Cross bending bidirectional residual stress manufacturing device and using method thereof

Abstract

The invention provides a cross bending bidirectional residual stress manufacturing device and a using method thereof.The cross bending bidirectional residual stress manufacturing device comprises an experiment table, a plurality of supporting roller mechanisms and an ejector rod mechanism, the supporting roller mechanisms are distributed on the experiment table at intervals, the ejector rod mechanism is located in a space defined by the supporting roller mechanisms, and the supporting roller mechanisms are arranged on the experiment table; the ejector rod mechanism is also arranged on the experiment table, the supporting roller mechanism is arranged at the end of the cross-shaped bending sample in the horizontal direction, the ejector rod mechanism is arranged in the middle of the cross-shaped bending sample, pressure can be applied to the middle of the cross-shaped bending sample in the vertical direction through the ejector rod mechanism, and meanwhile the cross-shaped bending sample can be accurately measured in cooperation with lifting of supporting rollers. Therefore, compression or stretching stress is formed on the upper surface of the cross-shaped bending sample. According to the method, the residual stress on the surface of the cross bending sample can be effectively and accurately manufactured and measured, and the problems that an existing surface bidirectional residual stress manufacturing process is complex, and a bidirectional residual stress value is difficult to accurately measure are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of residual stress measurement, and particularly relates to a cross-bending bidirectional residual stress manufacturing device and a using method thereof. Background Art

[0002] Instrumented indentation testing is a method for testing the mechanical properties of materials developed in recent years. In this method, an indenter with a millimeter or micron size is pressed into the surface of the material to be tested, and the load-depth curve during the indentation process is recorded. Based on a mathematical model, important mechanical property parameters such as the stress-strain curve, tensile strength, and fracture toughness of the material are calculated. Compared with traditional mechanical property testing methods, it has the advantages of micro-damage, rapidity, and on-site testing. However, since instrumented indentation is a local testing method, the residual stress in the material has a great influence on the test results.

[0003] Currently, there are different calculation methods for indentation mechanical properties considering residual stress, but they all have certain defects. The influence of residual stress on indentation mechanical properties still needs to be further studied in depth. Obtaining different residual stress states is a prerequisite for experimental research on the influence of residual stress. The current bidirectional stress manufacturing methods mainly include biaxial tension and biaxial bending methods. The biaxial tension method requires a large loading load and a large-sized specimen, the device is complex, and it is prone to instability when applying a compressive load, and it is not easy to achieve the loading of all stress states on a single specimen. The surface stress uniform area formed by the biaxial bending method is small. Since the size of the strain gauge is much larger than the indentation size, the residual stress of the bent specimen characterized by the method of pasting the strain gauge is not accurate enough. All existing biaxial bending devices have equal spans in both directions, and it is necessary to use large-sized raw materials to prepare cross specimens with equal lengths in both directions, and it is difficult to take samples from small-sized raw materials. In short, both the tension method and the bending method for manufacturing bidirectional residual stress require large-sized specimens, and the process of manufacturing bidirectional residual stress by the tension method is complex and the cost of experimental equipment is high, while the bidirectional residual stress manufactured by the bending method is difficult to accurately measure, which hinders the development of instrumented indentation measurement technology.

[0004] Due to the technical problems in the prior art that the bending method for manufacturing bidirectional surface residual stress requires large-sized specimens and the residual stress after bending is difficult to accurately measure, the present invention researches and designs a cross-bending bidirectional residual stress manufacturing device and a using method thereof. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects that the bending method for manufacturing bidirectional surface residual stress in the prior art requires large-sized specimens and the residual stress after bending is difficult to accurately measure, so as to provide a cross-bending bidirectional residual stress manufacturing device and a using method thereof.

[0006] To solve the above problems, the present invention provides a cross-bending bidirectional residual stress manufacturing device, which includes:

[0007] An experimental table, a roller mechanism, and a ejector rod mechanism. There are multiple roller mechanisms, and the multiple roller mechanisms are spaced apart on the experimental table. The ejector rod mechanism is located in the space surrounded by the multiple roller mechanisms, and the ejector rod mechanism is also arranged on the experimental table. The roller mechanism is arranged at the horizontal end of the cross-bending specimen, and the ejector rod mechanism is arranged at the middle position of the cross-bending specimen. Through the ejector rod mechanism, pressure can be applied to the middle position of the cross-bending specimen in the vertical direction, and at the same time, in cooperation with the lifting of the rollers, compressive or tensile stress can be formed on the upper surface of the cross-bending specimen.

[0008] In some embodiments,

[0009] Multiple bolt holes and one ejector rod hole are provided on the experimental table. The roller mechanism includes a roller, a bolt, and a nut. The roller is sleeved on the bolt, and the bolt is inserted into the bolt hole. Nuts are sleeved on the bolt above and below the roller. The end of the cross-bending specimen can be arranged at the upper or lower end of the roller to provide compressive or tensile stress to the cross-bending specimen.

