Heat dissipation clamp and welding heat affected zone fatigue crack propagation sample preparation method

Abstract

The invention relates to the technical field of heat affected zone fatigue detection, in particular to a heat dissipation clamp and a preparation method of a welding heat affected zone fatigue crack propagation sample. The invention provides a heat dissipation clamp and a welding heat affected zone fatigue crack propagation sample preparation method. The heat dissipation clamp comprises a clamp body. A heat dissipation fin plate is arranged on the clamp body, the heat dissipation fin plate comprises a shell, and a plurality of liftable fins are arranged on the shell; when the fins are not measured, the ends, far away from the shell, of all the fins are at the same height; when the fins are used for measuring an object to be measured, different fins move along the surface of the object to be measured, and the fin close to one side of the shell retracts into the shell. The method aims at solving the technical problem that in the prior art, no samples with fatigue crack propagation in the heat affected zone are welded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-affected zone fatigue detection, and particularly relates to a heat dissipation clamp and a method for preparing a welding heat-affected zone fatigue crack propagation sample. BACKGROUND

[0002] The heat-affected zone of an actual welded joint is extremely narrow in a macroscopic scale, and the width thereof is usually only a few tenths of a millimeter to several millimeters, which brings great difficulties to accurate positioning and accurate evaluation. This "narrow" characteristic triggers a series of chain problems: first, in the sample preparation stage, it is difficult to accurately define the boundary of the heat-affected zone (HAZ) on the metallographic sample by naked eye or conventional means, which leads to the fact that when a fatigue crack is pre-prepared on a compact tension sample, it is impossible to ensure that the crack tip can stably expand in the target area - the crack may accidentally deviate to the base material with better toughness or the weld metal with higher strength, so that the obtained data loses representativeness. Secondly, more complexly, the inside of this narrow HAZ is not homogeneous, but there is a significant microstructure gradient and mechanical property gradient from the coarse grain zone to the fine grain zone to the critical zone. In this small scale, the fatigue crack propagation behavior is sensitive to the local organization, and may accelerate, decelerate or path deviate, resulting in large dispersion of test data, and it is difficult to obtain stable and repeatable crack propagation rate curves, so that it is impossible to extract the rules with universality to accurately characterize the fatigue crack propagation resistance of the whole heat-affected zone.

[0003] The welding heat-affected zone in the actual welded joint is not an ideal flat strip area, and its morphology is deeply affected by the geometry of the joint. When the plate is welded with a U-shaped or V-shaped groove, the propagation of the heat source (arc) and the distribution of the heat flow are along the slope of the groove. This leads to the fact that the finally formed heat-affected zone (HAZ) profile is a curved surface or an irregular strip area in accordance with the shape of the groove, such as Figure 4 .

[0004] Although the Gleeble thermal simulation testing machine can accurately simulate the welding heat process, its traditional application is mostly limited to small size samples (such as 10 mm square samples) for studying the thermometallurgical behavior (such as phase transformation, grain growth) and basic mechanical properties (such as thermal plasticity, stress relaxation, impact performance) of materials. At present, there is a lack of a set of integrated device and method specially for 'welding heat-affected zone (HAZ) fatigue crack propagation performance test. This leads to the fact that researchers are difficult to obtain reliable HAZ region fatigue crack propagation data in accordance with international standards. The existing attempts often rely on manual sampling from large welded joints, and there are problems such as inaccurate sampling position, uncertain HAZ microstructure, and non-standard sample geometry, which leads to high dispersion of test results, poor repeatability, and difficulty in comparison between different studies.

[0005] Therefore, it is necessary to provide a heat dissipation clamp and a welding heat affected zone fatigue crack propagation sample preparation method. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art, and provide a heat dissipation clamp and a welding heat affected zone fatigue crack propagation sample preparation method, which aims to solve the technical problem of the lack of welding heat affected zone fatigue crack propagation samples in the prior art.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides a heat dissipation clamp, comprising a clamp body; a heat dissipation fin plate is arranged on the clamp body, the heat dissipation fin plate comprises a shell and a plurality of liftable fins arranged on the shell; when the fins are not measured, the ends of all fins away from the shell are at the same height; when the fins measure the measured object, different fins move along the surface of the measured object, and the fins on the side close to the shell are retracted into the shell.

