A wedge-shaped fixture suitable for axial tension fatigue test

Abstract

The present invention relates to a wedge-shaped clamp suitable for axial tensile fatigue test, which can realize the application of tensile fatigue load to a flat test piece whose side of the clamping section is a wedge surface. The clamping section of the test piece is placed in the groove of the wedge block, and the side of the clamping section is connected to the inner wedge surface of the wedge block; the outer wedge surface of the wedge block is connected to the wedge surface of the wedge groove in the groove block, and presses the vertical surface on the other side of the wedge groove when subjected to tensile load; the protruding part at the bottom of the wedge block cooperates with the longitudinal notch of the groove block; the groove block is connected to the fatigue testing machine clamp through a threaded hole. The present invention can realize the clamping of a flat test piece under tensile fatigue load, and has the following advantages: less processing requirements for the clamping section of the flat test piece; the clamp has no indentation on the test piece to avoid affecting the test results; the test piece is guaranteed not to bend in the width direction during the clamping process; the test piece is clamped by the tensile load of the fatigue testing machine, and no bolts or the like are required for clamping, and the structure is compact; it is easy to disassemble and assemble; and it has good interchangeability.

Description

Technical Field

[0001] The invention belongs to the field of design and manufacture of axial tensile fatigue test fixtures, and in particular relates to a wedge-shaped fixture suitable for axial tensile fatigue tests. Background Art

[0002] Turbine components of aircraft engines and marine gas turbines often work in high temperature environments and bear huge fatigue loads, which are prone to fatigue damage and have a serious impact on the safety of the engine. Therefore, it is necessary to carry out fatigue tests on key parts of turbine components to assess the fatigue life of the structure. For flat test pieces, the existing solutions are mainly friction clamping and wedge clamping.

[0003] Chinese utility model patent CN 208026559 U provides a test piece clamping solution, which clamps the test piece through a combination of a lead screw and a wedge-shaped slider. The clamping principle is to rotate the lead screw to push the two wedge-shaped sliders so that the wedge-shaped sliders clamp the test piece. In essence, the clamping and loading are achieved through the friction between the test piece and the wedge-shaped sliders, and there is no wedge surface connection between the test piece and the wedge-shaped sliders. In actual use, since the lateral width of the test piece is reduced after stretching, the clamping force of the slider on the test piece decreases, and the friction force decreases, this type of clamp is prone to slipping when a large load is applied. Similar solutions also include Chinese utility model patents CN 203324096 U, CN 206974814 U, CN 208636142 U, etc.

[0004] In Chinese utility model patent CN 206876477 U, the clamping force of the wedge-shaped slider is provided by hydraulic pressure, which solves the problem of reduced clamping force during stretching. However, the introduction of hydraulic equipment increases the complexity and cost of the clamp. Similar solutions also include Chinese utility model patents CN 202582995 U, CN 207689272 U, CN 206038419 U, etc.

[0005] Chinese invention patent CN 106736658 A provides a clamping solution for a blade test piece, which is to clamp the wedge-shaped fixture by tightening the bolts and then clamp it by the pins on the wedge-shaped fixture. However, the pin holes on the test piece often become a weak point, which is prone to fatigue fracture and affects the effectiveness of the test.

[0006] Chinese invention patent CN 104330304 A provides a clamping solution for brittle materials, which uses a wedge-shaped clamp to clamp the test piece. However, the clamp is bulky and cannot be placed in a high-temperature furnace for heating. At the same time, the wedge-shaped clamp has poor interchangeability for test pieces of different sizes.

[0007] Chinese utility model patent CN 206281714 U uses an anchor head with a wedge-shaped through hole to clamp the tensile test piece. In this solution, the test piece needs to be connected to the clamping block through an adhesive, which greatly limits the use of the clamp under high temperature conditions.

[0008] The upper clamp of Chinese invention patent CN 109470468 A provides a solution for clamping the test piece using double wedge surfaces. The disadvantage of this solution is that the embedded wedge groove is difficult to process and the wedge clamp is bulky, which limits its use in high-temperature furnaces.

[0009] In summary, the existing clamping schemes have the following deficiencies: (1) If the connection between the fixture and the test piece is friction clamping, in order to increase friction, the clamping surface of the clamp must be designed to be a rough surface, often with sharp protrusions. This design will cause pits in the test piece during the clamping process, which may affect the cracking position and fatigue life of the test piece; at the same time, under the condition of large tensile force, the friction clamping will slip. (2) If the connection between the fixture and the test piece is wedge clamping, and the wedge surface is set in the thickness direction of the test piece (equivalent to the thickness gradually increasing), then the utilization rate of the test piece blank will be low. (3) At the same time, friction clamping and wedge clamping often require the use of fasteners such as bolts for clamping, and fasteners such as bolts are prone to adhesion at high temperatures. (4) In addition, the above-mentioned fixtures often have problems such as large size and inconvenient disassembly and assembly.