[0010] In some embodiments,

[0011] The cross-bending specimen includes the middle position and at least two arms. The arms are the ends. One end of each arm is connected to the middle position, and the other end extends away from the middle position. The multiple bolt holes are arranged at intervals along the extension direction of the arms of the cross-bending specimen, so that the roller mechanism can be set on different bolt holes according to the length of the arms, and the roller mechanism can also be set on different bolt holes according to the position of the stress to be applied.

[0012] In some embodiments,

[0013] The at least two arms include a first arm, a second arm, a third arm, and a fourth arm. One end of the first arm is connected to the middle position, and the other end extends away from the middle position. One end of the second arm is connected to the middle position, and the other end extends away from the middle position. One end of the third arm is connected to the middle position, and the other end extends away from the middle position. One end of the fourth arm is connected to the middle position, and the other end extends away from the middle position. The extension directions of the first arm and the second arm are opposite to each other, and the extension directions of the third arm and the fourth arm are opposite to each other.

[0014] In some embodiments,

[0015] The supporting roller extends along the width direction of the arm of the cross-bending specimen to form the length direction of the supporting roller. The width direction of the arm of the cross-bending specimen is perpendicular to the extending direction of the arm. One supporting roller cooperates with two bolts. One end of the length direction of the supporting roller penetrates through one bolt, and at least one nut is arranged above and below the bolt. There is a bolt hole on the test bench that cooperates with the bolt, and the bolt can be inserted into the bolt hole. The other end of the length direction of the supporting roller penetrates through one bolt, and at least one nut is also arranged above and below the bolt. There is a bolt hole on the test bench that cooperates with the bolt, and the bolt can be inserted into the bolt hole.

[0016] In some embodiments,

[0017] The bolt on one side of the supporting roller is located on one side of the arm and is spaced from the arm after passing through the supporting roller. The bolt on the other side of the supporting roller is located on the other side of the arm and is spaced from the arm after passing through the supporting roller, so that the arm is located between the two bolts.

[0018] In some embodiments,

[0019] The ejector rod mechanism includes an ejector rod, a flange, and an ejector rod spacer. At least part of the ejector rod is located below the test bench. The flange is arranged in the ejector rod hole. The lower end of the flange is connected to the ejector rod, and the upper end of the flange is connected to the ejector rod spacer. The ejector rod spacer is located below the middle position of the cross-bending specimen. The ejector rod can move upward to drive the ejector rod spacer to move upward through the flange, so as to apply an upward pressure to the middle position of the cross-bending specimen.

[0020] In some embodiments,

[0021] The top surface of the ejector rod spacer is a spherical structure. The flange is a thrust bearing. The lower end of the ejector rod is connected to a threaded screw, a jack, or an electric cylinder.

[0022] In some embodiments,

[0023] The arm of the cross-bending specimen is located between the nuts below the supporting roller. When the ejector rod moves upward, the supporting roller can apply tensile stress to the cross-bending specimen; and / or, the arm of the cross-bending specimen is located between the nuts above the supporting roller. When the supporting roller moves upward, the supporting roller can apply compressive stress to the cross-bending specimen.

[0024] The present invention also provides a method for using the cross-bending biaxial residual stress manufacturing device as described above, which includes:

[0025] S1. Process a cross-bending specimen and place it on the experimental table. Adjust the roller spacing and roller height in two directions of the cross specimen according to the desired surface stress state of the specimen.

[0026] S2. Establish a finite element model of the cross-bending process based on the specimen size, roller spacing, and roller height in step S1, conduct simulation calculations of the cross-bending process, obtain the residual stress distribution nephogram on the surface of the specimen after bending, and extract the displacement values of the ejector rod and rollers at this time from the simulation results.

[0027] S3. Load the specimen through the ejector rod mechanism and / or the nuts on the rollers. When the displacements of the ejector rod and rollers reach the values in step S2, stop further loading and maintain this state.

[0028] S4. Select the approximate position of instrumented indentation according to the simulation results, conduct instrumented indentation tests on the cross-bending specimen, measure the accurate position of the indentation on the cross-bending specimen, determine the bidirectional residual stress value at this position before indentation according to the simulation results, and use this value to correct the instrumented indentation test results or establish a new mechanical property calculation model for instrumented indentation.

[0029] A cross-bending bidirectional residual stress manufacturing device and its usage method provided by the present invention have the following beneficial effects:

[0030] 1. In the present invention, the ejector rod mechanism is arranged on the experimental table and located in the space surrounded by multiple roller mechanisms. The ejector rod mechanism can apply pressure to the middle position of the cross-bending specimen in the vertical direction, and at the same time cooperate with the lifting of the rollers, so as to form compressive or tensile stress on the upper surface of the cross-bending specimen, and can effectively and accurately manufacture and measure the residual stress on the surface of the cross-bending specimen. The device and method of the present invention are simple and flexible, with low cost, and solve the problems of complex surface bidirectional residual stress manufacturing process and difficult accurate measurement of bidirectional residual stress values at present.

