Abstract:
A method and system for increasing a transportation component&#39;s resistance to failure comprising shot-peening at least one area of the component to create a compressive surface layer on the component.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation in part of and claims priority to application Ser. No. 13/941,049 filed on Jul. 12, 2013 which is herein incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention is directed to systems and processes for manufacturing transportation system components such as, but not limited to, railcar frames, bolsters, couplers, yokes, and wheels. 
       BACKGROUND 
       [0003]    One of skill in the art would understand that transportation system components, such as frames, bolsters, couplers, yokes, and wheels used in railcar applications are critical components from the standpoint of both functionality and safety. Frames, bolsters, wheels, and similar components support the weight of the railcar and its cargo as well as form part of the interface with the railway with its corresponding imperfections. Couplers and yokes are subject to stress as the result of coupling and uncoupling the connection between railcars. These components are subject to mechanical stresses as the result of stopping and starting the train and vibratory stress as the result of rail imperfections. Because of the heavy and sometimes hazardous payload or in the case of passenger trains, human lives, functionality and safety require that these components are designed to avoid unexpected failure. With respect to functionality, that portion of railcar components which are coupling components must be designed and constructed in a manner that ensures proper repeated coupling of one railcar to another. Secure coupling of one railcar to another must, of course, also be maintained until deliberately released. 
         [0004]    Coupling is typically accomplished by moving a trailing railcar such that the coupling assembly thereof is brought into engaging contact with the coupling assembly of an immediately leading railcar. Because of the mass of a typical railcar, significant stresses may be imparted to the railcar coupling components during this process. Similarly, once engaged, railcar coupling components may also be subjected to significant stresses upon placing a train of railcars into motion, during motion, and upon the deceleration and stopping of the train. These stresses may be mechanical in nature, such as impact, tension or shearing forces produced during railcar coupling and decoupling, or vibratory in nature, such as may occur during the rolling movement of a railcar. Similar mechanical stresses may also be placed on the coupling components of a moving train of railcars as accelerations and decelerations of the train impart tension or compression forces to the coupling components of adjacent railcars. 
         [0005]    As should be obvious, the failure of railcar components such as those described herein, particularly while a train of railcars is in motion, could be catastrophic. Therefore, from the standpoint of safety, railcar components must be designed and manufactured so as to prevent such stresses from causing component damage or failure. 
         [0006]    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. It would, therefore, be desirable to implement such improvements so as to increase railcar component strength and durability and mitigate such stress failures. The invention is so directed. 
       SUMMARY 
     Shot-Peening Mass Transit and Railcar Components 
       [0007]    An aspect of the invention is directed to an improvement in mass transit and railcar component manufacturing processes resulting from shot-peening. Particularly, it has been discovered that shot-peening certain areas of railcar components may improve the fatigue life of those components. As used herein such areas may be areas of high stress, particularly those areas of railcar components subject forces resulting in tension. 
         [0008]    Improvement of the fatigue life of such components is understood to occur by way of increasing the residual compressive surface stresses of the component material through the plastic deformation thereof. The shot-peening media used in 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 component surface being peened. 
         [0009]    Surface finish in the highly stressed areas of mass transit and railcar components 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 when shot-peening highly stressed areas of railcar components. 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. 
         [0010]    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. 
       Metal Formulations 
       [0011]    Mass transit and railcar components 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 components. 
       Shot-Peening System 
       [0012]    The invention is also directed to automated or semi-automated systems and methods of shot-peening railcar components in the desired areas. Embodiments of such systems and methods may employ a conveying system(s) or other automated means for transporting such components along a processing path. As a mass transit or railcar component travels along the processing path, the areas of interest on the component are shot-peened by shot-peening devices that comprise shot-peening 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 component areas. 
         [0013]    Conveying systems for use in a shot-peening 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 a component to be processed to a shot-peening area where it is picked up by a robot and presented to one or more shot-emitting mechanisms such that the component areas of interest are shot-peened. 
