Arcuate vibration fatigue test fixture

Abstract

This invention relates to the field of testing device design technology, and provides an arc-shaped vibration fatigue testing fixture, including a base, a lower curvature adjustment pad, a limiting pad (optional), and an upper curvature adjustment pad. This invention, through its arc-shaped clamping end design, can transfer the maximum stress at the clamping end to the working section of the specimen, effectively avoiding stress concentration at the clamping end. Furthermore, it improves testing efficiency, saves costs, has wide applicability, can amplify vibration response (increase vibration frequency), significantly improves detection efficiency, shortens the testing cycle, and has versatility.

Description

Technical Field

[0001] This invention relates to the field of testing and inspection, and particularly to the design of test fixtures for vibration fatigue testing. Addressing the stress concentration problem at the clamping ends of traditional fixtures in high-frequency vibration testing, this invention proposes an arc-shaped vibration fatigue test fixture. Background Technology

[0002] In vibration fatigue testing, uneven stress distribution near the clamping end of the standard specimen is one of the main reasons why the clamping end fractures before the working section. Traditional clamping fixtures typically employ a straight-segment design at the clamping end. Finite element analysis shows that the stress is highest at the center of symmetry of this straight segment, sometimes even exceeding the maximum stress level of the working section. This makes the specimen highly susceptible to fracture at the clamping end, preventing the acquisition of effective data from the target working section. Since high-frequency vibration testing requires high natural frequencies, especially with high-strength materials and under high-temperature conditions, the problem of clamping end fracture is particularly prominent. Traditional improvement methods involve modifying the specimen design, but these methods are computationally intensive and have limited effectiveness, becoming a significant challenge in the testing process. Summary of the Invention

[0003] The purpose of this invention The present invention aims to introduce an arc-shaped clamping end design method, which optimizes the stress state of the specimen by adjusting the curvature of the arc, and intends to make the stress distribution at the clamping end where the specimen contacts the fixture more uniform, thereby reducing the technical problem of stress concentration at the clamping end of the specimen under the traditional straight-segment clamping state.

[0004] The technical solution of this invention is: An arc-shaped vibration fatigue test fixture is provided, including a base 1, a lower curvature adjustment pad 2, a limiting pad 3, and an upper curvature adjustment pad 5; The lower curvature adjustment pad 2, the limiting pad 3, and the upper curvature adjustment pad 5 are stacked in an upper, middle, and lower configuration and fixed together by fasteners; the lower curvature adjustment pad 2 is fixedly connected to the base; the base is a table for vibration fatigue testing or is fixed to the table. The lower curvature adjustment pad 2 has at least one edge 2a, and the upper curvature adjustment pad has at least one edge 5a. The at least one edge of the upper curvature adjustment pad and the at least one edge of the lower curvature adjustment pad correspond one-to-one to form at least one set of edges, and each set of edges coincides in the vertical direction projection. Each edge is a concave arc shape, and its vertical projection is an arc. The curvature of each edge in at least one edge of the lower curvature adjustment pad 2 is different; The limiting pad has a lateral opening groove 8, which corresponds to the standard specimen clamping end of the vibration fatigue test. The standard specimen clamping end is installed in the lateral opening groove and is clamped and fixed by the lower curvature adjusting pad 2 and the upper curvature adjusting pad 5. A set of corresponding edges of the upper curvature adjusting pad and the lower curvature adjusting pad 5 are in close contact with the standard specimen.

[0005] Furthermore, the span of each set of edges is the same. Even further, the span of each set of edges is the same as the opening width of the lateral opening slot.

[0006] Furthermore, the base, lower curvature adjustment pad 2, limiting pad 3, and upper curvature adjustment pad 5 all have vertical mounting holes. The fasteners include locking pads 6 and bolts 7, which match the mounting holes to fix the base, lower curvature adjustment pad 2, limiting pad 3, and upper curvature adjustment pad 5 together. Even further, the limiting pad 3 has multiple mounting holes; horizontal rotation of the limiting pad 3 allows its lateral openings to align with each set of edges.

[0007] Furthermore, the upper and lower curvature adjustment pads form four sets of edges, which are evenly distributed circumferentially. Even further, the arc curvature of the four sets of edges is 1 / 13, 1 / 14, 1 / 15, and 1 / 16, respectively.

[0008] Furthermore, the thickness of the limiting pad is not greater than the thickness of the standard sample clamping end.

[0009] Furthermore, the base 1 is fixed to the test machine table by bolts.

[0010] Furthermore, the upper and lower curvature adjustment pads and the limiting pads are all square.