[0031] 2. The present invention also sets multiple bolt holes on the experimental table, and the multiple bolt holes are arranged at intervals along the extension direction of the arm of the cross-bending specimen, so that the roller mechanism can be set on different bolt holes according to the length of the arm, and the roller mechanism can also be set on different bolt holes according to the position where the stress needs to be applied, which is applicable to cross-bending specimens of different sizes, and can conveniently form any combination of bidirectional residual stress of any size on the material surface, solving the problem that the existing bending method for manufacturing bidirectional surface residual stress requires large-size specimens.

[0032] 3. The present invention also sleeved the nuts on the bolt and above and below the supporting roller. The end of the cross-bending specimen can be arranged at the upper or lower end of the supporting roller to provide compressive or tensile stress to the cross-bending specimen, and can apply and provide different directions and different types of stress to the cross-bending specimen, improving the stress application range and the versatility of the residual stress manufacturing device of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the overall structure diagram of the cross-bending two-way residual stress manufacturing device of the present invention;

[0034] Figure 2 is the top view of the test bench of the present invention;

[0035] Figure 3 is the overall structure diagram of the cross-bending two-way residual stress manufacturing device of the present invention after installing the bending specimen;

[0036] Figure 4 is the residual stress nephogram of one direction of the cross specimen in Embodiment 1 of the present invention;

[0037] Figure 5 is the residual stress nephogram of the other direction of the cross specimen in Embodiment 1 of the present invention;

[0038] Figure 6 is the residual stress nephogram of one direction of the cross specimen in Embodiment 2 of the present invention;

[0039] Figure 7 is the residual stress nephogram of the other direction of the cross specimen in Embodiment 2 of the present invention;

[0040] Figure 8 is the schematic diagram of specimen installation in Embodiment 3 of the present invention;

[0041] Figure 9 is the residual stress nephogram of one direction of the cross specimen in Embodiment 3 of the present invention;

[0042] Figure 10 is the residual stress nephogram of the other direction of the cross specimen in Embodiment 3 of the present invention;

[0043] Figure 11 is the schematic diagram of specimen installation in Embodiment 4 of the present invention.

[0044] The reference numerals are shown as:

[0045] 1, bolt; 2, test bench; 3, square steel; 4, ejector rod; 5, flange; 6, ejector rod spacer; 7, bolt hole; 8, supporting roller; 9, nut; 10, ejector rod hole; 11, cross-bending specimen; 111, arm; 112, middle position. Detailed implementation manners

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0048] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.

[0049] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal", and "top, bottom" are generally based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus cannot be construed as limiting the protection scope of the present invention; the orientation words "inner, outer" refer to the inside and outside relative to the contour of each component itself.

[0050] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "upper" etc. can be used here to describe the spatial positional relationship of a device or feature shown in the figure with other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figure. For example, if the device in the attached drawing is inverted, the device described as "above or over other devices or structures" will then be positioned "below or under other devices or structures". Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations are made for the spatial relative descriptions used here.

[0051] In addition, it should be noted that the use of terms such as "first", "second" etc. to define components is merely for the convenience of differentiating the corresponding components. Without additional statements, the above terms have no special meanings, and thus should not be construed as limiting the protection scope of the present invention.

[0052] As Figures 1-11 shown, the present invention provides a cross-bending bi-directional residual stress manufacturing device, which includes:

[0053] An experimental bench 2, a roller mechanism and a jack mechanism. There are multiple roller mechanisms, and the multiple roller mechanisms are spaced apart on the experimental bench. The jack mechanism is located in the space surrounded by the multiple roller mechanisms, and the jack mechanism is also arranged on the experimental bench 2. The roller mechanism is arranged at the horizontal end of the cross-bending specimen 11, and the jack mechanism is arranged at the middle position 112 of the cross-bending specimen. Through the jack mechanism, pressure can be applied vertically to the middle position of the cross-bending specimen 11, and at the same time, in cooperation with the lifting of the rollers, compressive or tensile stress can be formed on the upper surface of the cross-bending specimen 11.

[0054] In the present invention, by arranging the jack mechanism on the experimental bench and in the space surrounded by multiple roller mechanisms, the jack mechanism can apply pressure vertically to the middle position of the cross-bending specimen, and at the same time, in cooperation with the lifting of the rollers, compressive or tensile stress can be formed on the upper surface of the cross-bending specimen, so that the residual stress on the surface of the cross-bending specimen can be effectively and accurately manufactured and measured. The device and method of the present invention are simple and flexible, with low cost, and solve the problems of complex manufacturing process of surface bi-directional residual stress and difficulty in accurately measuring the numerical value of bi-directional residual stress at present.

