A positioning and anti-buckling device for fatigue testing of plate-shaped materials

Abstract

The present invention relates to the technical field of fatigue performance testing of industrial products, and discloses a positioning and anti-buckling device for fatigue testing of plate-like materials, comprising an anti-buckling member, a fastener, and a positioning unit. The number of anti-buckling members is two, and the two anti-buckling members are attached to each other and connected by a fastener. Each anti-buckling member is provided with a lubricating member positioning groove. The anti-buckling member and the lubricating member positioning groove are both I-shaped, and a lubricating member is provided in the lubricating member positioning groove. The anti-buckling member on the side away from the lubricating member positioning groove is provided with an extensometer positioning groove and a center screw hole. A fixing rod is detachably connected to the center screw hole. The positioning unit is used to position the test sample horizontally and vertically. The technical solution of the present invention can make the test sample evenly stressed during the test, can position the test sample, and can use a unidirectional or bidirectional extensometer to test the test sample, thereby reducing the test error and improving the accuracy of the test.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue performance testing of industrial products, and in particular to a positioning and anti-buckling device for fatigue testing of plate-shaped materials. Background Art

[0002] With the development of my country's automobile industry, the lightweighting of automobiles has been particularly prominent in terms of energy conservation and emission reduction. The original heavy body materials and components have been gradually replaced by new materials such as high-strength steel, aluminum alloy, and magnesium alloy. These new materials have the characteristics of light weight and high strength. The thickness of many new materials used in automobiles is less than 2.5mm. For new materials with a thickness of less than 2.5mm, when conducting fatigue tests with compressive direction, especially when conducting fatigue tests with axial strain control (ε min When <0), buckling in the compressive direction will cause instability and ideal test data cannot be obtained. Therefore, an anti-buckling device is needed to assist in the test.

[0003] Existing anti-buckling devices primarily consist of two anti-buckling members and bolt fasteners. Each anti-buckling member has a strip-shaped lubricant positioning groove, within which a lubricant is positioned. The anti-buckling member on the side away from the lubricant positioning groove has an extensometer positioning groove. The bolt fasteners are used to secure the test sample between the two anti-buckling members. During use, the lubricant is first installed in the lubricant positioning groove, then the test sample is clamped between the two anti-buckling members and secured with the bolt fasteners. Finally, the extensometer is installed on the test sample, the rubber band on the extensometer is secured in the extensometer positioning groove, and the test sample is clamped at both ends using a test fixture for testing.

[0004] This technical solution has the following disadvantages when used: 1. When the test sample is subjected to an axial strain-controlled fatigue test, the test sample is subjected to uneven force, resulting in inaccurate test results and large errors; 2. Since no test sample positioning device is set when installing the test sample, it is impossible to ensure that the test sample is installed in the appropriate position of the anti-buckling member, resulting in inaccurate test results; 3. The national standard GB / T26077-2021 stipulates that when conducting fatigue tests on plate materials, it is recommended to use a bidirectional extensometer to test the test sample, and take its average value as the control parameter of the test. If the conditions are not met, a unidirectional extensometer can be used, but this technical solution can only meet the use requirements of a unidirectional extensometer. Summary of the Invention

[0005] The present invention aims to provide a positioning and anti-buckling device for fatigue testing of plate-like materials, which can ensure that the test sample is subjected to uniform force during the test, locate the installation position of the test sample when installing the test sample, and also use a bidirectional extensometer to test the test sample.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a positioning and anti-buckling device for fatigue testing of plate-like materials, including a fixing unit and a positioning unit, the fixing unit including an anti-buckling part and a fastener, the number of anti-buckling parts is two, each anti-buckling part is in contact with each other and connected by a fastener, the two anti-buckling parts are provided with a lubricating part positioning groove, the anti-buckling part and the lubricating part positioning groove are both I-shaped, a lubricating part is provided in the lubricating part positioning groove, an extensometer positioning groove and a center screw hole are provided on the anti-buckling part away from the lubricating part positioning groove, a fixing rod is detachably connected to the center screw hole, and the positioning unit is used to position the test sample horizontally and vertically.

[0007] The beneficial effects of this solution are as follows: when it is necessary to fix the test sample, the lubricating part is first fixed in the lubricating part positioning groove so that the anti-buckling part and the lubricating part become a whole, and then the test sample is clamped between the two lubricating parts. Specifically, one of the anti-buckling parts is first placed on the positioning unit, and then the test sample is placed on the anti-buckling part. The positioning unit is used to position the test sample horizontally and vertically so that the test sample is in a suitable position on the anti-buckling part. The other anti-buckling part is fitted on the test sample, and the two anti-buckling parts are fixed together with fasteners. The positioning unit is removed, and the fixed test sample is tested.

