Abstract:
A method and system for increasing a railcar transportation axle&#39;s resistance to failure comprising treating at least one area of the axle to create a compressive surface layer on the component in order to reduce the occurrences of stress related surface defects.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to provisional application 61/990,288 filed on May 8, 2014 and is incorporated by reference in its entirety as if fully recited herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention is directed to systems and processes for manufacturing transportation system components such as, but not limited to, railcar and light rail axles. 
       BACKGROUND 
       [0003]    One of skill in the art would understand that railcar axles are critical components from the standpoint of both functionality and safety. Axles support the weight of the railcar and its cargo as well as form part of the interface with the railway with its corresponding imperfections. Because of the heavy and sometimes hazardous payload or in the case of passenger trains, human lives, functionality and safety require that axles are designed to avoid unexpected failure. Stresses experienced by railcar axles may be mechanical in nature, such as impact, tension or shearing forces, or such stresses may be vibratory in nature, such as may occur during the rolling movement of a railcar. 
         [0004]    As should be obvious, the failure of railcar axles such as those described herein, particularly while a train of railcars is in motion, could be catastrophic. Therefore, from the standpoint of safety, railcar axles must be designed and manufactured so as to prevent such stresses from causing component damage or failure. Such designs generally entail adding additional material to the axle to improve its strength and durability. The addition of material adds additional weight which may reduce the efficiency of rail transportation. 
         [0005]    Nonetheless, improvements to the manufacturing process may provide greater resistance to stress related failure, improving safety and reducing cost as the result of lengthening component life and reduction in the amount of material used to achieve the necessary strength and resistance to fatigue. It would, therefore, be desirable to implement such improvements so as to increase railcar axle strength and durability and mitigate such stress failures without requiring the addition of material and corresponding weight to an axle. The invention is so directed. 
       SUMMARY 
       [0006]    A first aspect of the invention is directed to an improvement in a mass transit and railcar axle manufacturing processes resulting from shot-peening. Particularly, it has been discovered that shot-peening certain areas of railcar axles may improve the fatigue life of those axles. As used herein such areas may be areas of high stress, particularly those areas of railcar axles subject to forces resulting in tension being applied to the axle. 
         [0007]    This improvement is understood to occur by way of increasing the residual compressive surface stresses of the axle material through the plastic deformation thereof. The shot-peening media used in embodiments of the invention may vary. For example, metallic, ceramic, or glass media may be used as long as it can produce an acceptable amount of plastic deformation of the axle surface being peened. 
         [0008]    Surface finish in the highly stressed areas of mass transit and railcar axles may also be a factor in fatigue life. Particularly, a better surface finish increases fatigue life. Consequently, consideration should also be given to the resulting surface finish in order to reduce irregularities in the finish when shot-peening highly stressed areas of railcar axles. To this end, the size of the shot-peening media and the intensity at which it is applied may be controlled in a manner intended to produce a more ideal surface finish. For example, it would be understood that larger media would likely produce an increased level of residual compressive surface stress, but might also produce an unacceptable surface finish. 
         [0009]    In light of the foregoing concerns, certain embodiments of the invention may also employ a multi-step, sequential shot-peening process. For example, shot-peening with media of one type and/or size may be followed by shot-peening with media of another type and/or size. 
         [0010]    In addition to surface finish quality as described above, shot peening media may achieve greater improvements in fatigue resistance if the media is applied so as to strike the surface at about a 90 degree angle to the plane of such surface. 
         [0011]    A second aspect of the invention is directed to an improvement in a mass transit and railcar manufacturing process resulting from roller burnishing. As was described earlier herein, increasing the residual compressive surface stresses of an axle through the plastic deformation of the surface layer of an axle may increase the axle&#39;s fatigue life. Roller burnishing is a process in which a burnishing head is applied to the surface to be treated and caused to move along the surface resulting in a deformation of the surface layer. An axle shape may be particularly suitable to roller burnishing as, by its nature, it may be rotated while a burnishing head is applied to the axle surface. Roller burnishing may also be used to improve the surface finish of a railcar axle and may be used alone or in conjunction with a milling operation to remove surface imperfections that may result from the manufacturing process. 
