Tool test piece and prefabrication method for surface opening microcracks of tool test piece

Abstract

The invention provides a tool test piece and a prefabrication method of a surface opening microcrack thereof, and the method comprises the steps: manufacturing a positioning pin hole and a counterbore which penetrate through two metal workpieces in the length direction in the two metal workpieces, splicing the two metal workpieces, and enabling a positioning pin to penetrate through the positioning pin holes of the two metal workpieces to position the two metal workpieces, the method comprises the following steps: firstly, mounting a fastening adjusting assembly in counterbores of two metal workpieces, adjusting the distance between the two metal workpieces by the fastening adjusting assembly, forming a prefabricated microcrack in an abutted seam between the two metal workpieces, and finally, carrying out molding processing treatment on the two metal workpieces to obtain a prefabricated microcrack tool test piece with a preset configuration. According to the tool test piece disclosed by the invention, the opening width of the micro-crack is adjustable, extremely small cracks can be formed, the crack opening is stable, and meanwhile, the prepared tool test piece is relatively small in total volume and mass, convenient to adjust and suitable for different nondestructive testing environments.

Description

Technical Field

[0001] The invention relates to the technical field of aerospace device detection, and in particular to a tooling test piece and a method for prefabricating open microcracks on its surface. Background Art

[0002] In the field of aerospace, the main load-bearing components of aircraft usually adopt a complex configuration design combining skin and ribs to provide sufficient structural strength and stability. However, under working conditions, micro-crack defects are prone to occur on the surface of these components. If these defects are not discovered and handled in time, they may pose a serious threat to the safety and reliability of the aircraft. Therefore, regular maintenance and surface non-destructive testing have become important means to ensure the structural integrity of aircraft. The accuracy of non-destructive testing technology is crucial for the timely detection of micro-cracks. In order to calibrate real cracks and verify the effectiveness of non-destructive testing technology, it is usually necessary to prepare artificial micro-cracks on the surface of commonly used aircraft materials such as aluminum alloys. In this process, the width control of the prefabricated cracks becomes the most critical factor because it directly affects the accuracy and reliability of the non-destructive testing results.

[0003] At present, the methods for preparing artificial microcracks mainly include fatigue tensile test method and feeler gauge clamping method. The fatigue tensile test method prefabricates an incision in the middle part of the standard tensile specimen of aluminum alloy, and performs axial fatigue loading on a universal testing machine, so that fatigue cracks initiate and expand at the prefabricated incision. By controlling the fatigue load level, the crack width can be controlled. However, for complex configurations with ribs, due to the large surface curvature and irregular shape of the specimen, it is difficult to clamp the test bench for tension and compression tests, and deformation is easy to occur during the experiment, resulting in inaccurate crack position distribution and width control. In addition, the microcracks produced by the fatigue tensile method usually only exist in a small section of the tip of the opening, which is difficult to meet the needs of comprehensive testing.

[0004] On the other hand, the feeler gauge clamping method simulates cracks by making two identical aluminum alloy sliders and placing feeler gauges of known thickness on their opposite surfaces. Although this method can control the crack width more accurately (basically equal to the feeler gauge thickness), the resulting open crack width is often larger due to the thickness of the feeler gauge. At the same time, since the relative positions of the aluminum alloy blocks are not fixed, additional clamping devices are required, resulting in a larger overall volume and mass of the simulated cracked parts, making them inconvenient to move. In addition, cracks in planar structures are difficult to meet the detection requirements for curved surface configurations and still require additional processing.

[0005] In summary, the existing crack preparation methods have many shortcomings in preparing artificial microcracks, especially when dealing with complex configurations with ribs, it is difficult to meet the accuracy and reliability requirements of non-destructive testing technology. Therefore, it is necessary to develop a more effective, accurate and applicable crack preparation method for complex configurations. Summary of the invention

[0006] The present invention provides a tooling test piece and a method for prefabricating open microcracks on its surface, aiming to solve at least one of the above technical problems.