         [0014]    In another conveying system embodiment, components may be placed on a specialized conveyor that includes individual component supporting carriers. These carriers may be designed to accommodate a particular component. The carriers may include component 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 component are presented to one or more shot-emitting mechanisms for shot-peening as the component travels along the processing path. 
         [0015]    In still another embodiment, components may be placed on a specialized conveyor that may include component specific supporting jigs or similar support elements that are designed to support and retain a component through only limited points of contact, thereby leaving the areas of interest on the component exposed for shot-peening and eliminating the need for rotation or tilting of the component. Such an embodiment may be particularly useful when the component is large and unwieldy such as the case for railcar frames and bolsters. In such an embodiment, the conveyor may also be specially designed to permit access to various component surfaces by a shot-peening device. 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 component surfaces from below. In such embodiments, the areas of interest on the component may be shot-peened by stationary shot-emitting mechanisms, and/or by one or more robots equipped with shot-emitting mechanisms, as the component travels along the processing path. Such an embodiment may be employed to shot-peen critical inner surfaces of components such as frames and bolsters by causing one or more shot-emitting mechanisms to be inserted into openings in the frame or bolster outer surface. 
         [0016]    In systems of the invention, shot-peening may occur while a component is in motion—either rotationally or during travel along the processing path on an associated conveying device. Alternatively, shot-peening may occur while the motion of a component is temporarily halted, such as at one or more predetermined shot-peening stations. 
         [0017]    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 
         [0018]    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: 
           [0019]      FIGS. 1   a - 1   b  are top and side views, respectively, of an exemplary railcar coupler illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0020]      FIGS. 2   a - 2   b  are top and side views, respectively, of another variety of exemplary railcar coupler illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0021]      FIGS. 3   a - 3   b  are top and side views, respectively, of yet another exemplary railcar coupler illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0022]      FIGS. 4   a - 4   c  are top, side and bottom views, respectively, of an exemplary railcar bolster illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0023]      FIGS. 5   a - 5   b  are side and top views, respectively, of an exemplary railcar yoke illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0024]      FIGS. 6   a - 6   b  are side and top views, respectively, of another variety of exemplary railcar yoke illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0025]      FIGS. 7   a - 7   d  are inside, outside, top, and bottom views, respectively, of an exemplary railcar side frame illustrating high stress areas that may be shot-peened according to an embodiment of the invention; 
           [0026]      FIG. 8  schematically represents an exemplary embodiment of a railcar component shot-peening system and process whereby a conveyor transports components to a shot-peening area where each component is picked up by a multi-axis robot and presented to another multi-axis robot that is equipped with a shot-emitting mechanism; 
           [0027]      FIG. 9  schematically represents an exemplary embodiment of a railcar component shot-peening system and process whereby a conveyor belt transports a component to a shot-peening area where it is picked up by a multi-axis robot and presented to fixed position shot-emitting mechanism; 
           [0028]      FIG. 10  schematically represents another exemplary embodiment of a railcar component shot-peening system and process wherein components are placed on a specialized conveyor that includes individual conveyor carriers that are designed to rotate the component via a powered actuator such that the areas of interest on the component are presented to one or more multi-axis robotic shot-emitting mechanisms for shot-peening; 
           [0029]      FIG. 11  schematically represents another exemplary embodiment of a railcar component shot-peening system and process wherein components are placed on a specialized conveyor that includes individual conveyor carriers that are designed to rotate the component via a powered actuator such that the areas of interest on the component are presented to one or more fixed position shot-emitting mechanisms for shot-peening; 
           [0030]      FIG. 12  schematically represents an alternative embodiment of the railcar component shot-peening systems and processes of  FIGS. 8-9 , in which the respective multi-axis robot and fixed position shot-emitting device thereof have been replaced with a human operator; 
           [0031]      FIG. 13  schematically represent an alternative embodiment of the railcar component shot-peening systems and process of  FIG. 10  in which the multi-axis robot shot-emitting devices thereof have been replaced with one or more human operators; 
           [0032]      FIG. 14  schematically represent an alternative embodiment of the railcar component shot-peening systems and process of  FIG. 11  in which the fixed position shot-emitting devices thereof have been replaced with one or more human operators; and 
           [0033]      FIG. 15  schematically represents another alternative embodiment of a railcar component shot-peening system and process whereby components are transported through a shot-peening area on a specialized conveyor that leaves exposed the areas on the component that are to be shot-peened. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0034]    The detailed description that follows makes reference to railcar components generally for ease of description. The embodiments described may be applied to other transit component devices, particularly those used in mass transit applications. 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. 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 metal formulations used in the fabrication of railcar components. 
