together to form a single piece which forms the negative shape of the cavity  509 . The curing process occurs in about five hours; however, the length of time can be greater or less in other exemplary embodiments. According to some exemplary embodiments, the process occurs at a temperature ranging between about 70° F. and 480° F. and at a pressure that is about one atmosphere; however, the temperature and/or the pressure can be altered in different exemplary embodiments. 
     According to another example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example silica sand mixed with a mineral belonging to the phyllosilicates group, with sodium silicate to form a mixture  530 . The sodium silicate is coated onto the aggregate material  510  according to some exemplary embodiments. The mixture  530  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. The mixture  530  is then cured by applying carbon dioxide to the mixture and increasing the temperature to about 1600° F. During the curing process, the mixture  530  is solidified to form the synthetic material  440  in the negative shape of the cavity  509 . The curing process occurs in about 9 hours; however, the length of time can be greater or less in other exemplary embodiments. The following chemical reaction takes place during the curing process: 
       Na 2 SiO 3 +CO 2 →Na 2 CO 3 +SiO 2  
 
     Based upon the reaction provided above, the sodium silicate forms a silicon oxide during the curing reaction while also facilitates bonding the aggregate material  510  to one another. Silicon oxide is the most abrasive component of sedimentary rocks. The silicon oxide content is increased as the reaction proceeds forward, thereby increasing the abrasiveness of the resulting synthetic material  440 . According to some exemplary embodiments, the reaction occurs at about room temperature and at about ten psi to about fifteen psi pressure; however, the temperature and/or the pressure can be altered in different exemplary embodiments. 
     According to another example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example silica sand, with clay based ceramic material to form a mixture  530 . However, other types of ceramic material are used in other exemplary embodiments. The mixture  530  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. The casting form  500 , along with the mixture  530 , is then placed in a furnace (not shown) and then fired where the mixture  530  is cored and ceramic bonds are formed. According to some exemplary embodiments, the temperature ranges from about 1745° F. to about 2012° F.; however, the temperature can be altered in other exemplary embodiments. When fired, ceramic bonds are formed and the aggregate material  510  bonds together into a single piece which forms the negative shape of the cavity  509 . The firing process occurs in about four to about six hours; however, the length of time can be greater or less in other exemplary embodiments. According to some exemplary embodiments, the process occurs at about room pressure; however, the pressure can be altered in different exemplary embodiments. 
     According to another example, the synthetic material  440  is produced by mixing the aggregate material  510 , for example Condensil® with an abrasive cement, for example Ceracem®, to form a mixture  530 . The Condensil® is formed from sand and is used as a component for high performance concrete. In certain exemplary embodiments, the Condensil® includes about 95% silicon oxide; however, the percent of silicon dioxide is variable in other exemplary embodiments. In certain exemplary embodiments, the Condensil® includes a minimum of about 92% silicon oxide. According to some exemplary embodiments which use Condensil® and Ceracem®, the mixture  530  is used to obtain a high strength, high abrasivity concrete. The mixture  530  is packed into the cavity  509  of the casting form  500 , which has a predetermined shape. The predetermined shape is a negative shape of the target cylinder  400  that is to be formed. However, as previously mentioned, the cavity  509  has a negative shape of a wheel (not shown) that, once formed, the wheel can be used in a traditional grinding wheel apparatus (not shown) according to some other exemplary embodiments. The mixture  530  is then cured to form a single piece which forms the negative shape of the cavity  509 . According to some exemplary embodiments, the curing process is performed at about room temperature and at about atmospheric pressure; however, the temperature and/or the pressure is altered in other exemplary embodiments. The curing process occurs in about 7 days; however, the length of time can be greater or less in other exemplary embodiments. As greater proportions of Condensil® are used, the synthetic material  440  exhibits increased abrasivity. Conversely, as greater proportions of Ceracem® are used, the synthetic material  440  exhibits increased compressive strength. The proportions of each of aggregate material  510  and the abrasive cement can be varied to alter the properties of the synthetic material  440  in accordance with testing desires. 
     Although some examples have been provided above for fabricating the synthetic material  440  and facilitating the bonding of the aggregate material  510 , the bonding methods include, but are not limited to, forming vitrified bonds, forming resinoid bonds, forming silicate bonds, forming shellac bonds, forming rubber bonds, and forming oxychloride bonds. 
     The resulting target cylinder  400  has an unconfined compressive strength of at least 18,000 psi. In certain exemplary embodiments, the resulting target cylinder  400  has an unconfined compressive strength ranging from about 18,000 psi to about 30,000 psi. In certain exemplary embodiments, the resulting target cylinder  400  has an unconfined compressive strength ranging from about 20,000 psi to about 28,000 psi. In certain exemplary embodiments, the resulting target cylinder  400  has an unconfined compressive strength ranging from about 22,000 psi to about 25,000 psi. 
     The resulting target cylinder  400  has an abrasiveness of at least 1.0 CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments, the resulting target cylinder  400  has an abrasiveness ranging from about one CAI to about two CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments, the resulting target cylinder  400  has an abrasiveness ranging from about two CAI to about four CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments, the resulting target cylinder  400  has an abrasiveness ranging from about four CAI to about six CAI when categorized pursuant to a Cerchar test. 
     According to some exemplary embodiments, iron and/or iron alloys are included within the composition of the synthetic material  440  which forms the target cylinder  400 . Iron in the form of cast iron particulates is included within the composition of the synthetic material  440  according to some exemplary embodiments. In another exemplary embodiment, iron in the form of steel buckshot is included within the composition of the synthetic material  440 . Although some examples have been provided for the forms of iron that can be included within the synthetic material  440 , other forms of iron can be included in the composition of the synthetic material  440  according to other exemplary embodiments. Iron and/or iron alloys are included within the composition of the synthetic material  440  for purposes of accelerating the wear rate of the cutting table  120  ( FIG. 1 ) and accelerating the testing duration. Iron reacts with diamond and therefore is able to accelerate the wear rate of the cutting table  120  ( FIG. 1 ). 
     According to some exemplary embodiments, Silicate alloys are included within the composition of the synthetic material  440  which forms the target cylinder  400 . Silicon Oxide in the form of Condensil® is included within the composition of the synthetic material  440  according to some exemplary embodiments. Silicon Oxide alloys are included within the composition of the synthetic material  440  for purposes of increasing the abrasiveness and accelerating the wear rate of the cutting table  120  ( FIG. 1 ) and accelerating the testing duration. 
