Fracture measuring point auxiliary positioning device for fracture toughness sample and use method

Abstract

The invention provides a fracture measuring point auxiliary positioning device for a fracture toughness sample and a use method.The fracture measuring point auxiliary positioning device comprises a mounting frame, seven telescopic units and two positioning parts, and each telescopic unit comprises two linkage rods hinged in a cross shape; every two adjacent telescopic units are hinged through the end of the corresponding linkage rod, the two positioning parts are located at the left ends and the right ends of the seven telescopic units respectively, each positioning part comprises a first connecting rod and a second connecting rod, the installation frame is provided with a penetrating through groove, the marking claw penetrates through the through groove, and the seven telescopic units and the two positioning parts form a telescopic part. The telescopic parts are arranged in a rhombus shape. And when one rhombus deforms, the whole telescopic part can synchronously extend or compress. The marking claws at the two ends are located at the measuring points at the two ends of the sample respectively, the other marking claws can be automatically distributed at the equidistant positions, it is avoided that the positions of nine measuring points are determined one by one through measurement, and the device is suitable for fracture measurement of fracture toughness samples of different specifications.

Description

Technical Field

[0001] The invention relates to the technical field of metal material fracture mechanics performance detection technology, and in particular to a fracture surface measurement point auxiliary positioning device for a fracture toughness sample and a use method thereof. Background Art

[0002] Before the application of offshore structural steel, fracture toughness tests should be carried out in accordance with ISO 12135-2021, ASTM E1820-24, GB / T 21143-2014 and other standards. The most common one is the crack tip opening displacement test (CTOD). The above standards all require that after obtaining the test curve, 9 measuring points should be selected along the thickness direction of the specimen to determine the effectiveness of the initial crack length of the specimen. The position of the measuring point is first determined by locating the position of 0.01 times the thickness on both sides of the thickness direction, and then locating the remaining measuring points by dividing the distance between the above two measuring points into seven equal parts. Finally, the crack length data is measured according to the 9 positioning measuring points on the cross section of the specimen. Although effective control has been carried out during the early processing, due to the existence of processing tolerances, the thickness of each specimen fluctuates within the tolerance range required. For example, the thickness tolerance of the three-point bending specimen is 0.5% of the specimen width, and the tolerance of the compact tensile specimen is 1% of the specimen width. After a large number of tests were carried out, due to the differences in thickness of each sample, it was impossible to quickly and accurately locate the measurement points according to the same standard, which seriously affected the efficiency of the fracture toughness test of the material.

[0003] The commonly used methods at present are manual positioning method and tool microscope positioning method. The fracture surface of the fracture toughness specimen of metal materials is rectangular or square. When processing the specimen, the two surfaces along the thickness direction of the specimen should be parallel to each other. At the same time, the direction of the machined notch is perpendicular to the specimen, and the inner surface of the notch is a plane. After the fracture toughness test is completed, the specimen that has not been broken into two parts continues to be loaded according to the test method until the two parts of the specimen are completely disconnected. Since the machined notch is a plane, the positioning of the measuring point is usually completed on the fractured specimen by manually calculating the position of the measuring point, measuring and positioning, marking and other steps. The manual positioning method calculates the position of each measuring point from the surface by measuring the thickness of the specimen, and locates the measuring point by multiple caliper measurements. Since the measuring points are evenly and symmetrically distributed along the thickness direction of the specimen, it is still necessary to determine at least 5 lengths and 9 marking operations to determine 9 measuring points. The manual positioning method is time-consuming and labor-intensive, and the positioning accuracy and marking accuracy cannot be fully guaranteed. The tool microscope positioning method places the sample fracture on the stage under the lens, adjusts the focal length and light intensity so that the fracture can be clearly displayed through the acquisition software, and determines the sample thickness by manual selection or automatic identification in the software, and then automatically divides it into equal parts, finally realizing the simultaneous positioning and measurement. Although the tool microscope positioning method has a fast measurement speed, it requires manual positioning and focusing before use. For large-sized samples, due to the large thickness, there may be problems such as the field of view not being able to fully cover the sample size, and the image edge distortion causing large measurement errors. In addition, the stage of the tool microscope generally has an upper load limit, and for heavier large-sized samples, it cannot meet the need to fix it on the stage. In addition, since the standard does not make strict requirements on the parallelism of the two end faces in the length direction of the sample, the end faces may not be strictly processed during sample processing, resulting in the cross section of the measured sample not completely coinciding with the focal plane of the tool microscope. Other related technologies that can be found in the prior art mainly focus on the analysis of crack length measurement results, and do not mention what measures are taken to improve the accuracy and efficiency of measuring point location positioning. For example, CN115718032A discloses a sample positioning device and positioning method for a CTOD test, but does not involve precise positioning of the relevant measurement. Summary of the invention