[0007] The present invention provides a method for prefabricating open microcracks on the surface of a tooling specimen, comprising the following steps: Step 1, providing two metal workpieces, and smoothing the opposite surfaces of the two metal workpieces; Step 2, making a positioning pin hole and a countersunk hole on each of the metal workpieces that penetrate the metal workpieces along the length direction; Step 3, splicing the two metal workpieces so that the positioning pin holes on the two metal workpieces are aligned with each other, and the countersunk holes on the two metal workpieces are aligned with each other; Step 4, installing positioning pins in the positioning pin holes of the two metal workpieces to position the two metal workpieces to form a workpiece assembly; Step 5, installing a tightening adjustment component in the countersunk holes of the two metal workpieces, wherein the tightening adjustment component can adjust the distance between the two metal workpieces so that a prefabricated microcrack is formed in the joint between the two metal workpieces; Step 6: Perform a forming process on the workpiece assembly to obtain a prefabricated microcrack tooling specimen with a preset configuration.

[0008] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, in step 2, the step of making a countersunk hole penetrating the metal workpiece along the length direction on each of the metal workpieces comprises: An end hole extending in the length direction is formed on one side surface of the metal workpiece, and then a connecting hole communicating with the end hole is formed on the other side surface of the metal workpiece; The end hole is coaxially arranged with the connecting hole, and the diameter of the end hole is larger than the diameter of the connecting hole.

[0009] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, in step 2, the diameters of the locating pin holes on the two metal workpieces are the same at least on the opposite sides of the two metal workpieces.

[0010] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, in step 3, the step of splicing the two metal workpieces comprises: The surfaces of the two metal workpieces having the connecting holes are used as opposite surfaces, the connecting holes on the two metal workpieces are aligned with each other, and the positioning pin holes on the two metal workpieces are aligned with each other for splicing.

[0011] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, the fastening and adjusting assembly includes a bolt and a nut. In step 5, the step of installing the fastening and adjusting assembly in the countersunk holes of the two metal workpieces includes: Step 5-1, inserting a bolt into the countersunk hole from the surface of the first metal workpiece having the end hole, so that the head of the bolt abuts against the step surface between the end hole and the connecting hole of the first metal workpiece, and the tail of the bolt extends into the end hole of the second metal workpiece; Step 5-2: insert a nut into the countersunk hole from the surface of the second metal workpiece having the end hole, and thread the nut onto the bolt.

[0012] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, the width of the prefabricated microcracks between the two metal workpieces is adjusted by adjusting the tightness between the bolt and the nut.

[0013] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, in step 6, the step of performing a molding process on the workpiece assembly includes: Step 6-1, performing milling processing on the workpiece component to form a rib plate and a curved surface skin configuration on the surface of the workpiece component, and performing polishing processing on the machined surface of the workpiece component; Step 6-2, hollowing out the workpiece assembly by wire cutting process to form a hollow hole penetrating the workpiece assembly along the width direction of the workpiece assembly, and obtaining a prefabricated micro-crack tooling specimen with a rib plate and a curved surface skin.

[0014] According to the method for prefabricating open microcracks on the surface of a tooling specimen provided by the present invention, in the step 1, after smoothing the opposing surfaces of the two metal workpieces, the average roughness of the opposing surfaces of the two metal workpieces is made to be 0.8, and the flatness of the opposing surfaces of the two metal workpieces is made to be 0.01.

[0015] The present invention also provides a tooling test piece, comprising: A first metal test piece, comprising a first countersunk hole penetrating the first metal test piece along a length direction; a second metal test piece, arranged opposite to the first metal test piece, comprising a second countersunk hole penetrating the second metal test piece along a length direction, the second countersunk hole corresponding to the first countersunk hole; A fastening and adjusting assembly, which is inserted into the first countersunk hole and the second countersunk hole and is used for assembling the first metal test piece and the second metal test piece; The joint between the first metal test piece and the second metal test piece forms a prefabricated microcrack, and the width of the prefabricated microcrack is adjusted by adjusting the tightness of the fastening adjustment component.

[0016] According to the fixture specimen provided by the present invention, the fastening and adjusting assembly includes a bolt and a nut, the first countersunk hole and the second countersunk hole both include an end hole and a connecting hole coaxially arranged, and the diameter of the end hole is larger than the diameter of the connecting hole; The surfaces of the first metal test piece and the second metal test piece having the connecting hole are arranged opposite to each other, the bolt is passed through the end hole of the first metal test piece to the end hole of the second metal test piece, and the nut is arranged in the end hole of the second metal test piece and is threadedly connected with the bolt.