     In certain exemplary embodiments, the content of Condensil® varies from about zero percent to about fifty percent of the weight of cement. In certain exemplary embodiments, the content of Condensil® varies from about five percent to about twenty-five percent of the weight of cement. In certain exemplary embodiments, the content of Condensil® varies from about five percent to about ten percent of the weight of cement. 
     According to some exemplary embodiments, iron composes about five percent to about ten percent of the total composition of the synthetic material  440 ; however the iron content is higher or lower according to other exemplary embodiments. In the exemplary embodiments where iron is included to form the synthetic material  440 , the unconfined compressive strength of the target cylinder  400  is at least 12,000 psi. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the unconfined compressive strength of the target cylinder  400  ranges from about 12,000 psi to about 30,000 psi. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the unconfined compressive strength of the target cylinder  400  ranges from about 18,000 psi to about 25,000 psi. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the unconfined compressive strength of the target cylinder  400  ranges from about 22,000 psi to about 25,000 psi. In the exemplary embodiments where iron is included to form the synthetic material  440 , the abrasiveness of the target cylinder  400  is at least one CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the abrasiveness of the target cylinder  400  ranges from about 2 CAI to about 4 CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the abrasiveness of the target cylinder  400  ranges from about 4 CAI to about 6 CAI when categorized pursuant to a Cerchar test. In certain exemplary embodiments where iron is included to form the synthetic material  440 , the abrasiveness of the target cylinder  400  ranges from about 1 CAI to about 6 CAI when categorized pursuant to a Cerchar test. 
     The fabrication of the target cylinder  400  is repeatable so that an initially formed target cylinder  400  is substantially similar and has similar properties, such as unconfined compressive strength, abrasiveness, and composition, to a subsequently formed target cylinder  400 . Once target cylinder  400  is formed, the target cylinder  400  can be used in the VTL test as described above. The target cylinder&#39;s first end  410  is coupled to the rotating table  310  ( FIG. 3 ), thereby positioning the exposed portion  422  adjacent the tool holder  320  ( FIG. 3 ) that has the cutter  100  ( FIG. 3 ) mounted therein. Upon performing the VTL test using target cylinder  400 , the abrasive wear resistance and/or the impact resistance for the PDC cutter  100  ( FIG. 3 ) can be determined. 
     The abrasive wear resistance is determined as a wear ratio, which is defined as the volume of target cylinder  400  that is removed to the volume of the PDC cutter  100  ( FIG. 3 ) that is removed. Alternatively, instead of measuring volume, the distance that the PDC cutter  100  ( FIG. 3 ) travels across the target cylinder  400  can be measured and used to quantify the abrasive wear resistance for the PDC cutter  100  ( FIG. 3 ). Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the VTL test. 
     The target cylinder  400  is able to test for abrasive wear resistance of cutters  100  ( FIG. 1 ) with a minimum consumption of time, target material, and test cutters. The target cylinder  400  is formed having at least one of a higher unconfined compressive strength, a higher abrasiveness, and/or an inclusion of iron and/or iron alloy when compared to prior art conventional target cylinders. The target cylinder  400  can be made according to the same construction each time giving the test repeatability and continuity over the testing of numerous different cutter types. 
     According to some exemplary embodiments, the fabrication of the synthetic material  440  is performed in a press (not shown). This process facilitates fabrication of the synthetic material  440  so that the synthetic material  440  has a higher compressive strength. 
       FIG. 6  shows a top perspective view of a target cylinder  600  in accordance with ah alternative exemplary embodiment of the invention. Referring to  FIG. 6 , the target cylinder  600  is cylindrically shaped and includes a first end  610 , a second end  620 , and a sidewall  630  extending from the first end  610  to the second end  620 . According to this exemplary embodiment, the second end  620  is also referred to as an exposed portion  622  of the target cylinder  600  because the second end  620  is subjected to contact with the superhard component  100  ( FIG. 1 ) when the testing is performed. The exposed portion  622  is substantially planar. Although the target cylinder  600  is cylindrically shaped, the target cylinder  600  can be any other geometric or non-geometric shape without departing from the scope and spirit of the exemplary embodiment. The target cylinder  600  has a diameter  602  of approximately three feet and a height  604  of approximately four inches. However, in alternate exemplary embodiments, the diameter  602  and/or the height  604  can vary according to the description provided above without departing from the scope and spirit of the exemplary embodiment. For example, the target cylinder  600  can be dimensioned and shaped to be used in the conventional granite log test also. 
     The target cylinder  600  is fabricated using a first material  660  and a second material  680  that is positioned in a predetermined pattern along the exposed portion  622 , wherein the second material  680  is adjacent to and intervening within the first material  660 , and wherein the first material  660  is a synthetic material similar to synthetic material  440  ( FIG. 4 ). The synthetic first material  660  is formed from any of the materials and processes described above. According to some exemplary embodiments, the second material  680  is a natural rock type, such as granite. According to other exemplary embodiments, the second material  680  also is a synthetic material similar to synthetic material  440  ( FIG. 4 ). In certain exemplary embodiments, the second material  680  is the same as first material  660 . In some of the exemplary embodiments where the first material  660  is different than, the second material  680 , the first material  660  is either more or less abrasive than the second material  680  depending upon user desires. In some of the exemplary embodiments where the first material  660  is different than the second material  680 , the first material  660  has either a higher or lower unconfined compressive strength than the second material  680  depending upon user desires. In some of the exemplary embodiments where the first material  660  is different than the second material  680 , the first material  660  has either a higher or lower concentration of iron and/or iron alloys than the second material  680  depending upon user desires. 
     The fabrication of the target cylinder  600  is repeatable so that an initially formed target cylinder  600  is substantially similar to a subsequently formed target cylinder  600 . The predetermined pattern for the second material  680  is repeatable so that the test results can be compared between tests conducted over time. According to  FIG. 6 , the second material  680  is a granite slab that is about ¾ inches, or about twenty millimeters, wide and extends from the exposed portion  622  to the first end  610 . Although this exemplary embodiment uses a granite slab that is about ¾ inches, or about twenty millimeters, the width of the slabs can vary from about ⅕ inches, or about five millimeters, to about twelve inches in other exemplary embodiments or can also vary in width from one slab to another without departing from the scope and spirit of the exemplary embodiment. Additionally, although the second material  680  is shaped in substantially rectangular slabs, the second material  680  can be shaped in any other geometric or non-geometric shape without departing from the scope and spirit of the exemplary embodiment. Examples of the second material  680  include, but are not limited to, sandstone, limestone, marble, granite, wood, plastic, epoxy, synthetic materials described above, concrete, and other materials known to people having ordinary skill in the art. In alternative exemplary embodiments, the second material  680  can extend from the exposed portion  622  to a distance that is at least a portion of the height  604  without departing form the scope and spirit of the exemplary embodiment. In this exemplary embodiment, there are four pieces of second material  680 A,  680 B,  680 C, and  680 D, where each of the second materials  680 A,  680 B,  680 C, and  680 D are oriented to divide the exposed portion  622  into a first quadrant  690 , a second quadrant  692 , a third quadrant  694 , and a fourth quadrant  696 . Hence, the second material  680  is positioned in an “X-like” pattern. 