[0004] In view of this, the present invention proposes a fracture measuring point auxiliary positioning device for a fracture toughness specimen and a method for using the device, aiming to solve the problem of long time and low accuracy in locating the measuring point.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] On the one hand, the present invention proposes an auxiliary positioning device for fracture measurement points of fracture toughness specimens, including a mounting frame, seven telescopic units and two positioning parts, each telescopic unit includes two cross-hinged linkage rods, the middle positions of the two linkage rods are hingedly connected to each other through marking claws, and the two adjacent telescopic units are hingedly connected through the ends of the linkage rods, and the two positioning parts are respectively located at the left and right ends of the seven telescopic units, each positioning part includes a first connecting rod and a second connecting rod, the rear end of the first connecting rod and the front end of the second connecting rod are hinged through the marking claw, the front end of the first connecting rod is hinged to the front end of the adjacent telescopic unit, and the rear end of the second connecting rod is hinged to the rear end of the adjacent telescopic unit, the mounting frame has a through slot running through the upper and lower surfaces of the mounting frame, the marking claw passes through the through slot, the seven telescopic units and the two positioning parts form a telescopic part, and the telescopic part is arranged in a rhombus. When a rhombus is deformed, the entire telescopic part can be extended or compressed synchronously. When the fracture measuring point auxiliary positioning device is used to select the positions of nine measuring points on the fracture toughness specimen, it is only necessary to determine the positions of the measuring points at the two ends. The marking claws at the two ends are respectively located at the measuring points at the two ends of the specimen. The remaining marking claws will automatically be distributed at equally spaced positions under the deformation of the diamond structure of the telescopic part, thereby determining the positions of the other seven measuring points. The spacing between adjacent marking claws is equal, avoiding determining the positions of the nine measuring points one by one through measurement, greatly reducing the tediousness of the operation, improving the measurement efficiency, and being suitable for fracture measurement of fracture toughness specimens of different specifications.

[0007] Furthermore, the mounting frame is formed by extending along the thickness direction of the fracture toughness specimen, the through slot forms a slide rail on the upper surface of the mounting frame, and the marking claw passes through the through slot and is stuck in the slide rail to slide freely. Not only can the telescopic part be positioned on the mounting frame, but also when the telescopic part determines the measuring point position and telescopes, the marking claw slides along the slide rail so that multiple marking claws are always located in the same straight line direction, avoiding position deviation and improving the accuracy of positioning the measuring point position.

[0008] Furthermore, a fastening nut is provided at the upper end of the marking claw, and a tip portion is provided at the lower end. The tip portion passes through the through slot and extends out of the lower surface of the mounting frame, and the fastening nut passes through the slide rail and is blocked by the upper surface of the mounting frame. The tip portion facilitates marking the surface of the sample, thereby marking the position of the measuring point. The fastening nut cooperates with the upper surface of the mounting frame to ensure that the marking claw does not fall out of the through slot. At the same time, the distance between the marking claw and the sample is changed by screwing the fastening nut.

[0009] Furthermore, the left and right ends of the telescopic part are respectively provided with limit rods, and the limit rods extend vertically downward. The limit rods are respectively clamped on both sides of the sample fracture, which can not only position the fracture measurement point auxiliary positioning device, but also enable it to move along a straight line parallel to the fracture. By adjusting the distance between the limit rods at both ends, it can be applied to the precise positioning and marking of the fracture of fracture toughness samples of any size.

[0010] Furthermore, the linkage rods are hinged at the apex position of the front end and the apex position of the rear end of each rhombus through connecting pieces, so that there is no gap between the connected linkage rods and they can rotate smoothly, which is convenient for deformation of the telescopic part.

[0011] Furthermore, the through slot passes through the front surface and the rear surface of the mounting frame, the telescopic portion passes through the through slot, and the apex of the front end of the rhombus extends out of the front surface of the mounting frame, and the apex of the rear end of the rhombus extends out of the rear surface of the mounting frame. When the marking claw moves along the slide rail, the telescopic portion as a whole also moves in the through slot, and the through slot provides a space for deformation and telescopic expansion.