[0017] The above technical solution of the present invention has the following beneficial effects: The prefabrication method of the tooling specimen and the surface opening microcracks thereof of the present invention is to make positioning pin holes and countersunk holes penetrating the metal workpieces along the length direction on two metal workpieces, splice the two metal workpieces, use positioning pins to penetrate the positioning pin holes of the two metal workpieces to position the two metal workpieces, and then install the fastening adjustment component in the countersunk holes of the two metal workpieces. The fastening adjustment component can adjust the distance between the two metal workpieces so that the joint between the two metal workpieces forms prefabricated microcracks. Finally, the two metal workpieces are formed and processed to obtain a prefabricated microcrack tooling specimen with a preset configuration. The microcrack opening width of the tooling specimen prepared by the above method is adjustable, and extremely small cracks can be formed. The crack opening is stable, and the surface of the specimen is not easy to deform, which can ensure the number and distribution position of the cracks. At the same time, the overall volume and mass of the tooling specimen prepared are small, which is convenient to adjust and suitable for different non-destructive testing environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1A flow chart of a method for prefabricating open microcracks on the surface of a tooling specimen provided by an embodiment of the present invention; Figure 2 A three-dimensional structural diagram of a first metal workpiece provided with a positioning pin hole and a countersunk hole according to an embodiment of the present invention; Figure 3 for Figure 2 A front view of the first metal workpiece shown in ; Figure 4 for Figure 2 A cross-sectional view of a first metal workpiece shown in ; Figure 5 A three-dimensional structural diagram of a second metal workpiece provided with a positioning pin hole and a countersunk hole according to an embodiment of the present invention; Figure 6 for Figure 5 A front view of a second metal workpiece shown in ; Figure 7 for Figure 5 A cross-sectional view of a second metal workpiece shown in ; Figure 8 A three-dimensional diagram of a first metal workpiece and a second metal workpiece after being assembled according to an embodiment of the present invention; Fig. 9 for Figure 8 A front view of the first metal workpiece and the second metal workpiece after being assembled; Fig.10 for Figure 8 A cross-sectional view of the first metal workpiece and the second metal workpiece after being assembled; Fig.11 A three-dimensional diagram of a first metal workpiece and a second metal workpiece after forming and processing provided by an embodiment of the present invention; Fig.12 for Fig.11 A front view of the first metal workpiece and the second metal workpiece after forming and processing as shown in FIG. Fig.13 for Fig.11 A cross-sectional view of the first metal workpiece and the second metal workpiece after forming processing; Fig.14 This is the experimental data diagram of crack formation using the traditional fatigue tensile method; Fig.15 This is the experimental data diagram of crack formation using the traditional feeler gauge clamping method; Fig.16 This is a graph of experimental data of cracks formed by using the method for prefabricating open micro-cracks on the surface of a tooling specimen of the present invention.

[0020] Reference numerals: 1. First metal workpiece; 2. Second metal workpiece; 3. Positioning pin; 4. Bolt; 5. Nut; 101. First positioning pin hole; 102. First countersunk hole; 1021. First end hole; 1022. First connecting hole; 201. Second positioning pin hole; 202. Second countersunk hole; 2021. Second end hole; 2022. Second connecting hole; 1a. First metal specimen; 2a. Second metal specimen. DETAILED DESCRIPTION

[0021] 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 below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The purpose of the present invention is to provide a tooling specimen with microcracks, which may have a preset configuration, for example, a tooling specimen with a rib and a curved skin configuration, so as to simulate real cracks on the rib and skin surfaces of a spacecraft, thereby testing the specimen.

[0023] Specifically, see Figure 1-Figure 13 The present invention provides a method for prefabricating open microcracks on the surface of a tooling specimen, such as Figure 1 As shown, the prefabrication method comprises the following steps: Step 1: provide two metal workpieces and perform smoothing on the opposite surfaces of the two metal workpieces.