[0008] As a preferred, a first spring is arranged in the shell, and each fin is connected to one of the first springs to make the fin have a tendency to move away from the shell.

[0009] As a preferred, a track is arranged on the shell for the fins to move in the vertical direction, and the fins are provided with a color separation area along the length direction.

[0010] As a preferred, a clamping device is further included, the clamping device comprises clamping pieces; a clamping groove is arranged at the bottom of the clamp body; the clamping pieces are symmetrically arranged on both sides of the clamping groove and can enter the clamping groove to limit the measured object.

[0011] As a preferred, a second spring is arranged between the clamping pieces and the clamp body to make the clamping pieces always have a tendency to move away from the clamping groove.

[0012] As a preferred, the clamping device further comprises lifting rods capable of pushing the clamping pieces to move, and the lifting rods are connected by connecting rods; the bottom of the lifting rods is provided with a protrusion with a width gradually increasing, and the corresponding sides of the clamping pieces and the protrusion are vertical surfaces.

[0013] As a preferred, one of the first springs is connected with a connecting rod, and the connecting rod is lifted during the deformation of the first spring.

[0014] As a preferred, the materials in contact with the measured object are all selected to be red copper.

[0015] To achieve the above-mentioned purpose, in a second aspect, the present application provides a welding heat affected zone fatigue crack propagation sample preparation method, which uses the heat dissipation clamp described above, and comprises the following steps: S1, selecting a long strip-shaped measured object, using the heat dissipation fin plate for flatness test, and selecting the measured object with required flatness; S2, using the heat dissipation fin plate to test the measured object, and selecting the measured object with required flatness; S2. Machining the teeth onto the test object that meets the requirements; S3. The processed test object is clamped in the testing machine using a heat dissipation fixture, and the testing machine is evacuated. S4. Weld group A thermocouples at the geometric center of the object to be tested; weld group B and group C thermocouples at symmetrical positions of group A thermocouples in the width direction of the object to be tested. S5. Start the Gleeble system of the testing machine, run the preset welding thermal cycle program, and complete the thermal simulation treatment of the test object; S6. Process the heat-treated test material into a compact tensile specimen.

[0016] Preferably, the A group of thermocouples are the main control thermocouples, whose signals are directly fed back to the main control system for real-time adjustment of the current passing through the sample; the B and C groups of thermocouples are monitoring thermocouples, used to record and verify the actual temperature history of the two points in real time, ensuring that the simulation of the heat-affected zone is carried out within the preset temperature gradient range, and the temperature gradient between the B and C groups and the A group should be controlled at 50°C.

[0017] Compared with the prior art, the beneficial effects of the heat dissipation fixture and the method for preparing fatigue crack propagation samples in the heat-affected zone provided by the present invention are as follows: 1. The heat dissipation fins can be used for both flatness testing and contact with the test object in the Gleeble system testing machine for better heat dissipation.

[0018] 2. When the first spring is compressed, the lifting rod rises and drives the clamping plates to move closer together, thereby clamping the object to be tested. In the Gleeble system testing machine, it is not easy to move and the contact area with the object to be tested is increased, and the heat dissipation is also better.

[0019] 3. The unique elongated plate structure of this sample has been carefully optimized in terms of geometry to meet two major requirements at the same time: the two ends can be perfectly fitted to the wedge-shaped copper clamps of the Gleeble thermal simulator to ensure effective clamping, conductivity and rapid cooling; while the middle part has reserved enough material and space to be directly machined into a standard compact tensile (CT) specimen.

[0020] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a sample according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of a sample and a corresponding fixture in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of a sample and a corresponding fixture installed on the chuck of a testing machine according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the heat-affected zone outline in an embodiment of the present invention, which is a curved surface or an irregular strip-shaped area conforming to the shape of the bevel.

[0025] Figure 5 This is a schematic diagram showing the distribution of thermocouples in groups A, B, and C according to an embodiment of the present invention.

[0026] Figure 6 This is a schematic diagram of the structure for processing CT samples according to an embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram of the structure of another sample according to an embodiment of the present invention.

[0028] Figure 8 This is a schematic diagram of the structure of an embodiment of the present invention with added heat dissipation fins.