[0008] The existing lubricating part positioning groove is in the shape of a strip, and the lubricating part cannot completely wrap the test sample between the two anti-buckling parts. Part of the test sample will be wrapped by the anti-buckling part, resulting in uneven force on the test sample, large test error, and inaccurate test results. The lubricating part positioning groove of the present technical solution is in the shape of an I-beam, and the test sample between the two anti-buckling parts can be completely wrapped by the lubricating part. During the test, the overall force on the test sample is more uniform, the buckling probability of the test sample is reduced, and the accuracy of the test is improved.

[0009] When using a unidirectional extensometer for testing, fix the rubber band on the extensometer in the extensometer positioning groove so that the knife edge on the extensometer contacts the test sample and test the test sample.

[0010] When using a bidirectional extensometer for testing, two extensometers are fixed to either side of the test specimen, and the rubber bands on the extensometers are secured to the mounting rod. The specimen is then tested, and the average value is taken as the control parameter for the test. When securing the specimen, the positioning unit allows for both horizontal and vertical positioning of the specimen, ensuring that it is centered within the anti-buckling member. This reduces the risk of the specimen being misaligned due to objective factors. Since the specimen is centered within the anti-buckling member during testing, the extensometer measurement results are more accurate, reducing test errors and improving test precision.

[0011] Since the present technical solution is provided with a fixing rod and an extensometer positioning groove, and the fixing rod is detachably connected to the center screw hole, when testing the test sample, it is possible to choose to use a bidirectional extensometer or a unidirectional extensometer to test the test sample according to the actual situation of the test sample, and the scope of use is wider.

[0012] Compared with using a unidirectional extensometer to test the test sample, this technical solution can use a bidirectional extensometer to test the test sample due to the setting of the fixed rod. By taking the average value as the control parameter of the test, the test error is reduced and the accuracy of the test is improved.

[0013] Due to the positioning unit provided in this technical solution, the test sample can be positioned horizontally and vertically, and the test sample can be installed at a suitable position on the anti-buckling member, thereby reducing the large test error and inaccurate test results caused by inaccurate installation position of the test sample.

[0014] Furthermore, the anti-buckling part includes an upper clamping part, an anti-buckling part and a lower clamping part connected in sequence. The upper clamping part and the lower clamping part each include a clamping section and two fixed sections. The fixed sections are located on both sides of the clamping section. The fixed sections are cylindrical. The distance from the upper surface of the clamping section to the plane where the top of the fixed section is located is equal to the distance from the lower surface of the clamping section to the plane where the bottom of the fixed section is located. The height of the clamping section is smaller than the diameter of the fixed section. A bolt hole is provided at the center position of each fixed section.

[0015] The beneficial effects of this solution are as follows: the purpose of such arrangement of the fixing section is to stagger the position of the fixing section with the upper and lower clamping portions, thereby reducing the height of the upper and lower clamping portions, thereby reducing the length of the test sample, reducing the probability of buckling of the test sample during the test, and improving test accuracy. At the same time, the position of the fixing section can be staggered with the position of the test fixture, further shortening the length of the test sample and further reducing the probability of buckling of the test sample during the test. Because the distance from the upper surface of the clamping section to the plane where the top of the fixing section is located is equal to the distance from the lower surface of the clamping section to the plane where the bottom of the fixing section is located, and the bolt hole is located at the center of the fixing section, so that the bolt hole and the clamping section are on the same horizontal plane, the fastener can stably fix the test sample between the two anti-buckling members.

[0016] Furthermore, the fixing unit further includes a pressing plate, which is detachably connected to one side of the anti-buckling portion.

[0017] The beneficial effect of this solution is that when using a unidirectional extensometer to test a test sample, one side of the test sample is fixed with a pressing plate, and the extensometer is fixed on the other side of the test sample, which can prevent the test sample from sliding relative to each other in the horizontal direction during the test and improve the accuracy of the test.

[0018] Furthermore, the positioning unit includes a positioning block and a correction block, and there are two positioning blocks and two correction blocks. The positioning block is provided with a sample positioning groove and an anti-buckling member positioning groove, and both the correction block and the sample positioning groove are provided with scales.

[0019] The beneficial effects of this solution are as follows: when positioning the test sample, one of the anti-buckling parts is placed in the anti-buckling part positioning groove, and then the test sample is placed in the sample positioning groove. The test sample is positioned horizontally and vertically by cooperating with the correction block and the positioning block. After the positioning is completed, the other anti-buckling part is attached to the test sample, and the two anti-buckling parts are fixed by fasteners.