[0011] Furthermore, the shape of the lateral opening groove is adapted to the contour shape of the standard specimen clamping end, and restricts the horizontal displacement of the standard specimen. Its thickness can be adjusted according to different specimen thicknesses and is consistent with the thickness of the standard specimen. The length, width, and depth of the lateral opening groove can be designed according to the actual size of the specimen to adapt to different specimen forms.

[0012] The locking pad 6 serves as a buffer pad, which can prevent the upper curvature adjustment pad 5 from being worn and damaged due to repeated pressure from the bolt 7 and fatigue loading, thus extending its service life.

[0013] The bolts 7 can be 5 in total: one at the center of symmetry, which is consistent with the hole diameter of the standard sample 4, and passes through the locking pad 6, the upper curvature adjustment pad 5, the standard sample 4, and the lower curvature adjustment pad 2 in sequence, and finally connects to the base 1; one at each of the four corners, whose size can be consistent with the hole diameter of the standard sample 4, and passes through the locking pad 6, the upper curvature adjustment pad 5, the limiting pad 3, and the lower curvature adjustment pad 2 in sequence, and finally connects to the base 1; under a smaller excitation, only the three bolts near the sample clamping end can be used to complete the test.

[0014] The curvature parameter can be adjusted according to the stress distribution of the sample, or it can be optimized using a variable curvature curve.

[0015] The standard specimen can have its drilling position changed and its clamping method altered according to test requirements. For example, the drilling position can be designed only at the original through hole of the HB 5277 standard specimen, and the same holes can be drilled at the same position on the locking pad 6, the upper curvature adjustment pad 5, and the lower curvature adjustment pad 2, in order to reduce material usage and simplify the clamping method.

[0016] Another technical solution is to omit the limiting pad 3, specifically as follows: An arc-shaped vibration fatigue test fixture is provided, including a base 1, a lower curvature adjustment pad 2 and an upper curvature adjustment pad 5; The upper curvature adjustment pad 5 and the lower curvature adjustment pad 2 are fitted together vertically and fixed together by fasteners; the lower curvature adjustment pad 2 is fixedly connected to the base; the base is the table surface for vibration fatigue testing or is fixed to the table surface; The upper curvature adjustment pad 5 has a first horizontal cross-shaped groove on its mating surface, and the lower curvature adjustment pad 2 has a second horizontal cross-shaped groove on its mating surface. Each horizontal cross-shaped groove has four arc-shaped edges at its four ends. The first and second horizontal cross-shaped grooves correspond vertically, ensuring that the four arc-shaped edges of the first and second horizontal cross-shaped grooves correspond one-to-one. The vertical projections of the corresponding arc-shaped edges coincide. Each arc-shaped edge is a concave arc, projected vertically as an arc. The curvature of the four arc-shaped edges of each horizontal cross-shaped groove is different. The cross-shaped gap between the first and second horizontal cross-shaped grooves allows for clamping the standard specimen for vibration fatigue testing in all four directions. During clamping, the corresponding arc-shaped edges are in close contact with the standard specimen.

[0017] Furthermore, the thickness of the cross gap is no greater than the thickness of the standard sample clamping end.

[0018] Furthermore, the base, lower curvature adjustment pad 2, standard sample clamping end, and upper curvature adjustment pad 5 are all provided with vertical mounting holes. The fasteners include locking pads 6 and bolts 7. The bolts match the mounting holes to fix the base, lower curvature adjustment pad 2, standard sample clamping end, and upper curvature adjustment pad into a single unit.

[0019] Advantages of the present invention 1. Stress optimization: The present invention uses an arc-shaped clamping end design to transfer the maximum stress at the clamping end to the working section of the sample, effectively avoiding the stress concentration problem at the clamping end.

[0020] 2. Improved testing efficiency: By reducing the probability of breakage at the specimen clamping end, the test efficiency is significantly improved by reducing specimen loss and the time cost of repeated tests caused by clamping end breakage.

[0021] 3. Cost Savings: The secondary processing technology of this invention can be implemented based on existing fixtures, reducing material waste and remanufacturing costs. The curved fixture design concept of this invention, besides directly machining the entire fixture set, can also perform simple secondary processing on existing fixtures, reducing material loss and manufacturing costs. Alternatively, by machining only the shims between the sample and the fixture, the clamping purpose can also be achieved with lower economic indicators.

[0022] 4. Wide Applicability: The design method of this invention is not only applicable to HB 5277-2021 standard specimens, but can also be extended to other types of mechanical test specimens. Furthermore, the curvature can be adjusted according to the stress distribution of different specimens to further optimize the stress distribution at the clamping end. Simultaneously, this method is universally applicable to tests under high temperature and higher frequency conditions.