       The Casting Process 
       [0035]    Railcar components may be produced using a casting operation in which the molds may be formed using a sand material that has been treated to retain its shape during the casting operation. Generally a mold is comprised of at least two sections. A core is placed in one of the mold sections and the sections are caused to be held in proximity to one another, creating a hollow chamber, partially occupied by the core within the sections. The core serves to form open sections within the resulting cast shape formed by the casting process. Molten metal may then be introduced into an opening in at least one of the mold sections, filling the hollow chamber within to form the desired shape. When the metal has sufficiently cooled, the mold sections are disassembled and the core is broken apart for removal from the casting. 
         [0036]    When molten metal is introduced into the mold sections, the extreme heat of the metal may cause moisture contained in the casting sand to rapidly vaporize into steam. Such rapid vaporization may disturb the casting sand, resulting in imperfections in the surface of the shape formed as a result of the casting operation. Additional surface imperfections are often located at the parting lines formed at points where sections of the mold are held in contact with each other during the casting process. 
         [0037]    Imperfections on the surface of the casting may result in stress points which may result in areas of weakness. Because of this, producing a shape with a minimal number of imperfections may result in a more durable casting. 
       Shot Peening 
       [0038]    A shot peening process may increase the residual compressive surface stresses of a cast material through a process of plastic deformation. Testing and failure analysis has shown residual compressive surface stress may improve the durability of a railcar component 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 component. Referring to  FIGS. 1   a  &amp;  1   b , in an embodiment of the invention, a shot-peening process may be applied to areas of high stress in a railcar component. Such areas are illustrated as shaded areas in the exemplary coupler shown in the figure. One such shaded area is shown at  102 . 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 casting 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. 
         [0039]    Referring again to  FIGS. 1   a  &amp;  1   b , the area around the coupler connection  102  are shaded to indicate that this may be an area of high stress. Areas of high stress may be determined based on failure history of a particular component. Finite Element Analysis (FEA) may also be used to identify areas of high stress. The Association of American Railroads indicates areas of high stress in its AAR Manual of Standards and Recommended Practices. Those skilled in the art will realized that such failure data, FEA analysis, and reference materials such as the AAR Manual of Standards and Recommended Practices may be used to identify area that may benefit from the shot-peening method described herein.  FIGS. 1-7  represent exemplary embodiments of various railcar components shown with shaded areas that may be high stress areas based on the previously described failure data and reference materials. In  FIGS. 1   a  &amp;  1   b , additional areas that may be improved by the disclosed shot-peening process are illustrated at  104 ,  106 , and  108 . These additional areas are the couple shaft section and knuckle pivot shaft mounting hole respectively. 
         [0040]    Another embodiment of a rail car coupler is illustrated in  FIGS. 2   a  &amp;  2   b . High stress areas are illustrated by the shading at  202 - 208 .  202  represent the area surrounding the slot-shaped yoke connection at the end of the coupler opposite the coupling head.  204  represents an area on the coupler shaft where the shaft connects to the coupler head.  206  and  208  illustrate areas of the coupler head supporting the knuckle pivot shaft. These areas may be subject to the shot-peening process in exemplary embodiments of the invention. 
         [0041]    A third embodiment of a rail car coupler is illustrated in  FIGS. 3   a  &amp;  3   b . High stress areas are illustrated by the shading at  302 - 308 . Area  302  represents the casting area surrounding the round yoke connection at the end of the coupler opposite the coupling head.  304  represents an area on the coupler shaft where the shaft connects to the coupler head.  306  and  308  illustrate areas of the coupler head supporting the knuckle pivot shaft. These areas may be subject to the shot-peening method disclosed herein in exemplary embodiments of the invention to improve the coupler strength as a result of increasing the residual compressive surface stresses of the coupler casting material through plastic deformation. 
