A test device and method suitable for non-standard multi-component composite fatigue fracture

Abstract

The present invention discloses a test device and method suitable for non-standard multi-component composite fatigue fracture, belonging to the technical field of composite fatigue fracture testing. The device includes an upper fixture, a lower fixture, an auxiliary fixture, an adaptive supporter, a composite crack extension specimen, and a matching customized bolt and nut for fixing the auxiliary fixture and corresponding upper and lower fixture screws and a number of positioning bolts and nuts. The present invention can realize type I, type II, type III and type I-II composite, type I-III composite and type II-III composite fatigue fracture experiments with different composite ratios by replacing the auxiliary fixture; at the same time, the patent of the present invention can realize fatigue fracture tests of specimens of different thicknesses by adding an adaptive supporter. The use of the adaptive supporter reduces the problem of assembly accuracy of the specimen and the device, and also solves the difficult problem of composite crack size effect test research. The use of auxiliary fixtures and adaptive supports makes the operation of the entire device convenient, fast, economical and practical.

Description

Technical Field

[0001] The invention discloses a test device and a method suitable for non-standard multi-component composite fatigue fracture, belonging to the technical field of composite fatigue fracture testing. Background Art

[0002] Fatigue and fracture are common failure modes of mechanical parts, and are also one of the most serious forms of failure. Due to the asymmetry of loads borne by engineering structures, the randomness of crack generation, and the anisotropy of materials, cracks in actual engineering components are often not of a single type. The stress field near the crack tip contains stresses of type I, type II, and type III cracks at the same time, that is, cracks in the structure often present a composite state.

[0003] The crack tip field and fatigue fracture behavior of composite cracks are affected by uncertain factors such as sample material, geometric dimensions, stress state, and loading form. It is difficult to unify the existing experimental research conclusions. In addition, due to the complexity of composite fatigue fracture problems and the diversity of samples, a unified composite fatigue fracture test standard has not yet been formed. Therefore, it is necessary to formulate relevant composite crack fracture test standards to regulate composite fatigue fracture test research, among which the development of test equipment is the prerequisite for solving the problem of composite fatigue fracture test standardization.

[0004] Compound crack types include I-II, I-III and II-III compound cracks, etc. The experimental study of each compound crack requires a corresponding loading fixture, and the material cost and processing cost are relatively high. In addition, the size effect of fatigue fracture problems cannot be ignored. If the influence of the size effect is considered, several loading fixtures are required, which greatly increases the test cost. This patent develops a compound loading fixture that can achieve different compound crack tip states by replacing small fixture auxiliary parts; and by adding adaptive supports to adapt to tests of specimens of different thicknesses. It is simple to operate, easy to implement, and saves material and processing costs. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a test device and method suitable for non-standard multi-component composite fatigue fracture to solve the above-mentioned problems existing in the prior art. The present invention can perform fatigue fracture tests of different types of composite cracks by replacing the corresponding auxiliary fixtures, and can realize fatigue fracture tests of samples of different thicknesses by adding adaptive supports.

[0006] The present invention provides a test device suitable for non-standard multi-component composite fatigue fracture, comprising: a fixture 10, a fixture 20, an auxiliary fixture, a composite crack extension specimen 40, and an adaptive support 34 that can cooperate with the auxiliary fixture to automatically adapt to composite crack extension specimens 40 of different thicknesses;

[0007] The clamp 10 is a pair of U-shaped hooks, with through holes on the clamping ends, and the tail ends of the clamping ends are connected to the interface of the electronic universal testing machine to transfer the tensile and compressive loads applied by the testing machine;

[0008] The second fixture 20 is two fan-shaped arc plates, which are arranged symmetrically at the center of the two fan-shaped arc plates. There are seven groups of through holes on the fan-shaped arc plates. The center of each group of through holes is placed on the same radius of the fan-shaped arc plate and arranged at equal arc spacing. The two groups of through holes at the two ends are in a 90-degree arc relationship relative to the center of the fan-shaped arc plate. The arc interval between each group of through holes is 15°. The outermost arc of the second fixture 20 and the arc line distributed by the through holes inside it are three concentric circles; a rectangular notch is provided at the central angle of the fan-shaped arc plate, and a groove 21 is provided in the middle of the length direction of the side of the rectangular notch away from the arc, and through holes 24 for assembly with auxiliary fixtures are provided on both sides of the groove 21; the second fixture 20 achieves different composite fatigue fracture test experimental purposes by replacing different auxiliary fixtures;

[0009] The clamp 10 is fixedly connected to any set of through holes on the clamp 2 20 by bolts and nuts, so that the load applied to the clamp 10 is transmitted to the composite crack extension specimen 40 in different directions through the clamp 2 20;

[0010] The composite crack extension specimen 40 is a plate-like structure, and the specimen dimensions are close to those of a standard CT specimen. A fixing hole 42 is provided on the composite crack extension specimen 40 for connecting with the auxiliary fixture and the adaptive support 34.

