CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/613,895, filed on January 5, 2018, the entire contents of which are fully incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with government support under grant 69A3551747132 awarded by the U.S. Department of Transportation. The U.S. government has certain rights in the invention.

BACKGROUND

[0003] The present disclosure is directed to the repair of damage in rails. More specifically, the present disclosure is directed to systems, methods, and devices for fixing rail surface side wear damage on site.

[0004] Rail track damages occur inevitably with time and frequent use of railways by trains. The damages could be minor (such as deterioration of surface finish), rail head corrugation, longitudinal and transverse shelling, crack, spalling, fatigue damage, shear, worn rail head, and plastic deformation lip, which lead to vibration and noise level increase to the train and may cause discomfort to passengers. If not fixed in time, the rail track damage could lead to passenger injury or death. [0005] Generally, to fix major damages on rail tracks, it has been necessary to take the tracks out and replace them with a section of new track, which is costly and time-consuming. For minor wears, the rail is grinded to restore the smooth surface for normal operation.

[0006] Therefore, there exists a need for a system and method for repairing rail track damage that does not require removal and replacement of tracks, and may instead be performed on site.

BRIEF SUMMARY OF THE DISCLOSURE

[0007] Various aspects of the present disclosure related to devices, vehicles, and methods for repairing damage in a rail.

[0008] In one exemplary aspect of the present disclosure, there is provided a rail damage repair device, comprising: a pretreatment device configured to perform a first treatment on a damaged surface of a portion of a rail on site; a printer configured to print a powder directly onto the damaged surface, wherein the powder includes a metal or a composite; and a welding device configured to weld the powder to the damaged surface so as to generate a welded surface.

[0009] In another exemplary aspect of the present disclosure, there is provided a vehicle configured to operate on a rail, comprising: a motive device configured to cause the vehicle to travel along the rail; a plurality of wheels; and a rail damage repair device, comprising: a pretreatment device configured to perform a first treatment on a damaged surface of a portion of a rail on site, a printer configured to print a powder directly onto the damaged surface, wherein the powder includes a metal or a composite, and a welding device configured to weld the powder to the damaged surface so as to generate a welded surface.

[0010] In another exemplary aspect of the present disclosure, there is provided a method of repairing a rail on site, comprising: performing a treatment on a damaged surface of a portion of the rail on site; printing a powder directly onto the damaged surface, wherein the powder includes a metal or a composite; and welding the powder to the damaged surface so as to generate a welded surface.

[0011] In this manner, various aspects of the present disclosure provide for improvements in at least the technical fields of rail transportation and rail repair.

[0012] This disclosure can be embodied in various forms, including hardware or circuits controlled by computer-implemented methods, computer program products, computer systems and networks, user interfaces, and application programming interfaces; as well as hardware- implemented methods, signal processing circuits, memory arrays, application specific integrated circuits, field programmable gate arrays, and the like. The foregoing summary is intended solely to provide a general idea of various aspects of the present disclosure, and does not limit the scope of the disclosure in any way.

DESCRIPTION OF THE DRAWINGS

[0013] These and other more detailed and specific features of various aspects are more fully disclosed in the following description, reference being had to the accompanying drawings, in which:

[0014] FIG. 1 illustrates a cross-sectional view of an exemplary rail for use with various aspects of the present disclosure;

[0015] FIG. 2 illustrates a partial cross-sectional view of an exemplary damaged rail for use with various aspects of the present disclosure;

[0016] FIG. 3 illustrates a partial cross-sectional view of another exemplary damaged rail for use with various aspects of the present disclosure; [0017] FIG. 4 illustrates an exemplary repair system according to various aspects of the present disclosure;

[0018] FIG. 5 illustrates an exemplary repair device according to various aspects of the present disclosure;

[0019] FIG. 6 illustrates an exemplary repair method according to various aspects of the present disclosure;

[0020] FIG. 7 illustrates an exemplary pretreatment according to the exemplary repair method of FIG. 6;

[0021] FIGS. 8A through 8F illustrates an exemplary rail at various stages of a repair method according to various aspects of the present disclosure; and

[0022] FIG. 9 illustrates an exemplary mold for use with various aspects of the present disclosure.

DETAILED DESCRIPTION

[0023] In the following description, numerous details are set forth, such as configurations, operations, and the like, in order to provide an understanding of one or more aspects of the present disclosure. It will be readily apparent to one skilled in the art that these specific details are merely exemplary and not intended to limit the scope of this application.