     Specifically, second material  680 A is positioned at substantially ninety degrees to second material  680 D and second material  680 B. Second material  680 B is positioned at substantially ninety degrees to second material  680 A and second material  680 C. Second material  680 C is positioned at substantially ninety degrees to second material  680 B and second material  680 D. Second material  680 D is positioned at substantially ninety degrees to second material  680 C and second material  680 A. Thus, four equally sized quadrants  690 ,  692 ,  694 , and  696  are formed; however, the angles between the second materials  680 A,  680 B,  680 C, and  680 D can be varied so at least one quadrant is sized differently that the other quadrants. Although four quadrants  690 ,  692 ,  694 , and  696  are formed at the exposed portion  622 , greater or fewer quadrants can be formed at the exposed portion  622  by using more or less second material  680  slabs positioned interveningly between the first material  660  without departing from the scope and spirit of the exemplary embodiment. Optionally, the second material  680  can be oriented in a manner where a first material core  669  is formed at substantially the center of the target cylinder  600 . Although not illustrated, alternatively, the second material  680  can be oriented in a manner where second material  680  also is positioned at substantially the center of the target cylinder  600 . 
     The first material  660  forms the first quadrant  690 , the second quadrant  692 , the third quadrant  694 , and the fourth quadrant  696 . The first material  660  is any synthetic material having one or more properties of any one of compressive strength, abrasiveness, and/or iron content as previously mentioned with respect to  FIG. 4 . The first material  660  optionally can have additives included therein so long that the desired property requirements are still achieved. According to this exemplary embodiment, the first material  660  also extends from the exposed portion  622  to the first end  610 . 
     In one exemplary embodiment, the difference of unconfined compressive strength between the second material  680  and the first material  660  ranges from about 1,000 psi to about 60,000 psi. In other exemplary embodiments, the difference of unconfined compressive strength between the second material  680  and the first material  660  ranges from about 4,000 psi to about 60,000 psi. In other exemplary embodiments, the difference of unconfined compressive strength between the second material  680  and the first material  660  ranges from about 6,000 psi to about 60,000 psi. In other exemplary embodiments, the difference of unconfined compressive strength between the second material  680  and the first material  660  ranges from about 10,000 psi to about 60,000 psi. In other exemplary embodiments, the difference of unconfined compressive strength between the second material  680  and the first material  660  ranges from about 15,000 psi to about 60,000 psi. 
     In this exemplary embodiment, second materials  680 A,  680 B,  680 C, and  680 D are fabricated from the same type of second material  680 . However, according to certain alternative exemplary embodiments, one or more of second materials  680 A,  680 B,  680 C, and  680 D can be made from a different types of second materials  680 , such as granite and marble slabs. Thus, each of second materials  680 A,  680 B,  680 C, and  680 D can be made from a different type of second material  680  or one or more of second materials  680 A,  680 B,  680 C, and  680 D can be made from the same type of second material  680  without departing from the scope and spirit of the exemplary embodiment. 
     Similarly, in this exemplary embodiment, each of the first quadrant  690 , the second quadrant  692 , the third quadrant  694 , and the fourth quadrant  696  are formed from the same type of first material  660 . However, according to certain alternative exemplary embodiments, one or more of the first quadrant  690 , the second quadrant  692 , the third quadrant  694 , and the fourth quadrant  696  can be made from a different type of first material  660 . Thus, each of the first quadrant  690 , the second quadrant  692 , the third quadrant  694 , and the fourth quadrant  696  can be made from a different type of first material  660  or one or more of the first quadrant  690 , the second quadrant  692 , the third quadrant  694 , and the fourth quadrant  696  can be made from the same type of first material  660  without departing from the scope and spirit of the exemplary embodiment. 
     The surface area of the target cylinder&#39;s exposed portion  622  is a combination of the first material  660  and the second material  680 . In one exemplary embodiment, the percentage range of first material  660  is about five percent to about ten percent, while the percentage range of second material  680  is about ninety percent to about ninety-five percent. In another exemplary embodiment, the percentage range of first material  660  is about ten percent to about twenty-five percent, while the percentage range of second material  680  is about seventy-five percent to about ninety percent. In another exemplary embodiment, the percentage range of first material  660  is about twenty percent to about thirty-five percent, while the percentage range of second material  680  is about sixty-five percent to about eighty percent. In another exemplary embodiment, the percentage range of first material  660  is about thirty percent to about forty-five percent, while the percentage range of second material  680  is about fifty-five percent to about seventy percent. In another exemplary embodiment, the percentage range of first material  660  is about forty percent to about fifty-five percent, while the percentage range of second material  680  is about forty-five percent to about sixty percent. In another exemplary embodiment, the percentage range of first material  660  is about fifty percent to about sixty-five percent, while the percentage range of second material  680  is about thirty-five percent to about fifty percent. In another exemplary embodiment, the percentage range of first material  660  is about sixty percent to about seventy-five percent, while the percentage range of second material  680  is about twenty-five percent to about forty percent. In another exemplary embodiment, the percentage range of first material  660  is about seventy percent to about eighty-five percent, while the percentage range of second material  680  is about fifteen percent to about thirty percent. In another exemplary embodiment, the percentage range of first material  660  is about eighty percent to about ninety percent, while the percentage range of second material  680  is about ten percent to about twenty percent. In another exemplary embodiment, the percentage range of first material  660  is about ninety percent to about ninety-five percent, while the percentage range of second material  680  is about five percent to about ten percent. 