[0029] Figure 9 This is a schematic diagram showing the structural changes of the heat dissipation fins during the measurement process of the heat dissipation fins in an embodiment of the present invention.

[0030] Figure 10 This is a schematic diagram of the installation structure of the clamping device according to an embodiment of the present invention.

[0031] Figure 11 This is a schematic diagram of the clamping device in an embodiment of the present invention during clamping.

[0032] in: 1-Clamp body; 11-Clamping groove; 2-Heat dissipation fin; 21-Shell; 22-Fin; 23-First spring; 3-Clamping device; 31-Clamping piece; 33-Second spring; 34-Lifting rod; 341-Protrusion; 35-Connecting rod. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] In the description of this invention, it should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to or indirectly connected to the other element.

[0035] In the description of this invention, it should be noted that the terms "center," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0036] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Example 1: See Figures 1-3The present invention provides a special sample in the form of a long strip plate, preferably with dimensions of 140mm (length) × 40mm (width) × 12mm (thickness). After processing, the sample surface must undergo rigorous treatment to ensure it is smooth and free of any oil, oxide scale, or other contaminants, in order to achieve low contact resistance and uniform heat conduction with the fixture. The thermal simulation fixture consists of a pair of wedge-shaped copper clamps, with rectangular grooves machined on their clamping surfaces to match the sample dimensions. This groove design ensures that when the metal sample is clamped, its large surface area achieves three-dimensional surface contact with the copper clamps, rather than uncontrollable line or point contact. Copper is chosen as the fixture material due to its extremely high thermal conductivity. Combined with the large clamping force provided by the wedge clamping mechanism, this ensures that during the thermal simulation process, the current can pass uniformly through the sample cross-section, and the heat can be quickly dissipated through the fixtures, thereby accurately realizing the rapid cooling process required during the welding thermal cycle and meeting the stringent requirements of various welding thermal simulation processes, including high-strength steel.

[0038] Welding thermal simulation (see) Figure 5 This includes sample loading and sealing, thermocouple arrangement and function, and temperature field monitoring.

[0039] Sample loading and sealing: Place the prepared standard sample into the sample chamber of the Gleeble testing machine and firmly clamp it using the wedge-shaped copper clamps. Then seal the sample chamber and start the vacuum system to extract and maintain the vacuum level in the chamber below 1 Pa to effectively prevent the sample from oxidizing at high temperatures.

[0040] Thermocouple arrangement and function: At the geometric center of the side of the sample with a width of 40mm, a capacitor discharge spot welder is used to precisely weld group A thermocouples. This thermocouple serves as the main control thermocouple, and its signal is directly fed back to the Gleeble main control system to adjust the current through the sample in real time, thereby accurately controlling the sample temperature and ensuring that it strictly follows the preset thermal cycling curve.

[0041] Temperature field monitoring: To monitor the temperature field uniformity on the sample during thermal simulation, thermocouples B and C are precisely welded 10 mm to each side of thermocouple A along the same axis (i.e., along the 140 mm length of the sample). These two sets of thermocouples serve as monitoring thermocouples and do not participate in system control. They are only used to record and verify the actual temperature history at these two points in real time, ensuring that the simulation of the heat-affected zone (HAZ) is carried out within the preset temperature gradient range. The temperature gradient between B and C and group A should be controlled at 50°C.

[0042] After the above preparations are completed, start the Gleeble system and run the preset welding thermal cycle program to complete the thermal simulation treatment of the sample.

[0043] Continue preparations for the compact stretching sample, see [reference needed].Figure 6 To ensure that fatigue pre-cracks propagate accurately along the weld heat-affected zone (HAZ), specimen preparation and positioning are crucial. The key is to precisely align the centerline of the notch in the compact tensile (CT) specimen with the centerline of the target HAZ (e.g., a coarse-grained region). The specific procedure is as follows: First, a long strip containing the complete joint is cut from the weld joint after macroscopic metallographic examination. Then, a CT specimen is machined at the center of this strip to ensure representative sampling. The characteristic width (W) of the specimen is recommended to be 25 mm according to standards. To obtain an accurate 10 mm thickness (B) and eliminate surface defect layers (such as recast layers, HAZ, or microcracks) caused by rough machining such as wire cutting, the two surfaces of the specimen are finished, removing approximately 1 mm of material from each side. This process aims to obtain parallel test surfaces with accurate dimensions and consistent surface conditions, thereby ensuring the accuracy of the crack propagation driving force (ΔK) calculation and the comparability of test results. Unless otherwise specified, other geometric parameters, machining accuracy, and test procedures of the specimen strictly follow standards such as GB / T 6398.