[0024] Rails and Rail Damage

[0025] A railway typically consists of a plurality of rails (for example, two rails) which extend parallel to one another, rail ties which support the rails and extend perpendicular to the rails, and fasteners which connect the rails to the rail ties. Rails may be made from ore or recycled steel, through the use of a series of roller mills, shears, and heat treatments. The steel used for rails is intended to be hard, wear resistant, and crack resistant. These properties are achieved through the control of elements introduced into the steel during the forge process. The microstructure of rail steel is made of pearlite. These pearlites have a mixture of ferrite and cementite (iron carbide), and form parallel plates.

[0026] The hardness of this steel is measured as a Brinell Hardness Number (HB or BHN) and the typical hardness for this steel is about 280 HB. However, most modem train rails undergo a heat treatment; this heat treatment process can increase a rail’s base hardness from 280 HB to 390 HB. This is equivalent to a Rockwell Hardness C (HRC) of 30 to 42.

[0027] More specifically, scraps of ore or recycled steel are placed in a furnace and heated to about 1650 °C, for example through the use of an electric current. Carbon and manganese are added to the forging process to make 880-grade steel. In practice, however, the present disclosure may be used with any rail material and is not limited to structural steel grade 880. Subsequently, the molten alloy is transported via a ceramic tube to prevent exposure to oxygen. The molten metal flows into molds that are extruded and cut by acetylene torches to form rectangular blocks called blooms.

[0028] The blooms are then transferred again into a furnace in which they are reheated to 1250 °C over six to seven hours. This process softens the steel for shaping into the rails. The newly reheated blooms are subjected to a rolling mill, which elongates the bloom to as much as four times its lengths; subsequently, the elongated blooms are sheared to length. During these shaping processes, the blooms are kept at or near 1250 °C. Therefore, between individual processes, the blooms are held in furnaces to reheat back to the target temperature. The final shaping of the steel is performed by a series of mills until the steel conforms to a standard“T” rail shape, as will be described in more detail below. [0029] Finally, the rails are trimming so that the ends are as nearly square as possible, and the rails are laid out to cool to approximately 90 °C. After cooling, the rails are run through a set of rollers to flex the rails vertically and horizontally. This process straightens the rails and corrects any warpage that may have been introduced due to the heating, shaping, and cooling.

[0030] FIG. 1 illustrates an exemplary rail 100 from a cross-sectional perspective. The rail 100 includes a head 101, a web 102, and a base (or foot) 103. The base 103 is attached to a support, such as a rail tie, by a fastener (not shown). In use, the head 101 contacts the wheel or wheels of rolling stock which travels along the rail.

[0031] After time and repeated use of a rail that is fixed to a track, the rail may develop wear. This phenomenon may also occur when an abnormally heavy load causes separation and/or cutting of the steel tracks due to friction. Three common types of rail wear are side wear, vertical wear, and corrugation wear.

[0032] Side wear typically occurs at the side of the rail head which contacts the wheels of rolling stock. The continual load on the rails changes the head profile of the rail from a symmetric shape to an asymmetric shape, as illustrated in FIGS. 2 and 3. FIG. 2 illustrates an expanded view of the head 101 of the rail 100 of FIG. 1, which has experienced side wear without profile grinding. Due to the side wear, the surface of the head 101 has changed from its undamaged shape 201 (illustrated as a dotted line) to a damaged surface shape 202, including a portion that has flowed beyond the boundaries of the undamaged shape 201. FIG. 3 illustrates an expanded view of the head 101 of the rail 100 of FIG. 1, which has experienced side wear with profile grinding. Due to the side wear and profile grinding, the surface of the head 101 has changed from its undamaged shape 301 (illustrated as a dotted line) to a damaged surface shape 302. As illustrated in FIG. 3, both the corner and top surfaces of the head 101 have been worn. Side wear may occur anywhere along a rail, but often occurs where the tracks curve or turn. Side wear occurs more often as the radius of curvature of the curve or turn decreases.

[0033] Corrugation wear bears several similarities to side wear, but includes a regularly-repeated or wavelike pattern to the surface of the rail. Side wear, vertical wear, and corrugation wear may cause bumps and passenger discomfort in high-speed rolling stock that passes over the rail.

[0034] Repair of Damage

[0035] As compared to other repair methods, the repair systems and methods according to the present disclosure may be performed by comparatively-simple equipment, may be applied to high-alloy steel, may be performed in a single pass, and is conducted more rapidly.

[0036] The present disclosure provides for a system and method in which a mobile 3D printer moves on a railway and 3D-prints metal or composite powders on site where the rail track is damaged. The printed surface has a dimension accuracy and surface finish that is substantially the same as the original rail tracks, and also provides the same or better mechanical strength and hardness as the original. The present disclosure may be applied to any surface of the rail that exhibits damage, including the top and side surfaces. That is, the systems and methods described therein may be utilized with both horizontal and vertical surfaces.