[0012] Furthermore, a handle is provided on the front surface or the rear surface of the mounting frame. The operator holds the handle and applies a certain pressure, so that the tip portion leaves a positioning line on the sample surface.

[0013] Furthermore, a scale is provided on the upper surface of the mounting frame to facilitate determination of the position of each marking claw.

[0014] On the other hand, the present invention provides a method for using a fracture measurement point auxiliary positioning device for a fracture toughness specimen, using the fracture measurement point auxiliary positioning device, the method comprising the following steps:

[0015] Step 1: Adjust the limit rods at both ends of the measuring point auxiliary positioning device to the same width as the thickness of the sample, and clamp the limit rods to the outer surface of the sample;

[0016] Step 2: Position the middle marking claw at the center of the two limit rods according to the scale, and tighten the fastening nut corresponding to the middle marking claw;

[0017] Step 3: Determine the positions of the leftmost and rightmost marking claws, and the remaining marking claws are automatically distributed at equal intervals under the restriction of the slide rail and the linkage rod;

[0018] Step 4. Tighten the fastening nuts on the upper ends of all marking claws, fix the telescopic part on the slide rail, with the tip in contact with the upper surface of the sample, hold the handle tightly and apply pressure to pull the telescopic part back and forth to complete the operation of marking the measuring point positioning line.

[0019] Furthermore, in step three, according to the sample thickness H, the distance L between the leftmost and rightmost marking claws is adjusted to L=0.98H, thereby determining the positions of the leftmost and rightmost marking claws.

[0020] Compared with the prior art, the fracture measurement point auxiliary positioning device and use method for fracture toughness specimens described in the present invention have the following advantages:

[0021] (1) When the fracture measuring point auxiliary positioning device is used to select the nine measuring points on the fracture toughness specimen, it is only necessary to determine the measuring points at the two ends. The marking claws at the two ends are respectively located at the measuring points at the two ends of the specimen. The remaining marking claws will automatically be distributed at equally spaced positions under the deformation of the diamond structure of the telescopic part, thereby determining the positions of the other seven measuring points. The spacing between adjacent marking claws is equal, avoiding the need to determine the positions of the nine measuring points one by one through measurement, greatly reducing the tediousness of the operation and improving the measurement efficiency.

[0022] (2) The limit rods are clamped on both sides of the specimen fracture to position the fracture measuring point auxiliary positioning device, and can be moved along a straight line parallel to the fracture. By adjusting the distance between the limit rods at both ends, it can be used for the precise positioning and marking of the fracture toughness specimen of any size.

[0023] (3) The auxiliary positioning device for fracture measuring points has a simple structure, is easy to carry and maintain, is easy to adjust, and can quickly realize automatic equal division of the measuring points to be located. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 It is a schematic diagram of the fracture measurement point auxiliary positioning device of the present invention used for a fracture toughness specimen;

[0026] Figure 2 It is a structural schematic diagram of the fracture measurement point auxiliary positioning device of the present invention;

[0027] Figure 3 for Figure 2 A top view of

[0028] Figure 4 It is a structural schematic diagram of the telescopic part of the present invention;

[0029] Figure 5 It is a structural schematic diagram of the mounting frame of the present invention;

[0030] Figure 6 for Figure 5 Top view of the .

[0031] Description of reference numerals:

[0032] 1. Mounting frame; 2. Telescopic part; 3. Marking claw; 4. Linking rod; 5. First connecting rod; 6. Second connecting rod; 7. Connecting piece; 8. Through slot; 9. Fastening nut; 10. Tip; 11. Slide rail; 12. Handle; 13. Limit rod. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. The embodiments described in the present invention are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0034] It should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0035] The present invention proposes a fracture measuring point auxiliary positioning device for fracture toughness specimens, such as Figure 1-3 As shown, the fracture measurement point auxiliary positioning device includes a mounting frame 1, seven telescopic units and two positioning parts, each telescopic unit includes two cross-shaped hinged linkage rods 4, the middle positions of the two linkage rods 4 are hinged to each other through a marking claw 3, and the two adjacent telescopic units are hinged to each other through the ends of the linkage rod 4, and the two positioning parts are respectively located at the left and right ends of the seven telescopic units, and each positioning part includes a first link rod 5 and a second link rod 6, the rear end of the first link rod 5 and the front end of the second link rod 6 are hinged through the marking claw 3, the front end of the first link rod 5 is hinged to the front end of the adjacent telescopic unit, and the rear end of the second link rod 6 is hinged to the rear end of the adjacent telescopic unit, and the mounting frame 1 has a through groove 8 that runs through the upper and lower surfaces of the mounting frame 1, and the marking claw 3 passes through the through groove 8. The seven telescopic units and the two positioning parts form a telescopic part 2, and the telescopic part 2 is arranged in a rhombus shape, and forms a structure with eight rhombuses and nine marking claws 3. The connection between two adjacent rhombuses is connected by a marking claw 3, and the left and right ends of the eight rhombuses are both marking claws 3.

