A material shear fatigue performance testing method

Abstract

A method for testing the shear fatigue performance of materials, using a special shear fatigue device, the hardness of the material used in the shear fatigue device is not less than 500 HV; first, assemble the shear fatigue device and the sample so that the upper active shear blade (6), the lower active shear blade A (7) and the lower active shear blade B (8) are all tightly fitted to the sample; ensure that the sample and the shear fatigue device form an integrated structure so that the cross section subjected to the alternating shear force remains unchanged; finally, fix the shear fatigue device with the installed sample on a fatigue testing machine, set the load and frequency, and conduct a shear fatigue experiment, so as to obtain the shear fatigue life of the material under the specified stress. The present invention breaks through the bottleneck of the existing material shear fatigue performance testing method, has a simple device, is easy to operate, has low cost, a wide range of applications, and excellent technical effects; on this basis, it can also be expanded to obtain more extended applications. The present invention has foreseeable and relatively huge economic value and social value.

Description

Technical Field

[0001] The invention relates to the field of technical solution design and application technology for material shear fatigue performance testing, and in particular provides a material shear fatigue performance testing method. Background Art

[0002] In the prior art, in the field of materials science, especially in the engineering application of metal structures, "shear fatigue" refers to the fatigue damage caused by components being subjected to alternating shear forces. In actual working conditions, many components such as bolts, welds, gears, rivets and connecting keys are subjected to alternating shear forces. Determining the shear fatigue performance of these components can provide experimental basis for actual engineering.

[0003] In the testing practice of the existing technology, the shear fatigue performance testing methods for materials are very limited, and the applicable objects of the relevant methods are usually relatively single and not universal; and there is no effective method for the shear fatigue performance measurement of general materials. For the usual axial tension and axial compression fatigue, threads are set at both ends of the sample or the test machine can directly clamp the sample, so that the sample and the test machine form an integral structure, which is convenient for avoiding the common idle stroke stage when applying alternating loads and thus avoiding experimental errors.

[0004] However, the above statement is basically limited to theoretical existence; because for the shear fatigue determination of materials, it is difficult for the sample to form a whole with the test machine. The key problem is that there is a gap between the sample and the testing machine or experimental device, which will inevitably cause the appearance of empty strokes under the action of alternating loads, causing the application of alternating loads to be inconsistent with the actual value, which is also a bottleneck in the shear fatigue performance test of materials. Due to the gap between the sample and the testing machine or test device, during the loading process of the alternating load, the cross-section affected by the shear force will also change in real time, and only fatigue life with large deviations can be obtained. In the prior art, a Chinese patent application document entitled "A Bolt Shear Fatigue Test Fixture Device" with publication number CN202582991U discloses a usable device, in which: since the sample itself is a bolt, it can be fixed in a threaded hole, so that the sample to be tested and the test device form an integrated structure, which effectively avoids the existence of a gap. However, this device has great limitations. It is only suitable for samples with bolt structures. Moreover, due to the presence of threaded structures on the surface of the bolts, notches are inevitably introduced, which leads to stress concentration when subjected to force, causing early fracture of the sample. Therefore, samples with this type of thread cannot be extended to other more general working conditions.

[0005] In practical engineering, a simple and effective method is needed to measure the shear fatigue properties of materials, but there is no feasible method at present. Therefore, people are eager to obtain a test method with excellent technical effects suitable for the shear fatigue properties of materials. Summary of the invention

[0006] The purpose of the present invention is to provide a testing method which has excellent technical effect and is applicable to the shear fatigue performance of materials, so as to solve the defects of the prior art and realize the real determination of the shear fatigue performance of materials.

[0007] The present invention provides a material shear fatigue performance testing method, which is characterized by: using a special shear fatigue device for material shear fatigue performance testing; the hardness of the material used in the shear fatigue device is required to be not less than 500HV; that is, in the process of alternating shear load loading, the shear device is rigid and has no macroscopic elastic deformation;

[0008] The overall structure of the shear fatigue device is as follows: the middle part is a large cylindrical structure, and the two ends are small cylindrical structure A10 and small cylindrical structure B11, and the small cylindrical structure A10 and the small cylindrical structure B11 are the clamping ends of the fatigue device; together they constitute a coaxial overall structure; wherein: the shear fatigue device of the overall structure is divided into two parts: an upper shear couple 1 and a lower shear couple 2; the upper shear couple 1 and the lower shear couple 2 are centrally symmetrical structures and are combined into an integral arrangement in a centrally symmetrical form; the joint surface between the two is a cross section parallel to the axial direction of the large cylinder; the sample slot 9 is arranged at the center position of the large cylinder along the height direction, and is also perpendicular to the axial direction of the large cylinder and is a through slot structure that runs through the diameter of the large cylinder;