[0024] Specifically, a first metal workpiece 1 and a second metal workpiece 2 are provided, and the opposing surfaces of the first metal workpiece 1 and the second metal workpiece 2 are smoothed so that the average roughness of the opposing surfaces of the first metal workpiece 1 and the second metal workpiece 2 is 0.8 (i.e., Ra0.8), and the flatness of the opposing surfaces of the first metal workpiece 1 and the second metal workpiece 2 is 0.01, and the roughness of other surfaces of the first metal workpiece 1 and the second metal workpiece 2 is processed to Ra3.2.

[0025] Step 2: Make a positioning pin hole and a countersunk hole on each metal workpiece that penetrates the metal workpiece along the length direction.

[0026] Among them, Figure 2-Figure 4 As shown, the first metal workpiece 1 is subjected to through-hole drilling processing, and at least one first positioning pin hole 101 is made on the first metal workpiece 1 along the length direction, and then at least one first countersunk hole 102 is made on the first metal workpiece 1 along the length direction, and the first positioning pin hole 101 and the first countersunk hole 102 are arranged at intervals.

[0027] Specifically, the step of making the first countersunk hole 102 penetrating the first metal workpiece 1 along the length direction on the first metal workpiece 1 includes: making a first end hole 1021 extending along the length direction on one side surface of the first metal workpiece 1, and then making a first connecting hole 1022 connected to the first end hole 1021 on the other side surface of the first metal workpiece 1. The first end hole 1021 and the first connecting hole 1022 are coaxially arranged, and the diameter of the first end hole 1021 is greater than the diameter of the first connecting hole 1022. The first end hole 1021 and the first connecting hole 1022 are combined to form the first countersunk hole 102, and a step surface is formed at the junction of the first end hole 1021 and the first connecting hole 1022.

[0028] The first positioning pin hole 101 may be a cylindrical hole or a conical hole.

[0029] like Figure 5-Figure 7 As shown, the second metal workpiece 2 is subjected to through-hole drilling processing, and at least one second positioning pin hole 201 is made on the second metal workpiece 2 along the length direction, and then at least one second countersunk hole 202 is made on the second metal workpiece 2 along the length direction, and the second positioning pin hole 201 and the second countersunk hole 202 are arranged at intervals.

[0030] Specifically, the step of making the second countersunk hole 202 penetrating the second metal workpiece 2 along the length direction on the second metal workpiece 2 includes: making a second end hole 2021 extending along the length direction on one side surface of the second metal workpiece 2, and then making a second connecting hole 2022 connected to the second end hole 2021 on the opposite other side surface of the second metal workpiece 2. The second end hole 2021 and the second connecting hole 2022 are coaxially arranged, and the diameter of the second end hole 2021 is greater than the diameter of the second connecting hole 2022. The second end hole 2021 and the second connecting hole 2022 are combined to form the second countersunk hole 202, and a step surface is formed at the junction of the second end hole 2021 and the second connecting hole 2022.

[0031] The second positioning pin hole 201 may be a cylindrical hole or a conical hole.

[0032] Furthermore, the first locating pin hole 101 and the second locating pin hole 201 have the same end diameter at least on the opposite side of the first metal workpiece 1 and the second metal workpiece 2. In order to prevent a very small coaxiality error, preferably, on the opposite side of the first metal workpiece 1 and the second metal workpiece 2, the ends of the first locating pin hole 101 and the second locating pin hole 201 are both provided with a chamfered structure.

[0033] In a preferred embodiment, the first locating pin hole 101 and the second locating pin hole 201 are spliced ​​and combined to form a tapered pin hole with a certain taper, and the overall taper is 1:50. Among them, on the opposite sides of the first metal workpiece 1 and the second metal workpiece 2, the end face diameter of the first locating pin hole 101 is larger than the end face diameter of the second locating pin hole 201. A conical locating pin can be inserted into the conical pin hole to connect the two metal workpieces and realize the positioning of the two metal workpieces. Compared with the use of interference fit for assembly of cylindrical pin holes and cylindrical locating pins, the use of conical pin holes and conical locating pins for assembly in this embodiment is conducive to fine-tuning the final crack width during the crack making process, and has the advantages of easy installation, good self-locking, and convenient disassembly.

[0034] The diameters of the first end hole 1021 and the second end hole 2021 are the same, and the diameters of the first connection hole 1022 and the second connection hole 2022 are the same.