[0010] It can be seen that the design of the existing wedge-shaped fixture cannot fully meet the requirements of the high-temperature fatigue test of the test piece. Therefore, it is necessary to design a flat test piece fixture that has few requirements for the test piece clamping section, compact structure, small size, and easy disassembly and assembly. Summary of the invention

[0011] In order to overcome the problems in the prior art, the present invention provides a wedge-shaped fixture suitable for axial tensile fatigue testing to meet the requirements of axial tensile fatigue of flat test pieces. Specific requirements include: (1) no idle travel between the fixture and the test piece during the loading process; (2) the loading axis remains unchanged during the loading process; (3) few requirements are placed on the clamping section of the test piece; (4) the structure is compact and the size is small, so it can be placed in a high-temperature furnace for heating; (5) it is easy to disassemble and assemble; and (6) it has good interchangeability with different test pieces.

[0012] The solution of the present invention is: a wedge-shaped fixture suitable for axial tensile fatigue test, which is used to clamp the test piece, the wedge-shaped fixture comprises a wedge block and a slot block, the clamping section of the test piece is placed in the slot of the wedge block; the wedge block is in the basic shape of a column, the upper and lower surfaces are horizontal planes when laid flat, and the left and right side surfaces are respectively an outer wedge surface and a vertical surface; the vertical surface is provided with a groove, and the two sides of the groove are inner wedge surfaces; the upper end of the slot block is provided with a wedge-shaped groove, and the two side surfaces of the wedge groove are respectively a wedge surface and a vertical surface; the side surface of the clamping section of the test piece is connected to the inner wedge surface of the wedge block; the outer wedge surface of the wedge block is connected to the wedge surface of the wedge-shaped groove in the slot block, and presses the vertical surface on the other side of the wedge groove when subjected to a tensile load, and the protruding part at the bottom of the wedge block cooperates with the longitudinal notch of the slot block; the slot block is connected to the fixture of the fatigue testing machine through a threaded hole.

[0013] Furthermore, the test piece is in the basic shape of a flat plate, and the side surface of the clamping section is a wedge surface.

[0014] Furthermore, an outer wedge surface of the wedge block and the lower surface adopt an arc transition, and an inner wedge surface of the wedge block and the upper surface adopt an arc transition.

[0015] Furthermore, the bottom of the vertical surface of the wedge block has two left and right protruding parts, and the two side surfaces of the protruding parts are wedge surfaces.

[0016] Furthermore, the bottom surface of the wedge-shaped groove is a horizontal surface, the wedge surface of the wedge-shaped groove and its bottom surface are transitioned by a circular arc, the vertical surface of the wedge-shaped groove has two longitudinal grooves, and the side surfaces of the longitudinal grooves are wedge surfaces.

[0017] Furthermore, a transverse groove is provided at the bottom of the vertical surface of the wedge-shaped groove of the groove block, the depth of the transverse groove is greater than the protruding portion of the wedge block, the width is consistent with the height of the protruding portion of the wedge block, and the transverse groove is clearance-matched with the protruding portion.

[0018] Furthermore, the threaded hole is arranged at the bottom of the slot block; the distance between the axis of the threaded hole and the vertical plane of the wedge-shaped slot is half of the thickness of the test piece.

[0019] Furthermore, the radius of the circular arc transition portion between the outer wedge surface of the wedge block and its lower surface is smaller than the radius of the circular arc transition portion of the slot block.

[0020] Furthermore, the height of the wedge block is smaller than the depth of the wedge-shaped groove.

[0021] Furthermore, the protruding portion of the wedge block passes through the transverse groove of the groove block and cooperates with the longitudinal groove of the groove block.

[0022] Compared with the existing wedge-shaped clamp, the present invention has the following advantages:

[0023] 1. Fewer requirements for the clamping section of the test piece: First, due to the use of wedge clamping, the test piece does not need to have a long clamping section to provide friction, which allows the clamping section of the test piece to be appropriately shortened; secondly, the wedge surface of the test piece is on its side, rather than on the plane of the plate. Under this design, the test piece only needs to use wire cutting to process the side shape and use milling and grinding to process the surface of the plate. There is no need to deliberately process the wedge surface on the surface of the plate, which reduces the difficulty of processing and also reduces waste during the sampling process.