[0009] The shear fatigue device is also provided with an upper movable shear blade 6, a lower movable shear blade A7 and a lower movable shear blade B8; the sample slot 9 and the upper movable shear blade 6 together constitute an movable bin A12 of the upper shear couple, the sample slot 9 and the lower movable shear blade A7 together constitute an movable bin B13 of the lower shear couple, the sample slot 9 and the lower movable shear blade B8 together constitute an movable bin C14 of the lower shear couple, the movable bin A12, the movable bin B13 and the movable bin C14 are arranged parallel to the sample slot 9 and are also perpendicular to the axial direction of the large cylindrical structure in the shear fatigue device; the upper movable shear blade 6 cooperates with the lower movable shear blade A7 and the lower movable shear blade B8 to form a shear surface that can act on the cross section of the sample;

[0010] The specific process of the material shear fatigue performance test method is: first, assemble the shear fatigue sample according to the requirements: after assembly, the upper active shear blade 6, the lower active shear blade A7 and the lower active shear blade B8 are all closely fitted with the sample; ensure that the sample and the shear fatigue device form an integrated structure, ensure that the fatigue testing machine will not have an empty stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear force remains unchanged; during the experiment, the alternating load applied by the testing machine on the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device on the sample;

[0011] Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine, and the corresponding load and frequency are set to carry out the shear fatigue test.

[0012] The material shear fatigue performance testing method of the present invention preferably claims the following:

[0013] The upper shear couple 1 and the lower shear couple 2 are also provided with hole structures parallel to the axial direction of the small cylindrical structure A10 and the small cylindrical structure B11, and threaded connectors are provided in the holes;

[0014] The upper shear couple 1 is provided with a hole structure coaxial with the axis of the small cylindrical structure, and a threaded connection member is provided in the hole: bolt A3; the lower shear couple 2 is provided with two hole structures parallel to the axis of the small cylindrical structure, and threaded connection members are provided in the holes: bolt B4 and bolt C5;

[0015] Rotating the adjustment bolts A3, B4 and C5 can make the upper movable shear blade 6, the lower movable shear blade A7 and the lower movable shear blade B8 fit tightly against the sample; ensuring that the sample and the shear fatigue device form an integrated structure, ensuring that the fatigue testing machine will not have an idle stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross-section of the sample subjected to the alternating shear force remains unchanged.

[0016] The parallelism between the relative width surface and the relative thickness surface of the sample slot 9 is not greater than 40 μm;

[0017] In the material shear fatigue performance test method, when performing a shear fatigue test, if the upper shear couple 1 of the shear fatigue device is fixed, the lower shear couple 2 reciprocates up and down to apply an alternating shear load. During the upward movement of the lower shear couple 2, the sample is subjected to a force such as Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. If the lower shear couple 2 is fixed and the upper shear couple 1 reciprocates up and down to apply an alternating shear load, the force on the sample is just the opposite. The relationship between the shear stress τ on any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows

[0018]

[0019] ①Where w and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0020] In the shear fatigue device used in the material shear fatigue performance test method, a sample slot 9 is provided in the diameter direction at the center of the large cylinder in the height direction perpendicular to the axis by using the wire cutting method, the sample slot 9 is perpendicular to the axis of the device, and the parallelism between the relative surfaces of the width and the relative surfaces of the thickness of the sample slot 9 is not greater than 40 μm; then the cylinder is cut into two shear couples by using the wire cutting method; for the upper shear couple 1, the wire cutting is continued to be used, and the hole is expanded upward on the basis of the original sample slot 9, and the cut material is used as the upper active shear blade 6, and the small cylindrical end of the upper shear couple 1 is provided with a downward hole; the lower end of the bolt A3 is in contact with the upper active shear blade 6;

[0021] For the lower shear couple 2, continue to use wire cutting to expand the hole downward on the basis of the original sample slot 9, and the cut material is used as the lower active shear edge A7 and the lower active shear edge B7. Then drill upward from the middle position of the small cylindrical structure B11 of the lower shear couple 2 and the large cylindrical connection surface (two positions), and finally prepare bolts B4 and bolts C5. The upper ends of bolts B4 and bolts C5 are in contact with the lower active shear edge A7 and the lower active shear edge B8 respectively;

[0022] Finally, the contact surfaces of the two shear couples were polished with sandpaper so that the roughness of the contact surfaces of the upper shear couple 1 and the lower shear couple 2 was no more than 10 μm. The shape of the obtained shear fatigue device is as shown in the attached figure. Figure 1-7 As shown;

[0023] The width and thickness of the sample slot 9 are adjustable. Specifically, when implementing the scheme, the size of the sample can be determined according to the size of the actual product or component, and then the size of the sample slot 9 can be determined. For some components that are too large, samples of suitable size can be cut from the components. Therefore, this shear fatigue device can be used to measure the shear fatigue performance of products and components of various sizes. Therefore, this shear fatigue test method has a very wide range of applications. The shear fatigue sample is a rectangular parallelepiped, and its shape and size are as follows: Fig.10 shown. Fig.10 The width and thickness of the medium shear fatigue sample are matched with the size of the sample slot 9 of the shear fatigue apparatus.