     Referring to  FIGS. 5 and 6 , the target cylinder  600  is formed by obtaining the casting form  500  and positioning the second material  680  upright within the casting form  500  in a predetermined pattern. According to one exemplary embodiment, the casting form  500  is cylindrical; however, the casting form  500  can be any other geometric or non-geometric shape. The casting form  500  is filled with the aggregate material  510  and the cementing agent  520  so that the resulting mixture  530  surrounds at least a portion of the second material  680 . The mixture  530  is processed and hardened, thereby forming the first material  660 , which surrounds at least a portion of the second material  680 . Once hardened, the casting form  500  is removed and the exposed portion  622  is made smooth and substantially planar. The second material  680  is pre-fabricated according to some exemplary embodiments, regardless of whether the second material  680  is a natural material or a synthetic material. In other exemplary embodiments, the second material  680  is fabricated at the same time as the first material  660 ; for instance, when the second material  680  also is a synthetic material. 
     In some exemplary embodiments, an epoxy (not shown), such as Sikadur BTP®, is placed, or coated, onto the outer surfaces of the second material  680  which is to be bonded to the first material  660 . The epoxy is a two-part epoxy according to some exemplary embodiments. The two-part epoxy includes a glue and a catalyst. Once the epoxy is coated onto the second material  680 , the second material  680  is positioned within the casting form  500  according to the positions described above. The first material  660  is placed into the casting form  500  to surround the second material  680  and the epoxy. As the epoxy cures, the epoxy bonds to both the second material  680  and the first material  660 , thereby effectively bonding the second material  680  to the first material  660 . According to some exemplary embodiments, the epoxy cures in about fourteen days, however, other epoxies having longer or shorter cure times can be used in other exemplary embodiments. Upon the target cylinder  600  being cured and formed, the epoxy has a thickness ranging from about two millimeters to about fifteen millimeters; however, this thickness can be greater or less in other exemplary embodiments. 
     Alternatively, the target cylinder  600  is formed by obtaining a casting form  500  and filling it with the mixture  530 , which includes the aggregate material  510  and the cementing agent  520 . According to one exemplary embodiment, the casting form  500  is cylindrical; however, the casting form  500  can be any other geometric or non-geometric shape. The mixture  530  is processed, thereby forming the first material  660 . The first material  660  is then slotted or drilled in a predetermined pattern to accept the second material  680  therein. The second material  680  is inserted upright into the slots and bonded to the first material  660  using a bonding material known to people having ordinary skill in the art, such as cement or an epoxy. The casting form  500  is removed and the exposed portion  622  is made smooth and substantially planar. 
     Once target cylinder  600  is formed, the target cylinder  600  can be used in the VBM test as described above. The target cylinder&#39;s first end  610  is coupled to the rotating table  310  ( FIG. 3 ), thereby positioning the exposed portion  622  adjacent the tool holder  320  ( FIG. 3 ) that has the cutter  100  ( FIG. 3 ) mounted therein. Upon performing the VTL test using target cylinder  600 , the abrasive wear resistance and/or the impact resistance for the PDC cutter  100  ( FIG. 3 ) can be determined. During the test, the cutter  100  ( FIG. 3 ) repeatedly makes transitions between higher compressive strength material and lower compressive strength material. According to one example where the first material  660  has a higher compressive strength than the second material  680 , each time the cutter  100  ( FIG. 3 ) engages the end of one of the first material  660 , a front impact load is imparted to the cutting table  120  ( FIG. 1 ) and substrate  110  ( FIG. 1 ) as it passes across the first material  660 . When the cutter  100  ( FIG. 3 ) exits first material  660  and enters the second material  680 , the compressive stress on the cutting table  120  is unloaded or released, thereby creating a rebound test of the substrate  110  ( FIG. 1 ) to the cutting table  120  ( FIG. 3 ) at the contact face  115  ( FIG. 1 ) and hereby allows measurement of impact resistance. 
     Referring back to  FIG. 6 , the abrasive wear resistance is determined as a wear ratio, which is defined as the volume of target cylinder  600  that is removed to the volume of the PDC cutter  100  ( FIG. 3 ) that is removed. Alternatively, instead of measuring volume, the distance that the PDC cutter  100  ( FIG. 3 ) travels across the target cylinder  600  can be measured and used to quantify the abrasive wear resistance for the PDC cutter  100  ( FIG. 3 ). Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the VTL test. Impact resistance for the PDC cutter  100  ( FIG. 3 ) also can be determined using the same test by measuring the volume of diamond removed from the PDC cutter  100  ( FIG. 3 ) through chipage. Alternatively, the impact resistance for the PDC cutter  100  ( FIG. 3 ) can be determined by measuring the weight of diamond removed from the PDC cutter  100  ( FIG. 3 ) through chipage. Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the impact resistance using the VTL test. 
     The target cylinder  600  is able to test for both abrasive wear resistance and impact robustness of cutters  100  ( FIG. 1 ) with a minimum consumption of time, target material, and test cutters. The target cylinder  600  can be made according to the same construction each time giving the test repeatability and continuity over the testing of numerous different cutter types. According to some exemplary embodiments, the target cylinder  600  is entirely made from first material  660 . In other exemplary embodiments, the second material  680  is interveningly positioned at predetermined locations within the first material  660 . The formulation of the first material  660  is maintained over time to ensure the test results are comparative over time. Although one predetermined pattern for having the second material  680  be interveningly positioned within the first material  660  is illustrated with respect to  FIG. 6 , the second material  680  can be interveningly positioned within the first material  660  in any repeatable predetermined patterns, some of which are illustrated with respect to  FIGS. 7-9 . 
       FIG. 7  shows a top perspective view of a target cylinder  700  in accordance with a second alternative exemplary embodiment of the invention. Target cylinder  700  is similar to target cylinder  600  except that additional second material  680 E,  680 F,  680 G, and  680 H are positioned within the target cylinder  700  and extend from the exposed portion  622  to a portion of the height  604 . The exposed portion  622  is substantially planar. Second material  680 E is positioned between second materials  680 A and  680 B so that it substantially bisects the angle formed between second materials  680 A and  680 B. Similarly, second material  680 F is positioned between second materials  680 B and  680 C so that it substantially bisects the angle formed between second materials  680 B and  680 C. Similarly, second material  680 G is positioned between second materials  680 C and  680 D so that it substantially bisects the angle formed between second materials  680 C and  680 D. Also, second material  680 H is positioned between second materials  680 D and  680 A so that it substantially bisects the angle formed between second materials  680 D and  680 A. Hence, second materials  680  are positioned in a “spoke-like” pattern. Although additional second material  680 E,  680 F,  680 G, and  680 H extends from the exposed portion  622  to a distance that is a portion of the height  604 , at least one of additional second material  680 E,  680 F,  680 G, and  680 H can extend from the exposed portion  622  to the first end  610  without departing from the scope and spirit of the exemplary embodiment. The alternative exemplary embodiments presented with respect to target cylinder  600  also apply to target cylinder  700 . For example, one or more of the second materials  680 A,  680 B,  680 C,  680 D,  680 B,  680 F,  680 G, and  680 H can be made of different, types of second materials  680 . The target cylinder  700  is fabricated according to the processes described with respect to target cylinder  600  ( FIG. 6 ). 