[0011] The adaptive support 34 includes an upper plate 341, a lower plate 342, a connecting rod 343 and a conical spring 35; the upper plate 341 and the lower plate 342 are connected by the connecting rod 343 and the conical spring 35; connecting rods 343 are arranged on both sides of the adaptive support 34, the upper end of the connecting rod 343 is connected to the side of the upper plate 341, and can rotate around the connection point, and the lower end of the connecting rod 343 is arranged in a groove on the side of the lower plate 342, and can slide along the groove; annular grooves are opened on the lower surface of the upper plate 341 and the upper surface of the lower plate 342, and the two ends of the conical spring 35 are arranged in the annular grooves, and through holes are arranged in the annular grooves for matching and connecting with the auxiliary clamp and the composite crack extension specimen 40.

[0012] Furthermore, the composite crack extension specimen 40 is provided with a machined notch 44 extending from the edge of the composite crack extension specimen 40 and inside the composite crack extension specimen 40 along the width direction of the composite crack extension specimen 40. The machined notch 44 is arranged in the middle of one side of the composite crack extension specimen 40 along its length direction, and the closed end 43 of the machined notch 44 located inside the composite crack extension specimen 40 is peak-shaped, and the peak line of the closed end 43 of the machined notch 44 is coplanar with the prefabricated fatigue crack surface; the fixing holes 42 are symmetrically arranged on both sides of the machined notch 44, and the hole center line of the fixing holes 42 is perpendicular to the prefabricated fatigue crack surface.

[0013] Furthermore, the upper plate 341 and the lower plate 342 of the adaptive supporter 34 are hard metal plates.

[0014] Furthermore, the auxiliary fixture is an "L"-shaped solid part, including auxiliary fixture 31, auxiliary fixture 32 and auxiliary fixture 33. During the test, the direction of the "L"-shaped part is changed to assemble with fixture 20 to form a total loading fixture of different composite crack specimens I-II composite type, I-III composite type and II-III composite type; different forms of loading fixtures can transfer the force applied on the machine to the specimen, thereby realizing the application of different composite loads;

[0015] In order to realize the connection between different auxiliary clamps and the second clamp 20 and the specimen, the specific openings and assembly on the auxiliary clamps are as follows: through holes are respectively set on both sides of the end faces of the auxiliary clamps 31 and 32, one end is connected to the second clamp 20 through the through holes by bolts, and the other end is connected to the composite crack extension specimen 40 by bolts and nuts; the auxiliary clamp 33 has a through hole set at its narrow face end, which is connected to the second clamp 20 by bolts, and a threaded hole set at its wide face end, which is connected to the composite crack extension specimen 40 by bolts; an adaptive support 34 is set between the auxiliary clamp and the composite crack extension specimen 40, so as to be used for fatigue fracture test of specimens with different thicknesses.

[0016] The method of using the above device for composite fatigue fracture test includes the following three situations:

[0017] Case 1: The test method for the Ⅰ-Ⅱ composite crack fatigue fracture test includes the following steps:

[0018] Step 1.1: A set of auxiliary clamps 31 are respectively fixed to the two sides of the composite fatigue fracture specimen 40 through the through holes of the composite crack extension specimen 40 by bolts and nuts, and the plate-shaped plane of the auxiliary clamp 31 and the plate-shaped plane of the composite crack extension specimen 40 are parallel to each other and closely fitted; the auxiliary clamp 31 that has been assembled with the specimen is assembled into the groove of the clamp 2 20 and fixed firmly to the clamp 2 20 by bolts passing through the through holes, and one side end face of the auxiliary clamp 31 is aligned and overlapped with the plane of one side of the clamp 20, and the end face of the other side auxiliary clamp protrudes relative to the side of the clamp 20;

[0019] Step 1.2: The two clamps 10 are connected to the first set of 90° through holes on the two clamps 20 through two sets of bolts respectively, and connected to the electronic universal testing machine through the U-hook clamping end to transmit the load, so that the specimen is in a type I loading state and the crack is an open type;

[0020] Step 1.3: sequentially adjust the two fixtures 10 to connect the second group of 75° through holes, the third group of 60° through holes, the fourth group of 45° through holes, ..., the sixth group of 15° through holes on the two fan-shaped arc plates through bolts, and connect the clamping end of the fixture 10 to the electronic universal testing machine to transmit the load, so that the specimen is subjected to different degrees of type I-II composite loading state, and the cracks are both open and sliding types;

[0021] Step 1.4: Adjust the two U-shaped hooks to connect with the seventh group of 0° through holes on the two fan-shaped arc plates through two groups of bolts, and connect the clamping ends of the U-shaped hooks to the electronic universal testing machine to transmit the load, so that the composite crack extension specimen 40 is in a type II loading state, and the crack is a sliding type;