[0024] The sample preparation process and requirements are as follows: first determine the loading direction of the shear fatigue load. For the rectangular sample of the present invention, the loading direction of the load is along the thickness direction of the sample; then use wire cutting to process the blank of suitable size (the blank has a certain processing allowance); finally, polish it one by one with coarse sandpaper and fine sandpaper (the last sandpaper used is 2000#), so that there are no wire cutting marks on the four sides of the sample along the length direction, the surface roughness is not more than 10μm, and the parallelism of the relative surfaces is not more than 20μm.

[0025] The material shear fatigue performance test method meets the following specific operating requirements:

[0026] First, fix the upper movable shear blade 6 to the upper end of the movable chamber A12 of the upper shear couple 1 with strong glue; then, match the upper shear couple 1 with the lower shear couple 2, respectively install the lower movable shear blade A7 and the lower movable shear blade B8 in the movable chamber B13 and the movable chamber C14 of the lower shear couple 2, align the sample slots 9 of the upper shear couple 1 and the lower shear couple 2, and load the sample into the sample slot 9; then adjust the positions of the lower movable shear blade A7 and the lower movable shear blade B8 so that the outer contours of the lower movable shear blade A7 and the lower movable shear blade B8 are completely fitted with the outer contour of the lower shear couple 2; then, Tighten bolts B4, C5 and A3 in sequence. In the process of tightening bolts B4 and C5, lower active shear blades A7 and B8 will be closely fitted to the sample respectively. In the process of tightening bolt A3, the fastening force of bolt A3 will break through the bonding effect of super glue, so that upper active shear blade 6 will be closely fitted to the sample. Thus, the sample and the shear fatigue device form an integrated structure, so that the fatigue testing machine will not have an idle stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear load remains unchanged.

[0027] Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine. The testing machine achieves the fixing effect by clamping the small cylindrical structure A10 and the small cylindrical structure B11 at both ends of the shear fatigue device; then the corresponding alternating shear load and frequency are set to carry out the shear fatigue test.

[0028] During the experiment, the alternating load applied by the testing machine to the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device to the sample.

[0029] When conducting a shear fatigue test, if the upper shear couple 1 of the shear fatigue device is fixed, the lower shear couple 2 reciprocates up and down to apply an alternating shear load. During the upward movement of the lower shear couple 2, the force on the sample is as follows: Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. If the lower shear couple 2 is fixed and the upper shear couple 1 reciprocates up and down to apply an alternating shear load, the force on the sample is just the opposite. The relationship between the shear stress τ on any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows:

[0030]

[0031] ①Where w and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0032] The present invention designs a material shear fatigue performance testing method with strong operability and excellent technical effect. The present invention breaks through the limitations of the previous methods for measuring the shear fatigue performance of materials, making the measurement of the shear fatigue performance of materials simple and convenient. It has the outstanding characteristics of simple method, easy operation, low cost, wide applicability and excellent technical effect, and on this basis, it can also be expanded to obtain more extended applications. The present invention has predictable and relatively huge economic value and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0034] Figure 1 It is the outer contour diagram of the whole shear fatigue device;

[0035] Figure 2 It is the front view of the shear fatigue device;

[0036] Figure 3 It is the left view of the shear fatigue device;

[0037] Figure 4 This is the front view of the upper shear couple of the shear fatigue device;

[0038] Figure 5 It is the left view of the upper shear couple of the shear fatigue device;

[0039] Figure 6 This is the front view of the lower shear couple of the shear fatigue device;

[0040] Figure 7 It is the left view of the lower shear couple of the shear fatigue device;

[0041] Figure 8 The upper shear couple is fixed, and the schematic diagram of the force on the sample during the upward movement of the lower shear couple;

[0042] Fig. 9 Schematic diagram of the force on the sample when the upper shear couple is fixed and the lower shear couple moves downward

[0043] Fig.10 The shape and size diagram of the shear fatigue specimen;

[0044] Fig.11 This is the shear fatigue fracture morphology of Ti-6Al-4V alloy fasteners. DETAILED DESCRIPTION

[0045] Example 1

[0046] A material shear fatigue performance testing method, which uses a special shear fatigue device for material shear fatigue performance testing; the hardness of the material used in the shear fatigue device is required to be not less than 500HV; that is, during the process of alternating shear load loading, the shear device is rigid and has no macroscopic elastic deformation;