[0044] This invention designs an "integrated standard sample" that bridges thermal simulation and fatigue testing. The sample employs a unique elongated plate structure measuring 140mm x 40mm x 12mm, with carefully optimized geometry to simultaneously meet two major requirements: both ends perfectly fit the wedge-shaped copper clamps of the Gleeble thermal simulator, ensuring effective clamping, conductivity, and rapid cooling; while the middle section provides ample material and space for direct machining into a standard compact tensile (CT) specimen. This integrated design fundamentally overturns the outdated process of blindly sampling from large, irregular welded joints. The core of this method lies in pre-setting precise geometric benchmarks on the sample before Gleeble thermal simulation, allowing the simulated narrow HAZ regions (such as coarse-grained regions) to be pre- and precisely positioned along the fatigue crack propagation path of the future CT specimen. This includes precise control of the thermal field using master and monitoring thermocouples, and a set of finishing guidelines from the thermal simulation sample to the final CT specimen, ensuring that the target microstructure is not damaged during processing.

[0045] Example 2: Since the heat dissipation effect of the fixture and the flatness of the sample are important in this invention, it is necessary to improve the heat dissipation effect of the fixture and measure the flatness of the sample.

[0046] See Figure 1 This invention provides a method for preparing fatigue crack propagation samples in the heat-affected zone of a weld, using a heat dissipation fixture, and includes the following steps: S1. Select a long strip-shaped object to be tested (e.g., ... Figure 1The flatness of the heat dissipation fins 2 of the test object is tested, and the test object that meets the flatness requirements is selected. After the sample is processed, its surface must be strictly treated to ensure that it is smooth and free of any oil, oxide scale or other contaminants, so as to achieve low contact resistance and uniform heat conduction with the fixture.

[0047] See Figures 8-11 The flatness test uses a heat dissipation fixture, including a fixture body 1. A heat dissipation fin 2 is provided on the fixture body 1. The heat dissipation fin 2 includes a housing 21 and multiple liftable fins 22 on the housing 21. When the fins 22 are not being measured, the ends of all fins 22 away from the housing 21 are at the same height. When the fins 22 are measuring the object to be measured, different fins 22 move along the surface of the object, with the fins 22 closer to the housing 21 retracting into the housing 21. A first spring 23 is provided inside the housing 21, and a fin 22 is connected to each first spring 23, causing the fin 22 to tend to move away from the housing 21. The housing 21 is provided with a track for the fins 22 to move vertically, and the fins 22 have color-separated areas along their length. The device also includes a clamping device 3, which comprises clamping plates 31. A clamping groove 11 is provided at the bottom of the clamping body 1. The clamping plates 31 are symmetrically arranged on both sides of the clamping groove 11 and can enter the clamping groove 11 to limit the object to be measured. A second spring 33 is provided between the clamping plates 31 and the clamping body 1 so that the clamping plates 31 always tend to move away from the clamping groove 11. The clamping device 3 also includes a lifting rod 34 that can push the clamping plates 31 to move. The lifting rods 34 are connected to each other by a connecting rod 35. The bottom of the lifting rod 34 is provided with a protrusion 341 that gradually increases in width. The side of the clamping plate 31 corresponding to the protrusion 341 is a vertical surface. A connecting rod 35 is connected to one of the first springs 23. The first spring 23 drives the connecting rod 35 to rise and fall during deformation. All parts in contact with the object to be measured are made of copper.