[0023] 5. Vibration response amplification: According to the simulation results, after the fixture is improved, the vibration response is amplified (vibration frequency increases) for the same sample, which can greatly improve the detection efficiency and shorten the test cycle.

[0024] 6. Versatile design: The curved fixture design is not only applicable to fatigue standard specimens, but can also be extended to the design, manufacturing and mechanical performance testing of other types of specimens (such as engine blades). The curvature can be adjusted according to the stress distribution of different specimens to further optimize the stress distribution at the clamping end. Attached Figure Description

[0025] Figure 1 : A schematic diagram of the structure of the present invention; Figure 2 : Side view of the structure of the present invention; Figure 3 Top view of the structure of the present invention; Figure 4: A longitudinal sectional view of the structure of this invention; Figure 5 Assembly diagram of base, lower curvature adjustment pad, standard sample, limiting pad, upper curvature adjustment pad and bolts; Figure 6 Assembly diagram of base, lower curvature adjustment pad, standard sample and limiting pad; Assembly diagram of the limiting pad; Figure 7 Assembly diagram of the base, lower curvature adjustment pad and limit pad; Figure 8 Assembly diagram of the base and the lower curvature adjustment pad; Figure 9 : A 3D view of the base; Figure 10 : 3D view, top view, and bottom view of the upper curvature adjustment pad; Figure 11 : 3D view of the limiting pad; Figure 12 : A 3D view of the locking pad; Figure 13 : A three-dimensional view of the standard specimen; Figure 14 Schematic diagram of stress distribution at the contact edge between a traditional straight-line fixture and the sample; Figure 15 : A schematic diagram of the stress distribution at the contact edge between the arc-shaped fixture and the sample in this patent; Figure 16 Comparison of stress distribution at the vibration clamping end simulated by finite element analysis software (comparison between traditional clamps and the present invention); Figure 17 Comparison of stress distribution at the vibration clamping end simulated by finite element analysis software (comparison between traditional clamps and the present invention); Figure 18 : A schematic diagram of the upper curvature adjustment pad in the technical solution without a limit pad; Among them: base 1, lower curvature adjustment pad 2, limit pad 3, standard sample 4, upper curvature adjustment pad 5, locking pad 6, bolt 7, side opening groove 8, edge 2a, edge 5a. Detailed Implementation

[0026] The disclosed examples will be described more fully with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described, and these examples should not be construed as limited to those set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0027] Example 1, see appendix Figure 1-17 An arc-shaped vibration fatigue test fixture is provided, comprising a base 1, a lower curvature adjustment pad 2, a limiting pad 3, and an upper curvature adjustment pad 5; The lower curvature adjustment pad 2, the limiting pad 3, and the upper curvature adjustment pad 5 are stacked in an upper, middle, and lower configuration and fixed together by fasteners; the lower curvature adjustment pad 2 is fixedly connected to the base; the base is a table for vibration fatigue testing or is fixed to the table. The lower curvature adjustment pad 2 has at least one edge, the upper curvature adjustment pad has at least one edge, and the at least one edge of the upper curvature adjustment pad 5 corresponds one-to-one with the at least one edge of the lower curvature adjustment pad to form at least one set of edges, and each set of edges coincides in the vertical direction projection; each edge is a concave arc shape, and the vertical direction projection is an arc. The curvature of each edge in at least one edge of the lower curvature adjustment pad 2 is different; The limiting pad has a lateral opening groove, which corresponds to the standard specimen clamping end of the vibration fatigue test. The standard specimen clamping end is installed in the lateral opening groove and is clamped and fixed by the lower curvature adjusting pad 2 and the upper curvature adjusting pad 5. A set of corresponding edges of the upper curvature adjusting pad and the lower curvature adjusting pad 5 are in close contact with the standard specimen.

[0028] The span of each set of edges is the same. The span of each set of edges is the same as the opening width of the lateral opening slot.

[0029] The base, lower curvature adjustment pad 2, limiting pad 3, and upper curvature adjustment pad 5 all have vertical mounting holes. The fasteners include locking pads 6 and bolts 7, which match the mounting holes to fix the base, lower curvature adjustment pad 2, limiting pad 3, and upper curvature adjustment pad 5 together. The limiting pad 3 has multiple mounting holes, and horizontal rotation of the limiting pad 3 allows its lateral opening groove to match each set of edges.

