Abstract:
Automated apparatus and method to determine physical properties of materials as they are moved relative to each other while in contact are disclosed. Physical properties between materials of interest (e.g., galling resistance, coefficient of friction, and wear rate) are derived under a variety of conditions including dry unlubricated condition, at ambient and at extreme high and low temperatures, lubricated, or when submerged.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority and benefit of U.S. provisional patent application 61/006,714 entitled “METALS GALLING TESTER” filed Jan. 29, 2008, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    Physical properties of materials (e.g., resistance to galling, coefficient of friction, and wear rate) as they are moved relative to each other while in contact are measured. 
         [0004]    2. Related Art 
         [0005]    Wear-resistant couples are used in literally thousands of applications in which the couples slide while in contact with each other. The vast majority of such wear-resistant couples are made from metals. However, some couples are made from ceramics or from mixtures that include some ceramics and other solid materials. 
         [0006]    In the process of designing mechanical equipment made from materials such as metals and ceramics, it is important to have knowledge of suitable pairs of materials or material coatings that must move in contact with each other at a high level of contact pressure so that undesirable events such as galling may be prevented. Galling of metals, also referred to as “cold welding”, is said to occur when one surface in contact adheres to the other surface with such strong adhesion that a part of one of the surfaces is torn away, and both surfaces become damaged. This phenomenon occurs at temperatures far below softening or melting point of metals, hence the term “cold welding”. 
         [0007]    Galling can occur between metal surfaces that are dry and unlubricated, or lubricated, or wetted by some fluid. Different pairs of metals moving in contact under a high level of stress have different resistance to galling, and the designer must select a metal pair that has a high enough degree of galling resistance, hereinafter referred to as “GR”, to prevent damage to surfaces of the coupling parts. 
         [0008]    A non-exhaustive list of areas in which knowledge of GR is important include:
       Sleeve-type bearings, where shafts rotate in supporting sleeves, sometimes with considerable forces pressing the parts together;   Internal parts for valves, where the parts are forced together by high pressure gas or steam or liquid that the valves are containing, as they slide against each other while the valves are operated; and   Material selection for nuts and bolts and machine screws, where there is sliding of contact surfaces of threads as the nuts, bolts, and/or screws are tightened, usually with high contact pressure.       
 
         [0012]    There are thousands of similar industrial applications where GR between metal pairs is important to know, to assure reliable product designs. Knowledge of GR for couples is important to enable sound design. 
         [0013]    It is also significant to have information on coefficient of friction, hereinafter referred to as “COF”, of couples, so that inherent resistance of the material pair to slide, one on the other, is known. This knowledge allows a design in which adequate force is supplied to produce sliding motion required in the equipment under design. The COF can be defined as the force required to produce sliding between two parts held together in contact, divided by the force that is holding them together. Less force is required to produce sliding when COF is low. Thus, in some instances, selection of metal couples should be considered for adequate GR, and also for lowest, or at least adequately low, COF. 
         [0014]    Considering the importance of having these types of knowledge, there is surprisingly limited information available in the technical literature on GR and COF between various load-bearing metal couples. This is true even for those that have been in common use for many years. In addition, new metal alloys, new galling resistant coatings, and coating methods are introduced every year. There is much information on their strength and hardness and bond strength. However, there is an almost complete lack of data on their GR or COF, when used in contact with themselves or in combination with large number of other alternatives. Examples include new metal carbide and metal nitride coatings that can be extremely useful in preventing wear and galling and in lowering friction between parts, but virtually no data is available for their threshold GR, i.e., the contact pressure at which galling commences for that particular couple, nor for their COF. There is also similar lack of information on wear rates, hereinafter referred to as “WR”, of couples. 
       SUMMARY 
       [0015]    The disclosed exemplary embodiments relate to method(s) and apparatus(es) for determining physical properties between materials of interest such as, e.g., GR, COF, and/or WR. 
         [0016]    To determine GR of two materials, the exemplary embodiments move samples of materials to be in contact with each other with a known amount of thrust force. Samples are rotated against each other while in forced contact and subsequently inspected to determine GR. 
         [0017]    In the exemplary embodiments, to determine COF, samples are moved to be in contact with each other with a known amount of thrust force. Then the torque required to rotate the materials is measured. The COF is calculated based on the applied thrust and torque. 