[0035] The number of the first positioning pin holes 101 and the number of the second positioning pin holes 201 are the same, and the number of the first countersunk holes 102 and the second countersunk holes 202 are also the same.

[0036] like Figure 2 and Figure 5 As shown, in this embodiment, considering the stability of the assembly of the tooling test piece, two first positioning pin holes 101 and four first countersunk holes 102 are provided on the first metal workpiece 1, and the two first positioning pin holes 101 are distributed on the two side edges of the first metal workpiece 1, and the distribution of the four first countersunk holes 102 can be determined according to actual conditions, and no limitation is made here. Similarly, the distribution of the second positioning pin holes 201 and the second countersunk holes 202 on the second metal workpiece 2 is similar, and no further description is given here.

[0037] Step 3, splicing the two metal workpieces so that the locating pin holes on the two metal workpieces are aligned with each other, and the countersunk holes on the two metal workpieces are aligned with each other.

[0038] Specifically, Figure 4 , Figure 7 and Figure 8 As shown, with the surface of the first metal workpiece 1 having the first connecting hole 1022 and the surface of the second metal workpiece 2 having the second connecting hole 2022 as the opposing surfaces of the first metal workpiece 1 and the second metal workpiece 2, the first connecting hole 1022 and the second connecting hole 2022 are aligned with each other, and the first positioning pin hole 101 and the second positioning pin hole 201 are aligned with each other, and the first metal workpiece 1 and the second metal workpiece 2 are spliced.

[0039] Step 4: Install the positioning pins in the positioning pin holes of the two metal workpieces to position the two metal workpieces to form a workpiece assembly.

[0040] Specifically, Figure 8-Figure 10 As shown, the positioning pins 3 are inserted into the first positioning pin holes 101 and the second positioning pin holes 201, and the first metal workpiece 1 and the second metal workpiece 2 can be positioned by the positioning pins 3. The number of the positioning pins 3 is the same as the number of the first positioning pin holes 101 or the second positioning pin holes 201.

[0041] Step 5, installing the fastening adjustment component in the countersunk holes of the two metal workpieces, the fastening adjustment component can adjust the distance between the two metal workpieces so that prefabricated micro cracks are formed in the joint between the two metal workpieces.

[0042] like Figure 8-Figure 10 As shown, in the present embodiment, the fastening and adjusting assembly includes a bolt 4 and a nut 5. Of course, in other embodiments, the fastening and adjusting assembly may also be other types of structures, such as a telescopic assembly, etc., as long as it can fix the first metal workpiece 1 and the second metal workpiece 2 and adjust the distance between the first metal workpiece 1 and the second metal workpiece 2.

[0043] Specifically, the steps of installing the fastening and adjusting assembly in the countersunk holes of two metal workpieces include: Step 5-1, insert the bolt 4 from the surface of the first metal workpiece 1 having the first end hole 1021 into the first countersunk hole 102 and the second countersunk hole 202, so that the head of the bolt 4 abuts against the step surface between the first end hole 1021 and the first connecting hole 1022, and at the same time, the tail of the bolt 4 extends into the second end hole 2021 of the second metal workpiece 2.

[0044] Step 5 - 2 , insert the nut 5 into the second countersunk hole 202 from the surface of the second metal workpiece 2 having the second end hole 2021 , and thread the nut 5 onto the bolt 4 .

[0045] The number of the tightening adjustment components is the same as the number of the first countersunk holes 102 or the second countersunk holes 202. The joint between the first metal workpiece 1 and the second metal workpiece 2 forms a prefabricated microcrack, and the width of the prefabricated microcrack between the first metal workpiece 1 and the second metal workpiece 2 is adjusted by adjusting the tightness between the bolt 4 and the nut 5.

[0046] Step 6: Perform forming processing on the workpiece assembly to obtain a prefabricated microcrack tooling specimen with a preset configuration.

[0047] See also Figure 8 , Figure 11-13 Specifically, the steps of forming the workpiece assembly include: Step 6-1, perform milling processing on the workpiece component (specifically, Figure 8The milling process is performed at the processing position 1 shown in the figure), so that the surface of the workpiece component forms a rib plate and a curved surface skin configuration, and the processing surface of the workpiece component is polished.