[0055] In some embodiments,

[0056] A plurality of bolt holes 7 and one ejector rod hole 10 are provided on the test bench 2. The roller mechanism includes rollers 8, bolts 1 and nuts 9. The rollers 8 are sleeved on the bolts 1, and the bolts 1 are inserted into the bolt holes 7. Nuts 9 are sleeved on the bolts 1 both above and below the rollers 8. The end of the cross-bending specimen 11 can be arranged at the upper end or the lower end of the rollers 8 to provide compressive or tensile stress to the cross-bending specimen.

[0057] In the present invention, nuts are also sleeved on the bolts both above and below the rollers, and the end of the cross-bending specimen can be arranged at the upper end or the lower end of the rollers to provide compressive or tensile stress to the cross-bending specimen, so that different directions and different types of stress can be applied and provided to the cross-bending specimen, the stress application range is increased, and the versatility of the residual stress manufacturing device of the present invention is improved.

[0058] The cross-bending bidirectional residual stress manufacturing device of the present invention includes a test bench, a roller mechanism and an ejector rod mechanism, wherein:

[0059] There are a plurality of bolt holes and one ejector rod hole on the test bench. The plurality of bolt holes are arranged in a cross shape on the test bench, and the ejector rod hole is located at the center of the test bench. A flange with internal threads is installed above the ejector rod hole, and the flange is concentric with the ejector rod hole. The roller mechanism includes rollers, bolts and nuts. The ejector rod mechanism includes an ejector rod, a flange and an ejector rod pad.

[0060] The test bench is used to fix the roller mechanism and connect the flange of the ejector rod mechanism. The roller mechanism is fixed on the test bench through the bolt holes. The ejector rod mechanism is connected to the test bench through the flange. The roller mechanism is used to fix the specimen and apply a load on the specimen. The ejector rod mechanism is used to apply a load on the specimen.

[0061] The bolt holes can be a plurality of circular holes or long strip holes, and the ejector rod mechanism uses a threaded screw, a jack or an electric cylinder for loading.

[0062] In some embodiments,

[0063] The cross-bending specimen 11 includes the middle position 112 and at least two arms 111. The arms 111 are the ends. One end of each arm is connected to the middle position 112, and the other end extends away from the middle position 112. A plurality of the bolt holes 7 are arranged at intervals along the extending direction of the arms 111 of the cross-bending specimen 11, so that the roller mechanism can be set on different bolt holes 7 according to the length of the arm, and the roller mechanism can also be set on different bolt holes 7 according to the position of the stress to be applied.

[0064] The present invention also sets a plurality of bolt holes on the test bench, and the plurality of bolt holes are arranged at intervals along the extending direction of the arms of the cross-bending specimen, so that the roller support mechanism can be set on different bolt holes according to the length of the arms, and the roller support mechanism can also be set on different bolt holes according to the position of the stress to be applied, which is applicable to cross-bending specimens of different sizes, and can conveniently form bidirectional residual stresses of any size combination on the material surface, solving the problem that large-size specimens are required in the existing technology for manufacturing bidirectional surface residual stresses by the bending method.

[0065] In some embodiments,

[0066] At least two arms 111 include a first arm, a second arm, a third arm and a fourth arm. One end of the first arm is connected to the middle position 112, and the other end extends away from the middle position 112. One end of the second arm is connected to the middle position 112, and the other end extends away from the middle position 112. One end of the third arm is connected to the middle position 112, and the other end extends away from the middle position 112. One end of the fourth arm is connected to the middle position 112, and the other end extends away from the middle position 112. The extending directions of the first arm and the second arm are opposite to each other, and the extending directions of the third arm and the fourth arm are opposite to each other.

[0067] This is a preferred structural form of the cross-bending specimen of the present invention. By setting the arms as the first arm and the second arm that extend in two opposite directions respectively, rollers can be set on these two arms respectively, so as to apply stress to these two arms and detect the residual stress. The third arm and the fourth arm that extend in two opposite directions respectively can also have rollers set on these two arms respectively, so as to apply stress to these two arms and detect the residual stress. The extending directions of the first arm and the first arm are on the same straight line and extend in opposite directions. The extending directions of the third arm and the fourth arm are on the same straight line and extend in opposite directions. The extending directions of the first arm and the third arm are preferably perpendicular to each other.

[0068] In some embodiments,

[0069] The supporting roller 8 extends along the width direction of the arm 111 of the cross-bending specimen 11 to form the length direction of the supporting roller 8. The width direction of the arm 111 of the cross-bending specimen 11 is perpendicular to the extending direction of the arm 111. One supporting roller 8 cooperates with two bolts 1. One end of the length direction of the supporting roller 8 penetrates through one bolt 1, and at least one nut 9 is arranged above and below the bolt 1 located on the supporting roller 8. The test bench 2 has a bolt hole 7 that cooperates with the bolt 1, and the bolt 1 can be inserted into the bolt hole 7. The other end of the length direction of the supporting roller 8 penetrates through one bolt 1, and at least one nut 9 is also arranged above and below the bolt 1 located on the supporting roller 8. The test bench 2 has a bolt hole 7 that cooperates with the bolt 1, and the bolt 1 can be inserted into the bolt hole 7.