         [0012]    Application of at least one of the shot-peening or roller burnishing methods as described herein may increase the strength and durability of existing axle designs or allow axles to be fabricated using less metal material while retaining the strength and resistance to fatigue required in railcar and mass transit applications. The resulting axles may be lighter; resulting in improvements to the cargo capacity of the railcar situated atop these axles and reduced fuel costs. In addition, application of at least one of a shot-peening or roller burnishing method as described herein may also permit the elimination of the process of skim cutting frequently performed to improve axle surface quality. 
         [0013]    It is a common practice to repurpose axles nearing the end of their service life by subjecting the axle to a machining process that reduces the radial dimension of an axle to that of an axle designed for applications requiring less load bearing capacity. For example, an axle originally designed for a 125 ton application may be machined to a size suitable for a 100 ton application. Generally such a machining process removes material that may have developed stress related imperfections; however, the machining applied may result in circumferential striation imperfections. Such imperfections may allow the formation of stress cracks, reducing the durability of the resulting axle. The application of at least one of shot-peening or roller burnishing, if applied as part of, or after the machining process may remove or greatly reduce any imperfections resulting from the removal of material from the axle. 
         [0014]    Mass transit and railcar axles may be formed from various metal formulations. The described design and manufacturing process improvements are independent of metal formulation and therefore may equally be applied to various metal formulations used to manufacture railcar axles. 
         [0015]    The invention is also directed to automated or semi-automated systems and methods of treating, as described herein, of railcar axles in the desired areas. Embodiments of such systems and methods may employ a conveying system(s) or other automated means for transporting such axles along a processing path. As a mass transit or railcar axle travels along the processing path, the areas of interest on the axle are treated by at least one of roller burnishing or shot-peening devices. Shot-peening may be performed by mechanisms such as centrifugal blast wheels and air blast devices. For example, one or a plurality of multi-axis robots may be located along the travel path and equipped with shot-emitting mechanisms for this purpose. In another embodiment, a number of stationary shot-emitting devices may be employed instead of or in conjunction with shot-peening robots. Alternatively, an operator may manually operate a shot-peening mechanism to effect shot-peening of the desired axle areas. 
         [0016]    Conveying systems for use in a treatment operation according to the invention may take several forms. For example, a conveying system useable in the invention may comprise a conveyor belt of some type that transports an axle to be processed to a shot-peening area where it is picked up by a robot and presented to one or more treatment mechanisms such that the axle areas of interest are treated. 
         [0017]    In another conveying system embodiment, axles may be placed on a specialized conveyor that includes individual axle supporting carriers. These carriers may be designed to accommodate a particular axle design. The carriers may include axle retaining elements that are designed to rotate or tilt, such as by motor power or by contact with trip dogs, such that various areas of interest on a axle are presented to one or more treatment mechanisms for treatment as the axle travels along the processing path. 
         [0018]    In still another embodiment, axles may be placed on a specialized conveyor that may include axle specific supporting jigs or similar support elements that are designed to support and retain an axle through only limited points of contact, thereby leaving the areas of interest on the axle exposed for treatment and eliminating the need for rotation or tilting of the axle. In such an embodiment, the conveyor may also be specially designed to permit access to various axle surfaces by treatment devices. For example, the conveyor may be two parallel but spaced apart belts such that one or more shot-peening devices may be positioned along the conveyor path and in the space between the belts for shot-peening one or more axle surfaces from below. In such embodiments, the areas of interest on the axle may be shot-peened by stationary shot-emitting mechanisms, and/or by one or more robots equipped with shot-emitting mechanisms, as the axle travels along the processing path. 
         [0019]    In systems of the invention, treatment may occur while an axle is in motion—either rotationally or during travel along the processing path on an associated conveying device. Alternatively, treatment may occur while the motion of an axle is temporarily halted, such as at one or more predetermined treatment stations. 
         [0020]    The invention is also directed to automated or semi-automated systems and methods of roller burnishing of railcar axles. Such systems and methods may comprise conveyor devices that allow the axles to be affixed to carriers which position the axles for treatment. Further, such carriers may allow the axles to be rotated as the roller burnishing devices is applied to the axle. In a typical application, wheels may be applied near the ends of axles. Either shot-peening or roller burnishing systems and methods may be applied to axles alone or axles to which wheels have been applied. As a result, the disclosed systems and methods may be applied to newly manufactured axles or those axles that have been in service and to which wheels have been affixed. 