[0037] FIG. 4 illustrates an example of a rail damage repair system 400. As illustrated in FIG. 4, the rail damage repair system 400 includes a vehicle 410 configured to operate on a rail 420. The vehicle 410 includes an engine 411 (an example of a“motive device”), a plurality of wheels 412, and a rail damage repair device 413, which may include various elements such as a 3D printer as will be described in more detail below. In this manner, the vehicle 410 acts as a mobile unit that houses a 3D printer and is mobile on a railway with the engine as a driving system. Metal powders and/or composite powders in a predetermined mix are stored in a component of the vehicle 410 for use on site. A cleaning unit and a surface truing unit may also be housed in the rail damage repair system. For purposes of illustration, the rail 420 includes a portion having a damaged surface 421.

[0038] FIG. 5 illustrates an example of a rail damage repair device 500, such as the rail damage repair device 413 illustrated in FIG. 4. As illustrated in FIG. 5, the rail damage repair device 500 includes a processor 501, a memory 502, a pretreatment device 503, a printer 504 which may be a 3D printer, and a welder 505. Various elements of the rail damage repair device 500 are connected to one another via a bus 506. While FIG. 5 illustrates the rail damage repair device 500 as a fully integrated device, the present disclosure is not so limited. For example, some or all of the pretreatment device 503, the printer 504, and the welder 505 may be provided as standalone devices. Furthermore, the processor 501 and memory 502 may be parts of a remote device, such as a control computer or a server, and operatively connected to some or all of the pretreatment device 503, the printer 504, and the welder 505 via a wired or wireless connection. The rail damage repair device 500 may further include one or more sensors to facilitate the repair process. Examples of such sensors include optical sensors, thermal sensors, and the like.

[0039] FIGS. 6-7 illustrate an exemplary method of repairing a rail on site, which may be implemented by the rail damage repair system 400 illustrated in FIG. 4 and/or the rail damage repair device 500 illustrated in FIG. 5. FIGS. 8A-8F illustrate an exemplary rail at various stages of the exemplary repair method. At step S601, the repair device is moved to the damaged surface. For example, the vehicle 410 is moved along the rail 420 to the portion having the damaged surface 421. At step S602, one or more pretreatment operations are performed. An example of the pretreatment operations is illustrated in FIG. 7. [0040] While FIG. 7 illustrates three pretreatment operations performed in a particular order, the present disclosure is not so limited. In practice, the pretreatment operations may be performed in any order. Furthermore, some of the pretreatment operations may be performed multiple times or not at all. The particular pretreatment operations performed or the order in which the operations are performed may depend on the printing and welding processes used. As illustrated in FIG. 7, the pretreatment operations begin with step S701, in which one or more grooves or channels are machined or otherwise generated in the damaged surface. This may be done in order to reduce any effects of shear in subsequent repair operations.

[0041] Specifically, in order to minimize the effects of mechanical stress, it is possible to machine or otherwise generate grooves or channels in the damaged surface to reduce the effects of shear stress and/or to improve the adhesion of new material to the damaged surface. This results in a rail profile as illustrated in FIGS. 8A-8B. FIG. 8 A illustrates a cross-sectional view of the rail head 101 which includes a plurality of grooves 801 generated with respect to the previous rail profile, shown as a dotted line. FIG. 8B illustrates a perspective view of the rail head 101 including the plurality of grooves 801 and shows that the grooves 801 extend along the rail. To create the rail profile illustrated in FIGS. 8A-8B, different processes may be used, such as the machining of the rail profile with a CNC mill or a carbide ball mill.

[0042] As further illustrated in FIG. 7, the pretreatment operations include step S702, in which the damaged surface is cleaned. This operation may be performed in order to improve the quality of subsequent printing. The cleaning operation may include ultrasonic cleaning followed by polishing down to a particular surface finish, such as 1 pm roughness (Ra). The polishing may be conducting using a diamond paste on SiC papers, and may be followed by etching using a solution, such as an HCl-based solution. Cleaning may be performed using acetone. [0043] The pretreatment operations further include step S703, in which an undamaged portion of the rail, such as a side surface of the rail head 101, is preheated. The preheating operation may be utilized to minimize the effects of thermal stress. FIG. 8C illustrates a cross-sectional view of the rail head 101 during the preheating operation. As illustrated in FIG. 8C, a plurality of thermal elements 802, such as heating plates, are applied to the undamaged side surfaces of the rail head 101. The thermal elements 802 may be configured to heat the rail head 101 to at least 800 °C.