[0070] This is the preferred connection relationship among the supporting roller, bolt, nut and arm of the present invention, that is, the supporting roller is fixed to the test bench through the bolts and nuts at both ends. Through the supporting roller, contact can be made with the arm of the cross-bending specimen to apply compressive or tensile stress to the arm, so as to realize the application of stress to the cross-bending specimen and effective detection.

[0071] In some embodiments,

[0072] The bolt 1 on one side of the supporting roller 8 is located on one side of the arm 111 and is spaced from the arm 111 after passing through the supporting roller 8. The bolt 1 on the other side of the supporting roller 8 is located on the other side of the arm 111 and is spaced from the arm 111 after passing through the supporting roller 8, so that the arm 111 is located between the two bolts 1.

[0073] The present invention further preferably clamps the arm between the bolts on both sides connected to the supporting roller, so that the arm is located between the two bolts. By adjusting the bolts, the height of the supporting roller can be adjusted, so as to adjust the magnitude of the stress applied to the arm and ensure the uniformity of the magnitude of the stress applied to the arm.

[0074] In some embodiments,

[0075] The ejector mechanism includes an ejector rod 4, a flange 5 and an ejector rod spacer 6. At least part of the ejector rod 4 is located below the test bench 2. The flange 5 is arranged in the ejector rod hole 10. The lower end of the flange 5 is connected to the ejector rod 4, and the upper end of the flange 5 is connected to the ejector rod spacer 6. The ejector rod spacer 6 is located below the middle position 112 of the cross-bending specimen 11. The ejector rod 4 can move upward to drive the ejector rod spacer 6 to move upward through the flange 5, so as to apply an upward pressure to the middle position 112 of the cross-bending specimen 11.

[0076] The ejector rod mechanism of the present invention preferably includes an ejector rod, a flange, and an ejector rod spacer. The flange can be disposed in the ejector rod hole. The lower end of the flange is connected to the ejector rod, and the upper end is connected to the ejector rod spacer. The ejector rod spacer can be lifted by the upward movement of the ejector rod, thereby applying pressure to the middle position of the cross-bending specimen, achieving the arm bending of the cross-bending specimen and generating tensile or compressive stress, and achieving the purpose of stress application and accurate detection.

[0077] In some embodiments,

[0078] The top surface of the ejector rod spacer 6 is a spherical structure, the flange 5 is a thrust bearing, and the lower end of the ejector rod 4 is connected to a threaded screw, a jack, or an electric cylinder.

[0079] The present invention further preferably has the top surface of the ejector rod spacer as a spherical structure, which can increase the contact area with the middle position of the cross-bending specimen and improve the uniformity of stress application. The lower end of the ejector rod can apply an upward thrust to the lower end of the ejector rod through a threaded screw, a jack, or an electric cylinder, so that the ejector rod can lift the ejector rod spacer upward, thereby applying an upward pressure to the middle position of the cross-bending specimen.

[0080] As Figure 1 shown, a cross-bending biaxial residual stress manufacturing device provided by the present invention includes a test bench 2, a support roller mechanism, and an ejector rod mechanism. There are a plurality of bolt holes 7 and one ejector rod hole 10 on the test bench 2. The bolt holes 7 are arranged in a cross shape on the test bench, and the ejector rod hole 10 is located at the center of the test bench. A flange 5 with internal threads is installed above the ejector rod hole 10, and the flange 5 is concentric with the ejector rod hole 10. The support roller mechanism includes support rollers 8, bolts 1, and nuts 9. The ejector rod mechanism includes an ejector rod 4, a flange 5, and an ejector rod spacer 6. The top surface of the ejector rod spacer 6 is spherical, and a thrust bearing is fixed to the bottom surface to prevent excessive friction between the ejector rod 4 and the ejector rod spacer 6 when a screw is used as the ejector rod 4 for loading, resulting in difficult loading.

[0081] The test bench 2 is used to fix the support roller mechanism and the flange. The support roller mechanism is fixed to the test bench 2 through the bolt holes 7, and the ejector rod 4 is connected to the test bench 2 through the flange 5. The ejector rod mechanism is loaded by a threaded screw, a jack, or an electric cylinder. Square steel 3 is fixed at the four corners of the test bench 2.