[0047] The overall structure of the shear fatigue device is as follows: the middle part is a large cylindrical structure, and the two ends are small cylindrical structure A10 and small cylindrical structure B11. The small cylindrical structure A10 and the small cylindrical structure B11 are the clamping ends of the test machine of the shear fatigue device; together they constitute a coaxial overall structure; wherein: the shear fatigue device of the overall structure is divided into two parts: an upper shear couple 1 and a lower shear couple 2; the upper shear couple 1 and the lower shear couple 2 are centrally symmetrical structures and are combined into an integral arrangement in a centrally symmetrical form; the joint surface between the two is a cross section parallel to the axial direction of the large cylinder; the sample slot 9 is arranged at the center position of the large cylinder along the height direction, and is also perpendicular to the axial direction of the large cylinder and is a through slot structure that runs through the diameter of the large cylinder;

[0048] The shear fatigue device is also provided with an upper movable shear blade 6, a lower movable shear blade A7 and a lower movable shear blade B8; the sample slot 9 and the upper movable shear blade 6 together constitute an movable bin A12 of the upper shear couple, the sample slot 9 and the lower movable shear blade A7 together constitute an movable bin B13 of the lower shear couple, the sample slot 9 and the lower movable shear blade B8 together constitute an movable bin C14 of the lower shear couple, the movable bin A12, the movable bin B13 and the movable bin C14 are arranged parallel to the sample slot 9 and are also perpendicular to the axial direction of the large cylindrical structure in the shear fatigue device; the upper movable shear blade 6 cooperates with the lower movable shear blade A7 and the lower movable shear blade B8 to form a shear surface that can act on the cross section of the sample;

[0049] The specific process of the material shear fatigue performance test method is: first, assemble the shear fatigue sample according to the requirements: after assembly, the upper active shear blade 6, the lower active shear blade A7 and the lower active shear blade B8 are all closely fitted with the sample; ensure that the sample and the shear fatigue device form an integrated structure, ensure that the fatigue testing machine will not have an empty stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear force remains unchanged; during the experiment, the alternating load applied by the testing machine on the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device on the sample;

[0050] Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine, and the corresponding load and frequency are set to carry out the shear fatigue test.

[0051] The upper shear couple 1 and the lower shear couple 2 are also provided with hole structures parallel to the axial direction of the small cylindrical structure A10 and the small cylindrical structure B11, and threaded connectors are provided in the holes;

[0052] The upper shear couple 1 is provided with a hole structure coaxial with the axis of the small cylindrical structure, and a threaded connection member is provided in the hole: bolt A3; the lower shear couple 2 is provided with two hole structures parallel to the axis of the small cylindrical structure, and threaded connection members are provided in the holes: bolt B4 and bolt C5;

[0053] Rotating the adjustment bolts A3, B4 and C5 can make the upper movable shear blade 6, the lower movable shear blade A7 and the lower movable shear blade B8 fit tightly against the sample; ensuring that the sample and the shear fatigue device form an integrated structure, ensuring that the fatigue testing machine will not have an idle stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross-section of the sample subjected to the alternating shear force remains unchanged.

[0054] The parallelism between the relative width surface and the relative thickness surface of the sample slot 9 is not greater than 40 μm;

[0055] In the material shear fatigue performance test method, when performing a shear fatigue test, if the upper shear couple 1 of the shear fatigue device is fixed, the lower shear couple 2 reciprocates up and down to apply an alternating shear load. During the upward movement of the lower shear couple 2, the sample is subjected to a force such as Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. If the lower shear couple 2 is fixed and the upper shear couple 1 reciprocates up and down to apply an alternating shear load, the force on the sample is just the opposite. The relationship between the shear stress τ on any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows

[0056]

[0057] ②W and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0058] In the shear fatigue device used in the material shear fatigue performance test method, a sample slot 9 is provided in the diameter direction at the center of the large cylinder in the height direction perpendicular to the axis by using the wire cutting method, the sample slot 9 is perpendicular to the axis of the device, and the parallelism between the relative surfaces of the width and the relative surfaces of the thickness of the sample slot 9 is not greater than 40 μm; then the cylinder is cut into two shear couples by using the wire cutting method; for the upper shear couple 1, the wire cutting is continued to be used, and the hole is expanded upward on the basis of the original sample slot 9, and the cut material is used as the upper active shear blade 6, and the small cylindrical end of the upper shear couple 1 is provided with a downward hole; the lower end of the bolt A3 is in contact with the upper active shear blade 6;

[0059] For the lower shear couple 2, continue to use wire cutting to expand the hole downward on the basis of the original sample groove 9, and the cut material is used as the lower active shear edge A7 and the lower active shear edge B7. Then drill upward from the middle position of the small cylindrical structure B11 of the lower shear couple 2 and the large cylindrical connection surface (two positions), and finally prepare bolts B4 and bolts C5. The upper ends of bolts B4 and bolts C5 are in contact with the lower active shear edge A7 and the lower active shear edge B7 respectively;

[0060] Finally, the contact surfaces of the two shear couples were polished with sandpaper so that the roughness of the contact surface between the upper shear couple 1 and the lower shear couple 2 was no more than 10 μm. The shape and size of the obtained shear fatigue device are as shown in the attached figure. Figure 1-7 shown.