         [0021]    In certain embodiments, a paint or other coating may be applied to the treated surfaces of axles. Such a coating may serve the dual purpose of protecting the treated surface from environmental degradation and also provide an indication that an axle may have been subject to damage that may result in a reduction of the effectiveness of the surface treatments disclosed herein. 
         [0022]    In addition to the novel features and advantages mentioned above, other benefits will be readily apparent from the following descriptions of the drawings and exemplary embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    In addition to the features mentioned above, other aspects of the present invention will be readily apparent from the following descriptions of the drawings and exemplary embodiments, wherein like reference numerals across the several views refer to identical or equivalent features, and wherein: 
           [0024]      FIG. 1  is a view of an exemplary railcar axle upon which wheels and bearings have been installed; 
           [0025]      FIG. 2  is a top view of an exemplary railcar axle illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0026]      FIG. 3  is a diagram of an exemplary roller burnisher in contact with a surface to be treated; 
           [0027]      FIG. 4  schematically represents an exemplary embodiment of a railcar axle treatment system and process whereby a conveyor transports axles to a treatment area where each axle is picked up by a multi-axis robot and presented to another multi-axis robot that is equipped with a treatment mechanism; 
           [0028]      FIG. 5  schematically represents an exemplary embodiment of a railcar axle treatment system and process whereby a conveyor belt transports an axle to a treatment area where it is picked up by a multi-axis robot and presented to fixed position treatment mechanism; 
           [0029]      FIG. 6  schematically represents another exemplary embodiment of a railcar axle treatment system and process wherein axles are placed on a specialized conveyor that includes individual conveyor carriers that are designed to rotate the axle via a powered actuator such that the areas of interest on the axle are presented to one or more multi-axis robotic treatment mechanisms; 
           [0030]      FIG. 7  schematically represents another exemplary embodiment of a railcar axle treatment system and process wherein axles are placed on a specialized conveyor that includes individual conveyor carriers that are designed to rotate the axle via a powered actuator such that the areas of interest on the axle are presented to one or more fixed position treatment mechanisms; 
           [0031]      FIG. 8  schematically represents an alternative embodiment of the railcar axle treatment systems and processes of  FIGS. 4-5 , in which the respective multi-axis robot and fixed position treatment device thereof have been replaced with a human operator; 
           [0032]      FIG. 9  schematically represents an alternative embodiment of the railcar axle treatment systems and process of  FIG. 6  in which the multi-axis robot shot-emitting devices thereof have been replaced with one or more human operators; 
           [0033]      FIG. 10  schematically represent an alternative embodiment of the railcar axle surface treatment systems and process of  FIG. 7  in which the fixed position treatment devices thereof have been replaced with one or more human operators; and 
           [0034]      FIG. 11  schematically represents another alternative embodiment of a railcar axle treatment system and process whereby axles are transported through a treatment area on a specialized conveyor that leaves exposed the areas on the axle that are to be treated. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0035]    One of ordinary skill in the art will understand that the stresses encountered in railcar applications are often greater than other applications due to the high weight levels often encountered when transporting freight using railcars. Increasingly railcars are being used to transport materials such as oil and compressed natural gas. Such substances are highly flammable and pose significant hazards in the event of component failure. However, other transit applications may be equally demanding, particularly when passenger safety becomes an issue as may be the case in mass-transit applications. One ordinarily skilled in the art will understand that the process improvements disclosed herein are equally applicable to the numerous and well known applications for railcar axles, including, but not limited to, freight transportation and commuter transportation. In addition, those ordinarily skilled in the art will realize that various metal formulations are used in the fabrication of railcar axles and understand that the treatment system and processes described herein may be equally applicable to each such formulation after any adjustments for the characteristics of the different metal formulations. 
         [0036]    Railcar axles may be produced using a forging process. Such a process may introduce surface irregularities; examples may include cracks, scratches, and bumps that result in higher stress levels in the area of the irregularity when the axle is in use. Such areas of higher stress may lead to decreased axle fatigue life. The treatment methods described herein may also be used to reduce or eliminate the decrease in axle life as the result of defects. It will be understood that the treatment methods and systems described herein may be equally applicable to methods of manufacturing axles that differ from those described above. 