[0036] When one rhombus is deformed, the entire telescopic part 2 can be extended or compressed synchronously. When the fracture measuring point auxiliary positioning device is used to select nine measuring point positions on the fracture toughness specimen, it is only necessary to determine the measuring point positions at the two ends. The marking claws 3 at the two ends are respectively located at the measuring point positions at the two ends of the specimen. The remaining marking claws 3 will automatically be distributed at equally spaced positions under the deformation of the rhombus structure of the telescopic part 2, thereby determining the positions of the other seven measuring points. The spacing between adjacent marking claws 3 is equal, avoiding the need to determine the positions of the nine measuring points one by one through measurement, greatly reducing the cumbersomeness of the operation, improving the measurement efficiency, and being suitable for fracture measurement of fracture toughness specimens of different specifications.

[0037] The mounting frame 1 is formed by extending along the thickness direction of the fracture toughness specimen, and the through slot 8 forms a slide rail 11 on the upper surface of the mounting frame 1. The marking claw 3 passes through the through slot 8 and is stuck in the slide rail 11 to slide freely. Not only can the telescopic part 2 be positioned on the mounting frame 1, but also when the telescopic part 2 determines the measuring point position and telescopes, the marking claw 3 slides along the slide rail 11 so that multiple marking claws 3 are always located in the same straight line direction, avoiding position deviation and improving the accuracy of positioning the measuring point position.

[0038] As a preferred example of the present invention, Figure 4 As shown, a fastening nut 9 is provided at the upper end of the marking claw 3, and a tip portion 10 is provided at the lower end. The tip portion 10 passes through the through slot 8 and extends out of the lower surface of the mounting frame 1. The fastening nut 9 passes through the slide rail 11 and is blocked by the upper surface of the mounting frame 1. The tip portion 10 is convenient for marking the surface of the sample, thereby marking the measuring point position. The fastening nut 9 and the upper surface of the mounting frame 1 cooperate to ensure that the marking claw 3 does not fall from the through slot 8. At the same time, the distance between the marking claw 3 and the sample is changed by screwing the fastening nut 9. Specifically, loosening the fastening nut 9 can enable the marking claw 3 to move along the slide rail 11. When the measuring point position is determined using the marking claw 3, tightening the fastening nut 9 will position the marking claw 3 at the current position and prevent the marking claw 3 from being offset, which affects the accuracy of the measuring point position determination.

[0039] Furthermore, the marking claw 3 located in the middle is fixed so that it cannot rotate, and the marking claw 3 is ensured to be the center positioning point each time the measurement is performed. By cooperating with the marking claws 3 located at both ends, the purpose of quickly finding the positions of all measuring points is achieved.

[0040] For the telescopic part 2, the left and right ends of the telescopic part 2 are respectively provided with limit rods 13, and the limit rods 13 extend vertically downward. When the fracture measurement point auxiliary positioning device of the present invention is in use, the limit rods 13 are respectively clamped on both sides of the sample fracture, which can not only position the fracture measurement point auxiliary positioning device, but also enable it to move along a straight line parallel to the fracture. By adjusting the distance between the limit rods 13 at both ends, it can be applied to the precise positioning and marking of the fracture of fracture toughness samples of any size.

[0041] The linkage rods 4 are hinged at the apex position of the front end and the apex position of the rear end of each rhombus through the connecting piece 7, so that there is no gap between the connected linkage rods 4 and they can rotate smoothly, which is convenient for the deformation of the telescopic part 2.

[0042] As a preferred example of the present invention, Figure 5-6 As shown, the through slot 8 passes through the front and rear surfaces of the mounting frame 1, the telescopic portion 2 passes through the through slot 8, and the apex of the front end of the rhombus extends out of the front surface of the mounting frame 1, and the apex of the rear end of the rhombus extends out of the rear surface of the mounting frame 1. When the marking claw 3 moves along the slide rail 11, the telescopic portion 2 as a whole also moves in the through slot 8, and the through slot 8 provides a space for deformation and expansion.