[0082] In some embodiments,

[0083] The arm 111 of the cross-bending specimen 11 is located between the support roller 8 and the nut 9 below the support roller 8, and the support roller 8 can apply tensile stress to the cross-bending specimen when the ejector rod 4 moves upward; and / or, the arm 111 of the cross-bending specimen 11 is located between the support roller 8 and the nut 9 above the support roller 8, and the support roller 8 can apply compressive stress to the cross-bending specimen 11 when the ejector rod 4 moves upward.

[0084] The present invention also sleeved nuts on the bolt, both above and below the supporting roller. The end of the cross-bending specimen can be set at the upper or lower end of the supporting roller to provide compressive stress (preferably through the upward movement of the supporting roller) or tensile stress (preferably through the upward movement of the ejector rod) to the cross-bending specimen, enabling the application and provision of different directions and different types of stress to the cross-bending specimen, improving the stress application range, and enhancing the versatility of the residual stress manufacturing device of the present invention.

[0085] The present invention also provides a method for using the cross-bending two-way residual stress manufacturing device as described above, which includes:

[0086] S1, Process the cross-bending specimen 11 and place the cross-bending specimen 11 on the experimental bench, and adjust the distance between the supporting rollers and the height of the supporting rollers in two directions of the cross-specimen according to the desired surface stress state of the specimen.

[0087] S2, Establish a finite element model of the cross-bending process according to the specimen size, the distance between the supporting rollers, and the height of the supporting rollers in step S1, conduct simulation calculations of the cross-bending process, obtain the residual stress distribution nephogram on the surface of the specimen after bending, and extract the displacement values of the ejector rod and the supporting rollers at this time from the simulation results.

[0088] S3, Load the specimen through the ejector rod mechanism and / or the nuts on the supporting rollers. When the displacements of the ejector rod and the supporting rollers reach the values in step S2, stop further loading and maintain this state.

[0089] S4, Select the approximate position of instrumented indentation according to the simulation results, conduct instrumented indentation tests on the cross-bending specimen, measure the accurate position of the indentation on the cross-bending specimen, determine the two-way residual stress value at this position before indentation according to the simulation results, and use this value to correct the results of the instrumented indentation test or establish a new mechanical property calculation model for instrumented indentation.

[0090] The method for using the cross-bending two-way residual stress manufacturing device of the present invention can effectively and accurately manufacture and measure the residual stress on the surface of the cross-bending specimen, and is also applicable to cross-bending specimens of different sizes, conveniently forming any combination of two-way residual stress on the material surface, solving the problem that the existing bending method for manufacturing two-way surface residual stress requires large-size specimens. It can also apply and provide different directions and different types of stress to the cross-bending specimen, improving the stress application range and enhancing the versatility of the method for using the residual stress manufacturing device of the present invention.

[0091] The method for using the cross-bending two-way residual stress manufacturing device provided by the present invention includes the following steps:

[0092] Example 1

[0093] (1) Process the cruciform bending specimen 11. As shown, place the cruciform bending specimen 11 on the test bench, and adjust the roller spacing and roller height in two directions of the cruciform specimen according to the surface stress state of the specimen to be obtained. In this embodiment, a bidirectional tensile stress state with equal magnitudes in both directions is to be obtained. Therefore, the roller spacings in the two directions are set to be the same, which is 450 mm, and the roller height is 20 mm. Figure 3 As shown, place the cruciform bending specimen 11 on the test bench, and adjust the roller spacing and roller height in two directions of the cruciform specimen according to the surface stress state of the specimen to be obtained. In this embodiment, a bidirectional tensile stress state with equal magnitudes in both directions is to be obtained. Therefore, the roller spacings in the two directions are set to be the same, which is 450 mm, and the roller height is 20 mm.

[0094] (2) Establish a finite element model of the cruciform bending process according to the specimen size, roller spacing, and roller height in step (1), conduct simulation calculations of the cruciform bending process, and obtain the residual stress distribution nephogram on the surface of the specimen after bending. As shown in and, a bidirectional tensile stress state is obtained in the cruciform intersection area on the upper surface of the specimen. Extract the displacement values of the ejector rod 4 and the roller 8 at this time from the simulation results, which are 10 mm and 0 mm respectively. Since it is a bidirectional tensile stress state, only the ejector rod 4 needs to be loaded and the roller remains stationary. Figure 4 and Figure 5 As shown in and, a bidirectional tensile stress state is obtained in the cruciform intersection area on the upper surface of the specimen. Extract the displacement values of the ejector rod 4 and the roller 8 at this time from the simulation results, which are 10 mm and 0 mm respectively. Since it is a bidirectional tensile stress state, only the ejector rod 4 needs to be loaded and the roller remains stationary.

[0095] (3) Load the specimen through the ejector rod mechanism or the nut on the roller. When the displacements of the ejector rod and the roller reach the values in step (2), stop further loading and maintain this state.