         [0037]    Referring to  FIG. 1 , axles  100  used in railcar applications are typically supported by bearings  102  located at the ends of the axle. Inward of each bearing  102  is a wheel mounting surface  104  to which a wheel  106  is affixed by being pressed onto the axle, subject to a cryogenic process, or both. Referring to  FIG. 2  which illustrates an axle without wheels or bearings attached, inward of each wheel mounting surface  106  may be a transition  108  from the wheel mounting surface to a section of reduced diameter  110  that may taper towards the center point of the axle  100 . As will be noted, there are several transition areas in a typical axle as illustrated. These transition areas may be subject to surface imperfections as the result of the axle manufacturing process. 
         [0038]    Due to the forces applied during travel along sections of railroad track, forces may cause axles to deflect slightly. As illustrated in  FIG. 1 , forces applied to wheels represented by  150  and bearing surfaces  152  may result in the deflection of an axle in the direction shown by the arrow  154 . The deflection illustrated in  FIG. 1  is greatly exaggerated for sake of clarity of explanation. When an axle and wheel assembly is at rest, a compressive force may result along the area indicated by  156  and a corresponding tension may be applied along the area indicated by  158 . As a result of the rolling motion of the wheel and axle assembly, the areas of compressive force  156  and tension  158  move around the axle corresponding to the position of the axle relative to the forces applied by the railcar and the rails. Over the normal service life of an axle and wheel assembly, a given area of a railcar axle may see a compressive force change to a tension and back to a compressive force many thousands of times (cycles). As the axle experiences tension, small imperfections may develop in the surface of the axle. When viewed microscopically, these imperfections may resemble small cracks or tears. As an axle experiences cycles of compression and tension during use, these cracks or tears may increase in size and depth and result in a catastrophic failure of an axle if allowed to persist over time. As described herein, methods may be employed to form a compressive layer on the surface of an axle. The layer may serve to prevent the surface of a treated axle from entering a state of tension during the compression-tension cycle experienced by the axle during use. The formation of surface cracks or tears may be reduced by preventing the axle surface layer from entering a state of tension or reducing the amount of that tension. As a result, formation of a compressive surface layer may prolong the service life of an axle. Alternatively, with the formation of the described compressive layer, an axle with a smaller cross sectional area, and as a result, a lower weight, may be substituted for a larger and heavier, non-treated axle with no loss in service life. 
       Roller Burnishing 
       [0039]    Roller burnishing is a method imparting a compressive surface layer on the burnished surface. As illustrated in  FIG. 3 , roller burnishing may be performed using a burnishing device  302  that is applied to a surface to be burnished  304 . The device may comprise a hardened contact point  306 , that is applied to the surface to be burnished  304 . A force  305  sufficient to form the desired compressive layer  308  may be applied to burnishing device and the device may be caused to move along the surface. The contact point  306  may vary in shape depending upon the treated surface contour. For example, a relatively flat surface may be treated using a cylindrical shape whereas a shape with one or more curved components may be treated more effectively using a spherical shape. In instances where the surface to be treated may have embedded imperfections, a milling operation may be performed prior to the burnishing operation to remove such imperfections. 
       Shot-Peening 
       [0040]    A shot-peening process may increase the residual compressive surface stresses of axle material through a process of plastic deformation. Testing and failure analysis has shown residual compressive surface stress may improve the durability of railcar axles in areas that are subject to high levels of tensioning force. Additionally, surface quality after a shot-peening process may be an additional factor in the durability of a treated axle. Referring to  FIG. 2 , in an embodiment of the invention, a shot-peening process may be applied to areas of high stress in a railcar axle  100 . Examples of such areas are illustrated at  108  and  110 . In order to produce a higher quality surface area, the shot-peening media used in the invention may be varied in size and intensity of application and may comprise metallic, ceramic, or glass media. The effects of such variables are dependent upon the axle material and shot applicators and as a result, a shot-peening process should be carefully controlled with regard to the shot applied and the rate of application in order to produce a uniform surface texture. A multi-step shot-peening system that may be employed to produce such a uniform surface is described herein. 