[0043] In order to facilitate the operator to operate the fracture measurement point auxiliary positioning device, a handle 12 is provided on the front surface or the rear surface of the mounting frame 1. The operator holds the handle 12 and applies a certain pressure, so that the tip 10 leaves a positioning line on the sample surface.

[0044] The upper surface of the mounting frame 1 is provided with scales to facilitate determination of the position of each marking claw 3 .

[0045] As a preferred example of the present invention, the material of the fracture measurement point auxiliary positioning device is alloy structural steel, so that the fracture measurement point auxiliary positioning device has high hardness and good wear resistance, avoiding wear of the marking claw 3 when moving on the sample surface, and also avoiding the reduction of accuracy caused by rust and deformation, while being easy to process and not easy to deform. Further, the material of the fracture measurement point auxiliary positioning device is 42CrMo steel.

[0046] The present invention also provides a method for using the measuring point auxiliary positioning device, using the above-mentioned measuring point auxiliary positioning device, comprising the following steps:

[0047] Step 1: Adjust the limit rods 13 at both ends of the measuring point auxiliary positioning device to be the same width as the thickness of the sample, and clamp the limit rods 13 to the outer surface of the sample;

[0048] Step 2: Position the middle marking claw 3 at the center of the two limit rods 13 according to the scale, and tighten the fastening nut 9 corresponding to the middle marking claw 3;

[0049] Step 3: determine the positions of the leftmost and rightmost marking claws 3, and the remaining marking claws 3 are automatically distributed at positions with equal spacing under the restriction of the slide rail 11 and the linkage rod 4;

[0050] Step 4: Tighten the fastening nuts 9 on the upper ends of all marking claws 3, fix the telescopic part 2 on the slide rail 11, and make the tip 10 contact the upper surface of the sample. Hold the handle 12 tightly and apply pressure to pull the telescopic part 2 back and forth to complete the operation of marking the measuring point positioning line.

[0051] Furthermore, in step 1, grease is applied to the outer surface of the sample in contact with the limiting rod 13 to ensure that when the telescopic part 2 is pulled by the handle 12, the limiting rod 13 can move smoothly along the surface of the sample.

[0052] Furthermore, in step three, according to the sample thickness H, the distance L between the leftmost and rightmost marking claws 3 is adjusted to L=0.98H, thereby determining the positions of the leftmost and rightmost marking claws 3.

[0053] The fracture measuring point auxiliary positioning device and the use method of the present invention for fracture toughness specimens can realize batch marking of measuring points of fracture toughness specimens of different specifications and sizes, and the marking is completed at one time, which has the advantages of high marking efficiency, accurate positioning, low cost, convenience, and strong applicability, and provides an important auxiliary means for efficient and accurate detection of fracture toughness specimens. At the same time, the fracture measuring point auxiliary positioning device has a simple structure, is easy to carry and maintain, is easy to adjust, and can quickly realize automatic equal division of the measuring points to be located.

[0054] The materials, number of tests, width and thickness of fracture toughness specimens 1-5 are shown in Table 1. The crack tip opening displacement test was performed on fracture toughness specimens 1-5, and nine measuring points were obtained by manual positioning method, and the specific results are shown in Table 2; nine measuring points were obtained by microscope software positioning method, and the specific results are shown in Table 3; nine measuring points were obtained by using a fracture measuring point auxiliary positioning device and use method for fracture toughness specimens of the present invention, and the specific results are shown in Table 4.

[0055] Table 1

[0056] Table 2

[0057] Table 3

[0058] Among them, “ / ” means that the error of the located measuring point is large.