       FIG. 8  shows a top perspective view of a target cylinder  800  in accordance with a third alternative exemplary embodiment of the invention. Target cylinder  800  is similar to target cylinder  600  ( FIG. 6 ) except that the shape and positioning of the second material  880  is different than the shape and positioning of the second material  680 A,  680 BF,  680 C, and  680 D ( FIG. 6 ). Referring to  FIG. 8 , the target cylinder  800  includes a first material  860  and a second material  880  that is positioned in a predetermined pattern along the exposed portion  622 , wherein the second material  880  is adjacent to and intervening within the first material  860 . The fabrication of the target cylinder  800  is repeatable so that an initially formed target cylinder  800  is substantially similar to a subsequently formed target cylinder  800 . The predetermined pattern for the second material  880  is repeatable so that the test results can be compared between tests conducted over time. The first material  860  is similar to the first material  660  ( FIG. 6 ). Similarly, second material  880  is similar to the second material  680  ( FIG. 6 ). According to  FIG. 8 , the second material  880  is a cylindrical column that extends from the exposed portion  622  to the first end  610 . In this exemplary embodiment, forty second materials  880  are positioned within the target cylinder  800  in a predetermined pattern and are surrounded by the first material  860 . However, greater or fewer second materials  880  can be used without departing from the scope and spirit of the exemplary embodiment. According to some alternative exemplary embodiments, the second material  880  extends from the exposed portion  622  to a portion of the height  604  without departing form the scope and spirit of the exemplary embodiment. In using this target cylinder  800 , the PDC cutters  100  ( FIG. 3 ) are subjected to glancing blows against the second material  880 . The alternative exemplary embodiments presented with respect to target cylinder  600  ( FIG. 6 ) also apply to target cylinder  800 . For example, one or more of the second materials  880  can be made of different types of second materials  880 . The target cylinder  800  is fabricated according to the processes described with respect to target cylinder  600  ( FIG. 6 ). 
       FIG. 9  shows a top perspective view of a target cylinder  900  in accordance with a fourth alternative exemplary embodiment of the invention. Target cylinder  900  is similar to target cylinder  800  ( FIG. 8 ) except that the shape and positioning of the second material  980  is different than the shape and positioning of the second material  880  ( FIG. 8 ). Referring to  FIG. 9 , the target cylinder  900  includes a first material  960  and a second material  980  that is positioned in a predetermined pattern along the exposed portion  622 , wherein the second material  980  is adjacent to and intervening within the first material  960 . The fabrication of the target cylinder  900  is repeatable so that an initially formed target cylinder  900  is substantially similar to a subsequently formed target cylinder  900 . The first material  960  is similar to the first material  660  ( FIG. 6 ). Similarly, second material  980  is similar to the second material  680  ( FIG. 6 ). According to  FIG. 9 , the second material  980  is a triangular column that extends from the exposed portion  622  to the first end  610 . In this exemplary embodiment, thirty-three second materials  980  are positioned within the target cylinder  900  in a predetermined pattern and are surrounded by the first material  960 . However, greater or fewer second materials  980  can be used without departing from the scope and spirit of the exemplary embodiment. According to some alternative exemplary embodiments, the second material  980  extends from the exposed portion  622  to a portion of the height  604  without departing form the scope and spirit of the exemplary embodiment. The alternative exemplary embodiments presented with respect to target cylinder  600  ( FIG. 6 ) also apply to target cylinder  900 . For example, one or more of the second materials  980  can be made of different types of second materials  980 . The target cylinder  900  is fabricated according to the processes described with respect to target cylinder  600  ( FIG. 6 ). 
       FIG. 10  shows a side perspective view of a target cylinder  1000  in accordance with a fifth alternative exemplary embodiment of the invention. Target cylinder  1000  is similar to target cylinder  600  ( FIG. 6 ) except that openings or slots  1090  are formed at the surface of the exposed portion  622 . The openings or slots  1090  are void of any material. Referring to  FIG. 10 , the target cylinder  1000  includes a first material  1060  and one or more openings or slots  1090  positioned in a predetermined pattern along the exposed portion  622 , wherein the openings or slots  1090  are adjacent to and intervening within the first material  1060 . The fabrication of the target cylinder  1000  is repeatable so that an initially formed target cylinder  1000  is substantially similar to a subsequently formed target cylinder  1000 . The first material  1060  is similar to the first material  660  ( FIG. 6 ). According to  FIG. 10 , the opening or slot  1090  is a circular cylindrical opening that extends from the exposed portion  622  to the first end  610 . In this exemplary embodiment, forty openings or slots  1090  are positioned within the target cylinder  1000  in a predetermined pattern and are surrounded by the first material  1060 . However, greater or fewer openings or slots  1090  can be used without departing from the scope and spirit of the exemplary embodiment. According to some alternative exemplary embodiments, the openings or slots  1090  extend from the exposed portion  622  to a distance that is a portion of the height  604  without departing form the scope and spirit of the exemplary embodiment. According to some exemplary embodiments, the shape of the openings or slots  1090  can be varied without departing from the scope and spirit of the exemplary embodiments. For example, the second material for any of the previously described embodiments can be replaced with an opening or slot  1090 . In using this target cylinder  1000 , the PDC cutters  100  ( FIG. 3 ) are subjected to glancing blows against the openings or slots  1090  rather than against the second material  980  ( FIG. 9 ). The openings or slots  1090  are formed after the first material  1060  is formed. According to one example, once the processing of the aggregate material  510  ( FIG. 5 ) and the cementing agent  520  ( FIG. 5 ) is completed and the first material  1060  is formed, the opening or slots  1090  are formed via drilling. The alternative exemplary embodiments presented with respect to target cylinder  600  ( FIG. 6 ) also apply to target cylinder  1000 . 