       Treatment Systems 
       [0041]    Referring again to  FIG. 2 , the areas  108  adjacent to the wheel mounting surface  106  may also be areas of high stress. As illustrated at  108 , areas adjacent to wheel mounting surfaces  106  may be prone to striation defects. Using the systems and methods described herein, these striations may be reduced or eliminated to improve the surface quality of the axel and thus improve resistance to fatigue related failures. Because axle designs and materials may vary slightly by manufacturer, high stress areas may vary from one design to another. Areas of high stress may be determined based on failure history of a particular axel design or through the use of finite element analysis (FEA). Those skilled in the art will realize that such failure data, FEA analysis, and reference materials such as the AAR Manual of Standards and Recommended Practices may be used to identify areas that may benefit from the shot-peening method described herein. 
         [0042]    Several exampled embodiments of axle treatment systems will now be described. Each embodiment will be illustrated with references to a treatment area and may describe one or more treatment robots. As discussed earlier herein, treatment processes which take place in the treatment area or using treatment robots may comprise shot-peening, roller burnishing, or combinations of both. 
         [0043]    One exemplary embodiment of a railcar axle treating system  800  and process is schematically represented in  FIG. 4 . In this exemplary embodiment, a conveyor  802  transports axle  100  to a treatment area  806  where each axle is picked up by a part handling robot  808  and is presented to another robot  810  that is equipped with a treatment mechanism  812 . Both the part-handling robot  808  and treatment robot  810  may be multi-axis robots for maximized process flexibility. 
         [0044]    In this particular example, the conveyor  802  is represented as a belt conveyor. It should be understood, however, that other types of conveyors may also be employed such as, without limitation, chain conveyors, roller conveyors, and conveyors which make use of individual carriers that travel in or along tracks or guides. 
         [0045]    In the exemplary system  800  of  FIG. 4 , the part-handling robot  808  is shown to be equipped with an end effector  814  that is adapted for grasping and removing an axle  100  from the conveyor  802 , and for releasably retaining the axle in multiple orientations during presentation thereof to the treatment robot  810 . In addition, the end effector may be configured to allow the axle to rotate to expose additional axle surface areas. End effectors for part handling are well known in the art and, therefore, are not described in detail herein. 
         [0046]    In embodiments utilizing shot-peening in the axle treatment process, a shot-emitting mechanism  812  of the treatment robot  810  may be of various designs. For example, the shot-emitting mechanism  812  may be an air blast system where the shot media is introduced into an air stream and ejected from a nozzle against an object to be peened. Alternatively, shot media may be introduced to a spinning centrifugal blast wheel that rotates at high speed to sling the shot media against an object to be peened. Shot-emitting mechanisms of the invention are not limited to air blast or centrifugal blast wheels, however. Rather, any shot-peening device now known or developed in the future may be used in the present invention provided it is capable of producing an acceptable level of plastic deformation on the peened railcar axle surface. 
         [0047]      FIG. 5  schematically represents another exemplary embodiment of a railcar axle treatment system  900  and process, which is very similar to the system  800  and process represented in  FIG. 4 . Particularly, this exemplary system  900  again includes the conveyor  802  and part-handling robot  808  of the system  800  of  FIG. 4 . As illustrated in the figure, the embodiment is shown transporting axles  100  to a treatment area  806  where each axle is picked up by the part-handling robot  808 . In this system  900 , however, the part-handling robot  808  presents axles  100  to be treated to a fixed-position treatment device  910  rather than to a robot equipped with a treatment mechanism. 
         [0048]    In the system  900  of  FIG. 5 , the conveyor  802  and part-handling robot  808  may respectively be of any design/type/construction discussed above with respect to the system of  FIG. 4 . Similarly, although the system of  FIG. 5  employs a fixed-position treatment device  910 , in embodiments where the treatment mechanism includes a shot-peening device, any of the various types of shot-emitting mechanisms described above with respect to the system  800  of  FIG. 4  may be used in the system  900  of  FIG. 5 . 
         [0049]      FIG. 6  schematically represents another exemplary embodiment of a railcar axle treatment system  1000  and process. In this treatment system  1000 , a conveyor  1002  having a plurality of individual carriers  1004  transports axles  100  to a treatment area  1008 . Each axle is treated while residing on an associated carrier  1004 , by a treatment robot  1010  that is equipped with a treatment mechanism  1012 . The treatment robot  1010  may again be a multi-axis robot for maximized process flexibility. In embodiments that utilize a shot-peening treatment, any of the various types of shot-emitting mechanisms described above with respect to the system  800  of  FIG. 4  may be employed by the system  1000  of  FIG. 6 . 