         [0018]    In the exemplary embodiments, to determine WR, lengths of the materials are measured. Then, similar to determining GR, samples are moved to be in contact with each other with a known amount of thrust force, and are rotated against each other while in forced contact. Afterwards, the lengths of samples are again measured, and WR is calculated based on length reductions. 
         [0019]    One exemplary embodiment of an apparatus arranged to determine physical properties between materials as they are moved relative to each other includes first and second members respectively arranged to secure first and second test samples and a controllable drive unit. Members can move with respect to one another so that the test samples come into contact with each other. 
         [0020]    In this embodiment, the controllable drive unit linearly drives at least one member toward the other with a controlled magnitude of thrust force and rotates at least one member with respect to the other with a controlled magnitude of torque while the test samples are in contact. The drive unit can be a single unit or can be implemented as a combination of controllable linear and rotational drive units. One or both thrust and torque magnitudes are adjustably controllable. 
         [0021]    In the exemplary embodiment, first member is hollow and extends along a longitudinal axis with second member coaxially received therewithin. Movement along and rotation about the axis is permitted. That is, second member is slidably and rotably received within first member with first and second test samples carried by these members at their distal ends coming into rotational sliding contact with controlled thrust and torque. 
         [0022]    The exemplary apparatus includes a drive shaft coupled to and axially aligned with second member and also coupled to both linear and rotational drive units. In this manner, thrust and torque from the drive units can be applied to second member and ultimately to second test sample. When both torque and thrust are applied to second member, first member can be fixed in relation to the drive units, for example, by fixedly attaching to a frame assembly. 
         [0023]    In an example aspect, both members secure samples in sample holders preferably located at respective distal end portions away from drive units. This conveniently allows distal end portions and carried samples to be projected into an environmental control chamber that does not contain the drive units. The chamber can be used to subject samples to extreme temperatures, high or low, or be used to immerse samples in liquids without subjecting the drive units to same extreme environments. 
         [0024]    To further protect drive units from extreme temperatures, thermal impediment can be located between first member and frame assembly. The thermal impediment can be hollow and axially aligned with a hollow part of the first member. 
         [0025]    The exemplary apparatus includes an attachment to allow an externally applied torque to rotate at least one member with respect to the other while test samples are in forced contact due to thrust applied by the linear drive unit. 
         [0026]    Preferably, test samples are cylinders with common dimensions on at least their contacting end surfaces. Also preferably, the cylindrical test samples include a recess formed at a center portion of contacting end surfaces. 
         [0027]    The exemplary apparatus provides for convenient testing of physical properties of materials of interest including metals and other wear-resistant solid material couples under a variety of conditions including dry unlubricated conditions, at ambient and at extreme high and low temperatures, lubricated, or submerged in liquids. Significantly, the exemplary apparatus provides these and other advantages in a self-contained, all inclusive bench-top equipment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The foregoing and other objects, features, and advantages of the invention will be more apparent from the following more particular description of exemplary embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout various views. 
           [0029]      FIG. 1  illustrate multiple views of typical test samples, and a tool for inserting and removing samples in and out of an apparatus; 
           [0030]      FIG. 2  illustrates a first exemplary embodiment of an apparatus arranged to determine physical properties between test samples; 
           [0031]      FIG. 3  illustrates a second exemplary embodiment of an apparatus arranged to determine physical properties between test samples; 
           [0032]      FIG. 4  illustrates a third exemplary embodiment of an apparatus arranged to determine physical properties between test samples in which test samples are subjected to extreme temperatures; 
           [0033]      FIG. 5  illustrates a fourth exemplary embodiment of an apparatus arranged to determine physical properties between test samples in which test samples are subjected to a liquid; 
           [0034]      FIG. 6  an exemplary embodiment of a control panel for use with the apparatus; and 
           [0035]      FIG. 7  illustrates an exemplary method to determine physical properties between test samples. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0036]    In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, and so on. However, it will be apparent that the technology described herein may be practiced in other embodiments that depart from these specific details. That is, those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the described technology. 
         [0037]    In some instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description with unnecessary detail. All statements herein reciting principles, aspects, embodiments and examples are intended to encompass both structural and functional equivalents. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
         [0038]    Due to the preponderance of metal couples, present discussion concentrates on metal couples. But it should be understood that the discussion also applies fully to non-metallic and partly metallic couples including ceramics, carbides, and so on. 
         [0039]    As noted, there is surprisingly very little data available in the technical literature on physical properties such as GR, COF, WR, etc. between various load-bearing couples, even for couples that have been in common use for many years. In addition, new materials such as metal alloys and ceramics for load-bearing applications are being continually introduced, and there is very little data for these as well. 