[0020] Since the positioning block is provided with scales, the test sample can be positioned horizontally and vertically by the scales on the positioning block, so that the test sample is in a suitable position on the anti-buckling member, thereby improving the accuracy of the test.

[0021] The placement of the correction block can be determined according to different test conditions, so that the fixed position of the test sample can meet different test requirements.

[0022] Furthermore, the anti-buckling member is made of titanium alloy.

[0023] The beneficial effects of this solution are: compared with traditional carbon steel materials, titanium alloy materials have high strength and low density, and have good anti-buckling and anti-fatigue properties.

[0024] Furthermore, the lubricating element is made of a polytetrafluoroethylene film with a thickness of 0.5-2.0 mm.

[0025] The beneficial effects of this solution are: selecting polytetrafluoroethylene film as the lubricating element has good anti-creep performance and lubricating performance under long-term working conditions.

[0026] Furthermore, the extensometer positioning groove adopts an arc-shaped design.

[0027] The beneficial effects of this solution are: during the test, the rubber band on the extensometer is prevented from breaking due to stress concentration when in a taut state; the extensometer positioning groove can longitudinally position the extensometer to prevent the extensometer from longitudinally deviating during the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A three-dimensional diagram of a positioning and anti-buckling device for fatigue testing of plate-like materials according to the present invention;

[0029] Figure 2 An exploded view of a positioning and anti-buckling device for fatigue testing of plate-like materials according to the present invention;

[0030] Figure 3This is a stress-strain hysteresis curve diagram of the half-life of the test sample of the present invention when the thickness is 0.6 mm and the fatigue life is less than 1000 times;

[0031] Figure 4 This is a half-life strain-life curve diagram of the test sample of the present invention when the thickness is 0.6 mm and the fatigue life is less than 1000 times;

[0032] Figure 5 This is a half-life load-life curve diagram of the present invention when the test sample thickness is 0.6 mm and the fatigue life is less than 1000 times;

[0033] Figure 6 This is a stress-strain hysteresis curve diagram of the half-life of the test sample of the present invention when the thickness is 1.4 mm and the fatigue life is less than 1000 times;

[0034] Figure 7 This is a half-life strain-life curve diagram of the test sample of the present invention when the thickness is 1.4 mm and the fatigue life is less than 1000 times;

[0035] Figure 8 This is a half-life load-life curve diagram of the present invention when the thickness of the test sample is 1.4 mm and the fatigue life is less than 1000 times. DETAILED DESCRIPTION

[0036] The following is further described in detail through specific implementation methods:

[0037] The figure marks in the drawings of the specification include: anti-buckling member 1, pressing plate 2, test sample 3, extensometer 4, fastening bolt 5, gasket 6, fastening nut 7, upper clamping part 8, lower clamping part 9, anti-buckling part 10, clamping section 11, fixing section 12, bolt hole 13, lubricating part positioning groove 14, lubricating part 15, extensometer positioning groove 16, center threaded hole 17, fixing rod 18, positioning block 19, specimen positioning groove 20, anti-buckling member positioning groove 21, correction block 22.

[0038] Example

[0039] like Figure 1 The device for positioning and preventing buckling of plate-shaped materials for fatigue testing includes a fixing unit and a positioning unit.

[0040] like Figure 2 As shown, the fixing unit includes an anti-buckling member 1, a pressure plate 2, and a fastener. When using a unidirectional extensometer 4, the pressure plate 2 is used to secure the test sample 3 to prevent lateral slippage due to lateral pressure from the extensometer 4. In this embodiment, the anti-buckling member 1 is made of titanium alloy, and the fasteners are bolt fasteners. Specifically, there are four sets of bolt fasteners, each set of which includes a fastening bolt 5, a washer 6, and a fastening nut 7.

[0041] like Figure 2 As shown, there are two anti-buckling members 1, each of which is a symmetrical I-shaped plate structure. The two anti-buckling members 1 are attached to each other and connected by bolt fasteners. Each anti-buckling member 1 includes an upper clamping portion 8, a lower clamping portion 9 and an anti-buckling portion 10. The anti-buckling portion 10 is located between the upper clamping portion 8 and the lower clamping portion 9. The upper clamping portion 8 and the lower clamping portion 9 have the same structure, and the upper clamping portion 8, the lower clamping portion 9 and the anti-buckling portion 10 are integrally formed. The upper clamping portion 8 and the lower clamping portion 9 both include a clamping section 11 and two fixed sections 12. The fixed sections 12 are located on both sides of the clamping section 11, and the fixed sections 12 and the clamping section 11 are integrally formed. The fixed sections 12 are cylindrical, and the distance from the upper surface of the clamping section 11 to the plane where the top of the fixed section 12 is located is equal to the distance from the lower surface of the clamping section 11 to the plane where the bottom of the fixed section 12 is located. The height of the clamping section 11 is smaller than the diameter of the fixed section 12, and a bolt hole 13 is opened at the center of each fixed section 12.