         [0042]      FIGS. 4   a - 4   c  illustrate an exemplary embodiment of a railcar bolster. Areas identified as high stress areas of typical bolsters include the areas  402  immediately inboard of the spring seat surfaces on each end of the bolsters. An additional area subject to high stress is the areas surrounding pass-through openings formed to allow brake actuation hardware to pass through the bolster. Such areas are illustrated at  406 . Areas  402  and  406  may be subject to the shot-peening method disclosed herein in exemplary embodiments of the invention to improve the bolster strength as a result of increasing the residual compressive surface stresses of the bolster casting material through plastic deformation. 
         [0043]    Yoke assemblies are used in many railcar trucks to connect the coupler to the railcar structure. Such yokes are subject to high stress where they contact the coupler and the railcar body.  FIGS. 5   a  &amp;  5   b  illustrate an exemplary yoke embodiment. Areas of high stress are indicated by the shaded areas at  502 ,  504 , and  506 . These areas may be subject to the shot-peening method described herein to improve the yoke strength as a result of increasing the residual compressive surface stresses of the casting material at high stress areas such as those illustrated at  502 ,  504 , and  506  through plastic deformation.  FIGS. 6   a  and  6   b  illustrate another yoke embodiment. As with  FIGS. 5   a  and  5   b , areas of high stress in the yoke are in the area where the yoke contacts the coupler assembly  604  and the railcar structure  602 . In embodiments of the invention, these areas may be subject to the shot-peening method described herein to improve their strength and resistance to failure. 
         [0044]      FIGS. 7   a - 7   d  illustrate inside, outside, top, and bottom views of a railcar side frame. As will be recognized by one skilled in the art, such a side frame supports the wheel/axle assemblies and provides a connection to the bolster by way of a set of load support springs between the bolster ends and the side frame. Testing and research of reference materials such as AAR standards materials indicates that there are areas of high stress and therefore potential failure in railcar side frames. These areas are illustrated by shading where  702  indicates the area adjacent to the axle bearing mounting slot and  704  &amp;  706  indicate areas in the area of the spring seat section of the side frame. Applying the shot-peening method described herein may improve side frame strength and thus reduce the occurrence of failures while in use. 
         [0045]    In addition to the railcar components illustrated in the above figures, the method described herein may also be applied to railcar wheels to improve the strength of such components as the result of increasing the residual compressive surface stresses of the wheel materials in areas of high stress. 
         [0046]    One exemplary embodiment of a railcar component shot-peening system  800  and process is schematically represented in  FIG. 8 . In this exemplary embodiment, a conveyor  802  transports a bolster  804  to a shot-peening area  806  where each bolster is picked up by a part handling robot  808  and is presented to another robot  810  that is equipped with a shot-emitting mechanism  812 . Both the part-handling robot  808  and shot-peening robot  810  may be multi-axis robots for maximized process flexibility. 
         [0047]    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. 
         [0048]    In the exemplary system  800  of  FIG. 8 , the part-handling robot  808  is shown to be equipped with an end effector  814  that is adapted for grasping and removing a bolster  804  from the conveyor  802 , and for releasably retaining the bolster in multiple orientations during presentation thereof to the shot-peening robot  810 . End effectors for part handling are well known in the art and, therefore, are not described in detail herein. 
         [0049]    The shot-emitting mechanism  812  of the shot-peening 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 component surface. 
         [0050]      FIG. 9  schematically represents another exemplary embodiment of a railcar component shot-peening system  900  and process, which is very similar to the system  800  and process represented in  FIG. 8 . Particularly, this exemplary system  900  again includes the conveyor  802  and part-handling robot  808  of the system  800  of  FIG. 8 . As illustrated in the figure, the embodiment is shown transporting side frames  904  to a shot-peening area  806  where each side frame is picked up by the part-handling robot  808 . In this system  900 , however, the part-handling robot  808  presents side frames  904  to be peened to a fixed-position shot-emitting device  910  rather than to a robot equipped with a shot-emitting mechanism. 