         [0040]    Because of the absence of information in technical literature, persons that have a need to know historically have had to do their own testing, or they have contracted with a testing laboratory. This has resulted in an immense amount of duplication of effort worldwide, because testers have unknowingly repeated hundreds of tests that others have done elsewhere. 
         [0041]    For GR, one of the reasons for there being such limited information worldwide is perhaps that there has been only one well known standard test procedure for GR, namely that published by The American Society For Testing Of Materials, also referred to as “ASTM”, and it has not been completely adequate or universally accepted. ASTM&#39;s longstanding basic testing method has been to force the end of a small diameter cylinder made from one material sample against a flat plate made from another material sample, typically in a press, and to rotate the cylinder through a single revolution. 
         [0042]    Recently, the ASTM procedure has been abandoned in favor of a new procedure due to a recognition that ASTM testing with a cylinder and plate can produce false and unreliable test results. When an end of a cylinder is pressed against a larger flat plate, there is an inherent stress concentration the around outer edge of the cylinder, making actual contact stress there considerably larger, by as much as 400% more, than is calculated by simply dividing applied force by area of the cylinder end. There are other shortcomings of the ASTM test procedure. These include one or more of the following:
       Previous data accumulated over decades of testing is now suspect—evidenced by the fact that supposedly identical tests have produced numerical GR results that vary by as much as 300%;   Not suitable for testing other than at ambient temperature—little data being available regarding high or low temperature effects on galling;   Not suitable for testing in the presence of liquids—little data being available regarding liquid effects;   Not suitable for testing with a large number of revolutions—little data being available regarding prolonged force application effects;   Requires a press or other large equipment to produce the contact force needed—test typically not conducted with equipment that is self-contained; and   Requires constant human effort and involvement—the test is expensive.       
 
         [0049]    These and other shortcomings have limited acceptability and use of the standard, and therefore the accumulation of data for GR has been hampered. The foregoing shortcomings have also hampered data accumulation for COF and WR of wear couples. 
         [0050]    In the new procedure, which has been embraced by ASTM, ends of two cylindrical samples of same diameter are pressed together. When two ends of same diameter are pressed together, force is applied evenly over surfaces of the cylinder ends. However, note that some of the shortcomings related to the ASTM procedure may also apply to the new procedure. 
         [0051]    These and other shortcomings of known test procedures are addressed by one or more exemplary embodiments described below. 
         [0052]      FIG. 1  provides multiple views of exemplary test samples  101 , which are also referred to as “coupons”. As seen, each test sample  101  is a cylinder with predetermined diameter (e.g. approximately 1.25″) and predetermined length (e.g. approximately 1.5″). For the remainder of this document, test samples are assumed to be cylindrically shaped unless specifically stated otherwise. Therefore, terms “sample”, “cylinder”, and “coupons” will be used interchangeably. Preferably, diameters of both cylinders  101  match. Each cylinder  101  includes a centrally located transverse through hole  102  with a predetermined diameter (e.g. approximately 0.50″). 
         [0053]    During testing, end surfaces  103  of cylinders  101  are engaged, i.e., are in contact with each other. Thus, for each cylinder  101 , one or both end surfaces  103  are prepared for testing. When both end surfaces  103  are prepared, cylinder  101  can accommodate two separate tests. In one aspect, preparation includes forming cylinders  101  themselves from materials of interest. Alternatively, end surfaces  103  of the samples  101  may be coated with materials of interest. 
         [0054]    Engaged end surface  103  of at least one cylinder  101 —preferably both—are formed to include a shallow recess  104  of a predetermined diameter (e.g. ½″) located in a center of the end surface  103 . The end surface center area experiences only limited relative movement (e.g., almost none at the center point) and that could compromise the validity of the test result if not removed. The diameter of the recess  104  is selected so that there is meaningful movement of all surface area in contact. 
         [0055]      FIG. 1  also illustrates an exemplary tool  106  that can be used to insert cylinders  101  into a test apparatus to determine physical properties. To facilitate installation and removal of cylinders  101  in and out of the apparatus, one or both ends of cylinder  101  include(s) a shallow central female threaded hole  105  of a predetermined diameter (e.g. ⅛″). Tool  106  includes a rod with a male thread  107  that matches the threaded hole  105 . The thread  107  can be screwed into the hole  105  so that cylinders  101  can be held while they are inserted into and removed from the test apparatus. 