[0048] After the machined surface of the workpiece assembly is polished, the average roughness of the machined surface of the workpiece assembly is 0.8.

[0049] Step 6-2: hollow out the workpiece components using wire cutting technology (specifically, see Fig.13 The processing position 2 shown in the figure is hollowed out to form a hollow hole that penetrates the workpiece component along the width direction of the workpiece component, thereby obtaining a prefabricated micro-crack tooling specimen with a rib plate and a curved surface skin.

[0050] In one embodiment, after the above step 5 is completed and before step 6, the following step may be further included: removing the locating pins from the locating pin holes of the two metal workpieces.

[0051] In this way, it is convenient to subsequently tighten and adjust the width of the micro-cracks by the adjustment component.

[0052] In this embodiment, the first metal workpiece and the second metal workpiece are first connected by bolts and nuts to form microcracks, and then the workpiece assembly is formed as a whole. After the forming process, the first metal workpiece forms the first metal test piece 1a, and the second metal workpiece forms the second metal test piece 2a, so that the tooling test piece can perfectly obtain the rib plate and skin configuration, the size of the prefabricated microcracks is stable, and this method will not cause the tooling test piece to deform, and can better restore the real cracks on the surface of the aircraft wing configuration. At the same time, it can also realize the free setting of the distribution position and opening width of the microcracks, while ensuring that there are no pits and scratches on the surface of the test piece.

[0053] The present invention also provides a tooling specimen prepared by the above-mentioned prefabrication method of the surface opening microcracks of the tooling specimen, which can be referred to Figure 11-13 As shown, the tooling test piece has a rib plate and curved skin configuration, and includes a first metal test piece 1a and a second metal test piece 2a. The first metal test piece 1a includes a first positioning pin hole 101 and a first countersunk hole 102 that penetrate the first metal test piece 1a along the length direction. The second metal test piece 2a is arranged opposite to the first metal test piece 1a, and the second metal test piece 2a includes a second positioning pin hole 201 and a second countersunk hole 202 that penetrate the second metal test piece 2a along the length direction. The second positioning pin hole 201 corresponds to the first positioning pin hole 101 one-to-one, and the second countersunk hole 202 corresponds to the first countersunk hole 102 one-to-one.

[0054] The tightening and adjusting assembly is inserted into the first countersunk hole 102 and the second countersunk hole 202, and is used to assemble the first metal test piece 1a and the second metal test piece 2a. The joint between the first metal test piece 1a and the second metal test piece 2a forms a prefabricated microcrack, and the width of the prefabricated microcrack is adjusted by adjusting the tightness of the tightening and adjusting assembly.

[0055] The first countersunk hole 102 includes a first end hole 1021 and a first connecting hole 1022. The first end hole 1021 and the first connecting hole 1022 are coaxially arranged and interconnected, and the diameter of the first end hole 1021 is larger than the diameter of the first connecting hole 1022. A step surface is formed at the junction of the first end hole 1021 and the first connecting hole 1022.

[0056] The second countersunk hole 202 includes a second end hole 2021 and a second connecting hole 2022. The second end hole 2021 and the second connecting hole 2022 are coaxially arranged and connected to each other. The diameter of the second end hole 2021 is larger than the diameter of the second connecting hole 2022. A step surface is formed at the junction of the second end hole 2021 and the second connecting hole 2022.

[0057] Among them, the first positioning pin hole 101 and the second positioning pin hole 201 have the same diameter at least on the opposite sides of the first metal specimen 1a and the second metal specimen 2a, the first end hole 1021 and the second end hole 2021 have the same diameter, and the first connecting hole 1022 and the second connecting hole 2022 have the same diameter.

[0058] In order to prevent a very small coaxiality error, preferably, on the opposite sides of the first metal test piece 1a and the second metal test piece 2a, the ends of the first locating pin hole 101 and the second locating pin hole 201 are both provided with chamfered structures.