[0022] Step 1.5: Replace the composite fatigue fracture specimens 40 of different thicknesses, add the adaptive support 34 between the composite crack extension specimen 40 and the auxiliary fixture 1 31, and then reassemble into a specimen assembly, and complete the matching and fixing with the fixture 2 20; repeat steps 1.2-1.4 to complete the loading of the composite crack extension specimens 40 of different thicknesses;

[0023] Case 2: The test method for the fatigue fracture test of the I-III composite crack includes the following steps:

[0024] Step 2.1: The two sets of auxiliary clamps 2 32 are fixed to the two sides of the composite fatigue fracture specimen 40 by bolts and nuts through the through holes of the composite crack extension specimen 40, and it is ensured that the two side planes of the groove of the auxiliary clamp 2 32 are parallel to and closely fit with the plate-like plane of the specimen; the auxiliary clamp 2 32 that has been assembled with the specimen is assembled into the groove of the clamp 2 20 and fixed firmly with the clamp 2 20 by bolts passing through the through holes, and it is ensured that the plate-like planes on both sides of the auxiliary clamp 2 32 coincide with the two side planes of the clamp 20;

[0025] Step 2.2: The two U-shaped hooks are connected to the first set of 90° through holes on the two sets of fan-shaped arc plates through two sets of bolts respectively, and the clamping ends of the U-shaped hooks are connected to the testing machine to transmit the load, so that the composite crack extension specimen 40 is in a type III loading state, and the crack is a tearing type;

[0026] Step 2.3: sequentially adjust the two U-shaped hooks through the two groups of bolts and the second group of 75° through holes, the third group of 60° through holes, the fourth group of 45° through holes, ..., the sixth group of 15° through holes on the two groups of fan-shaped arc plates, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the composite crack extension specimen 40 is subjected to different degrees of type I and type III composite loading states, and the cracks are both opening type and tearing type;

[0027] Step 2.4: Adjust the two U-shaped hooks to be connected to the seventh group of 0° through holes on the two groups of fan-shaped arc plates through two groups of bolts, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the crack of the composite crack extension specimen 40 is in a type I loading state, and the crack is an open type;

[0028] Step 2.5: Replace the sample with a composite fatigue fracture sample 40 of different thicknesses, add an adaptive support 34 between the composite crack extension sample 40 and the auxiliary fixture 2 32, and then reassemble the sample assembly to complete the matching and fixing with the auxiliary fixture 2 32; repeat steps 2.2-2.4 to complete the loading of the composite crack extension sample 40 of different thicknesses;

[0029] Case 3: The test method for II-III composite fatigue fracture test includes the following steps:

[0030] Step 3.1: The two sets of auxiliary clamps 3 33 are fixed to the two sides of the composite fatigue fracture specimen 40 by bolts and nuts through the through holes of the composite crack extension specimen 40, and the planes with screw holes of the auxiliary clamps 3 33 and the composite crack extension specimen 40 are parallel to each other and closely fitted; the auxiliary clamps 3 33 that have been assembled with the composite crack extension specimen 40 are assembled into the groove of the clamp 2 20 and fixed firmly with the clamp 2 20 by long bolts passing through the through holes, and one side plane of the auxiliary clamps 3 33 is overlapped with one side plane of the clamp 2 20;

[0031] Step 3.2: The two U-shaped hooks are connected to the first set of 90° through holes on the two sets of fan-shaped arc plates through two sets of bolts respectively, and the clamping ends of the U-shaped hooks are connected to the testing machine to transmit the load, so that the composite crack extension specimen 40 is in a type III loading state, and the crack is a tearing type;

[0032] Step 3.3: sequentially adjust the two U-shaped hooks through the two groups of bolts and the second group of 75° through holes, the third group of 60° through holes, the fourth group of 45° through holes, ..., the sixth group of 15° through holes on the two groups of fan-shaped arc plates, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the composite crack extension specimen 40 is subjected to different degrees of type II and type III composite loading states, and the cracks are both sliding type and tearing type;

[0033] Step 3.4: Adjust the two U-shaped hooks to connect with the seventh group of 0° through holes on the two groups of fan-shaped arc plates through two groups of bolts, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the crack of the composite crack extension specimen 40 is in a type II loading state, and the crack is a sliding type;

[0034] Step 3.5: Replace the sample with a composite crack extension sample 40 of different thicknesses, add an adaptive support 34 between the composite crack extension sample 40 and the auxiliary fixture three 33, and then reassemble it into a composite crack extension sample 40 combination, and complete the matching and fixing with the fixture two 20; repeat steps 3.2-3.4 to complete the loading of the composite crack extension sample 40 of different thicknesses.

[0035] Beneficial effects of the present invention:

[0036] 1) When the present invention is working, three different auxiliary clamps are assembled and fixed with the clamp 2 to form a clamp suitable for different composite cracks, and then the entire clamp 2 is connected to the sample by screws, and then the clamp 1 and the clamp 2 are connected by bolts and nuts, and the clamping end of the clamp 1 is connected to the fatigue tensile test and connected thereto, and the clamp 1 is driven by a common tension and compression testing machine, so that the load is transmitted to the sample through the clamp 2 and the auxiliary clamps, thereby meeting the requirements of fatigue fracture tests of type I, type II, type III and I-II, I-III, II-III composite cracks, and laying a foundation for realizing fatigue fracture failure assessment of key mechanical parts and engineering components under complex service conditions.