[0048] Specifically, the total width of the heat dissipation fins 2 must be greater than or equal to the width of the elongated test object. First, the surface of the test object is rigorously treated to ensure it is smooth and free of any oil, oxide scale, or other contaminants. Each side of the test object is then placed under the heat dissipation fins 2. Since the surfaces of the test object may not be perfectly horizontal after treatment, measurements are required. Initially, the bottom surfaces of the heat dissipation fins 2 are at the same height (the elastic force of the first spring 23 is the same). When the test object moves horizontally under the heat dissipation fins 2, if the surface of the test object is horizontal, the height to which each fin 22 rises is the same (e.g., ...). Figure 8 As shown), if the surface of the object being tested has a protrusion or a depression, the height at which one or more fins 22 move will differ from the others (e.g., Figure 9 (As shown).

[0049] S2. Machining the teeth onto the test object that meets the requirements, see [reference]. Figure 7 Since the test object must remain stationary throughout the experiment, simply fixing it by compression has certain drawbacks. After the test object is placed in the clamping groove 11, the clamping plate 31 moves towards the center and engages with the locking teeth to hold the test object in place, preventing it from moving or shaking. The clamping plate 31 is made of copper to improve heat dissipation. Furthermore, the locking teeth can be evenly distributed on the test object, with the clamping plate 31 and the locking teeth fitting together one-to-one.

[0050] S3. The processed test sample is clamped in the testing machine using a heat dissipation clamp, and the testing machine is evacuated. The prepared standard sample is placed in the sample chamber of the Gleeble testing machine and firmly clamped using the wedge-shaped copper clamp. The sample chamber is then sealed, and the vacuum system is activated to extract and maintain the vacuum level in the chamber below 1 Pa to effectively prevent the sample from oxidizing at high temperatures.

[0051] Furthermore, the object to be tested is placed into the clamping groove 11, with the clasps and clamping plates 31 corresponding to each other. When the upper and lower heat dissipation clamps come closer together, the fins 22 clamp the object to be tested. As they continue to come closer, the fins 22 compress the first spring 23, and a fixed plate is connected to the lower part of the first spring 23. When the first spring 23 is compressed, the fixed plate rises, and a connecting rod 35 is connected to the fixed plate. The connecting rod 35 rises (the number of connecting rods 35 can be selected according to the actual situation, and not every clamp body 1 needs to be equipped with one). The clamp body 1 is provided with a chamber for the clamping device 3. Lifting rods 34 are connected to both sides of the connecting rod 35. When the connecting rod 35 rises, it drives the lifting rod 34 to rise, and a protrusion 341 is connected to the bottom of the lifting rod 34. When the lifting rod 34 rises, the protrusion 341 will abut against the clamping plate 31, causing the clamping plates 31 at both ends to come closer together and thus penetrate into the clasps. The clamp body 1 has a cavity for the clamping plate to move left and right, but it cannot move up and down. The clamping plate is T-shaped. When the experiment is over and the two clamp bodies 1 move away from each other, the second spring 33 will drive the clamping plate 31 away from the teeth, and the object to be tested will be slowly released until it is removed. The fins 22 are made of copper, which increases the contact area when clamping the object to be tested, thus improving heat dissipation.

[0052] S4. Weld group A thermocouples to the geometric center of the object to be tested; weld group B and group C thermocouples to the symmetrical positions of group A thermocouples in the width direction of the object to be tested.

[0053] To monitor the temperature field uniformity on the sample during thermal simulation, thermocouples B and C were precisely welded 10 mm to each side of thermocouple A, along the same axis (i.e., along the 140 mm length of the sample). These two sets of thermocouples serve as monitoring thermocouples and do not participate in system control. They are only used to record and verify the actual temperature history at these two points in real time, ensuring that the simulation of the heat-affected zone (HAZ) is carried out within the preset temperature gradient range. The temperature gradient between groups B and C and group A should be controlled at 50°C.

[0054] S5. Start the Gleeble system of the testing machine, run the preset welding thermal cycle program, and complete the thermal simulation treatment of the test object.