[0030] The upper and lower curvature adjustment pads form four sets of edges, which are evenly distributed circumferentially. Furthermore, the curvature of the four sets of edges is 1 / 13, 1 / 14, 1 / 15, and 1 / 16, respectively.

[0031] The thickness of the limiting pad is equal to the thickness of the standard sample clamping end.

[0032] The base 1 is fixed to the test machine table with bolts.

[0033] The upper and lower curvature adjustment pads and the limiting pads are all square.

[0034] The shape of the lateral opening groove is adapted to the contour shape of the standard specimen clamping end and restricts the horizontal displacement of the standard specimen. Its thickness can be adjusted according to different specimen thicknesses and is consistent with the thickness of the standard specimen. The length, width and depth of the lateral opening groove can be designed according to the actual size of the specimen to adapt to different specimen forms.

[0035] The locking pad 6 serves as a buffer pad, which can prevent the upper curvature adjustment pad 5 from being worn and damaged due to repeated pressure from the bolt 7 and fatigue loading, thus extending its service life.

[0036] The bolts 7 can be 5 in total: one at the center of symmetry, which is consistent with the hole diameter of the standard sample 4, and passes through the locking pad 6, the upper curvature adjustment pad 5, the standard sample 4, and the lower curvature adjustment pad 2 in sequence, and finally connects to the base 1; one at each of the four corners, whose size can be consistent with the hole diameter of the standard sample 4, and passes through the locking pad 6, the upper curvature adjustment pad 5, the limiting pad 3, and the lower curvature adjustment pad 2 in sequence, and finally connects to the base 1; under a smaller excitation, only the three bolts near the sample clamping end can be used to complete the test.

[0037] The curvature parameter can be adjusted according to the stress distribution of the sample, or it can be optimized using a variable curvature curve.

[0038] The standard specimen can have its drilling position changed and its clamping method altered according to test requirements. For example, the drilling position can be designed only at the original through hole of the HB 5277 standard specimen, and the same holes can be drilled at the same position on the locking pad 6, the upper curvature adjustment pad 5, and the lower curvature adjustment pad 2, in order to reduce material usage and simplify the clamping method.

[0039] Example 2, see appendix Figure 18 Another technical solution is to omit the limiting pad 3, specifically as follows: An arc-shaped vibration fatigue test fixture is provided, including a base 1, a lower curvature adjustment pad 2 and an upper curvature adjustment pad 5; The upper curvature adjustment pad 5 and the lower curvature adjustment pad 2 are fitted together vertically and fixed together by fasteners; the lower curvature adjustment pad 2 is fixedly connected to the base; the base is the table surface for vibration fatigue testing or is fixed to the table surface; The upper curvature adjustment pad 5 has a first horizontal cross-shaped groove on its mating surface, and the lower curvature adjustment pad 2 has a second horizontal cross-shaped groove on its mating surface. Each horizontal cross-shaped groove has four arc-shaped edges at its four ends. The first and second horizontal cross-shaped grooves correspond vertically, ensuring that the four arc-shaped edges of the first and second horizontal cross-shaped grooves correspond one-to-one. The vertical projections of the corresponding arc-shaped edges coincide. Each arc-shaped edge is a concave arc, projected vertically as an arc. The curvature of the four arc-shaped edges of each horizontal cross-shaped groove is different. The cross-shaped gap between the first and second horizontal cross-shaped grooves allows for clamping the standard specimen for vibration fatigue testing in all four directions. During clamping, the corresponding arc-shaped edges are in close contact with the standard specimen.

[0040] Furthermore, the thickness of the cross gap is no greater than the thickness of the standard sample clamping end.

[0041] Furthermore, the base, lower curvature adjustment pad 2, standard sample clamping end, and upper curvature adjustment pad 5 are all provided with vertical mounting holes. The fasteners include locking pads 6 and bolts 7. The bolts match the mounting holes to fix the base, lower curvature adjustment pad 2, standard sample clamping end, and upper curvature adjustment pad into a single unit.

[0042] The groove shapes in the four directions of the first and second horizontal cross slots are adapted to the contour shape of the standard sample clamping end, and restrict the horizontal displacement of the standard sample. The thickness of the cross gap is consistent with the thickness of the sample, and its length, width and thickness can be designed according to the actual size of the standard sample to adapt to different sample forms.