[0044] After the one or more pretreatment operations are performed, the method includes step S602 in which a powder is printed directly onto the damaged, pretreated surface. The powder may be deposited on the damaged surface with a feed nozzle at a delivery angle. The vehicle 410 may include a ceramic tray designed for placement on the lower ends of the rail track so as to collect any dripping of the powders, a mold to facilitate the application of powders, and the like. The deposition may be performed in a controlled atmosphere in which an inert carrier gas such as argon is directed to the powder surface to replace oxygen in the air. A laser gun may be aimed on the rail track surface to liquefy the powders on to the rail track surface, after which the powders will solidify. This process proceeds in a layer-by-layer manner until the damage is fully fixed. FIG. 8D illustrates a cross-sectional view of the rail head 101 during the printing operation. As illustrated in FIG. 8D, the powders 803 are deposited onto the rail head 101 so as to approximate the shape of an undamaged rail.

[0045] The printing operation may utilize a Laser Powder Deposition (LPD) process. Such a process may be executed by driving the powder particles with the carrier gas to strike on the melt pool that is developed on the substrate. A laser beam is focused on the substrate. The incoming powder particles enter the laser beam threshold and begin melting. The LPD process may be an off-axis cladding process or a coaxial cladding process. For example, the coaxial cladding process may be used when independence of the cladding direction is preferred or required. The LPD process may be conducted in an envelope (such as a mold) filled with an inert gas, such as the carrier gas.

[0046] Due to the nature of side wear, the rail head 101 (the substrate) does not have a uniform and symmetric shape along its transverse direction. Therefore, the deposition process may be carried out longitudinally to avoid any elevation change during cladding. Adjacent clad paths may overlap, for example by 50%. The total number of layers and tracks of material deposited may depend on the degree and profile of the damage; however, the bottom layers will typically contain more tracks than the upper layers. The powder 803 is selected based on several factors, including strength, corrosion resistance, and laser compatibility. For structural steel grade 880, the powder 803 may be 304L stainless steel with a diameter range of 45 to 104 pm.

[0047] After printing, at step S604 a welding operation is performed to weld the powder to the damaged surface. FIG. 8E illustrates a cross-sectional view of the rail head 101 during the welding operation. The welding operation may be performed using a submerged arc welding (SAW) process, a thermite welding process, an electro gas welding (EGW) process, and the like. The SAW process, for example, may result in high quality metal welds, a smooth and uniform finish with no splatter, and a high deposition rate. However, the SAW process, for example, may only be applicable to mild and low-alloy steel.

[0048] In one example, the welding operation utilizes an EGW process. EGW is a welding process that involves welding together two different pieces of similar material, which may range in thickness from 0.5 to 4 inches. FIG. 9 illustrates an exemplary mold 900 for adapting the EGW process to a rail. As illustrated in FIG. 9, the mold 900 includes a first shoe 901 that is fixed (stationary) and a second shoe 902 that is allowed to float while the mold 900 moves along a track. The second shoe 902 may include one or more stepped portions 903 to allow access to the rail 100, if desired. For example, the stepped portions 903 may include feed lines or through holes to allow material to be added to or removed from the cavity containing the rail 100 and/or may allow a welding gun to operate on the surface of the rail 100. The first shoe 901 may include one or more clamps 904 (or braces).

[0049] In some aspects of the present disclosure, the printing and welding operations may be unified. For example, some printing technologies (such as LMD) may result in a sufficient bond by themselves and thus obviate the need for further welding. In such aspects of the present disclosure, the nozzle of the printer may be considered the“printer” itself and the laser of the printer may be considered the“welder.”

[0050] After printing and welding, at step S605 one or more post-processing operations may be performed. The post-processing operations may include one or more of a grinding operation, a cooling operation, an inspection operation, and the like. To effect the post-processing operations, the mobile rail repair device may include a grinder operable to grind any excess materials off the rail track surface and thus achieve the exact or nearly-exact surface dimension and surface finish on the rail track as compared to a new track. The mobile rail repair device may additionally or alternatively utilize a thermal element to perform a controlled cooling on the newly-repaired portion of track so as to return the rail to the ambient temperature.

[0051] FIG. 8F illustrates a cross-sectional view of the rail head 101 during the post-processing operation. As illustrated in FIG. 8F, the rail head 101 is processed with one or more processing elements 804. In a case where the processing operation is a grinding operation, the processing elements 804 may be a grinding or polishing wheel. In a case where the processing operation is a controlled cooling operation, the processing elements 804 may be thermal elements. In such a case, the processing elements 804 may be the same as the thermal elements 802 illustrated in FIG. 8C.