       FIG. 11  shows a side perspective view of a target cylinder  1100  in accordance with a sixth alternative exemplary embodiment of the invention. Referring to  FIG. 11 , the target cylinder  1100  is a cylindrically shaped log and includes a first end  1110 , a second end  1120  and a sidewall  1130  extending from the first end  1110  to the second end  1120 . According to this exemplary embodiment, the sidewall  1130  is also referred to as an exposed portion  1132  of the target cylinder  1100  because the sidewall  1130  is subjected to contact with the superhard component  100  ( FIG. 1 ) when the testing is performed. The target cylinder  1100  has a diameter  1102  of approximately six inches and a height  1104  of approximately two feet. However, in alternate exemplary embodiments, the diameter  1102  can range from about four inches to about six feet without departing from the scope and spirit of the exemplary embodiment. Additionally, in alternate exemplary embodiments, the height  1104  can range from about one inch to about twenty feet without departing front the scope and spirit of the exemplary embodiment. 
     The target cylinder  1100  includes a first material  1160  and a second material  1180  that is positioned in a predetermined pattern along the exposed portion  1132 , where the second material  1180  is adjacent to the first material  1160 . The fabrication of the target cylinder  1100  is repeatable so that an initially formed target cylinder  1100  is substantially similar to a subsequently formed target cylinder  1100 . The predetermined pattern for the second material  1180  is repeatable so that the test results can be compared between tests conducted over time. According to  FIG. 11 , the second material  1180  is a granite band that is about two inches wide and has an outer diameter equal to the target cylinder&#39;s diameter  1102 . Although this exemplary embodiment uses a granite band that is two inches wide for the second material  1180 , the width of the band can vary from about one-half inch to about twelve inches in other exemplary embodiments or can also vary in width from one band to another without departing from the scope and spirit of the exemplary embodiment. Second material  1180  is similar to second material  680  ( FIG. 6 ), as previously described, and can be fabricated from other natural rock types or synthetic materials as previously described. 
     The first material  1160  is a synthetic material band that is about two inches wide and has a outer diameter equal to the target cylinder&#39;s diameter  1102 . Although this exemplary embodiment uses a synthetic material band that is two inches wide, the width of the band can vary from about one-half inch to about twelve incites in other exemplary embodiments or can also vary in width from one band to another without departing from the scope and spirit of the exemplary embodiment. First material  1160  is similar to first material  660  ( FIG. 6 ), as previously described. 
     According to  FIG. 11 , target cylinder  1100  is formed using six first materials  1160 A,  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F and six second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F. The second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F are coupled to the first materials  1160 A,  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F in an alternating manner. In this exemplary embodiment, second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F are fabricated from the same material. However, according to certain alternative exemplary embodiments, one or more of second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F can be made from a different type of second material. Thus, each of second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F can be made from a different type of second material or one or more of second materials  1180 A,  1180 B,  1180 C,  1180 D,  1180 E, and  1180 F can be made from the same type of second material without departing from the scope and spirit of the exemplary embodiment. 
     Similarly, in this exemplary embodiment, first materials  1160 A.  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F are lubricated from the same material. However, according to certain alternative exemplary embodiments, one or more of first materials  1160 A,  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F can be made from a different type of first material. Thus, each of first materials  1160 A,  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F can be made from a different type of first material or one or more of first materials  1160 A,  1160 B,  1160 C,  1160 D,  1160 E, and  1160 F can be made from the same type of first material without departing from the scope and spirit of the exemplary embodiment. 
     The surface area of the target cylinder&#39;s  1100  exposed portion  1132  is a combination of the first material  1160  and the second material  1180 . In one exemplary embodiment, the percentage range of first material  1160  is about five percent to about ten percent, while the percentage range of second material  1180  is about ninety percent to about ninety-five percent. In another exemplary embodiment, the percentage range of first material  1160  is about ten percent to about twenty-five percent, while the percentage range of second material  1180  is about seventy-five percent to about ninety percent. In another exemplary embodiment, the percentage range of first material  1160  is about twenty percent to about thirty-five percent, while the percentage range of first material  1180  is about sixty-five percent to about eighty percent. In another exemplary embodiment, the percentage range of first material  1160  is about thirty percent to about forty-five percent, while the percentage range of second material  1180  is about fifty-five percent to about seventy percent. In another exemplary embodiment, the percentage range of first material  1160  is about forty percent to about fifty-five percent, while the percentage range of second material  1180  is about forty-five percent to about sixty percent. In another exemplary embodiment, the percentage range of first material  1160  is about fifty percent to about sixty-five percent, while the percentage range of second material  1180  is about thirty-five percent to about fifty percent. In another exemplary embodiment, the percentage range of first material  1160  is about sixty percent to about seventy-five percent, while the percentage range of second material  1180  is about twenty-five percent to about forty percent. In another exemplary embodiment, the percentage range of first material  1160  is about seventy percent to about eighty-five percent, while the percentage range of second material  1180  is about fifteen percent to about thirty percent. In another exemplary embodiment, the percentage range of first material  1160  is about eighty percent to about ninety percent, while the percentage range of second material  1180  is about ten percent to about twenty percent. In another exemplary embodiment, the percentage range of first material  1160  is about ninety percent to about ninety-five percent, while the percentage range of second material  1180  is about five percent to about ten percent. 
     The target cylinder  1100  is formed by obtaining a casting form (not shown) and loading the casting form from bottom to top with alternating bands of first material  1160  and second material  1180 . Each time the first material  1160  is loaded into the casting form, the first material  1160  is allowed to cool and harden before loading the second material  1180  above the first material  1160 . According to one exemplary embodiment, the casting form is cylindrical. Once the desired number of bands are formed and the desired height of the target cylinder  1100  is formed, the casting form is removed and the exposed portion  1132  is smoothened. 
     In some exemplary embodiments, an epoxy (not shown), such as Sikadur BTP®, is placed, or coated, onto the outer surface of either or both the second material  1180  and the first material  1160  prior to the second material  1180  being loaded on top of the first material  1160 . The epoxy is a two-part epoxy according to some exemplary embodiments. The two-part epoxy includes a glue and a catalyst. As the epoxy cures, the epoxy bonds to both the second material  1180  and the first material  1160 , thereby effectively bonding the second material  1180  to the first material  1160 . According to some exemplary embodiments, the epoxy cures in about fourteen days, however, other epoxies having longer or shorter cure times can be used in other exemplary embodiments. Upon the target cylinder  1100  being cured and formed, the epoxy has a thickness ranging from about two millimeters to about fifteen millimeters; however, this thickness can be greater or less in other exemplary embodiments. 