[0024] 2. Prevent the test piece from buckling in the width direction when it is loaded: Since the wedge surface of the test piece is located on the side, when the test piece is subjected to tension, the clamping section is subjected to pressure in the width direction. When the thickness of the test piece is relatively small, it is easy to buckle in the width direction. Therefore, the outer wedge surface of the wedge block is designed in the present invention, which pushes the wedge block when it is loaded, so that it presses the vertical surface of the wedge groove of the groove block to prevent the buckling of the test piece in the width direction.

[0025] 3. The fixture leaves no indentation on the test piece: In the present invention, the inner wedge surface and the upper surface of the wedge block are formed by arc transition, and the other surfaces in contact with the test piece are all flat, so there is no indentation on the test piece when it is loaded.

[0026] 4. The fixture consists of only two parts (excluding the test piece), with a compact structure, no need for additional fasteners, and is suitable for heating in a high-temperature furnace along with the test piece: The present invention does not use structures such as bolts, because bolts suitable for high-temperature environments need to be made of special high-temperature materials, which are relatively expensive; at the same time, bolts and nuts are prone to adhesion at high temperatures, affecting disassembly and assembly. The present invention uses several sets of wedge surfaces to achieve automatic clamping of the test piece under tensile load and keep the loading axis from deviating, so there is no need to design additional bolts. These designs ensure that the test piece has a compact structure and is suitable for heating in a high-temperature furnace.

[0027] 5. Easy to disassemble and assemble: In the unloaded state, the wedge block can be installed into the slot block from the side. When loaded, the protruding part of the wedge block is stuck into the longitudinal groove of the slot block to prevent the wedge block from sliding out or deviating from the loading axis. Therefore, you only need to install the fixture in the unloaded state before use.

[0028] 6. Good interchangeability for different test pieces: You only need to replace the wedge of appropriate size to adapt to test pieces of different thickness and width. The wedge is small in size, simple in shape, and has low raw material and processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the assembly diagram of the fixture of the present invention, which only shows the lower half of the entire fixture, and the upper half is exactly the same as the lower half. The test piece also only shows the clamping section. (a) is the appearance diagram; (b) is the appearance diagram after dissection, test piece 1, wedge block 2, slot block 3.

[0030] Figure 2 Schematic diagram of the test piece in the fixture of the present invention. The schematic diagram only shows the clamping section of the test piece. The shape of the test piece test section changes with the test requirements, so it is not shown.

[0031] Figure 3 The following are the appearance diagrams of the wedge block in the clamp of the present invention. (a) is the appearance diagram of the vertical surface side; (b) is the appearance diagram of the outer wedge surface side.

[0032] Figure 4 The following are the appearance diagrams of the slot block in the fixture of the present invention. (a) is the overall appearance diagram; (b) is the appearance diagram after longitudinal sectioning; (c) is the appearance diagram after transverse sectioning, showing the vertical surface of the wedge-shaped slot; (d) is the appearance diagram after transverse sectioning, showing the wedge surface of the wedge-shaped slot. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] like Figure 1-4 As shown, a wedge-shaped fixture suitable for axial tensile fatigue test of the present invention is used to clamp the test piece 1. The wedge-shaped fixture includes a wedge block 2 and a slot block 3, and the clamping section of the test piece 1 is placed in the groove of the wedge block 2. The wedge block 2 is in the basic shape of a columnar body. When placed flat, the upper and lower surfaces are horizontal surfaces, and the left and right side surfaces are respectively an outer wedge surface and a vertical surface; the vertical surface has a groove, and the two sides of the groove are inner wedge surfaces. The upper end of the slot block 3 has a wedge-shaped groove, and the two side surfaces of the wedge-shaped groove are respectively a wedge surface and a vertical surface. The side surface of the clamping section of the test piece 1 is connected to the inner wedge surface of the wedge block 2; the outer wedge surface of the wedge block 2 is connected to the wedge surface of the wedge-shaped groove in the slot block 3, and presses the vertical surface on the other side of the wedge-shaped groove when subjected to a tensile load. The protruding part at the bottom of the wedge block 2 cooperates with the longitudinal notch of the slot block 3. The slot block 3 is connected to the fixture of the fatigue testing machine through a threaded hole.

[0035] The test piece 1 is in the basic shape of a flat plate, and the side of its clamping section is a wedge surface. The outer wedge surface of the wedge block 2 and the lower surface are transitioned by a circular arc, and the inner wedge surface of the wedge block 2 and the upper surface are transitioned by a circular arc. The bottom of the vertical surface of the wedge block 2 has two left and right protrusions, and the two side surfaces of the protrusions are wedge surfaces. The bottom surface of the wedge-shaped groove is a horizontal surface, and the wedge surface of the wedge-shaped groove and its bottom surface are transitioned by a circular arc. The vertical surface of the wedge-shaped groove has two longitudinal grooves, and the side surfaces of the longitudinal grooves are wedge surfaces.