         [0051]    In the system  900  of  FIG. 9 , 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. 8 . Similarly, although the system of  FIG. 9  employs a fixed-position shot-emitting device  910 , any of the various types of shot-emitting mechanisms described above with respect to the system  800  of  FIG. 8  may be used in the system  900  of  FIG. 9 . 
         [0052]      FIG. 10  schematically represents an exemplary embodiment of a railcar coupler shot-peening system  1000  and process. In this shot-peening system  1000 , a conveyor  1002  having a plurality of individual carriers  1004  transports couplers  1006  to a shot-peening area  1008 . Each coupler is peened while residing on an associated carrier  1004 , by a shot-peening robot  1010  that is equipped with a shot-emitting mechanism  1012 . The shot-peening robot  1010  may again be a multi-axis robot for maximized process flexibility. Any of the various types of shot-emitting mechanisms described above with respect to the system  800  of  FIG. 8  may be employed by the system  1000  of  FIG. 10 . 
         [0053]    In this particular example, the conveyor system  1000  includes individual carriers  1004  equipped with component 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 shot-peening area  1008 . An actuator  1016  or actuator assembly capable of imparting rotational motion to a retained component such as the illustrated coupler  1006  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 a coupler  1006  is rotatably supported by the retaining elements  1012  of an associated carrier  1004  such that, when the carrier reaches a shot-peening location within the shot-peening area  1008 , the coupler may be rotated by the actuator  1016  while on the carrier so as to be presented in different orientations to the shot-peening robot  1010 . In this manner, various areas of a given component may be shot-peened without the need for a separate part-handling robot. 
         [0054]      FIG. 11  schematically represents another exemplary embodiment of a railcar component shot-peening 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. 10 . Particularly, this exemplary system  1100  also employs a conveyor system  1002  that includes individual carriers  1004  equipped with rotatable coupler retaining elements  1012  and an actuator  1016  or actuator assembly capable of imparting rotational motion to a retained component such that, when a given carrier reaches a predetermined shot-peening location  1102 ,  1104 ,  1106  within a shot-peening area  1108 , the coupler may be rotated by the actuator  1016  through different orientations while remaining on the carrier. 
         [0055]    In the system  1100  of  FIG. 11 , the components are presented in a given orientation at each shot-peening location  1102 ,  1104 , and  1106  to an associated fixed-position shot-peening device  1110 ,  1112 , and  1114 . Consequently, various areas of a given component may be shot-peened. The fixed-position shot-peening 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. 8 . While three individual fixed-position shot-peening devices  1110 ,  1114 , and  1116  are shown in  FIG. 11 , embodiments of the invention are not limited to any particular number of such devices. 
         [0056]    It would be understood by one of skill in the art that there are other ways to cause the rotation of a railcar component while the component is retained on a carrier  1004  of the system  1000  of  FIG. 10  or the system  1100  of  FIG. 11 . 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 shot-peening location  1110 ,  1112 ,  1114 . In such an embodiment, the motion of the carrier  1004  along the track  1014  is used to cause the rotation of the railcar component retaining elements  1012  and the railcar component. Cams, stops, and/or various other techniques may be used to produce a desired degree of rotation of the railcar component at each given shot-peening location  1110 ,  1112 ,  1114 . 
         [0057]      FIG. 12  schematically represents an alternative embodiment of the railcar component shot-peening systems and processes of  FIGS. 8 &amp; 9 . In this embodiment, the shot-peening robot  810  of the system of  FIG. 8  and the fixed position shot-peening device  910  of  FIG. 9  are replaced with a human operator  1200 . While not specifically shown in  FIG. 12 , the human operator  1200  would use a manually operable shot-emitting mechanism to shot peen areas of interest on a railcar component as the component 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. 