[0037] 2) When the present invention is working, the adaptive support device cooperates with the auxiliary fixture, and then is assembled and fixed with the second fixture to form a device suitable for samples of different thicknesses. The entire second fixture is connected to the sample by screws, and then the first fixture is connected to the second fixture by bolts and nuts, and the clamping end of the first fixture is connected to the fatigue tensile tester, and the first fixture is driven by a common tension and compression tester, so that the load is transmitted to the sample through the second fixture and the auxiliary fixture. Thus, the loading conditions of fatigue fracture samples of different sizes are met, providing conditions for the study of the size effect of composite cracks.

[0038] 3) The two sets of through holes designed on the fan-shaped plate of the second clamp in the present invention can transfer the applied load to the sample in the radial direction, and can fix the first clamp and the second clamp to avoid rotation that may affect the experimental results. The design of the two sets of through holes on the fan-shaped arc plate can save the fixing assembly of bolts and nuts, and the operation is simple and easy to implement.

[0039] 4) The present invention realizes three different composite crack fatigue fracture tests and composite fatigue fracture test research of samples of different sizes and thicknesses by replacing auxiliary fixtures (without changing the entire set of loading fixtures and samples). Compared with the previous loading fixtures that require complex processing, the present invention reduces the difficulty and cost of operation by replacing auxiliary fixtures to adjust to meet the fatigue fracture test of different types of cracks. The three auxiliary fixtures and lifting devices are simple in overall shape, easy to process and easy to operate.

[0040] 5) The specimens in the present invention can simultaneously meet the requirements of type I, type II, type III and composite fatigue crack growth tests, so the specimens in the present invention are also called CTS (compact tension shear) torsion specimens and CTT (compact tension tear) specimens; the unique structure of the CTS and CTT specimens in the present invention not only has a sufficiently long effective crack growth area, but also is easy to preform type I fatigue cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1( a ) is a schematic diagram of the structure of the Ⅰ-Ⅱ composite loading of scenario 1 of the present invention;

[0042] Figure 1(b) is a schematic diagram of the loading conditions of the specimen at different angles to achieve different composite ratios;

[0043] FIG2( a ) is a schematic diagram of the structure of Type I-III of Situation 2 of the present invention;

[0044] Figure 2(b) is a schematic diagram of the loading conditions of the specimen at different angles to achieve different composite ratios;

[0045] FIG3( a ) is a schematic diagram of the structure of type II-III of scenario 3 of the present invention;

[0046] Figure 3(b) is a schematic diagram of the loading conditions of the specimen at different angles to achieve different composite ratios.

[0047] Figure 4 It is a schematic diagram of the structure of the specimen;

[0048] Figure 5 is a schematic diagram of the structure of fixture 2;

[0049] FIG6( a ) is a schematic diagram of the overall structure of the adaptive lifting device;

[0050] FIG6( b ) is a side view of the overall structural schematic diagram of the adaptive lifting device;

[0051] Figure 7 is a schematic diagram of the structure of sample combination 1;

[0052] Figure 8 is a schematic diagram of the structure of sample combination 2;

[0053] Fig. 9 is a schematic diagram of the structure of sample combination three;

[0054] Fig.10 It is an overall schematic diagram of the present invention realizing three different composite loading forms.

[0055] In the figure: 10, clamp 1; 20, clamp 2; 21, groove; 22, auxiliary clamp first through hole; 23, auxiliary clamp second through hole; 24, screw hole; 31, auxiliary clamp 1; 32, auxiliary clamp 2; 33, auxiliary clamp 3; 34, adaptive support; 341, upper plate; 342, lower plate; 343, connecting rod; 35, conical spring; 40, composite crack extension specimen; 42, fixing hole; 43, closed end; 44, machined notch; 50, hexagon socket bolt; 51, C-grade nut; 52, fastening bolt; 53, A-grade nut; 54, long bolt DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with the specific implementation methods of the present invention and the corresponding drawings. The technical solutions provided by each example of the present invention are described in detail in conjunction with the drawings.

[0057] According to the present invention, a test device and method suitable for non-standard multi-component composite fatigue fracture are provided, which are used to test the composite fatigue fracture behavior of materials. Figure 1 shows the situation when composite type I-II is loaded, and it is subjected to tension and plane shear during the experiment; Figure 2 shows the situation when type I-III is loaded, and it is subjected to tension and anti-plane shear during the experiment; Figure 3 is a schematic diagram of the structure of type II-III, and it is subjected to plane shear and anti-plane shear during the experiment. According to ASTME647 standard, the specimen size is close to that of the standard CT specimen. The hexagon socket bolt 50 and the C-grade nut 51 are used to fix the clamp 10 and the clamp 2 20, the long bolt 54 is used to fix the auxiliary clamp and the clamp 2 20, and the tightening bolt 52 and the A-grade nut 53 are used to connect the auxiliary clamp and the specimen 40.