         [0056]      FIG. 2  illustrates a first exemplary test apparatus arranged to determine physical properties—e.g., GR, COF, and/or WR—between test samples. The apparatus includes a first member  5   a  arranged to secure a first test sample N, a second member  8  arranged to secure a second test sample R, and a controllable drive unit arranged to apply controlled magnitudes of thrust and torque. The controllable drive unit may be implemented as a single unit or as a combination of drive units  24 ,  12  separately providing thrust and torque. Apparatus can include a vertical plate  25 , which is a part of a frame assembly  25 ,  26 ,  27  supporting the apparatus. For simplicity, reference  25  will also be used to reference the frame assembly. 
         [0057]    Unless specifically stated otherwise, it can be assumed that both samples N, R are cylindrical as illustrated in  FIG. 1  and prepared with materials of interest. Thus, they may also be referred to as cylinders N, R. Also unless specifically stated otherwise, it may be assumed that engaging end surfaces  6 ,  9  of cylinders N, R—i.e. end surfaces that in contact—are dimensionally the same. 
         [0058]    First and second members  5   a  and  8  are arranged so that they can move relative to each other, which allows engaging surfaces  6 ,  9  of cylinders N, R to contact each other. First member  5   a  can be hollow and extend along a longitudinal axis. Second member  8  can be coaxially received within first member  5   a  so that relative movement along and a rotation about the axis is permitted. 
         [0059]    Relative movements between members  5   a,    8  are provided by the controllable drive unit, which, in one variant, can be implemented as a combination of a controllable linear drive unit  24  and a controllable rotational drive unit  12 . Linear drive unit  24  is arranged to drive at least one member  5   a,    8  towards the other member  8 ,  5   a  with controlled magnitude of thrust. Rotational drive unit  12  is arranged to rotate at least one member  5   a,    8  with respect to the other member  8 ,  5   a  with controlled magnitude of torque. Member  5   a,    8  being driven by drive unit  24  can be the same as or different from member  5   a,    8  being driven by drive unit  12 . The drive units will be described in further detail below. 
         [0060]    As illustrated in  FIG. 2 , first member  5   a  can be implemented as an elongated outer pipe  5   a  with a flange  5   b  formed at a proximal end portion thereof—i.e., end portion of pipe  5   a  closer to frame assembly  25  and the drive units  12 ,  24 . Flange  5   b,  which can be integrally formed with pipe  5   a,  fixes pipe  5   a  to frame assembly  25 . An inner end surface  6  of cylinder N, as mounted, will have been prepared for GR, COF, and/or WR testing, and is formed of either a base material of interest, or is a coating of interest that is to be tested. 
         [0061]    Second member  8  can also be implemented as an elongated inner pipe  8  that is slidably and rotationally received within outer pipe  5   a.  As arranged, cylinder R secured to second member  8  can be moved to be in contact with cylinder N secured to first member  5   a.  Cylinder R is also prepared with a material of interest, which can be same or different from the material of interest of cylinder N. 
         [0062]    While  FIG. 2  shows that first member  5   a  is fixed to frame assembly  25 , this is not strictly necessary. It is only necessary that relative movement between members  5   a,    8  is allowed so that cylinders N, R can come into contact and be rotated while in contact. Thus, one or both members  5   a,    8  can be arranged to move relative to frame assembly  25 . 
         [0063]    Members  5   a,    8  respectively include first and second sample holders arranged to secure samples N, R so that they are fixed to their respectively associated members. First sample holder can be implemented as a combination of inner fixed pipe  2  and pin  3   a  as illustrated in  FIG. 2 . Sample N is mounted in pipe  2  by pin  3   a,  which can be formed from a strong metal, that is passed through a centrally located hole  4  (same as the transverse hole  102  in  FIG. 1 ) drilled through sample N and through matching holes in pipe  2 . Inner fixed pipe  2  is fixedly attached to outer fixed pipe  5   a,  for example, through welding. For simplicity, reference “ 3   a ” will be associated with first sample holder hereinafter unless specifically stated otherwise. 
         [0064]    Second sample holder can be implemented also as pin  3   b  arranged to mount second sample R to movable inner pipe  8  through matching holes in pipe  8 , which is in a similar manner to mounting sample N to outer pipe  5   a.    