[0061] The width and thickness of the sample slot 9 are adjustable. Specifically, when implementing the scheme, the size of the sample can be determined according to the size of the actual product or component, and then the size of the sample slot 9 can be determined. For some components that are too large, samples of suitable size can be cut from the components. Therefore, this shear fatigue device can be used to measure the shear fatigue performance of products and components of various sizes. Therefore, this shear fatigue test method has a very wide range of applications. The shear fatigue sample is a rectangular parallelepiped, and its shape and size are as follows: Fig.10 shown. Fig.10 The width and thickness of the medium shear fatigue sample are matched with the size of the sample slot 9 of the shear fatigue apparatus.

[0062] The sample preparation process and requirements are as follows: first determine the loading direction of the shear fatigue load. For the rectangular sample of the present invention, the loading direction of the load is along the thickness direction of the sample; then use wire cutting to process the blank of suitable size (the blank has a certain processing allowance); finally, polish it one by one with coarse sandpaper and fine sandpaper (the last sandpaper used is 2000#), so that there are no wire cutting marks on the four sides of the sample along the length direction, the surface roughness is not more than 10μm, and the parallelism of the relative surfaces is not more than 20μm.

[0063] The material shear fatigue performance test method meets the following specific operating requirements:

[0064] First, fix the upper movable shear blade 6 to the upper end of the movable chamber A12 of the upper shear couple 1 with strong glue; then, match the upper shear couple 1 with the lower shear couple 2, respectively install the lower movable shear blade A7 and the lower movable shear blade B8 in the movable chamber B13 and the movable chamber C14 of the lower shear couple 2, align the sample slots 9 of the upper shear couple 1 and the lower shear couple 2, and load the sample into the sample slot 9; then adjust the positions of the lower movable shear blade A7 and the lower movable shear blade B8 so that the outer contours of the lower movable shear blade A7 and the lower movable shear blade B8 are completely fitted with the outer contour of the lower shear couple 2; then, Tighten bolts B4, C5 and A3 in sequence. In the process of tightening bolts B4 and C5, lower active shear blades A7 and B8 will be closely fitted to the sample respectively. In the process of tightening bolt A3, the fastening force of bolt A3 will break through the bonding effect of super glue, so that upper active shear blade 6 will be closely fitted to the sample. Thus, the sample and the shear fatigue device form an integrated structure, so that the fatigue testing machine will not have an idle stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear load remains unchanged.

[0065] Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine. The testing machine achieves the fixing effect by clamping the small cylindrical structure A10 and the small cylindrical structure B11 at both ends of the shear fatigue device; then the corresponding alternating shear load and frequency are set to carry out the shear fatigue test.

[0066] During the experiment, the alternating load applied by the testing machine to the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device to the sample.

[0067] When conducting a shear fatigue test, if the upper shear couple 1 of the shear fatigue device is fixed, the lower shear couple 2 reciprocates up and down to apply an alternating shear load. During the upward movement of the lower shear couple 2, the force on the sample is as follows: Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. If the lower shear couple 2 is fixed and the upper shear couple 1 reciprocates up and down to apply an alternating shear load, the force on the sample is just the opposite. The relationship between the shear stress τ on any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows:

[0068]

[0069] ①Where w and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0070] The present embodiment relates to a material shear fatigue performance testing method with strong operability and excellent technical effect. The present embodiment breaks through the limitations of the previous methods for measuring the shear fatigue performance of materials, making the measurement of the shear fatigue of materials simple and convenient. It has the outstanding characteristics of simple method, easy operation, low cost, wide applicability and excellent technical effect, and on this basis, it can be expanded to obtain more extended applications. The present embodiment has foreseeable huge economic value and social value.