[0052] The present disclosure may be implemented using hardware (such as dedicated and/or application-specific circuitry such as a Field-Programmable Gate Array or FPGA), using software, or using a combination of hardware and software. As an example of implementing the present disclosure using software, the requisite processing can be executed by installing a program in which the processing sequence is recorded in the memory of a specialized computer embedded in dedicated hardware, or can be executed by installing the program in a computer that can execute various processing.

[0053] For example, the program can be recorded on a hard disk, a solid-state drive (SSD), or a read only memory (ROM) in advance. Alternatively, the program can be temporarily or permanently stored on a removable recording medium such as a flash drive, a CD-ROM, a magnetic disk, a DVD, a Blu-Ray Disc (BD), or a semiconductor memory card. Additionally, the program may be transferred wirelessly or by wire to the computer from a remote site or server via a network such as a Local Area Network (LAN) or the Internet.

[0054] A rail damage repair device, system, or method in accordance with the present disclosure may be embodied in any one or more of the following configurations:

[0055] (1) A rail damage repair device, comprising: a pretreatment device configured to perform a first treatment on a damaged surface of a portion of a rail on site; a printer configured to print a powder directly onto the damaged surface, wherein the powder includes a metal or a composite; and a welding device configured to weld the powder to the damaged surface so as to generate a welded surface. [0056] (2) The rail damage repair device according to (1), wherein the pretreatment device includes a cleaning device configured to perform a cleaning operation on the damaged surface.

[0057] (3) The rail damage repair device according to (1) or (2), wherein the pretreatment device includes a mill configured to create at least one groove in the damaged surface.

[0058] (4) The rail damage repair device according to any one of (1) to (3), wherein the pretreatment device includes a thermal element configured to preheat the portion of the rail at a surface other than the damaged surface.

[0059] (5) The rail damage repair device according to (4), wherein the thermal element is configured to preheat a side surface of the rail to at least 800 °C.

[0060] (6) The rail damage repair device according to any one of (1) to (5), further comprising: a grinder configured to perform a second treatment on the welded surface.

[0061] (7) A vehicle configured to operate on a rail, comprising: a motive device configured to cause the vehicle to travel along the rail; a plurality of wheels; and a rail damage repair device, comprising: a pretreatment device configured to perform a first treatment on a damaged surface of a portion of a rail on site, a printer configured to print a powder directly onto the damaged surface, wherein the powder includes a metal or a composite, and a welding device configured to weld the powder to the damaged surface so as to generate a welded surface.

[0062] (8) The vehicle according to (7), wherein the pretreatment device includes a cleaning device configured to perform a cleaning operation on the damaged surface.

[0063] (9) The vehicle according to (7) or (8), wherein the pretreatment device includes a mill configured to create at least one groove in the damaged surface. [0064] (10) The vehicle according to any one of (7) to (9), wherein the pretreatment device includes a thermal element configured to preheat the portion of the rail at a surface other than the damaged surface.

[0065] (11) The vehicle according to (10), wherein the thermal element is configured to preheat a side surface of the rail to at least 800 °C.

[0066] (12) The vehicle according to (10) or (11), wherein the thermal element is configured to cool the welded surface to an ambient temperature.

[0067] (13) The vehicle according to any one of (7) to (12), further comprising: a grinder configured to perform a second treatment on the welded surface.

[0068] (14) A method of repairing a rail on site, comprising: performing a treatment on a damaged surface of a portion of the rail on site; printing a powder directly onto the damaged surface, wherein the powder includes a metal or a composite; and welding the powder to the damaged surface so as to generate a welded surface.

[0069] (15) The method according to (14), wherein the treatment includes performing a cleaning operation on the damaged surface.

[0070] (16). The method according to (14) or (15), wherein the treatment includes creating at least one groove in the damaged surface.

[0071] (17) The method according to any one of (14) to (16), wherein the treatment includes preheating the portion of the rail at a surface other than the damaged surface.

[0072] (18) The method according to (17), wherein the preheating includes preheating a side surface of the rail to at least 800 °C.

[0073] (19) The method according to any one of (14) to (18), further comprising: after the welding, cooling the portion of the rail to an ambient temperature. [0074] (20) The method according to any one of (14) to (19), further comprising: grinding the welded surface.

[0075] With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain aspects of the present disclosure, and should in no way be construed so as to limit the disclosure.

[0076] Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent upon reading the above description. The scope should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the technologies discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the application is capable of modification and variation.