[0042] like Figure 2 As shown, the test specimen 3 is clamped between two anti-buckling members 1. A lubricant positioning groove 14 is defined in the anti-buckling member 1 on the side of the test specimen 3. This groove 14 is I-shaped and comprises an upper horizontal portion, a lower horizontal portion, and a vertical portion that are sequentially connected. The upper horizontal portion is located on the upper clamping portion 8, the horizontal portion is located on the lower clamping portion 9, and the vertical portion is located on the anti-buckling portion 10. A lubricant 15 is provided between the test specimen 3 and the lubricant positioning groove 14. The shape of lubricant 15 matches that of the lubricant positioning groove 14 and is bonded to the groove 14. Lubricant 15 is a polytetrafluoroethylene film with a thickness of 0.5-2.0 mm. In this embodiment, the thickness of lubricant 15 is 1.0 mm.

[0043] like Figure 2 As shown, an extensometer positioning groove 16 and a central threaded hole 17 are provided on the side of the anti-buckling portion 10 away from the lubricating component positioning groove 14. Each extensometer positioning groove 16 is arc-shaped. There are two extensometer positioning grooves 16 on each anti-buckling portion 10, and the central threaded hole 17 is located between the two extensometer positioning grooves 16. A fixing rod 18 is connected to the inner thread of the central threaded hole 17.

[0044] like Figure 2As shown, the positioning unit includes a positioning block 19 and a correction block 22. There are two positioning blocks 19 and two correction blocks 22. The two positioning blocks 19 are identical plate-like structures. The two positioning blocks 19 are respectively located on the upper and lower sides of the anti-buckling member 1. A sample positioning groove 20 and an anti-buckling member positioning groove 21 are opened on the right side of the positioning block 19. The front and rear sides of the sample positioning groove 20 are engraved with scales. The correction block 22 is L-shaped, and the wide side of the correction block 22 is engraved with scales. The correction block 22 can be stuck on the front and rear sides of the sample positioning groove 20, and the scales on the wide side of the correction block 22 can coincide with the scales on the positioning block 19. The positioning block 19 can perform longitudinal and transverse positioning of the test sample 3 by cooperating with the correction block 22.

[0045] By setting the lubricating member positioning groove 14 on the anti-buckling member 1 into an I-shape and allowing the lubricating member 15 to completely wrap the test sample 3 between the two anti-buckling members 1, the force on the test sample 3 is made more uniform. At the same time, since the left side of the test sample 3 is flush with the anti-buckling portion 8, the anti-buckling device can perform axial strain controlled fatigue tests on test samples 3 with a thickness of 0.6mm-2.5mm. Figure 3-5 It can be seen that when the thickness of test sample 3 is 0.6 mm, the entire test procedure is continuous and without abnormalities, and a smooth and undistorted hysteresis loop can be obtained, and there is no visible buckling phenomenon. It should be noted that: Figure 4 The upper curve represents the strain peak (%), and the lower curve represents the strain valley (%). Figure 5 The upper curve represents the peak load (kN), and the lower curve represents the valley load (kN); Figure 6-8 It can be seen that when the thickness of test sample 3 is 1.4 mm and the strength is relatively high, the entire test process is continuous and without abnormalities, and a smooth and undistorted hysteresis loop can be obtained, and there is no visible buckling phenomenon. It should be noted that: Figure 7 The upper curve in the middle represents the strain peak (%), and the lower curve represents the strain valley value (%); Figure 8 The upper curve represents the load peak (kN), and the lower curve represents the load valley (kN); this shows that the anti-buckling device can test the test sample 3 with a thickness ranging from 0.6mm to 2.5mm and a relatively large tensile strength.

[0046] The specific implementation process is as follows:

[0047] When the test sample 3 needs to be fixed, the lubricating part 15 is first bonded to the lubricating part positioning groove 14, and then the anti-buckling part 1 on the left is placed in the anti-buckling part positioning groove 21 on the two positioning blocks 19, and the lubricating part 15 and the sample positioning groove 20 are placed on the same side, and the test sample 3 is placed in the sample positioning groove 20. The positioning block 19 cooperates with the correction block 22 to position the test sample 3 horizontally and vertically.