[0058] FIG. 1(a) is a schematic diagram of a type I-II loading test device. The composite crack extension specimen 40 is connected and fixed to the composite crack extension specimen 40 by two pieces of the auxiliary clamps 1 31 through the through holes thereon to form a specimen assembly. The specimen assembly is connected and fixed to the composite crack extension specimen 40 by two pieces of the clamps 2 20 through the screw holes thereon to the through holes of the auxiliary clamps 1 31 in the specimen assembly. The clamp 10 is connected to any two radially symmetrical through holes on the clamps 2 20, and its clamping end is connected to the testing machine. There are 7 through holes on the outer arc of the clamps 2 20, which are distributed at an angle of 15°. By changing the connection position of the clamps 10 and the through holes in the clamps 2 20, the angle between the load and the prefabricated crack is α, and the angle α is changed to 0°, 15°, 30°, 45°, 60°, 75°, and 90°, the composite loading of type I-II can be realized, and the composite crack extension specimen 40 will withstand type I-II loads with different composite ratios. As shown in Figure 1(b), when α = 90°, the loading direction is perpendicular to the crack, which is a type I loading condition and the crack is an opening type; when 0°<α<90°, it is a type I-II composite loading condition; when α = 0°, the loading direction is parallel to the crack, which is a type II loading condition and the crack is a sliding type.

[0059] FIG2(a) is a schematic diagram of a type I-III loading test device. The composite crack extension specimen 40 is fixed to the composite crack extension specimen 40 by two pieces of the auxiliary clamps 2 32 through the through holes thereon to form a specimen assembly. The specimen assembly is fixed to the composite crack extension specimen 40 by two pieces of the auxiliary clamps 2 32 through the screw holes thereon to the through holes of the auxiliary clamps 2 32 in the specimen assembly. The clamp 10 is connected to any two radially symmetrical through holes on the clamp 2 20, and its clamping end is connected to the testing machine. There are 7 through holes on the outer arc of the clamp 2 20, which are distributed at an angle of 15°. By changing the connection position of the clamp 10 and the through holes in the clamp 2 20, the angle between the load and the prefabricated crack is α, and the angle α is changed to 0°, 15°, 30°, 45°, 60°, 75°, and 90°, the composite loading of type I-III can be realized, and the composite crack extension specimen 40 will withstand type I-III loads with different composite ratios. As shown in Figure 2(b), when α = 90°, the loading direction is perpendicular to the crack, which is a type I loading condition and the crack is an opening type; when 0°<α<90°, it is a type I-III composite loading condition; when α = 0°, the loading direction is parallel to the crack surface, which is a type III loading condition and the crack is a tearing type.

[0060] FIG3(a) is a schematic diagram of a type II-III loading test device. The composite crack extension specimen 40 is formed by two pieces of the auxiliary clamps 3 33 screwed together with the composite crack extension specimen 40 through the screw holes thereon using fastening bolts 52 to form a specimen assembly. The specimen assembly is formed by two pieces of the clamps 2 20 screwed together with the through holes of the auxiliary clamps 3 33 in the specimen assembly through the screw holes thereon. The clamp 1 10 is connected to any two radially symmetrical through holes on the clamp 2 20, and its clamping end is connected to the testing machine. By selecting different symmetrical holes and changing the connection position of the through holes in the clamps 1 10 and the clamps 2 20, the angle between the load and the prefabricated crack is α, and the angle α is changed from 0° to 90°, the type II-III composite loading can be realized, and the composite crack extension specimen 3 is subjected to type II-III loads with different composite ratios. As shown in Figure 3(b), when α = 0°, the loading direction is parallel to the crack, which is a type II load condition and the crack is a sliding type; when 0°<α<90°, it is a type II-III composite load condition; when α = 90°, the loading direction is parallel to the crack surface, which is a type III load condition and the crack is a tearing type.

[0061] like Figure 4As shown, the plate-shaped specimen 40 is rectangular, and a machined notch 44 is provided on the specimen 40, extending from the edge of the specimen 40 along the width direction of the specimen 40 to the inside of the specimen 40; the machined notch 41 is provided in the middle of one side of the specimen 40 along its length direction, and the closed end 43 of the machined notch 44 located inside the specimen 40 is in a peak shape, and the peak line of the peak-shaped closed end 43 of the machined notch 44 is coplanar with the prefabricated fatigue crack surface; fixing holes 42 for the insulating connecting component to pass through are symmetrically provided on both sides of the machined notch 44, and the hole center connection line of the fixing holes 42 is perpendicular to the prefabricated fatigue crack surface.