[0036] The bottom of the vertical surface of the wedge-shaped groove of the slot block 3 has a transverse groove, the depth of the transverse groove is greater than the protruding part of the wedge block 2, the width is consistent with the height of the protruding part of the wedge block 2, and the transverse groove is in clearance with the protruding part. The threaded hole is arranged at the bottom of the slot block 3; the distance between the axis of the threaded hole and the vertical surface of the wedge-shaped groove is half the thickness of the test piece 1. The radius of the arc transition part between the outer wedge surface of the wedge block 2 and its lower surface is smaller than the radius of the arc transition part of the slot block 3. The height of the wedge block 2 is smaller than the depth of the wedge-shaped groove. The protruding part of the wedge block 2 passes through the transverse groove of the slot block 3 and is matched with the longitudinal groove of the slot block 3.

[0037] During the assembly of the fixture, the wedge block 2 is installed into the slot block 3 from the side, and the transverse groove of the slot block 3 provides a passage for the convex part of the wedge block 2 to enter and exit. Since the depth of the transverse groove of the slot block 3 is greater than the convex part of the wedge block 2, the width is consistent with the height of the convex part of the wedge block 2, and can be clearance-fitted, the radius of the arc transition part between the outer wedge surface and the lower surface of the wedge block 2 is smaller than the arc transition part of the slot block 3, and the height of the wedge block 2 is smaller than the depth of the wedge-shaped groove of the slot block 3, so this assembly process can be completed smoothly.

[0038] After assembly, the protruding portion of the wedge block 2 is aligned with the longitudinal groove of the slot block 3. When the fatigue testing machine applies a tensile load, the protruding portion of the wedge block 2 enters the longitudinal groove of the slot block 3 to prevent the wedge block 2 from shifting left and right.

[0039] The raised portion of the wedge block 2 is assembled with the longitudinal groove of the slot block 3 to ensure the centering of the fixture in the left and right directions. Since the distance between the axis of the threaded hole and the vertical plane of the wedge-shaped groove of the slot block 3 is half the thickness of the test piece 1, after the assembly is completed, the center axis of the test piece 1 is consistent with the loading axis, ensuring the centering of the fixture in the front and back directions.

[0040] When fatigue tests of test pieces 1 of different sizes need to be carried out, the original wedge block 2 can be replaced with a wedge block 2 with a wider groove to adapt to the new test requirements without changing the groove block 3. The wedge block 2 in the present invention is separated from the groove block 3, and all designs related to the size of the test piece 1 are concentrated on the wedge block 2, which improves the interchangeability of the fixture for test pieces of different widths.

[0041] During the actual test, the whole set of fixtures includes two fixtures of the present invention, which are divided into an upper fixture and a lower fixture, respectively connecting the clamping sections of the upper end and the lower end of the test piece 1. When using the fixture of the present invention to perform a tensile fatigue test, the specific method is as follows:

[0042] 1. In a relaxed state, assemble the upper and lower sets of fixtures. The specific method is:

[0043] a. Place the clamping section at one end of the test piece 1 in the groove of the wedge block 2, and the wedge surface on the side of the clamping section at one end of the test piece 1 cooperates with the inner wedge surface of the wedge block 2.

[0044] b. Install the wedge block 2 into the slot block 3 from the side. During this process, the raised portion of the wedge block 2 enters the slot block 3 along the transverse slot of the slot block 3. Finally, the raised portion of the wedge block 2 is aligned with the longitudinal slot of the slot block 3.

[0045] c. Install another set of fixtures on the clamping section at the other end of the test piece 1.

[0046] 2. Connect the threaded hole of the slot block 3 in the upper fixture to the fixture of the fatigue testing machine, and hang the assembled test piece 1 and the upper and lower fixtures on the fatigue testing machine. Displace the wedge block 2 and slot block 3 of the upper and lower fixtures respectively, so that the protruding part of the wedge block 2 matches the longitudinal groove of the slot block 3.

[0047] 3. The position of the fixture and the test piece of the present invention is changed by adjusting the position of the chuck on the fatigue testing machine so that the test piece can enter the cavity of the high-temperature furnace.

[0048] 4. Connect the threaded hole of the slot block 3 in the lower fixture to the fixture of the fatigue testing machine.