[0048] Specifically, when using a uniaxial extensometer to perform fatigue tests with axial strain control (ε min <0), to minimize exposure of the test sample 3 outside the anti-buckling member 1, the rear side of the anti-buckling portion 10 is aligned with the test sample 3; the test sample 3 extends 1.5 mm from the front side of the anti-buckling member 10 for mounting the extensometer 4. A suitable correction block 22 is selected and placed in the specimen positioning groove 20 on the rear side of the positioning block 19, so that the rear side of the test sample 3 abuts the correction block 22. The test sample 3 is positioned horizontally and vertically using the scales on the specimen positioning groove 20 and the correction block 22, so that the test sample 3 is aligned with the rear side of the anti-buckling member 10. After positioning, the right anti-buckling member 1 is placed on the left anti-buckling member 1. Using a torque wrench, bolt fasteners are installed on the two anti-buckling members 1, securing the two anti-buckling members 1 together. The secured anti-buckling device is then removed from the positioning block 19 and correction block 22. Then, fix the rubber band on the extensometer 4 to the extensometer positioning groove 16 so that the blade on the extensometer 4 contacts the test sample 3 on the front side of the anti-buckling part 10, and fix the pressing sheet 2 to the anti-buckling member 1 on the rear side of the anti-buckling part 10 through a rubber band or other elastic band, press the test sample 3, and test the test sample 3.

[0049] Specifically, when using a biaxial extensometer to perform axial strain controlled fatigue testing (ε min <0), two extensometers 4 need to be installed on the test specimen 3 on either side of the anti-buckling portion 10. Therefore, the test specimen 3 needs to extend 1.5 mm beyond the anti-buckling portion 10 on both sides. Appropriate correction blocks 22 are selected and clamped onto the front and rear sides of the specimen positioning slot 20, respectively. The test specimen 3 in the specimen positioning slot 20 is clamped so that the test specimen 3 is in the middle of the anti-buckling member 1. The right anti-buckling member 1 is placed against the left anti-buckling member 1. Using a torque wrench, bolt fasteners are installed on the two anti-buckling members 1 to secure them together. The secured anti-buckling device is then removed from the positioning blocks 19 and correction blocks 22. The extensometer 4 is then installed, the fixing rod 18 is mounted on the center threaded hole 17, and the rubber band on the extensometer 4 is secured to the fixing rod 18 so that the blade on the extensometer 4 contacts the test specimen 3. The test specimen 3 is then tested.

[0050] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A positioning and anti-buckling device for fatigue testing of plate-like materials, characterized by: The invention comprises a fixing unit and a positioning unit, wherein the fixing unit comprises an anti-buckling part and a fastener, wherein the number of the anti-buckling parts is two, each anti-buckling part is attached to each other and connected by a fastener, and the two anti-buckling parts are provided with a lubricating part positioning groove, and the anti-buckling part and the lubricating part positioning groove are both I-shaped, and a lubricating part is provided in the lubricating part positioning groove, and an extensometer positioning groove and a center screw hole are provided on the anti-buckling part away from the lubricating part positioning groove, and a fixing rod is detachably connected to the center screw hole, and the positioning unit is used to perform horizontal and vertical positioning of the test sample; the anti-buckling part comprises an upper clamping part, an anti-buckling part and a lower clamping part connected in sequence, and the upper clamping part and The lower clamping part includes a clamping section and two fixed sections. The fixed sections are located on both sides of the clamping section. The fixed sections are cylindrical. The distance from the upper surface of the clamping section to the plane where the top of the fixed section is located is equal to the distance from the lower surface of the clamping section to the plane where the bottom of the fixed section is located, and the height of the clamping section is less than the diameter of the fixed section. A bolt hole is provided at the center position of each fixed section; the fixing unit also includes a pressing plate, which is detachably connected to one side of the anti-buckling part; the positioning unit includes a positioning block and a correction block. There are two positioning blocks and two correction blocks. The positioning block is provided with a specimen positioning groove and an anti-buckling member positioning groove, and scales are provided on the correction block and the specimen positioning groove.

2. The positioning and anti-buckling device for fatigue testing of plate-shaped materials according to claim 1, characterized in that: The anti-buckling member is made of titanium alloy.

3. The positioning and anti-buckling device for fatigue testing of plate-like materials according to claim 2, characterized in that: The lubricating parts are made of polytetrafluoroethylene film with a thickness of 0.5-2.0mm.

4. The positioning and anti-buckling device for fatigue testing of plate-like materials according to claim 3, characterized in that: The extensometer positioning groove adopts arc design.

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