[0062] like Figure 5 As shown, the clamp 20 is a fan-shaped arc plate, the outermost arc of the clamp 20 and the arcs distributed by the seven groups of through holes inside it are three concentric circles, the first through holes 22 of the auxiliary clamp are distributed on the arc in the middle of the three concentric circles, and the first through holes 23 of the auxiliary clamp are distributed on the innermost arcs of the three concentric circles. The groove 21 is located in the middle of the length direction of the side away from the arc of the rectangular notch of the clamp 20, and is used for assembly and cooperation with the auxiliary clamp 1 31 and the auxiliary clamp 2 32. The screw hole 24 has the same diameter as the through holes at corresponding positions on the auxiliary clamp 1 31, the auxiliary clamp 2 32, and the auxiliary clamp 3 33. A concentric group of long bolts 54 will penetrate into the screw holes and pass through the through holes to fix the three auxiliary clamps to the clamp 2 20.

[0063] As shown in Fig. 6 (a) and (b), the adaptive support 34 is two hard metal plates with a pair of through holes, a group of annular grooves are opened on the inner side of the measuring plate to accommodate the conical spring 35, and a pair of conical springs 35 are arranged around the through hole in the middle, and a group of connecting rods 343 are respectively arranged on both sides of the upper and lower metal plates, the upper ends of which are connected to the upper plate 341 and the lower ends are connected to the notches of the lower plate 342. The adaptive support 34 is penetrated by the fastening bolts 52 and the through holes of the auxiliary fixture and the corresponding through holes of the specimen 40.

[0064] like Figure 7 As shown, the auxiliary fixture 31, the sample 40 and the adaptive support 34 are combined into a sample combination 1 by fastening bolts 52 and Class A nuts 53. The adaptive support 34 has a through hole at the same position as the corresponding through hole of the auxiliary fixture 31. The sample combination is used to make samples of different thicknesses meet the same loading fixture by adding an adaptive support that can automatically adapt to the thickness, and then conduct I-II composite crack fatigue fracture test.

[0065] like Figure 8As shown, the auxiliary fixture 2 32, the sample 40 and the adaptive support 34 are combined to form the sample combination 2 by fastening bolts 52 and Class A nuts 53. The adaptive support 34 has a through hole at the same position as the through hole corresponding to the auxiliary fixture 2 32. The sample combination is used to make samples of different thicknesses meet the same loading fixture by adding an adaptive support that can automatically adapt to the thickness, and then conduct I-III composite crack fatigue fracture test.

[0066] like Fig. 9 As shown, the auxiliary fixture 3 33, the specimen 40 and the adaptive support 34 are combined to form a specimen combination 3 by fastening bolts 52 and Class A nuts 53. The adaptive support 34 has a through hole at the same position as the corresponding screw hole of the auxiliary fixture 3 33. The specimen combination is used to make specimens of different thicknesses meet the same loading fixture by adding an adaptive support that can automatically adapt to the thickness, and then conduct II-III composite crack fatigue fracture test.

[0067] The embodiments of the present application have the following advantages:

[0068] 1. Provides a platform for various composite crack fatigue fracture experiments;

[0069] 2. Reduce the cost of the experiment, and other composite crack tests can be carried out by simply replacing the auxiliary fixture;

[0070] 3. The use of adaptive supports can meet the test requirements of specimens of different thicknesses;

[0071] 4. The experimental device is easy to operate, each component is replaceable, the experiment is accurate and efficient, and the error is small;

[0072] 5. The specimens have the same geometric dimensions, avoiding the influence of size effect.