         [0065]    As noted, samples N, R are preferred to be the same dimensionally, at least for engaging end surfaces  6 ,  9 . In  FIG. 2 , inner fixed pipe  2  is shaped similarly to inner movable pipe  8 , i.e., has the same diameter, and is also fitted within outer pipe  5   a.  This maximizes the chance that a matching contact will be established between engaging end surfaces  6 ,  9  of samples N, R. This is one of several ways to accomplish this purpose. 
         [0066]    Pins  3   a  (first sample holder) and  3   b  (second sample holder) can be slightly enlarged in center areas  10  thereof, e.g., by simple crowned machining. This allows samples N, R to rock slightly in position allowing their engaging end surfaces  6 ,  9  in contact to be positioned flatly against each other. 
         [0067]    Sample holders  3   a,    3   b  are both positioned at distal end portions of members  5   a,    8 , i.e., at end portions located away from frame assembly  25  and from drive units  12 ,  24  as illustrated in  FIG. 2 . While sample holders  3   a,    3   b  can be positioned anywhere along their respective members  5   a,    8 , distal end portions are preferred for reasons explained below. 
         [0068]    Physical properties information including GR, COF, and WR is important to have for couples operating at ambient temperatures. But in addition, it is also important to have information for products that operate at elevated temperatures, such as valves, or blowers, operating in contact with high temperature gases or steam or various molten materials. Similarly, there are equipments that must operate at very low temperatures, such as in equipment for the space program, and for equipment operating at cryogenic temperatures. 
         [0069]    It is known that properties such as GR, COF, and/or WR of materials may change at elevated or at very low temperatures. Thus numerical evaluation for these properties of materials only at room temperature may not be sufficient information for design in cases of elevated temperatures or at very low temperatures, where couples may be required to operate in critical applications. As an example, there is virtually no generally available data for the GR, COF, and/or WR of couples at very high or at very low temperatures. 
         [0070]    Similarly, there are occasions in which properties of materials operating in liquids is important such as for valves operating in contact with liquids in pipelines for example. Again, there is virtually no generally available data. 
         [0071]    As illustrated in  FIG. 4 , when sample holders are positioned at distal end portions of members  5   a,    8 , these end portions can be projected into an environmental control chamber  401  that does not contain the drive units  12 ,  24 . Samples N, R can be inserted into chamber  401  while avoiding subjecting the drive units  12 , 24  and other working parts of the apparatus to extreme environment within chamber  401 . Chamber  401  can be an oven or a cold-box to expose samples N, R to non-room temperature environment. In  FIG. 5 , distal end portions are projected into in a liquid environment contained within chamber  401  so that samples N, R are immersed in liquid. 
         [0072]    To further protect drive units  12 ,  24  from being subjected to thermal extremes, the exemplary apparatus includes a thermal impediment  30  adapted to impede thermal transfer between distal end portions of members  5   a,    8  and drive units  12 ,  24 . Thermal impediment  30  includes low thermal conducting first and second gaskets  31  installed at both distal and proximal end portions thereof. Thermal conductivities of gaskets  31  are lower than both first member  5   a  and frame assembly  25 . In so doing, effective thermal conductivity of impediment  30  is lower than first member  5   a  and frame assembly  25 . 
         [0073]    Thermal impediment  30  can be permanent. Preferably however, impediment  30  is detachably attached. In  FIG. 2 , proximal portion of first member  5   a,  without impediment  30 , is attached to frame assembly  25 . In  FIG. 4 , thermal impediment  30  is attached to frame assembly  25  and proximal portion of first member  5   a  attached to thermal impediment  30 . As seen, impediment  30  is hollow and axially aligned with a hollow part of first member  5   a  so that second member  8  remains slidably and rotationally received within first member  5   a.  A longer shaft  11  (described in further detail below) is used (compare  FIGS. 2 and 4 ) to accommodate added length due to impediment  30 . In another variant, longer second member  8  (not shown) can be used so that shaft  11  need not be exchanged to accommodate added length when thermal impediment  30  is attached. Longer second member  8  would also be slidably and rotationally received within thermal impediment  30 . 
         [0074]    It is noted above that relative movements between members  5   a,    8  are provided by the controllable drive unit, which can be implemented as a combination of linear drive unit  24  and rotational drive unit  12 . In one variant, linear drive unit  24  is implemented as a diaphragm actuator  24  as illustrated in  FIG. 2 . To power actuator  24 , compressed air is applied through a connection  40  of actuator  24 . This causes inner pipe  8  (second member) to move longitudinally towards distal end portion of relatively fixed outer pipe  5   a  (first member). Magnitude of thrust is adjusted by adjusting the applied air pressure. 