[0096] (4) Select the approximate position of instrumented indentation according to the simulation results, conduct instrumented indentation tests on the cruciform bending specimen, and measure the accurate position of the indentation on the cruciform bending specimen. After measurement, the accurate indentation position in this embodiment is shown by the black dots in. According to the simulation results, the bidirectional residual stress values at this position before indentation are 923 MPa and 924 MPa respectively (the bidirectional residual stress refers to the bidirectional residual stress along the surface of the specimen, that is, the residual stress along the horizontal and vertical directions of the cruciform specimen, that is, the stresses in 2 horizontal directions). This value can be used to correct the results of instrumented indentation tests or establish a new mechanical property calculation model for instrumented indentation. Figure 4 According to the simulation results, the bidirectional residual stress values at this position before indentation are 923 MPa and 924 MPa respectively (the bidirectional residual stress refers to the bidirectional residual stress along the surface of the specimen, that is, the residual stress along the horizontal and vertical directions of the cruciform specimen, that is, the stresses in 2 horizontal directions). This value can be used to correct the results of instrumented indentation tests or establish a new mechanical property calculation model for instrumented indentation.

[0097] Example 2

[0098] In this embodiment, an unequal bidirectional tensile residual stress state is created on the specimen surface. The difference from Example 1 is that different roller spacings are set in the two directions, which are 450 mm and 200 mm respectively. The bidirectional residual stresses at the obtained indentation positions are 884 MPa and 675 MPa respectively.

[0099] Example 3

[0100] In this embodiment, a residual stress state with tension and compression in two directions is created on the specimen surface. The fixed position of the specimen is as shown in Figure 8As shown, the difference from Example 1 is that two support rollers in one direction of the cross-shaped specimen are located below the specimen. After the ejector rod displacement reaches 10 mm (moving upward to lift the support rollers in the left and right directions upward to obtain compressive stress in the left and right directions, so the stress state on the surface of the specimen is that the front and rear arms are in tensile stress and the left and right arms are in compressive stress), turn the nuts of the two support rollers located below the specimen to move the support rollers upward by 20 mm. The obtained residual stress contour map is as Figure 10 and Figure 11 shown. The bidirectional residual stresses at the indentation positions obtained are -385 MPa and 343 MPa respectively.

[0101] Example 4

[0102] In this embodiment, compressive stresses are simultaneously created in two directions on the surface of the specimen. The fixing position of the specimen is as Figure 11 shown. The difference from Example 1 is that two pairs of support rollers are fixed at the cross-shaped part of the specimen. The support rollers at the ends of the cross-shaped specimen are located below the specimen. Turn the nuts below the support rollers at the ends of the cross-shaped specimen to raise the support rollers at the cross ends, forming a bidirectional compressive stress state at the cross-shaped part.

[0103] Figure 11 There is only a support roller above the specimen at the middle position. The support rollers at the left and right and front and rear ends all rise. The support roller at the middle position is above the specimen to block the specimen and prevent the specimen from moving upward. The function of this embodiment is to obtain a stress state where both the left and right and the front and rear are in compressive stress, while in Example 3, the left and right are in compressive stress and the front and rear are in tensile stress.

[0104] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and variations can still be made, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. A cross-bending bidirectional residual stress manufacturing device, characterized in that: include: A test bench (2), a supporting roller mechanism and a push rod mechanism, wherein the supporting roller mechanism is multiple and the multiple supporting roller mechanisms are spaced apart on the test bench, the push rod mechanism is located in a space surrounded by the multiple supporting roller mechanisms, and the push rod mechanism is also arranged on the test bench (2). The supporting roller mechanism is arranged at the end of the cross bending specimen (11) in the horizontal direction, and the push rod mechanism is arranged at the middle position (112) of the cross bending specimen. The push rod mechanism can apply pressure to the middle position of the cross bending specimen (11) in the vertical direction, and simultaneously cooperate with the lifting and lowering of the supporting rollers, thereby forming compressive or tensile stress on the upper surface of the cross bending specimen (11).

2. The cross-bending bidirectional residual stress manufacturing device according to claim 1 is characterized in that: The test bench (2) is provided with a plurality of bolt holes (7) and a push rod hole (10); the support roller mechanism comprises a support roller (8), a bolt (1) and a nut (9); the support roller (8) is inserted into the bolt (1); the bolt (1) is inserted into the bolt hole (7); the nut (9) is sleeved on the bolt (1) and located above and below the support roller (8); the end of the cross-bending specimen (11) can be arranged at the upper end or the lower end of the support roller (8) to provide compressive or tensile stress to the cross-bending specimen.

3. The cross-bending bidirectional residual stress manufacturing device according to claim 2 is characterized in that: The cross bending specimen (11) comprises the middle position (112) and at least two arms (111), wherein the arms (111) are the end portions, wherein one end of each arm is connected to the middle position (112) and the other end extends in a direction away from the middle position (112), and a plurality of bolt holes (7) are arranged at intervals along the extension direction of the arms (111) of the cross bending specimen (11), so that the supporting roller mechanism can be set on different bolt holes (7) according to the length of the arms, and the supporting roller mechanism can also be set on different bolt holes (7) according to the position of the stress to be applied.