         [0050]    In this particular example, the conveyor system  1000  includes individual carriers  1004  equipped with axle retaining elements  1012  (e.g., grippers, clamping assemblies, part nests, etc.). The carriers  1004  travel in or along a guide way such as a track  1014  that leads through the treatment area  1008 . An actuator  1016  or actuator assembly capable of imparting rotational motion to a retained axle  100  is associated with each carrier  1004  in this embodiment. For example, motors (e.g., servo motors) and cylinders may be used for this purpose. In any case, a component such as an axle  100  is rotatably supported by the retaining elements  1012  of an associated carrier  1004  such that, when the carrier reaches a location within the treatment area  1008 , the axle may be rotated by the actuator  1016  while on the carrier so as to be presented in different orientations to the treatment robot  1010 . In this manner, various areas of an axle may be treated without the need for a separate part-handling robot. 
         [0051]      FIG. 7  schematically represents another exemplary embodiment of a railcar axle treatment system  1100  and process, which uses the same carrier system  1004  or a similar carrier system to that used in the system  1000  and process represented in  FIG. 6 . Particularly, this exemplary system  1100  also employs a conveyor system  1002  that includes individual carriers  1004  equipped with rotatable axle retaining elements  1012  and an actuator  1016  or actuator assembly capable of imparting rotational motion to a retained axle such that, when a given carrier reaches a predetermined treatment location  1102 ,  1104 ,  1106  within a treatment area  1108 , the axle may be rotated by the actuator  1016  through different orientations while remaining on the carrier. 
         [0052]    In the system  1100  of  FIG. 7 , the axles are presented in a given orientation at each treatment location  1102 ,  1104 , and  1106  to an associated fixed-position treatment device  1110 ,  1112 , and  1114 . Consequently, various areas of an axle may be treated in a manner best suited to that particular area. In embodiments that treat axles using a shot-peening device, the fixed-position treatment devices  1110 ,  1112 , and  1114  may be equipped with any of the various types of shot-emitting mechanisms described above with respect to the system  800  of  FIG. 4 . While three individual fixed-position treatment devices  1110 ,  1114 , and  1116  are shown in  FIG. 5 , embodiments of the invention are not limited to any particular number of such devices. 
         [0053]    It would be understood by one of skill in the art that there are other ways to cause the rotation of a railcar axle while the axle is retained on a carrier  1004  of the system  1000  of  FIG. 6  or the system  1100  of  FIG. 7 . For example, and without limitation, in an alternative embodiment of the invention (not shown), each carrier  1004  may be equipped with one or more trip arms that contact a respective trip dog as the carrier reaches a given treatment location  1102 ,  1104 ,  1106 . In such an embodiment, the motion of the carrier  1004  along the track  1014  is used to cause the rotation of the railcar axle retaining elements  1012  and the railcar axle. Cams, stops, and/or various other techniques may be used to produce a desired degree of rotation of the railcar axle at each given treatment location  1102 ,  1104 ,  1106 . 
         [0054]      FIG. 8  schematically represents an alternative embodiment of the railcar axle treatment systems and processes of  FIGS. 4 &amp; 5 . In this embodiment, the treatment robot  810  of the system of  FIG. 4  and the fixed position treatment device  910  of  FIG. 5  are replaced with a human operator  1200 . While not specifically shown in  FIG. 8 , the human operator  1200  may use a manually operable shot-emitting mechanism to shot peen areas of interest on a railcar axle as the axle is presented to the operator by the part-handling robot  1202 . Guarding, shielding and/or various other safety devices may be provided within the shot-peening area to protect the operator  1200  during the shot-peening process. 
         [0055]      FIG. 9  schematically represents an alternative embodiment of the railcar axle treatment system and process of  FIG. 6 . In this embodiment, the treatment robot  1010  of the system  1000  of  FIG. 6  is replaced with a human operator  1200 . While not specifically shown in  FIG. 9 , the human operator  1200  may use a manually operable shot-emitting mechanism to shot peen areas of interest on a railcar axle as the axle is rotated through various orientations by an associated conveyor carrier  1004 . Guarding, shielding and/or various other safety devices may again be provided within the shot-peening area to protect the operator  1200  during the shot-peening process. 