         [0075]    In detail, inner pipe  8  is attached to shaft  11 , which passes slidably through a rotary actuator  12  (rotational drive unit). Shaft  11  has a keyway slot  13   a  and a square key  14  that engages in a matching keyway slot  13   b  in a bore of the rotary actuator  12 . Shaft  11  enters a cylindrical bearing assembly  15  at an opening  16  in an end cap  17  of the bearing assembly  15 , and then into a flanged tee-head  18  that is inside bearing assembly  15 , and is bolted to tee-head  18  by a bolt  19  into an end of shaft  11 . Tee-head  18  touches a ball-type thrust bearing  20   a  which in turn rests against an internal flat surface  21  in bearing assembly  15 . The bearing assembly  15  is attached by a coupling  22  to a stem  23  of diaphragm actuator  24 . 
         [0076]    Applying compressed air through connection  40  causes a stem  23  to extend out of actuator  24  with an adjustable force, depending on the air pressure applied. This force is transmitted through coupling  22  to bearing assembly  15 , which in turn transmits force through internal surface  21  to thrust bearing  20   a,  tee-head  18 , and to an end of shaft  11 . That force is transmitted along shaft  11 , to inner pipe  8 , then to sample R secured to inner pipe  8  towards sample N secured to outer pipe  5   a.  In the end, the thrust applied from drive unit  24  is applied to second member  8  (and thus, applied to sample R) through shaft  11 . In the embodiment of  FIG. 2 , shaft  11  is axially aligned to and coupled to the proximal end portion of second member  8  and is also coupled to linear drive unit  24 . 
         [0077]    While drive unit  24  is shown to be a pneumatic device in  FIG. 2 , drive unit  24  can also be powered by a variety of sources including electric, hydraulic, mechanical, and so on in which the applied power can be adjustably controlled. Also, drive unit  24  can be powered by a combination of power sources. 
         [0078]    Rotational drive unit  12  can be implemented as a pneumatic actuator  12  as illustrated in  FIG. 2  or an electric actuator  12  as illustrated in FIG.  3 . When power is applied to rotate the rotary actuator  12 , one or both members  5   a,    8  rotate with respect to each other. Rotation can be applied when samples N, R are in forced contact by thrust from linear drive unit  24 . 
         [0079]    Shaft  11  is also coupled to drive unit  12 . Thus, torque applied by drive unit  12  is applied to second member  8  (and thus, also to sample R) through shaft  11 . In detail, inner pipe  8  can be attached to shaft  11 , which passes slidably through rotary actuator  12 . Keyway slot  13   a  and square key  14  of shaft  11  that engages matching keyway slot  13   b  in a bore of rotary actuator  12  allows shaft  11  to be rotated by actuator  12 . 
         [0080]    Pneumatic actuator  12  in  FIG. 2  is an example of a reciprocating actuator that rotates one of the members  5   a,    8  back and forth over an arc typically of less than 360°. As illustrated, compressed air can be applied alternately to ends of the cylinder of pneumatic actuator  12 , so that it reciprocally rotates one member back and forth through an arc of 90° for example. This is useful for testing with reciprocal rotation. For testing with continuous rotation, i.e. over many revolutions, electric actuator  12  illustrated in  FIG. 3  may be used. Applying power to electric actuator  12  turns one of samples N, R continuously against the other. 
         [0081]    While electric and pneumatic devices are shown, rotational drive unit  12  may be powered through other sources including hydraulic, mechanical, and so on in which the applied power can be adjustably controlled. A device with a combination of power sources is also contemplated. Regardless of the power source, drive unit  12  may be capable of supplying reciprocal or continuous rotation, or both as the need arises. 
         [0082]    In a further detail of  FIG. 2 , to assure rolling rather than sliding rotary motion that could create fine metal particles inside bearing housing  15 , a second thrust bearing  20   b  is located in bearing housing  15 , disposed between tee head  18 , which rotates, and a Belleville washer  29 , which remains stationary. Belleville washer  29  is disposed between second bearing  20   b  and bearing housing cap  17 . Strength of the Belleville washer  29  is selected so that two bearings  20   a  and  20   b  and tee head  18  are always held in gentle compressive contact between inner bearing housing surface  21  and bearing housing end cap  17 . It is sufficient that the strength of Belleville washer  29  be slightly greater than force needed to retract shaft  11  slidably through rotary actuator  12 . 