[0055] S6. Process the heat-treated test specimen into a compact tensile specimen. Specimen preparation and positioning are crucial to ensure accurate propagation of fatigue pre-cracks along the weld heat-affected zone (HAZ). The key is to precisely align the centerline of the notch in the compact tensile (CT) specimen with the centerline of the target HAZ (e.g., a coarse-grained region). The specific procedure is as follows: First, cut a long strip containing the complete joint from the weld joint, as inspected by macroscopic metallography. Then, process the CT specimen at the center of this strip to ensure representative sampling. The characteristic width (W) of the specimen is recommended to be 25 mm according to the standard. To obtain an accurate 10 mm thickness (B) and eliminate surface defect layers (such as recast layers, HAZ, or microcracks) caused by rough machining such as wire cutting, the two surfaces of the specimen need to be finished, removing approximately 1 mm of material from each side. This process aims to obtain parallel test surfaces with accurate dimensions and consistent surface conditions, thereby ensuring the accuracy of the crack propagation driving force (ΔK) calculation and the comparability of test results. Unless otherwise specified, the other geometric parameters, machining accuracy and test procedures of the specimens shall be strictly implemented in accordance with standards such as GB / T 6398.

[0056] 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 or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat dissipation clamp, comprising a clamp body (1); characterized in that: A heat dissipation fin (2) is provided on the fixture body (1). The heat dissipation fin (2) includes a shell (21) and multiple liftable fins (22) are provided on the shell (21). When the fins (22) are not being measured, the ends of all fins (22) away from the shell (21) are at the same height. When the fins (22) are measuring the object to be measured, different fins (22) move along the surface of the object to be measured, and the fins (22) on the side closer to the shell (21) retract into the shell (21).

2. The heat dissipation clamp as described in claim 1, characterized in that: The housing (21) is provided with a first spring (23), and a fin (22) is connected to each first spring (23) so that the fin (22) tends to move away from the housing (21).

3. A heat dissipation clamp as described in claim 1, characterized in that: The housing (21) is provided with a track for the fins (22) to move in the vertical direction, and the fins (22) are provided with color-separated areas along the length direction.

4. A heat dissipation clamp as described in claim 2, characterized in that: It also includes a clamping device (3), which includes a clamping piece (31); a clamping groove (11) is provided at the bottom of the clamp body (1); the clamping piece (31) is symmetrically arranged on both sides of the clamping groove (11) and can enter the clamping groove (11) to limit the object to be measured.

5. A heat dissipation clamp as described in claim 4, characterized in that: A second spring (33) is provided between the clamping piece (31) and the clamp body (1) so that the clamping piece (31) always tends to move away from the clamping groove (11).

6. A heat dissipation clamp as described in claim 5, characterized in that: The clamping device (3) also includes a lifting rod (34) that can push the clamping piece (31) to move. The lifting rods (34) are connected by a connecting rod (35). The bottom of the lifting rod (34) is provided with a protrusion (341) whose width gradually increases. The corresponding side of the clamping piece (31) and the protrusion (341) is a vertical surface.

7. A heat dissipation clamp as described in claim 6, characterized in that: One of the first springs (23) is connected to a connecting rod (35), and the first spring (23) drives the connecting rod (35) to rise and fall during deformation.

8. A heat dissipation clamp as described in claim 1, characterized in that: All parts in contact with the test object are made of copper.

9. A method for preparing a sample with fatigue crack propagation in the heat-affected zone of a weld, using the heat dissipation fixture according to any one of claims 1-8, characterized in that: Includes the following steps: S1. Select a long strip-shaped object to be tested and use the heat dissipation fins (2) of the object to be tested to test the flatness. Select an object to be tested that meets the flatness requirements. S2. Machining the teeth onto the test object that meets the requirements; S3. The processed test object is clamped in the testing machine using a heat dissipation fixture, and the testing machine is evacuated. S4. Weld group A thermocouples at the geometric center of the object to be tested; weld group B and group C thermocouples at symmetrical positions of group A thermocouples in the width direction of the object to be tested. S5. Start the Gleeble system of the testing machine, run the preset welding thermal cycle program, and complete the thermal simulation treatment of the test object; S6. Process the heat-treated test material into a compact tensile specimen.

10. The method for preparing a sample with fatigue crack propagation in the heat-affected zone of a weld as described in claim 9, characterized in that: The thermocouples in group A are the main control thermocouples, whose signals are directly fed back to the main control system for real-time adjustment of the current passing through the sample. The thermocouples in groups B and C are monitoring thermocouples, used to record and verify the actual temperature history of these two points in real time, ensuring that the simulation of the heat-affected zone is carried out within the preset temperature gradient range. The temperature gradient between groups B and C and group A should be controlled at 50°C.

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