[0071] Example 2

[0072] Shear fatigue devices, such as Figure 1-7 The device includes an upper shear couple 1 and a lower shear couple 2 installed on a fatigue testing machine. The upper and lower shear couples are cut from a rotating body in the shape of a large cylinder in the middle and small cylinders at both ends. The upper shear couple 1 includes a small cylindrical structure A10, a fixing bolt A3, an upper movable shear blade 6, a movable bin A12 and a sample slot 9 and other structures; the lower shear couple 2 includes a small cylindrical structure B11, a fixing bolt B4 and a bolt C5, a lower movable shear blade A7 and a lower movable shear blade B8, a movable bin B13, a movable bin C14 and a sample slot 9 and other structures. The movable bin and the sample slot of the upper and lower shear couples are a matching combination. The movable shear blade can be firmly fixed on the sample by tightening the bolts A3, the bolts B4 and the bolts C5, eliminating the gap between the sample and the shear fatigue device.

[0073] Shear fatigue specimens, such as Fig.10 The sample is a rectangular parallelepiped. The roughness of the sample surface is required to be no greater than 10μm, and the parallelism of the relative surfaces is required to be no greater than 20μm.

[0074] The specific process of the material shear fatigue performance test method is: first, fix the upper movable shear blade 6 to the upper end of the movable chamber A12 of the upper shear couple 1 with a strong glue; then, match the upper shear couple 1 with the lower shear couple 2, respectively install the lower movable shear blade A7 and the lower movable shear blade B8 in the movable chamber B13 and the movable chamber C14 of the lower shear couple 2, align the sample slots 9 of the upper shear couple 1 and the lower shear couple 2, and install the sample in the sample slot 9; then adjust the positions of the lower movable shear blade A7 and the lower movable shear blade B8 so that the outer contours of the lower movable shear blade A7 and the lower movable shear blade B8 are aligned with the outer contours of the lower shear couple 2. The profile is completely fitted; then, bolts B4, bolts C5 and bolts A3 are tightened in sequence. In the process of tightening bolts B4 and bolts C5, lower active shear blades A7 and lower active shear blades B8 are respectively tightly fitted with the sample. In the process of tightening bolt A3, the tightening force of bolt A3 breaks through the bonding effect of super glue, so that upper active shear blade 6 is tightly fitted with the sample. Thus, the sample and the shear fatigue device form an integrated structure, so that the fatigue testing machine will not have an empty stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear load remains unchanged;

[0075] Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine. The testing machine achieves the fixing effect by clamping the small cylindrical structure A10 and the small cylindrical structure B11 at both ends of the shear fatigue device; then the corresponding alternating shear load and frequency are set to carry out the shear fatigue test.

[0076] During the experiment, the alternating load applied by the testing machine to the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device to the sample.

[0077] When conducting a shear fatigue test, if the upper shear couple 1 of the shear fatigue device is fixed, the lower shear couple 2 reciprocates up and down to apply an alternating shear load. During the upward movement of the lower shear couple 2, the force on the sample is as follows: Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. If the lower shear couple 2 is fixed and the upper shear couple 1 reciprocates up and down to apply an alternating shear load, the force on the sample is just the opposite. The relationship between the shear stress τ on any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows:

[0078]

[0079] ①Where w and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0080] When the sample breaks, the shear fatigue life at this stress and frequency can be obtained.

[0081] Example 3

[0082] Ti-6Al-4V alloy is a dual-phase titanium alloy. It is widely used in aerospace, shipbuilding and other fields due to its high specific strength, excellent corrosion resistance and excellent comprehensive mechanical properties. Ti-6Al-4V alloy fasteners are subjected to alternating shear forces under actual working conditions, and their failure mode is usually shear fatigue failure. Therefore, determining the shear fatigue performance of Ti-6Al-4V alloy fasteners has important engineering significance for their practical applications.

[0083] H11 steel (hardness 620HV) was selected as the material for the shear fatigue device. Figure 1-7 The dimensions of the shear fatigue device are as follows: the width of the sample slot is 8 mm and the thickness is 2 mm. For Ti-6Al-4V alloy fasteners, according to Fig.10 Processing shear fatigue samples: The sample length l = 20mm, width w = 7mm, thickness b = 1.8mm, surface roughness is not greater than 10μm, and the parallelism of the relative surfaces is not greater than 20μm.

[0084] First, fix the upper movable shear blade 6 to the upper end of the movable chamber A12 of the upper shear couple 1 with strong glue; then, match the upper shear couple 1 with the lower shear couple 2, respectively install the lower movable shear blade A7 and the lower movable shear blade B8 in the movable chamber B13 and the movable chamber C14 of the lower shear couple 2, align the sample slots 9 of the upper shear couple 1 and the lower shear couple 2, and load the sample into the sample slot 9; then adjust the positions of the lower movable shear blade A7 and the lower movable shear blade B8 so that the outer contours of the lower movable shear blade A7 and the lower movable shear blade B8 are completely fitted with the outer contour of the lower shear couple 2; then, according to Tighten bolts B4, C5 and A3 one by one. In the process of tightening bolts B4 and C5, lower active shear blade A7 and lower active shear blade B8 will fit closely with the sample respectively. In the process of tightening bolt A3, the tightening force of bolt A3 will break through the bonding effect of super glue, so that upper active shear blade 6 will fit closely with the sample. Thus, the sample and the shear fatigue device form an integrated structure, so that the fatigue testing machine will not have empty stroke when applying alternating shear load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to alternating shear force remains unchanged. Finally, the shear fatigue device with the installed sample is fixed on the MTS Landmark electro-hydraulic servo testing machine, and the corresponding alternating shear load spectrum and frequency are set to carry out the shear fatigue test.