         [0083]    Moreover, outer fixed pipe  5   a  can be mounted by flange  5   b  to vertical plate  25  of the whole frame assembly, which also includes another vertical plate  26 , a base plate  27 , and front and rear rectangular tie bars  28   a  and  28   b  that hold vertical plates  25  and  26  in place. Rotary actuator  12  can be mounted to the opposite side of vertical plate  25  and in alignment with flange  5   b.  Actuator  24  can be suitably mounted to vertical plate  26 . 
         [0084]    As noted, exemplary embodiments of the apparatus described thus far can be used to determine physical properties including GR, COF, and/or WR of materials. When determining GR, linear drive unit  24  drives members  5   a,    8  toward each other to cause test samples N, R to be in contact with a controlled amount of force. Then rotational drive unit  12  rotates one of samples N, R with respect to the other while samples are in forced contact. Rotational drive unit  12  is adapted to (a) continuously rotate at least one member  5   a,    8  with respect to the other over 360° and (b) reciprocally rotate, i.e., rotate back and forth, at least one member with respect to the other over an arc of less than 360°. 
         [0085]    When determining COF of materials, linear drive unit  24  drives members  5   a,    8  toward each other so that test samples N, R are in contact with a known amount of force. Then rotational drive unit  12  applies torque to rotate one of samples N, R with respect to the other while samples are in forced contact. Torque required to rotate the samples is measured or otherwise determined. As an example, torque can be determined by determining minimum power (pneumatic, electric, hydraulic, and so on) applied to rotational drive unit  12  required to barely turn sample R against sample N. Between torque and thrust, COF can be easily calculated. 
         [0086]    Alternatively to determine COF, torque can be provided externally. In  FIG. 2 , apparatus optionally includes an attachment  41  that allows torque to be applied from an external source. Externally applied torque can rotate at least one member  5   a,    8  with respect to the other  8 ,  5   a  while samples N, R and are in forced contact with each other due to thrust applied by linear drive unit  24 . This may be useful in situations where externally applied torque can be more precisely measured relative to torque from rotational drive unit  12 . 
         [0087]    Apparatus can also be used to determine WR of materials. To test WR, lengths of samples N, R are measured before and after subjecting them to torque while in forced contact. After initial length measurement, linear drive unit  24  drives members  5   a,    8  toward each other to cause test samples N, R to be in contact with a controlled amount of force. Then rotational drive unit  12  rotates one of samples N, R with respect to the other while samples are in forced contact. Rotational drive unit  12  is adapted to (a) continuously rotate at least one member  5   a,    8  with respect to the other over more than 360° and (b) reciprocally rotate at least one member with respect to the other through a predetermined arc. Afterwards, length reduction is measured and WR is calculated. 
         [0088]      FIG. 7  illustrates an exemplary test method M 700  for determining physical properties of sample materials. Here samples N, R are prepared in step S 710 . For example, a recess can be formed in center of an engaging end surface of one or both test samples N, R. Also, if samples themselves are not the materials of interest, then materials of interest can be coated to one or both engaging end surfaces of samples. In step S 720 , prepared samples N, R are secured respectively to members  5   a,    8 . Preferably, samples N, R are secured to distal end portions of members  5   a,    8 . 
         [0089]    After securing samples to members, using linear drive unit  24 , at least one member  5   a,    8  is longitudinally moved toward the other member  8 ,  5   a  so that the engaging surfaces of samples N, R are in contact with each other with a controlled magnitude of linear thrust in step S 730 . In one aspect, proximal end portion of one or both members are moved. 
         [0090]    In step S 740 , at least one member  5   a,    8  is rotated with respect to the other member  8 ,  5   a  using rotational drive unit  12  to effect sliding rotational motion between test samples with a controlled magnitude of rotational torque. 
         [0091]    For testing with reciprocal rotations, drive unit  12  can apply many cycles back and forth movements through an arc of less than 360°, e.g., 90°. For testing with continuous rotation, drive unit  12  can rotate samples through many revolutions. As will be appreciated, rotational drive unit  12  also might be started before or concurrently with initiation of thrust force. 