     Once target cylinder  1100  is formed, the target cylinder  1100  can be used in the granite log test as described above. The target cylinder&#39;s first end  1110  is coupled to the chuck  210  ( FIG. 2 ) and the second end  1120  is coupled to the tail stock  220  ( FIG. 2 ), thereby positioning the exposed portion  1132  adjacent the tool post  230  ( FIG. 2 ) that has the cutter  100  ( FIG. 2 ) mounted therein. Upon performing the granite log test using target cylinder  1100 , the abrasive wear resistance and/or the impact resistance for the PDC cutter  100  ( FIG. 2 ) can be determined. During the test, the cutter  100  ( FIG. 2 ) repeatedly makes transitions between the first material  1160  and the second material  1180 , wherein one of the first or second materials has a higher compressive strength than the other material. In the example where the first material  1160  has the higher compressive strength than the second material  1180 , each time the cutter  100  ( FIG. 2 ) engages the end of one of the first material  1160 , a front impact load is imparted to the cutting table  120  ( FIG. 1 ) and substrate  110  ( FIG. 1 ) as it passes across the first material  1160 . When the cutter  100  ( FIG. 2 ) exits first material  1160  and enters the second material  1180 , the compressive stress on the cutting table  120  ( FIG. 1 ) is unloaded or released, thereby creating a rebound test of the substrate  110  ( FIG. 1 ) to the cutting table  120  ( FIG. 1 ) at the contact face  115  ( FIG. 1 ). 
     The abrasive wear resistance is determined as a wear ratio, which is defined ax the volume of target cylinder  1100  that is removed to the volume of the PDC cutter  100  ( FIG. 2 ) that is removed. Alternatively, instead of measuring volume, the distance that the PDC cutter  100  ( FIG. 2 ) travels across the target cylinder  1100  can be measured and used to quantity the abrasive wear resistance for the PDC cutter  100  ( FIG. 2 ). Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the granite log test. Impact resistance for the PDC cutter  100  ( FIG. 2 ) also can be determined using the same test by measuring the volume of rock removed from the PDC cutter  100  ( FIG. 2 ) through chipage. Alternatively, the impact resistance for the PDC cutter  100  ( FIG. 2 ) can be determined by measuring the weight of rock removed from the PDC cutter  100  ( FIG. 2 ) through chipage. Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the impact resistance using the granite log test. 
     The target cylinder  1100  is able to test for both abrasive wear resistance and impact robustness of cutters  100  ( FIG. 1 ) with a minimum consumption of time, target material, and test cutters. The target cylinder  1100  can be made according to the same construction each time giving the test repeatability and continuity over the testing of numerous different cutter types. According to some exemplary embodiments, the target cylinder  1100  is entirely made from first material  1160 . The formulation of the first material  1160  and second material  1180  is maintained over time to ensure the test results are comparative over time. 
       FIG. 12  shows a top perspective view of a target cylinder  1200  in accordance with a seventh exemplary embodiment of the invention. Referring to  FIG. 12 , the target cylinder  1200  is cylindrically shaped and includes a first end  1210 , a second end  1220 , and a sidewall  1230  extending from the first end  1210  to the second end  1220 . According to this exemplary embodiment, the second end  1220  is also referred to as an exposed portion  1222  of the target cylinder  1200  because the second end  1220  is subjected to contact with the superhard component  100  ( FIG. 1 ) when the testing is performed. The exposed portion  1222  is substantially planar according to this exemplary embodiment. Although the target cylinder  1200  is cylindrically shaped, the target cylinder  1200  can be any other geometric or non-geometric shape without departing from the scope and spirit of the exemplary embodiment. The target cylinder  1200  has a diameter  1202  of approximately three feet and a height  1204  of approximately four inches. However, in alternate exemplary embodiments, the diameter  1202  and/or the height  1204  can vary according to the description provided above without departing from the scope and spirit of the exemplary embodiment. For example, the target cylinder  1200  can be dimensioned and shaped to be used in the conventional granite log test also, such that the sidewall  1230  becomes the exposed portion in those exemplary embodiments. 
     The target cylinder  1200  is fabricated similarly to the fabrication of target cylinder  400  ( FIG. 4 ) using the casting form  500  ( FIG. 5 ). However, instead of using the aggregate material  510  ( FIG. 5 ) and the cementing agent  520  ( FIG. 5 ) to form the target cylinder  400  ( FIG. 4 ), the target cylinder  1200  is formed using at least a first material component  1240  and a second material component  1250 , which is distinctive with respect to the first material component  1240 . 
     The first material component  1240  is a distribution of regular heterogeneities, which includes either spherical inclusions or any other inclusions of a different geometrical or non-geometrical shape. One example of the first material component  1240  is regular shape hard rock particles or inclusions, like granite for example. Another example of the first material component  1240  is regular shape silica inclusions, however, other examples of the first material component  1240  include, but are not limited to, any material whose Mohs relative hardness is greater than the relative hardness of quartz, like topaz, corundum, or diamond. According to some exemplary embodiments, the first material component  1240  is selected pursuant to a desired controlled hardness, which is relatively higher compared to the hardness of the second material component  1250 , and/or a desired controlled size, which can be small or large, such that the destruction process of the cutting element  100 , when being tested, is achievable within a reasonable time period, which is explained in further detail below. According to some exemplary embodiments, the Mohs relative hardness of the first material component  1240  ranges from about 7 to 10; in case hardness is expressed in terms of unconfined compressive strength, like in the case of natural or artificial rocks, the hardness of the first material component  1240  ranges from about 20,000 psi to 50,000 psi; however, the selected hardness range may be within a smaller range than provided or beyond the range provided. According to certain exemplary embodiments, the size of the first material component  1240  ranges from about 1 mm to about 100 mm; however, the selected size range may be within a smaller range than provided or beyond the range provided. According to several exemplary embodiments, the selection of the hardness of the first material component  1240  is based upon the selection of the size of the first material component  1240 . Alternatively, according to several exemplary embodiments, the selection of the size of the first material component  1240  is based upon the selection of the hardness of the first material component  1240 . 
     The second material component  1250  is a matrix material that is capable of cementing the first material component  1240  therein. One example of the second material component  1250  is cement, however, other examples of the second material component  1250  include, but are not limited to, plaster, gypsum or resin, provided that the ratio between the hardness of the first material component  1240  and the hardness of the second material component  1250  is sufficiently high. According to certain exemplary embodiments, the ratio between the hardness of the first material component  1240  and the hardness of the second material component  1250  ranges from about 2 to 4; however, the selected ratio may be within a smaller range than provided or beyond the range provided. 