Claims

1. An arc-shaped vibration fatigue testing fixture, characterized in that: It includes a base (1), a lower curvature adjustment pad (2), a limiting pad (3), and an upper curvature adjustment pad (5); The lower curvature adjustment pad (2), the limiting pad (3), and the upper curvature adjustment pad (5) are stacked in an upper, middle, and lower manner and fixed together by fasteners; the lower curvature adjustment pad (2) is fixedly connected to the base; the base is the table surface for vibration fatigue testing or is fixed to the table surface; The lower curvature adjustment pad (2) has at least one edge, the upper curvature adjustment pad has at least one edge, and at least one edge of the upper curvature adjustment pad (5) corresponds one-to-one with at least one edge of the lower curvature adjustment pad to form at least one set of edges, and each set of edges coincides in the vertical direction projection; each edge is a concave arc shape, and the vertical direction projection is an arc. The curvature of each edge of at least one edge of the lower curvature adjustment pad (2) is different; The limiting pad has a lateral opening groove, which corresponds to the standard specimen clamping end of the vibration fatigue test. The standard specimen clamping end is installed in the lateral opening groove and is clamped and fixed by the lower curvature adjustment pad (2) and the upper curvature adjustment pad (5). A set of corresponding edges of the upper curvature adjustment pad and the lower curvature adjustment pad (5) are in close contact with the standard specimen.

2. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The span of each group of edges is the same.

3. The arc-shaped vibration fatigue testing fixture as described in claim 2, characterized in that: The span of each set of edges is the same as the opening width of the lateral opening groove.

4. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The base (1), lower curvature adjustment pad (2), limit pad (3) and upper curvature adjustment pad (5) are all provided with vertical mounting holes. The fasteners include locking pads (6) and bolts (7). The bolts match the mounting holes to fix the base (1), lower curvature adjustment pad (2), limit pad (3) and upper curvature adjustment pad (5) together as a whole.

5. The arc-shaped vibration fatigue testing fixture as described in claim 4, characterized in that: The limiting pad (3) has multiple mounting holes. Horizontal rotation of the limiting pad (3) can make the lateral opening groove of the limiting pad (3) match each set of edges.

6. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The upper and lower curvature adjustment pads form four sets of edges, which are evenly distributed circumferentially.

7. The arc-shaped vibration fatigue testing fixture as described in claim 6, characterized in that: The curvature of the four sets of edges is 1 / 13, 1 / 14, 1 / 15, and 1 / 16.

8. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The thickness of the limiting pad is not greater than the thickness of the standard sample clamping end.

9. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The base 1 is fixed to the test machine table with bolts.

10. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The upper and lower curvature adjustment pads and the limiting pads are all square.

11. The arc-shaped vibration fatigue testing fixture as described in claim 1, characterized in that: The shape of the lateral opening groove is adapted to the contour shape of the standard specimen clamping end and restricts the displacement of the standard specimen in the horizontal direction.

12. An arc-shaped vibration fatigue testing fixture, characterized in that: Includes a base (1), a lower curvature adjustment pad (2), and an upper curvature adjustment pad (5); The upper curvature adjustment pad (5) and the lower curvature adjustment pad (2) are fitted together vertically and fixed together by fasteners; the lower curvature adjustment pad (2) is fixedly connected to the base; the base is the table surface for vibration fatigue testing or is fixed to the table surface; The upper curvature adjustment pad (5) has a first horizontal cross groove on its mating surface, and the lower curvature adjustment pad (2) has a second horizontal cross groove on its mating surface. Each horizontal cross groove has four arc-shaped edges at its four ends. The first horizontal cross groove and the second horizontal cross groove are vertically aligned, so that the four arc-shaped edges of the first horizontal cross groove and the four arc-shaped edges of the second horizontal cross groove are one-to-one aligned. The arc-shaped edges corresponding to the upper and lower positions are projected to coincide in the vertical direction. Each arc-shaped edge is a concave arc, and its vertical projection is an arc. The curvature of the four arc-shaped edges of each horizontal cross groove is different. The cross gap between the first horizontal cross groove and the second horizontal cross groove is used to clamp the standard specimen clamping end of the vibration fatigue test in all four directions. When clamping, the arc-shaped edges corresponding to the upper and lower positions are in close contact with the standard specimen.

13. The arc-shaped vibration fatigue testing fixture as described in claim 12, characterized in that: The thickness of the cross gap is no greater than the thickness of the standard sample clamping end.

14. The arc-shaped vibration fatigue testing fixture as described in claim 12, characterized in that: The base (1), lower curvature adjustment pad (2), standard sample clamping end and upper curvature adjustment pad (5) are all provided with vertical mounting holes. The fasteners include locking pads (6) and bolts (7). The bolts match the mounting holes to fix the base (1), lower curvature adjustment pad (2), standard sample clamping end and upper curvature adjustment pad into one unit.

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