         [0092]    After many rotations or cycles, samples N, R can be evaluated for GR in step S 770 , e.g., by inspection of test surfaces  6  and  9 . To inspect the surfaces when the apparatus illustrated in  FIG. 2  is used, air pressure is vented from diaphragm actuator  24  at air connection  40 , and internal springs (not shown) in actuator  24  cause stem  23  to retract back into actuator  24 . The retraction is transmitted through coupling  22  to bearing assembly  15 , which causes screw  19  to pull on shaft  1   1 , causing it to retract, causing sample R to be retracted. Samples N and R become loose on pins  3   a  and  3   b,  so that they can be removed, for inspection of tested surfaces  6  and  9 . 
         [0093]    Samples N, R can be evaluated for COF in step S 780 . For COF determination, magnitudes of both the linear thrust and rotational torque required to rotate at least one test sample while subjected to linear thrust are measured. In a simple case, magnitude of thrust is controlled, and therefore, is already known and it is thus only required to measure torque, which can be applied by either rotational drive unit  12  or from an external source through attachment  41 . 
         [0094]    In step S 790 , samples N, R can be evaluated for WR. To test WR of the materials being tested, lengths of the material samples are first measured precisely, before being secured to the test apparatus. For example, this can be a part of step S 710  of preparing samples N, R. Samples are then secured in the test apparatus, an appropriate thrust magnitude is exerted and one sample is rotated against the other a large number of counted times in steps S 730  and S 740 . Then in step S 790 , sample lengths are re-measured precisely. WR can be calculated based on length reduction of samples. 
         [0095]    If samples are to be subjected to a controlled environment such high or low temperatures or a liquid, then prior to performing steps S 730  and S 740 , end portions of members  5   a,   8  which hold samples N, R are projected into an environmentally controlled unit in step S 750 . Additionally, a thermal transfer can be impeded between distal and proximal end portions of members  5   a,    8  in step S 760  so as to protect drive units  12 ,  24  from being subjected to extreme temperatures. 
         [0096]    When it is desired to test GR or WR of samples over many rotations or cycles, apparatus may be connected to an automatic control panel as illustrated in  FIG. 6 . Alternatively, control panel may be included as a part of the test apparatus. 
         [0097]    Rotational drive unit can be equipped with position switches, for example, one at each end of the stroke for a reciprocating type unit, or one at the 0° start position for a continuous rotation type unit. Number of rotations or cycles desired for test is set on a presettable counter, and appropriate power level, e.g., air pressure level, and connected to linear drive unit  24  at connection  40 . A switch in control panel is turned to “RUN” position. A control circuit then applies power to rotational drive unit  12 , and apparatus rotates or cycles back and forth until preset number of rotations or cycles have completed and counter has counted down to zero. Power is then removed from rotational drive unit  12  automatically by control circuit, and apparatus stops operating. Inspection of test surfaces  6  and  9  is then conducted as described above. 
         [0098]    For convenience, control panel may also contain a power regulator for linear drive unit  24 , and also a regulator for rotational drive unit  12 , if such is used. Control panel may also contain lights and switches required for safe operation. 
         [0099]    The disclosed exemplary apparatus and method provides for convenient, fast, reliable determination of physical properties (GR, COF, WR, etc.) of materials overcoming at least same shortcomings of past procedures and equipment. Advantages may include:
       Apparatus can be a self-contained automatic bench-top testing machine;   Apparatus is simple and easy to use;   Apparatus can be automatic, when operated in conjunction with a presettable counter that can be preset for a large number of rotations or reciprocating cycles, allowing unattended operation with automatic shutoff after the preset rotations or cycles have been completed;   Apparatus uses inexpensive cylindrical test sample coupons, placed end to end;   Apparatus allows determining physical properties at elevated temperatures, up to 180° F. or higher, and down to cryogenic temperatures, defined as below −150° F., testing that has heretofore been generally unavailable at such extremes;   Apparatus allows determining physical properties of samples submerged in liquids, which also has heretofore been generally unavailable;   Apparatus provides valuable additional information on physical properties of useful pairs of materials of interest, at room temperature and also at temperature extremes, such information presently being generally unavailable in current literature; and   Apparatus allows determining physical properties of samples with continuous rotation in one direction, or with reciprocating action of the sample materials, for one or many cycles, as they are pressed together.       
 
         [0108]    Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the exemplary embodiments. Therefore, it will be appreciated that the scope of protection afforded by the claims fully encompasses other embodiments, and accordingly not to be unduly limited. All structural, and functional equivalents to the elements of the above-described embodiment that are known to those of ordinary skill in the art are intended to be encompassed. Moreover, it is not necessary for a device or method to address each and every problem described herein or sought to be solved by the present technology.