     The target cylinder  1200  is formed by mixing both first and second material components  1240 ,  1250  together, either while in the casting form  500  ( FIG. 5 ) and/or prior to being placed into the casting form  500  ( FIG. 5 ), such that the distribution of the first material component  1240  is kept as constant as possible throughout the volume of the target cylinder  1200  once formed. According to some exemplary embodiments, the mixing of the first and second material components  1240 ,  1250  is performed using an agitator (not shown); however, the mixing is performed using some other known device or method known to people having ordinary skill in the art according to alternative exemplary embodiments. Once the first and second, material components  1240 ,  1250  have been, mixed and placed within the casting form  500  ( FIG. 5 ), the mixture of the first and second material components  3240 ,  1250  are allowed to dry, cure, and/or harden. The casting form  500  ( FIG. 5 ) is then removed, either by breaking the casting form or by some other removal process, thereby forming the target cylinder  1200 . One or more of the surfaces  1210 ,  1220 ,  1230  of the target cylinder  1200  are optionally then smoothed and prepared for testing one or more cutters  100  and/or cutter types. 
     Once target cylinder  1200  is formed, the target cylinder  1200  can be used in the VTL test as described above. According to certain exemplary embodiments, the target cylinder&#39;s first end  1210  is coupled to the rotating table  310  ( FIG. 3 ), thereby positioning the exposed portion  1222  adjacent the tool holder  320  ( FIG. 3 ) that has the cutter  100  ( FIG. 3 ) mounted therein. Upon performing the VBM test using target cylinder  1200 , the abrasive wear resistance and/or the impact resistance for the PDC cotter  100  ( FIG. 3 ) can be determined. The abrasive wear resistance is determined pursuant to the description provided above. For example, the abrasive wear resistance is determined as a wear ratio, which is defined as the volume of target cylinder  1200  that is removed to the volume of the PDC cutter  100  ( FIG. 3 ) that is removed. In another example, the abrasive wear resistance is quantified by measuring the distance that the PDC cutter  100  ( FIG. 3 ) travels across the target cylinder  1200 . 
     The impact resistance for the PDC cutter  100  ( FIG. 3 ) also is determinable using this target cylinder  1200 . The PDC cutter  100  ( FIG. 3 ) is placed into contact with the exposed portion  1222  of the target cylinder  1200  and moved thereon creating impacts by repeatedly transitioning between the first material component  1240  and the second material component  1250 . These impacts are generated by moving at least one of the PDC cutter  1000  ( FIG. 3 ) and/or the target cylinder  1200  once they are in contact with one another. According to certain exemplary embodiments, the PDC cutter  100  ( FIG. 3 ) is stationary while the target cylinder  1200  is moved, such as by rotation. In another exemplary embodiment, the target cylinder  1200  is stationary, while the PDC cutter  100  ( FIG. 3 ) is moved, either in a circular motion or from the perimeter of the target cylinder  1200  towards the center of the target cylinder  1200  and back again in a repeatable manner. In yet other exemplary embodiments, both the target cylinder  1200  and the PDC cutter  100  ( FIG. 3 ) are moved to create the impacts. To measure the impact resistance, the destruction process of the PDC cutter  100  ( FIG. 3 ), specifically the cutting table  120  ( FIG. 1 ), is of a shorter time period than the time to noticeably wear the cutting table  120  ( FIG. 1 ), thereby not polluting the estimation of impact resistance by the occurrence of noticeable abrasive wear. 
     According to some exemplary embodiments for estimating the impact resistance for a PDC cutter  100  ( FIG. 1 ), a VTL test is performed on at least one PDC cutter  100  ( FIG. 1 ) of a single cutter type and at a constant surface speed between the PDC cutter  100  ( FIG. 1 ) and the exposed portion  1222  of the target cylinder  1200 , thereby providing a determination of the impact resistance of that cutter  100  ( FIG. 1 ) at that impact frequency. Thus, the impact resistance for identical PDC cutter types, which have not been subjected to the VTL test, is estimated using the results of the VTL test performed on the similar cutter  100  ( FIG. 1 ). According to certain exemplary embodiments, the impact resistance of the cutter type is determined using at least one of the mean, median, and/or mode of the results of the VTL tests that are performed on different cutters  100  ( FIG. 1 ) of the same cutter type. 
     In yet other exemplary embodiments, similar VTL tests are performed as described immediately above, except that multiple VTL tests are performed op different cutters  100  ( FIG. 1 ) of the same cutter type while varying the impact frequency from one test to another. Alternatively, the impact frequency is varied within the test also depending upon the desired conditions to be simulated. The impact frequency is changed by increasing or decreasing the speed of at least one of the cutter  100  ( FIG. 1 ) and/or the target cylinder  1200 . Thus, one or more cutters  100  ( FIG. 1 ) of one cutter type undergoes a VTL test at one impact frequency, while one or more cutters  100  ( FIG. 1 ) of the same cutter type undergoes a VTL test at a different impact frequency. These VTL tests are performed on one or more cutters  100  ( FIG. 1 ) of the same cutter type at various different impact frequencies. Pursuant to these VTL tests performed on cutters of the same type at different impact frequencies, a relationship is established between the impact resistance and the impact frequency. For example, a line graph is plotted with one of the variables, such as the impact frequency, on the x-axis, and the other variable, such as the impact resistance, on the y-axis, where each cutter type forms its own line. The relationship that is established is considered to be a field representative impact resistance criteria. Hence, once the relationship is established and an impact frequency range is determined for the field application of interest, the appropriate cutter type is selected. 
     According to certain exemplary embodiments, the VTL tests, mentioned above and for forming the relationships, are performed with the relative orientation of the cutter face, which is a top surface of the cutting table  120  ( FIG. 1 ), with respect to the exposed portion  1222  of the target cylinder  1200  being varied through either or both of the backrake and/or siderake angles. Varying either or both of the backrake and/or siderake angles facilitate simulation of the impacts occurring in different modes, such as axial, lateral, and torsional modes. 
     Although each exemplary embodiment has been described in detail, it is to be construed that any features and modifications that are applicable to one embodiment are also applicable to the other embodiments. Furthermore, although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons of ordinary skill in the art upon reference to the description of the exemplary embodiments. It should be appreciated by those of ordinary skill in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or methods for carrying out the same purposes of the invention. It should also be realized by those of ordinary skill in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the scope of the invention.