[0085] When conducting a shear fatigue test, the alternating load applied by the testing machine to the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device to the sample. Here, the upper shear couple 1 of the shear fatigue device is fixed, and the lower shear couple 2 reciprocates up and down to apply the alternating shear load. During the upward movement of the lower shear couple 2, the sample is subjected to the force as follows Figure 8 As shown; during the downward movement of the lower shear couple 2, the sample is subjected to the force Fig. 9 As shown. The relationship between the shear stress τ of any section of the sample that is subjected to shear force and the load F applied by the testing machine is as follows:

[0086]

[0087] ①Where w and b represent the width and thickness of the sample, respectively. Fig.10 shown.

[0088] When the sample is damaged, the shear fatigue life of the Ti-6Al-4V alloy fastener under the corresponding alternating shear load can be obtained. By repeating the same method and inputting different alternating shear loads, the shear stress-fatigue life curve (SN curve) of the Ti-6Al-4V alloy fastener can be determined. This curve has great theoretical and experimental basis for engineering practice.

Claims

1. A material shear fatigue performance test method, using a special shear fatigue device for material shear fatigue performance test; the hardness of the material used in the shear fatigue device is required to be not less than 500HV; The overall structure of the shear fatigue device is as follows: the middle part is a large cylindrical structure, and the two ends are small cylindrical structures A (10) and small cylindrical structures B (11). The small cylindrical structures A (10) and small cylindrical structures B (11) are the clamping ends of the testing machine of the shear fatigue device; together they constitute a coaxial overall structure; wherein: The shear fatigue device of the overall structure is divided into two parts: an upper shear couple (1) and a lower shear couple (2); the upper shear couple (1) and the lower shear couple (2) are of a centrally symmetrical structure and are combined into an integral arrangement in a centrally symmetrical form; the sample slot (9) is arranged at the center position of the large cylinder along the axial direction and is perpendicular to the axial direction of the large cylinder and is a through slot structure that penetrates the diameter of the large cylinder; The shear fatigue device is also provided with an upper movable shear blade (6), a lower movable shear blade A (7) and a lower movable shear blade B (8); the sample groove (9) and the upper movable shear blade (6) together constitute an movable chamber A (12) of the upper shear couple, the sample groove (9) and the lower movable shear blade A (7) together constitute an movable chamber B (13) of the lower shear couple, the sample groove (9) and the lower movable shear blade B (8) together constitute an movable chamber C (14) of the lower shear couple, the movable chamber A (12), the movable chamber B (13) and the movable chamber C (14) are arranged parallel to the sample groove (9) and perpendicular to the axial direction of the large cylindrical structure in the shear fatigue device; the upper movable shear blade (6) cooperates with the lower movable shear blade A (7) and the lower movable shear blade B (8) to form a shear surface capable of acting on the cross section of the sample; The specific process of the material shear fatigue performance testing method is as follows: first, assemble the shear fatigue sample according to the requirements; after assembly, make the upper active shear blade (6) and the lower active shear blade A (7) and the lower active shear blade B (8) fit closely with the sample; ensure that the sample and the shear fatigue device form an integrated structure, ensure that the fatigue testing machine will not have an empty stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear force remains unchanged; during the experiment, the alternating load applied by the fatigue testing machine on the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device on the sample; Finally, the shear fatigue device with the sample installed is fixed on the axial tension and compression fatigue testing machine, and the corresponding load and frequency are set to carry out the shear fatigue test; The upper shear couple (1) and the lower shear couple (2) are also provided with hole structures axially parallel to the small cylindrical structure A (10) and the small cylindrical structure B (11), and threaded connectors are provided in the holes; The upper shear couple (1) is provided with a hole structure coaxial with the axis of the small cylindrical structure, and a threaded connection member, bolt A (3), is provided in the hole; the lower shear couple (2) is provided with two hole structures parallel to the axis of the small cylindrical structure, and threaded connection members, bolt B (4) and bolt C (5), are provided in the holes; Rotating the adjustment bolt A (3), the bolt B (4) and the bolt C (5) can make the upper movable shear blade (6), the lower movable shear blade A (7) and the lower movable shear blade B (8) all fit tightly against the sample; ensuring that the sample and the shear fatigue device form an integrated structure, ensuring that the fatigue testing machine will not have an idle stroke when applying an alternating load, and will not be displaced perpendicular to the loading direction, so that the cross section subjected to the alternating shear force remains unchanged; The parallelism between the relative width surfaces and the relative thickness surfaces of the sample slot (9) is no greater than 40 μm; In the material shear fatigue performance test method, when performing a shear fatigue test, if the upper shear couple (1) of the shear fatigue device is fixed, and the lower shear couple (2) reciprocates up and down to apply an alternating shear load; the shear stress τ of any cross section of the sample subjected to the shear force and the load F applied by the testing machine are related as follows: ①W and b represent the width and thickness of the sample respectively; The invention is characterized in that: the shear fatigue device used in the material shear fatigue performance test method adopts a wire cutting method to set a sample groove (9) that penetrates the diameter direction at the center position of the large cylinder along the height direction perpendicular to the axis, the sample groove (9) is perpendicular to the axis of the device, and the parallelism of the relative surfaces of the width and the relative surfaces of the thickness of the sample groove (9) is not greater than 40μm; then the cylinder is cut into two shear couples by wire cutting; for the upper shear couple (1), wire cutting is continued to be used, and the hole is expanded upward on the basis of the original sample groove (9), and the cut material is used as the upper active shear blade (6), and the small cylindrical end of the upper shear couple (1) is provided with a downward hole; the lower end of the bolt A (3) is in contact with the upper active shear blade (6); For the lower shear couple (2), continue to use wire cutting to expand the hole downward on the basis of the original sample groove (9), and the cut material is used as the lower active shear blade A (7) and the lower active shear blade B (8); then drill holes upward (two positions) from the middle position of the small cylindrical structure B (11) of the lower shear couple (2) and the large cylindrical connection surface, and finally prepare bolts B (4) and bolts C (5), and the upper ends of bolts B (4) and bolts C (5) are in contact with the lower active shear blade A (7) and the lower active shear blade B (8) respectively; Finally, the contact surfaces of the two shear couples are polished with sandpaper so that the roughness of the contact surface between the upper shear couple (1) and the lower shear couple (2) is no greater than 10 μm; The width and thickness of the sample slot (9) are adjustable, so that for some oversized components, samples of suitable sizes can be cut from the components; The sample preparation process and requirements are as follows: first determine the loading direction of the shear fatigue load. For rectangular samples, the loading direction of the load is along the thickness direction of the sample; then use wire cutting to process the blank; finally, use coarse sandpaper and fine sandpaper to grind one by one. The final sandpaper used is 2000#, so that there are no wire cutting marks on the four sides of the sample along the length direction, the surface roughness is no more than 10μm, and the parallelism of the relative surfaces is no more than 20μm.