[0049] 5. Check the upper and lower clamps to ensure that the raised part of the wedge block 2 fits with the longitudinal groove of the groove block 3. Apply a certain tensile force through the fatigue testing machine.

[0050] 6. Close the high temperature furnace door and start heating.

[0051] 7. The test can begin after the temperature reaches the target value.

[0052] When the fatigue testing machine applies a tensile load, the tensile force is transmitted to the slot block 3 through the threaded hole at the bottom of the slot block 3; the slot block 3 transmits the tensile force to the wedge block 2 through the wedge surface of the wedge-shaped slot; the wedge block 2 transmits the tensile force to the test piece 1 through the inner wedge surface.

[0053] When disassembling the clamp involved in the present invention, the specific method is as follows:

[0054] 1. After the test is finished, stop heating and open the high temperature furnace door to cool down. Keep the tension stable during this period to prevent the tension from increasing sharply due to the cooling and shrinkage of the test piece 1 and the fixture.

[0055] 2. Raise the lower chuck of the fatigue testing machine until the tension is unloaded to 0.

[0056] 3. Remove the fatigue testing machine fixture connected to the threaded hole of the slot block 3 in the lower fixture of the present invention. Then lower the lower chuck of the fatigue testing machine.

[0057] 4. Remove the upper and lower fixtures and the test piece of the present invention from the upper chuck of the fatigue testing machine.

[0058] 5. Take out the wedge block 2 from the side of the slot block 3 and remove the test piece 1 from the wedge block 2 to complete the disassembly.

[0059] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A wedge-shaped fixture suitable for axial tensile fatigue testing, characterized in that: It is used to clamp a test piece (1), the wedge-shaped clamp comprises a wedge block (2) and a slot block (3), the clamping section of the test piece (1) is placed in the slot of the wedge block (2); the wedge block (2) is in the shape of a column, the upper and lower surfaces are horizontal surfaces when placed flat, and the left and right side surfaces are respectively an outer wedge surface and a vertical surface; the vertical surface is provided with a groove, and the two sides of the groove are inner wedge surfaces; the upper end of the slot block (3) is provided with a wedge-shaped groove, and the two side surfaces of the wedge-shaped groove are respectively a wedge surface and a vertical surface; the side surface of the clamping section of the test piece (1) is connected to the inner wedge surface of the wedge block (2); the outer wedge surface of the wedge block (2) is connected to the wedge surface of the wedge-shaped slot in the slot block (3), and presses the vertical surface on the other side of the wedge-shaped slot when subjected to a tensile load, and the protruding part at the bottom of the wedge block (2) cooperates with the longitudinal notch of the slot block (3); the slot block (3) is connected to the fatigue testing machine fixture through a threaded hole; The outer wedge surface of the wedge block (2) and the lower surface adopt an arc transition, and the inner wedge surface of the wedge block (2) and the upper surface adopt an arc transition; The bottom surface of the wedge-shaped groove is a horizontal surface, the wedge surface of the wedge-shaped groove and its bottom surface are transitioned by a circular arc, the vertical surface of the wedge-shaped groove is provided with two longitudinal grooves, and the side surfaces of the longitudinal grooves are wedge surfaces; The bottom of the vertical surface of the wedge-shaped groove of the groove block (3) has a transverse groove, the depth of the transverse groove is greater than the protruding portion of the wedge block (2), the width is consistent with the height of the protruding portion of the wedge block (2), and the transverse groove is clearance-matched with the protruding portion.

2. The wedge-shaped clamp according to claim 1, characterized in that: The test piece (1) is in the basic shape of a flat plate, and the side surface of its clamping section is a wedge surface.

3. The wedge-shaped clamp according to claim 1, characterized in that: The bottom of the vertical surface of the wedge block (2) has two left and right protruding parts, and the two side surfaces of the protruding parts are wedge surfaces.

4. The wedge-shaped clamp according to claim 1, characterized in that: The threaded hole is arranged at the bottom of the slot block (3); the distance between the axis of the threaded hole and the vertical plane of the wedge-shaped slot is half the thickness of the test piece (1).

5. The wedge-shaped clamp according to claim 1, characterized in that: The radius of the circular arc transition portion between the outer wedge surface of the wedge block (2) and its lower surface is smaller than the radius of the circular arc transition portion of the slot block (3).

6. The wedge-shaped clamp according to claim 1, characterized in that: The height of the wedge block (2) is smaller than the depth of the wedge-shaped groove.

7. The wedge-shaped clamp according to claim 1, characterized in that: The protruding portion of the wedge block (2) passes through the transverse groove of the groove block (3) and cooperates with the longitudinal groove of the groove block (3).

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