         [0058]      FIG. 12  illustrates an embodiment of the invention applying shot-peening to a yoke component  1204 . The previous figures have illustrated various railcar components but one skilled in the art would understand that the illustrated systems may be applied to other railcar components comprising couplers, yokes, side frames, bolsters, and wheels. 
         [0059]      FIG. 13  schematically represents an alternative embodiment of the railcar component shot-peening system and process of  FIG. 10 . In this embodiment, the shot-peening robot  1010  of the system  1000  of  FIG. 10  is replaced with a human operator  1200 . While not specifically shown in  FIG. 13 , the human operator  1200  would use a manually operable shot-emitting mechanism to shot peen areas of interest on a railcar component as the component 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. 
         [0060]      FIG. 14  schematically represents an alternative embodiment of the railcar coupler shot-peening system and process of  FIG. 11 . In this embodiment, the fixed-position shot-peening devices  1110 ,  1112 ,  1114  of the system  1100  of  FIG. 11  are replaced with a human operator  1200  who moves between the various shot-peening location  1102 ,  1104 ,  1106 , or with a plurality of human operators, one of which is stationed at each of the various shot-peening locations. While not represented in  FIG. 14 , it is also possible to use fewer human operators than the number of shot-peening 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 shot-peening locations  1102 ,  1104 ,  1106  shown. 
         [0061]    While not specifically shown in  FIG. 14 , the human operator(s)  1200  would use a manually operable shot-emitting mechanism(s) to shot peen areas of interest on a railcar component as the component is presented in various rotational orientations by an associated conveyor carrier  1004  at each shot-peening location  1102 ,  1104 , and  1106 . 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. 
         [0062]    Another exemplary embodiment of a railcar component shot-peening system  1500  and process is represented in  FIG. 15 . In this exemplary shot-peening system  1500 , a conveyor  1502  includes two parallel but separate belts  1504  and  1506  for transporting components (here illustrated as side frames  1510 ) to a shot-peening area  1508 . One skilled in the art will understand that side frames are used to illustrate the embodiment but that other railcar components may be shot-peened using such an embodiment. This embodiment may be particularly useful when the railcar component being shot-peened is large, heavy, or awkwardly shaped. The belts may be driven in a linked manner to ensure proper movement of the component, as would be understood by one of skill in the art. 
         [0063]    Component supporting jigs or similar support elements (neither shown) that are designed to support and retain a railcar component through only limited points of contact, may be associated with and move with each conveyor belt  1504  and  1506 . Alternatively, a component may rest directly on the conveyor belts  1504  and  1506 . In either case, areas of interest on the component are preferably left as exposed as possible to facilitate the shot-peening thereof. 
         [0064]    The spacing between the conveyor belts  1504  and  1506  allows one or more shot-peening devices to be positioned along the conveyor path and in the space between the belts for shot-peening one or more component surfaces from below the component. In this particular version of such an embodiment, the areas of interest on the side frame  1510  are shot peened by several individual fixed-position shot-peening devices  1512 ,  1514 , and  1516 . However, it should also be realized that robotic shot-peening devices may be substituted for some or all of the fixed-position shot-peening devices. In such a case, the shot-peening 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. 
         [0065]    In addition to the systems and processes represented by  FIGS. 8-15  it is also possible, depending on the design of a railcar component of interest and the areas thereof that are to be shot-peened, that a more simplistic shot-peening system may be employed. For example, it may be the case that all the areas of a given component that are to be shot-peened may be accessible to a shot-peening device without any required rotation or other reorientation of the component. In such a case, it may be possible to transport a component to a shot-peening area in a single set position, where a shot-peening robot or one or more fixed-position shot-peening devices can be used to shot peen the various areas of interest. Such a system may resemble the systems of  FIG. 8  or  9 , but without a need for the part-handling robot  808 . 
         [0066]    Shot-peening systems of the invention, such as the exemplary systems shown in  FIGS. 8-15  and described above, may utilize various types of shot media, as long as the media can produce an acceptable amount of plastic deformation of the knuckle surface. For example, metallic, ceramic, or glass media may be used. 
         [0067]    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. 
         [0068]    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. 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.