4. The cross-bending bidirectional residual stress manufacturing device according to claim 3 is characterized in that: The at least two arms (111) include a first arm, a second arm, a third arm and a fourth arm; one end of the first arm is connected to the middle position (112) and the other end extends in a direction away from the middle position (112); one end of the second arm is connected to the middle position (112) and the other end extends in a direction away from the middle position (112); one end of the third arm is connected to the middle position (112) and the other end extends in a direction away from the middle position (112); one end of the fourth arm is connected to the middle position (112) and the other end extends in a direction away from the middle position (112); the first arm and the second arm have extension directions that are opposite to each other, and the third arm and the fourth arm have extension directions that are opposite to each other.

5. The cross-bending bidirectional residual stress manufacturing device according to claim 3 is characterized in that: The support roller (8) extends along the width direction of the arm (111) of the cross bending specimen (11) to form the length direction of the support roller (8), and the width direction of the arm (111) of the cross bending specimen (11) is perpendicular to the extension direction of the arm (111). One support roller (8) is matched with two bolts (1). One end of the support roller (8) in the length direction is penetrated by a bolt (1), and at least one nut (9) is arranged above and below the support roller (8). The experimental table (2) has a bolt hole (7) that cooperates with the bolt (1), and the bolt (1) can be inserted into the bolt hole (7); the other end of the support roller (8) in the length direction is penetrated by a bolt (1), and at least one nut (9) is arranged above and below the support roller (8). The experimental table (2) has a bolt hole (7) that cooperates with the bolt (1), and the bolt (1) can be inserted into the bolt hole (7).

6. The cross-bending bidirectional residual stress manufacturing device according to claim 5 is characterized in that: The bolt (1) on one side of the supporting roller (8) is passed through the supporting roller (8) and is located on one side of the arm (111) and is spaced apart from the arm (111); the bolt (1) on the other side of the supporting roller (8) is passed through the supporting roller (8) and is located on the other side of the arm (111) and is spaced apart from the arm (111), so that the arm (111) is located between the two bolts (1).

7. The cross-bending bidirectional residual stress manufacturing device according to any one of claims 3 to 6, characterized in that: The push rod mechanism comprises a push rod (4), a flange (5) and a push rod pad (6); at least part of the structure of the push rod (4) is located below the experimental table (2); the flange (5) is arranged in the push rod hole (10); the lower end of the flange (5) is connected to the push rod (4); the upper end of the flange (5) is connected to the push rod pad (6); the push rod pad (6) is located below the middle position (112) of the cross bending specimen (11); the push rod (4) can move upward to drive the push rod pad (6) to move upward through the flange (5), thereby applying upward pressure to the middle position (112) of the cross bending specimen (11).

8. The cross-bending bidirectional residual stress manufacturing device according to claim 7 is characterized in that: The top surface of the push rod pad (6) is a spherical structure, the flange (5) is a thrust bearing, and the lower end of the push rod (4) is connected to a threaded screw, a jack or an electric cylinder.

9. The cross-bending bidirectional residual stress manufacturing device according to claim 7 or 8, characterized in that: The arm (111) of the cross-bending specimen (11) is located between the bottom of the support roller (8) and the nut (9) between the bottom of the support roller (8), and when the push rod (4) moves upward, tensile stress is formed on the upper surface of the cross-bending specimen; and / or, the arm (111) of the cross-bending specimen (11) is located between the top of the support roller (8) and the nut (9) between the top of the support roller (8), and when the support roller (8) moves upward, the support roller (8) can apply compressive stress to the cross-bending specimen (11).

10. A method for using the cross-bending bidirectional residual stress manufacturing device according to any one of claims 7 to 9, characterized in that: include: S1, processing a cross bending specimen (11), placing the cross bending specimen (11) on a test bench, and adjusting the support roller spacing and support roller height in two directions of the cross specimen according to the surface stress state of the specimen to be obtained; S2, establishing a finite element model of the cross bending process according to the sample size, support roller spacing and support roller height in step S1, performing simulation calculation of the cross bending process, obtaining a residual stress distribution cloud map on the surface of the sample after bending, and extracting the displacement values ​​of the push rod and the support roller at this time from the simulation results; S3, loading the sample through the push rod mechanism and / or the nut on the support roller, and when the displacement of the push rod and the support roller reaches the value in step S2, further loading is stopped and this state is maintained; S4, select the approximate position of the instrumented indentation according to the simulation results, perform the instrumented indentation test on the cross-bend specimen, measure the exact position of the indentation on the cross-bend specimen, and determine the bidirectional residual stress value at this position before indentation according to the simulation results. This value can be used to correct the instrumented indentation test results or establish a new instrumented indentation mechanical property calculation model.

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