[0059] Table 4

[0060]

[0061] It can be seen from Table 2-3 that the fracture measuring point auxiliary positioning device and the use method of the present invention for fracture toughness specimens can save 67-70% of the operation time compared with the traditional manual positioning method, and save 50-63% of the operation time compared with the tool microscope positioning method, and the qualified rate is increased to 100%, which is higher than the accuracy of the other two methods. The present invention is conducive to the efficient completion of the positioning of the measuring point, and is also conducive to improving the measurement accuracy and efficiency of the fracture crack length.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fracture measuring point auxiliary positioning device for a fracture toughness specimen, characterized in that: The invention comprises a mounting frame (1), seven telescopic units and two positioning parts, each telescopic unit comprises two cross-hinged linkage rods (4), the middle positions of the two linkage rods (4) are hingedly connected to each other through a marking claw (3), and two adjacent telescopic units are hingedly connected through the ends of the linkage rods (4), and the two positioning parts are respectively located at the left and right ends of the seven telescopic units, and each positioning part comprises a first link rod (5) and a second link rod (6), the rear end of the first link rod (5) and the front end of the second link rod (6) are hingedly connected through the marking claw (3), the front end of the first link rod (5) is hingedly connected to the front end of the adjacent telescopic unit, and the rear end of the second link rod (6) is hingedly connected to the rear end of the adjacent telescopic unit, and the mounting frame (1) has a through slot (8) running through the upper surface and the lower surface of the mounting frame (1), and the marking claw (3) passes through the through slot (8). The seven telescopic units and the two positioning parts form a telescopic part (2), and the telescopic part (2) is arranged in a rhombus.

2. The fracture measurement point auxiliary positioning device for fracture toughness specimens according to claim 1, characterized in that: The mounting frame (1) is formed by extending along the thickness direction of the fracture toughness specimen, the through slot (8) forms a slide rail (11) on the upper surface of the mounting frame (1), and the marking claw (3) passes through the through slot (8) and is stuck in the slide rail (11) to slide freely.

3. The fracture measurement point auxiliary positioning device for fracture toughness specimen according to claim 1, characterized in that: The upper end of the marking claw (3) is provided with a fastening nut (9), and the lower end is a tip portion (10). The tip portion (10) passes through the through slot (8) and extends out of the lower surface of the mounting frame (1). The fastening nut (9) passes through the slide rail (11) and is blocked by the upper surface of the mounting frame (1).

4. The fracture measurement point auxiliary positioning device for fracture toughness specimens according to claim 1, characterized in that: Limit rods (13) are respectively provided at the left and right ends of the telescopic portion (2), and the limit rods (13) extend vertically downward.

5. The fracture measurement point auxiliary positioning device for fracture toughness specimen according to claim 1, characterized in that: The linkage rod (4) is hinged at the front end vertex position and the rear end vertex position of each rhombus through a connecting piece (7).

6. The fracture measurement point auxiliary positioning device for fracture toughness specimens according to claim 1, characterized in that: The through slot (8) passes through the front and rear surfaces of the mounting frame (1), the telescopic portion (2) passes through the through slot (8), and the apex of the front end of the rhombus extends out of the front surface of the mounting frame (1), and the apex of the rear end of the rhombus extends out of the rear surface of the mounting frame (1).

7. The fracture measurement point auxiliary positioning device for a fracture toughness specimen according to claim 1, characterized in that: A handle 12 is provided on the front or rear surface of the mounting frame 1 .

8. The fracture measurement point auxiliary positioning device for a fracture toughness specimen according to claim 1, characterized in that: The upper surface of the mounting frame (1) is provided with a scale.

9. A method for using a fracture measurement point auxiliary positioning device for a fracture toughness specimen, characterized in that: The auxiliary positioning device for fracture measurement points according to any one of claims 1 to 8 is used, and the method for using the device comprises the following steps: Step 1: Adjust the limiting rods (13) at both ends of the measuring point auxiliary positioning device to the same width as the thickness of the sample, and clamp the limiting rods (13) to the outer surface of the sample; Step 2: Position the middle marking claw (3) at the center of the two limit rods (13) according to the scale, and tighten the fastening nut (9) corresponding to the middle marking claw (3); Step 3: Determine the positions of the leftmost and rightmost marking claws (3), and the remaining marking claws (3) are automatically distributed at positions with equal spacing under the restriction of the slide rail (11) and the linkage rod (4); Step 4: Tighten the fastening nuts (9) on the upper ends of all the marking claws (3), fix the telescopic part (2) on the slide rail (11), and make the tip (10) contact the upper surface of the sample. Grip the handle (12) and apply pressure to pull the telescopic part (2) back and forth to complete the operation of marking the measuring point positioning line.

10. The method for using the fracture measurement point auxiliary positioning device for a fracture toughness specimen according to claim 9, characterized in that: In the step three, the distance L between the leftmost and rightmost marking claws (3) is adjusted to L=0.98H according to the sample thickness H, thereby determining the positions of the leftmost and rightmost marking claws (3).

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