         [0056]      FIG. 10  schematically represents an alternative embodiment of the railcar axle treatment system and process of  FIG. 7 . In this embodiment, the fixed-position treatment devices  1110 ,  1112 ,  1114  of the system  1100  of  FIG. 7  are replaced with a human operator  1200  who moves between the various treatment locations  1102 ,  1104 ,  1106 , or with a plurality of human operators, one of which is stationed at each of the various treatment locations. While not represented in  FIG. 10 , it is also possible to use fewer human operators than the number of treatment locations present, such that one or more of multiple operators covers more than one location. For example, two operators may be used to cover the three treatment locations  1102 ,  1104 ,  1106  shown. 
         [0057]    While not specifically shown in  FIG. 10 , the human operator(s)  1200  may use a manually operable shot-emitting mechanism(s) to shot peen areas of interest on a railcar axle as the axle is presented in various rotational orientations by an associated conveyor carrier  1004  at each treatment location  1102 ,  1104 , and  1106 . Guarding, shielding and/or various other safety devices may again be provided within the treatment area to protect the operator  1200  during a shot-peening process. 
         [0058]    Another exemplary embodiment of a railcar axle treatment system  1500  and process is represented in  FIG. 11 . In this exemplary treatment system  1500 , a conveyor  1502  includes two parallel but separate belts  1504  and  1506  for transporting axles  100  to a treatment area  1508 . The belts may be driven in a linked manner to ensure proper movement of the axle, as would be understood by one of skill in the art. 
         [0059]    Axle supporting jigs or similar support elements (neither shown) that are designed to support and retain a railcar axle through only limited points of contact, may be associated with and move with each conveyor belt  1504  and  1506 . Alternatively, an axle may rest directly on the conveyor belts  1504  and  1506 . In either case, areas of interest on the axle are preferably left as exposed as possible to facilitate the treatment thereof. 
         [0060]    The spacing between the conveyor belts  1504  and  1506  allows one or more treatment devices to be positioned along the conveyor path and in the space between the belts for treating one or more axle surfaces from below the axle. In this particular version of such an embodiment, the areas of interest on the axle  100  are treated by several individual fixed-position treatment devices  1512 ,  1514 , and  1516 . However, it should also be realized that robotic treatment devices may be substituted for some or all of the fixed-position treatment devices. In such a case, the treatment robot(s) may again be a multi-axis robot(s) for maximized process flexibility and to reach into the space between the conveyor belts from one or more angles. 
         [0061]    In addition to the systems and processes represented by  FIGS. 4-11  it is also possible that a more simplistic treatment system may be employed. For example, it may be the case that all the areas of a given axle that are to be treated may be accessible to a treating device without any required rotation or other reorientation of the axle. In such a case, it may be possible to transport an axle to a treatment area in a single set position, where a treatment robot or one or more fixed-position treatment devices can be used to treat the various areas of interest. Such a system may resemble the systems of  FIG. 4  or  5 , but without a need for the part-handling robot  808 . 
         [0062]    Treatment systems of the invention, such as the exemplary systems shown in  FIGS. 4-11  and described above, which used a shot-peening process to treat an axle may utilize various types of shot media, as long as the media can produce an acceptable amount of plastic deformation of the axle surface. For example, metallic, ceramic, or glass media may be used. 
         [0063]    Embodiments of the invention may also employ multi-step shot-peening, wherein the shot-peening operation is a sequential process of shot-peening with different media and/or media of different sizes. For example, shot-peening with metallic media may be followed by shot-peening with ceramic and/or glass media. Similarly, shot-peening with media of a first size may be followed by shot-peening with media of a smaller size, the second shot-peening operation using media of the same or a dissimilar composition to that of the first shot-peening operation. Shot-peening processes of interest to the invention may be found, for example, in U.S. Pat. No. 7,946,009. 
         [0064]    Any embodiment of the present invention may include any of the optional or preferred features of the other embodiments of the present invention. The exemplary embodiments herein disclosed are not intended to be exhaustive or to unnecessarily limit the scope of the invention. The exemplary embodiments were chosen and described in order to explain the principles of the present invention so that others ordinarily skilled in the art may practice the invention. Having shown and described exemplary embodiments of the present invention, those skilled in the art will realize that many variations and modifications may be made to the described invention. 
         [0065]    Many of those variations and modifications will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.