2. The material shear fatigue performance testing method according to claim 1, characterized in that: The material shear fatigue performance test method meets the following specific operating requirements: First, the upper movable shear blade (6) is fixed to the upper end of the movable chamber A (12) of the upper shear couple (1) with strong glue; then, the upper shear couple (1) is matched with the lower shear couple (2), and the lower movable shear blade A (7) and the lower movable shear blade B (8) are respectively installed in the movable chamber B (13) and the movable chamber C (14) of the lower shear couple (2), and the sample grooves (9) of the upper shear couple (1) and the lower shear couple (2) are aligned, and the sample is installed in the sample groove (9); then, the positions of the lower movable shear blade A (7) and the lower movable shear blade B (8) are adjusted so that the outer contours of the lower movable shear blade A (7) and the lower movable shear blade B (8) are aligned with the outer contour of the lower shear couple (2). Completely fit; then, tighten the bolt B (4), bolt C (5) and bolt A (3) in sequence. In the process of tightening the bolt B (4) and bolt C (5), the lower movable shear blade A (7) and the lower movable shear blade B (8) will fit tightly with the sample. In the process of tightening the bolt A (3), the tightening force of the bolt A (3) will break through the bonding effect of the super glue, so that the upper movable shear blade (6) and the sample will fit tightly. As a result, the sample and the shear fatigue device form an integrated structure, so that the fatigue testing machine will not have an idle stroke when applying an alternating load, and the sample will not be displaced in a direction perpendicular to the loading direction, so that the cross section subjected to the alternating shear load remains unchanged; Finally, the shear fatigue device with the sample installed is fixed on the fatigue testing machine, and the testing machine achieves the fixing effect by clamping the small cylindrical structure A (10) and the small cylindrical structure B (11) at both ends of the shear fatigue device; then, the corresponding alternating shear load and frequency are set, and the shear fatigue test can be carried out; During the experiment, the alternating load applied by the testing machine to the shear fatigue device in real time is completely converted into the alternating shear load applied by the shear fatigue device to the sample.

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