Claims

1. A test device suitable for non-standard multi-component composite fatigue fracture, characterized in that: include: A clamp 1 (10), a clamp 2 (20), an auxiliary clamp, a composite crack extension specimen (40), and an adaptive support (34) that can cooperate with the auxiliary clamp to automatically adapt to composite crack extension specimens (40) of different thicknesses; The clamp 1 (10) is a pair of U-shaped hooks, with through holes provided on the clamping ends, and the tail ends of the clamping ends are connected to the interface of the electronic universal testing machine to transmit the tensile and compressive loads applied by the testing machine; The second clamp (20) is two fan-shaped arc plates, which are arranged symmetrically at the center of the two fan-shaped arc plates. The fan-shaped arc plates are provided with seven groups of through holes. The center of each group of through holes is placed on the same radius of the fan-shaped arc plate and arranged at equal arc spacing. The two groups of through holes at the two ends are at an arc angle of 90 degrees relative to the center of the fan-shaped arc plate. The arc interval between each group of through holes is 15°. The outermost arc of the second clamp (20) and the arc line distributed by the through holes inside it are three concentric circles. A rectangular notch is provided at the central angle of the fan-shaped arc plate. A groove (21) is provided in the middle of the length direction of the side of the rectangular notch away from the arc. Through holes (24) for assembly with auxiliary clamps are provided on both sides of the groove (21). The second clamp (20) can achieve different composite fatigue fracture test experimental purposes by replacing different auxiliary clamps. The clamp one (10) is fixedly connected to any group of through holes on the clamp two (20) by means of bolts and nuts, so that the load applied to the clamp one (10) is transmitted to the composite crack extension specimen (40) in different directions through the clamp two (20); The composite crack extension specimen (40) is a plate-shaped structure, and the specimen dimensions are close to those of a standard CT specimen. A fixing hole (42) is provided on the composite crack extension specimen (40) for connecting with an auxiliary fixture and an adaptive support (34). The adaptive supporter (34) comprises an upper plate (341), a lower plate (342), a connecting rod (343) and a conical spring (35); the upper plate (341) and the lower plate (342) are connected via the connecting rod (343) and the conical spring (35); connecting rods (343) are provided on both sides of the adaptive supporter (34); the upper end of the connecting rod (343) is connected to the side of the upper plate (341) and can rotate around the connection point; the lower end of the connecting rod (343) is arranged in a groove on the side of the lower plate (342) and can slide along the groove; an annular groove is provided on the lower surface of the upper plate (341) and the upper surface of the lower plate (342); the two ends of the conical spring (35) are arranged in the annular groove; a through hole is provided in the annular groove for matching and connecting with the auxiliary fixture and the composite crack extension specimen (40); The composite crack extension specimen (40) is provided with a machined notch (44) extending from the edge of the composite crack extension specimen (40) and inside the composite crack extension specimen (40) along the width direction of the composite crack extension specimen (40); the machined notch (44) is provided at the middle of one side of the composite crack extension specimen (40) along its length direction, and the closed end (43) of the machined notch (44) located inside the composite crack extension specimen (40) is in a peak shape, and the peak line of the closed end (43) of the machined notch (44) is coplanar with the prefabricated fatigue crack surface; the fixing holes (42) are symmetrically provided on both sides of the machined notch (44), and the hole center line of the fixing holes (42) is perpendicular to the prefabricated fatigue crack surface; The upper plate (341) and the lower plate (342) of the adaptive support (34) are hard metal plates; The auxiliary fixture is an "L"-shaped solid part, including auxiliary fixture one (31), auxiliary fixture two (32) and auxiliary fixture three (33). During the test, the direction of the "L"-shaped part is changed to assemble with fixture two (20) to form a total loading fixture for different composite crack specimens of I-II composite type, I-III composite type and II-III composite type; different forms of loading fixtures can transfer the force applied on the machine to the specimen, thereby realizing the application of different composite loads; In order to realize the connection between different auxiliary fixtures and the second fixture (20) and the specimen, the specific openings and assembly of the auxiliary fixtures are as follows: through holes are respectively provided on both sides of the end faces of the auxiliary fixtures one (31) and the second fixture (32), one end of which is connected to the second fixture (20) through a bolt passing through the through hole, and the other end is connected to the composite crack extension specimen (40) through a bolt and a nut; the auxiliary fixture three (33) is provided with a through hole at its narrow face end, connected to the second fixture (20) through a bolt, and a threaded hole is provided at its wide face end, connected to the composite crack extension specimen (40) through a bolt; an adaptive support (34) is provided between the auxiliary fixture and the composite crack extension specimen (40), so as to be used for fatigue fracture tests of specimens of different thicknesses.