[0059] In a preferred embodiment, the first locating pin hole 101 and the second locating pin hole 201 are spliced ​​and combined to form a tapered pin hole with a certain taper, and the overall taper is 1:50. Among them, on the opposite sides of the first metal test piece 1a and the second metal test piece 2a, the end face diameter of the first locating pin hole 101 is larger than the end face diameter of the second locating pin hole 201. During the assembly process, a conical locating pin can be inserted into the conical pin hole to connect the two metal test pieces and realize the positioning of the two metal test pieces. Compared with the use of interference fit for assembly of cylindrical pin holes and cylindrical locating pins, the use of conical pin holes and conical locating pins for assembly in this embodiment is conducive to fine-tuning the final crack width during the crack production process, and has the advantages of easy installation, good self-locking, and convenient disassembly.

[0060] In one embodiment, the tightening and adjusting assembly includes a bolt 4 and a nut 5. The surfaces of the first metal test piece 1a and the second metal test piece 2a having connection holes are arranged opposite to each other. The bolt 4 penetrates from the first end hole 1021 of the first metal test piece 1a into the first countersunk hole 102 and the second countersunk hole 202. The head of the bolt 4 abuts against the step surface between the first end hole 1021 and the first connection hole 1022, and the tail of the bolt 4 extends into the second end hole 2021 of the second metal test piece 2a. The nut 5 is arranged in the second end hole 2021 of the second metal test piece 2a and is threadedly connected with the tail end of the bolt 4. The width of the microcrack between the first metal test piece 1a and the second metal test piece 2a is adjusted by adjusting the tightness between the bolt 4 and the nut 5.

[0061] The present invention obtains tightly fitting micro cracks by splicing two high-precision smooth flat metal workpieces and utilizing the errors formed during the processing. The tooling specimen prepared by the preparation method of the present invention has an extremely small crack opening width, a stable size, and can ensure the number and distribution of cracks; at the same time, the overall volume and mass of the tooling specimen are small, which is convenient for adjustment; the crack width can also be fine-tuned by changing the tightness of the bolts, and is suitable for different non-destructive testing environments.

[0062] The following combination Figure 14-16 The crack widths of the tooling specimens prepared by the prefabrication method of the present invention and the tooling specimens prepared by the traditional method were compared, as follows: like Fig.14 As shown in the figure, a notch is prefabricated in the middle of the aluminum alloy standard tensile specimen by the traditional fatigue tensile method, and the specimen is subjected to axial fatigue loading to form a crack at the notch. Four points are selected as marking points in the extension direction of the crack, and the crack widths at the four marking points are 8.12μm, 2.79μm, 3.27μm and 3.87μm respectively.

[0063] like Fig.15 As shown in the figure, the crack is formed by the traditional feeler gauge clamping method. (a) shows feeler gauges of different thicknesses, (b) shows two identical aluminum alloy sliders, and (c) shows the clamping device. The two aluminum alloy sliders are placed on the clamping device, and a feeler gauge is placed between the two aluminum alloy sliders. The clamping device clamps the two aluminum alloy sliders so that a crack is formed in the gap between the two aluminum alloy sliders. Among them, the width of the crack formed by this method at the narrowest position is 41.25μm.

[0064] like Fig.16As shown, a crack is formed on the surface of a tooling specimen using the prefabrication method of the present invention, and four points are selected as marking points in the extension direction of the crack. The crack widths at the four marking points are 6.06 μm, 5.09 μm, 5.45 μm and 5.93 μm respectively. The average width of the crack is 5.63 μm.

[0065] It can be seen that compared with the traditional crack prefabrication method, the cracks prepared by the prefabrication method of the present invention have smaller average width and standard deviation, stable crack opening, and the specimen surface is not easy to deform. The number and distribution position of the cracks can be guaranteed, and the crack width can be adjusted according to actual needs; at the same time, the overall volume and mass of the prepared tooling specimen are small, which is convenient for adjustment and suitable for different non-destructive testing environments.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for prefabricating open microcracks on the surface of a tooling specimen, characterized in that: The following steps are involved: Step 1, providing two metal workpieces, and smoothing the opposite surfaces of the two metal workpieces; Step 2, making a positioning pin hole and a countersunk hole on each of the metal workpieces that penetrate the metal workpieces along the length direction; Step 3, splicing the two metal workpieces so that the positioning pin holes on the two metal workpieces are aligned with each other, and the countersunk holes on the two metal workpieces are aligned with each other; Step 4, installing positioning pins in the positioning pin holes of the two metal workpieces to position the two metal workpieces to form a workpiece assembly; Step 5, installing a tightening adjustment component in the countersunk holes of the two metal workpieces, wherein the tightening adjustment component can adjust the distance between the two metal workpieces so that a prefabricated microcrack is formed in the joint between the two metal workpieces; Step 6: Perform a forming process on the workpiece assembly to obtain a prefabricated microcrack tooling specimen with a preset configuration.

2. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 1, characterized in that: In step 2, the step of making a countersunk hole penetrating the metal workpiece along the length direction on each of the metal workpieces comprises: An end hole extending in the length direction is formed on one side surface of the metal workpiece, and then a connecting hole communicating with the end hole is formed on the other side surface of the metal workpiece; The end hole is coaxially arranged with the connecting hole, and the diameter of the end hole is larger than the diameter of the connecting hole.

3. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 2, characterized in that: In step 2, the diameters of the positioning pin holes on the two metal workpieces are the same at least on the opposite sides of the two metal workpieces.

4. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 2 or 3, characterized in that: In step 3, the step of splicing the two metal workpieces comprises: The surfaces of the two metal workpieces having the connecting holes are used as opposite surfaces, the connecting holes on the two metal workpieces are aligned with each other, and the positioning pin holes on the two metal workpieces are aligned with each other for splicing.

5. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 4, characterized in that: The fastening and adjusting assembly includes a bolt and a nut. In step 5, the step of installing the fastening and adjusting assembly in the countersunk holes of the two metal workpieces includes: Step 5-1, inserting a bolt into the countersunk hole from the surface of the first metal workpiece having the end hole, so that the head of the bolt abuts against the step surface between the end hole and the connecting hole of the first metal workpiece, and the tail of the bolt extends into the end hole of the second metal workpiece; Step 5-2: insert a nut into the countersunk hole from the surface of the second metal workpiece having the end hole, and thread the nut onto the bolt.

6. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 5, characterized in that: The width of the prefabricated micro-cracks between the two metal workpieces can be adjusted by adjusting the tightness between the bolt and the nut.

7. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 1, characterized in that: In step 6, the step of performing a forming process on the workpiece assembly includes: Step 6-1, performing milling processing on the workpiece component to form a rib plate and a curved surface skin configuration on the surface of the workpiece component, and performing polishing processing on the machined surface of the workpiece component; Step 6-2, hollowing out the workpiece assembly by wire cutting process to form a hollow hole penetrating the workpiece assembly along the width direction of the workpiece assembly, and obtaining a prefabricated micro-crack tooling specimen with a rib plate and a curved surface skin.

8. The method for prefabricating open microcracks on the surface of a tooling specimen according to claim 1, characterized in that: In the step 1, after the opposing surfaces of the two metal workpieces are smoothed, the average roughness of the opposing surfaces of the two metal workpieces is 0.8, and the flatness of the opposing surfaces of the two metal workpieces is 0.

01.

9. A tooling test piece, characterized in that: include: A first metal test piece, comprising a first countersunk hole penetrating the first metal test piece along a length direction; a second metal test piece, arranged opposite to the first metal test piece, comprising a second countersunk hole penetrating the second metal test piece along a length direction, the second countersunk hole corresponding to the first countersunk hole; A fastening and adjusting assembly, which is inserted into the first countersunk hole and the second countersunk hole and is used for assembling the first metal test piece and the second metal test piece; The joint between the first metal test piece and the second metal test piece forms a prefabricated microcrack, and the width of the prefabricated microcrack is adjusted by adjusting the tightness of the fastening adjustment component.

10. The tooling test piece according to claim 9, characterized in that: The tightening and adjusting assembly includes a bolt and a nut, the first countersunk hole and the second countersunk hole each include an end hole and a connecting hole that are coaxially arranged, and the diameter of the end hole is larger than the diameter of the connecting hole; The surfaces of the first metal test piece and the second metal test piece having the connecting hole are arranged opposite to each other, the bolt is passed through the end hole of the first metal test piece to the end hole of the second metal test piece, and the nut is arranged in the end hole of the second metal test piece and is threadedly connected to the bolt.

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