2. The method for using the test device according to claim 1 to conduct a composite fatigue fracture test, characterized in that: The following three situations are included: Case 1: The test method for the Ⅰ-Ⅱ composite crack fatigue fracture test includes the following steps: Step 1.1: A set of auxiliary clamps 1 (31) are respectively passed through the through holes of the composite crack extension specimen (40) by bolts and nuts to be relatively fixed to the two sides of the composite crack extension specimen (40), and it is ensured that the plate-shaped plane of the auxiliary clamp 1 (31) and the plate-shaped plane of the composite crack extension specimen (40) are parallel to each other and closely fit; the auxiliary clamp 1 (31) that has been assembled with the specimen is assembled into the groove of the clamp 2 (20) and is firmly fixed to the clamp 2 (20) by passing bolts through the through holes, and it is ensured that the end face of one side of the auxiliary clamp 1 (31) is aligned and overlapped with the plane of one side of the clamp 2 (20), and the end face of the other side of the auxiliary clamp protrudes relative to the side face of the clamp 2 (20); Step 1.2: The two clamps 1 (10) are connected to the first set of 90° through holes on the two clamps 2 (20) through two sets of bolts respectively, and connected to the electronic universal testing machine through the U-hook clamping end to transmit the load, so that the specimen is in a type I loading state and the crack is an open type; Step 1.3: sequentially adjust the two clamps 1 (10) to connect the second group of 75° through holes, the third group of 60° through holes, the fourth group of 45° through holes, ..., the sixth group of 15° through holes on the two fan-shaped arc plates through bolts, and connect the clamping end of the clamp 1 (10) to the electronic universal testing machine to transmit the load, so that the specimen is subjected to different degrees of type I-II composite loading state, and the cracks are both opening type and sliding type; Step 1.4: Adjust the two U-shaped hooks to connect with the seventh group of 0° through holes on the two fan-shaped arc plates through two groups of bolts respectively, and connect the clamping ends of the U-shaped hooks to the electronic universal testing machine to transmit the load, so that the composite crack extension specimen (40) is in a type II loading state, and the crack is a sliding type; Step 1.5: Replace the composite crack extension specimen (40) with a different thickness, add an adaptive support (34) between the composite crack extension specimen (40) and the auxiliary fixture (31), and then reassemble the specimen assembly to complete the matching and fixing with the fixture (20); repeat steps 1.2-1.4 to complete the loading of the composite crack extension specimen (40) with different thicknesses; Case 2: The test method for the fatigue fracture test of the I-III composite crack includes the following steps: Step 2.1: The two sets of auxiliary clamps 2 (32) are fixed to the two sides of the composite crack extension specimen (40) by bolts and nuts through the through holes of the composite crack extension specimen (40), and it is ensured that the two side planes of the groove of the auxiliary clamp 2 (32) are parallel to and closely fit with the plate-like plane of the specimen; the auxiliary clamp 2 (32) that has been assembled with the specimen is assembled into the groove of the clamp 2 (20) and fixed firmly to the clamp 2 (20) by bolts passing through the through holes, and it is ensured that the plate-like planes on both sides of the auxiliary clamp 2 (32) coincide with the two side planes of the clamp 2 (20); Step 2.2: The two U-shaped hooks are connected to the first set of 90° through holes on the two sets of fan-shaped arc plates through two sets of bolts, and the U-shaped hook clamping ends are connected to the testing machine to transmit the load, so that the composite crack extension specimen (40) is in a type III loading state, and the crack is a tearing type; Step 2.3: sequentially adjust the two U-shaped hooks through the two sets of bolts and the second set of 75° through holes, the third set of 60° through holes, the fourth set of 45° through holes, ..., the sixth set of 15° through holes on the two sets of fan-shaped arc plates, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the composite crack extension specimen (40) is subjected to different degrees of composite loading states of type I and type III, and the cracks are both opening type and tearing type; Step 2.4: Adjust the two U-shaped hooks to be connected to the seventh group of 0° through holes on the two groups of fan-shaped arc plates through two groups of bolts, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the crack of the composite crack extension specimen (40) is in a type I loading state and the crack is an open type; Step 2.5: Replace the specimen with a composite crack extension specimen (40) of different thicknesses, add an adaptive support (34) between the composite crack extension specimen (40) and the second auxiliary fixture (32), and then reassemble the specimen assembly to complete the matching and fixing with the second auxiliary fixture (32); repeat steps 2.2-2.4 to complete the loading of the composite crack extension specimen (40) of different thicknesses; Case 3: The test method for II-III composite fatigue fracture test includes the following steps: Step 3.1: The two sets of auxiliary clamps 3 (33) are fixed to the two sides of the composite crack extension specimen (40) by respectively passing bolts and nuts through the through holes of the composite crack extension specimen (40), and the planes with screw holes of the auxiliary clamps 3 (33) and the composite crack extension specimen (40) are ensured to be parallel to each other and closely fit; the auxiliary clamps 3 (33) that have been assembled with the composite crack extension specimen (40) are assembled into the groove of the clamp 2 (20) and fixed firmly to the clamp 2 (20) by passing long bolts through the through holes, and the planes on one side of the auxiliary clamps 3 (33) are ensured to coincide with the planes on one side of the clamp 2 (20); Step 3.2: The two U-shaped hooks are connected to the first set of 90° through holes on the two sets of fan-shaped arc plates through two sets of bolts, and the U-shaped hook clamping ends are connected to the testing machine to transmit the load, so that the composite crack extension specimen (40) is in a type III loading state, and the crack is a tearing type; Step 3.3: sequentially adjust the two U-shaped hooks through the two sets of bolts and the second set of 75° through holes, the third set of 60° through holes, the fourth set of 45° through holes, ..., the sixth set of 15° through holes on the two sets of fan-shaped arc plates, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the composite crack extension specimen (40) is subjected to different degrees of composite loading states of type II and type III, and the cracks are both sliding type and tearing type; Step 3.4: Adjust the two U-shaped hooks to be connected to the seventh set of 0° through holes on the two sets of fan-shaped arc plates through two sets of bolts, and connect the clamping ends of the U-shaped hooks to the testing machine to transmit the load, so that the crack of the composite crack extension specimen (40) is in a type II loading state, and the crack is a sliding type; Step 3.5: Replace the specimen with a composite crack extension specimen (40) of different thicknesses, add an adaptive support (34) between the composite crack extension specimen (40) and the auxiliary fixture three (33), and then reassemble into a composite crack extension specimen (40) assembly, and complete the matching and fixing with the fixture two (20); repeat steps 3.2-3.4 to complete the loading of the composite crack extension specimen (40) of different thicknesses.

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