A heat dissipation clamp and a method for preparing a welded heat-affected zone fatigue crack propagation sample

Abstract

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 welded heat affected zone fatigue crack propagation sample, which comprises a clamp body, a heat dissipation fin plate arranged on the clamp body, wherein the heat dissipation fin plate comprises a shell and a plurality of liftable fins arranged on the shell; when the fins are not measured, all the fins are away from the shell at the same height; when the fins measure the measured object, different fins move along the surface of the measured object, and the fins close to the shell are retracted into the shell. The present application aims to solve the technical problem that there is no sample for welded heat affected zone fatigue crack propagation in the prior art.

Description

Technical Field

[0001] This invention relates to the technical field of fatigue testing in the heat-affected zone, and particularly to a heat dissipation fixture and a method for preparing fatigue crack propagation samples in the heat-affected zone of a weld. Background Technology

[0002] The heat-affected zone (HAZ) of actual welded joints is extremely narrow on a macroscopic scale, typically only a fraction of a millimeter to a few millimeters wide. This presents significant challenges for precise positioning and accurate assessment. This narrowness leads to a series of interconnected problems: First, during specimen preparation, it is difficult to accurately define the HAZ boundary on metallographic specimens using the naked eye or conventional methods. This makes it impossible to ensure that the crack tip stably propagates within the target area when fatigue cracks are pre-induced on compact tensile specimens—the crack may unexpectedly deviate into the tougher base metal or the stronger weld metal, rendering the obtained data unrepresentative. Second, and more complexly, the interior of this narrow HAZ is not homogeneous but contains significant microstructure and mechanical property gradients from coarse-grained to fine-grained and then to the critical region. Within this tiny scale, fatigue crack propagation behavior is sensitively influenced by local microstructure, potentially experiencing acceleration, deceleration, or path deflection. This results in highly dispersed test data, making it difficult to obtain stable and repeatable crack propagation rate curves, and thus impossible to extract universally applicable patterns to accurately characterize the fatigue crack propagation resistance of the entire HAZ.

[0003] In actual welded joints, the heat-affected zone (HAZ) is not an ideal, flat, banded region; its morphology is profoundly influenced by the joint geometry. When plates are welded using U-shaped or V-shaped bevels, the propagation of the heat source (arc) and the distribution of heat flow occur along the bevel's slope. This results in the final HAZ profile being a curved surface or an irregular banded region conforming to the bevel shape, such as... Figure 4 .

[0004] While the Gleeble thermal simulation testing machine can accurately simulate the welding thermal process, its traditional applications are mostly limited to small-sized samples (such as 10mm square specimens) for studying the thermometallurgical behavior (such as phase transformation and grain growth) and fundamental mechanical properties (such as thermoplasticity, stress relaxation, and impact performance) of materials. Currently, there is a lack of an integrated device and method specifically for testing the fatigue crack propagation performance of the weld heat-affected zone (HAZ). This makes it difficult for researchers to obtain reliable HAZ fatigue crack propagation data that conforms to international standards. Existing attempts often rely on manual sampling from large welded joints, which suffers from problems such as inaccurate sampling locations, uncertain HAZ microstructure, and non-standard specimen geometry, resulting in high dispersion, poor repeatability, and difficulty in comparing different studies.

[0005] Therefore, it is necessary to propose a heat dissipation fixture and a method for preparing fatigue crack propagation samples in the heat-affected zone of welding. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heat dissipation fixture and a method for preparing fatigue crack propagation samples in the weld heat-affected zone, which aims to solve the technical problem that there are no samples with fatigue crack propagation in the weld heat-affected zone in the prior art.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a heat dissipation fixture, comprising a fixture body; a heat dissipation fin is provided on the fixture body, the heat dissipation fin comprising a shell and a plurality of liftable fins provided on the shell; when the fins are not being measured, the ends of all fins away from the shell are at the same height; when the fins are measuring an object to be measured, different fins move along the surface of the object to be measured, and the fins closer to the shell retract into the shell.

[0008] Preferably, a first spring is provided inside the housing, and a fin is connected to each first spring so that the fin tends to move away from the housing.

[0009] Preferably, the housing is provided with a track for the fins to move in the vertical direction, and the fins are provided with color-separated areas along their length.

[0010] Preferably, the device also includes a clamping device, which includes clamping plates; a clamping groove is provided at the bottom of the clamping body; the clamping plates are symmetrically arranged on both sides of the clamping groove and can enter the clamping groove to limit the object to be measured.

[0011] Preferably, a second spring is provided between the clamping piece and the clamping body so that the clamping piece always tends to move away from the clamping groove.

[0012] Preferably, the clamping device further includes a lifting rod capable of pushing the clamping piece to move, and the lifting rods are connected by a connecting rod; the bottom of the lifting rod is provided with a protrusion whose width gradually increases, and the side of the clamping piece corresponding to the protrusion is a vertical surface.

[0013] Preferably, one of the first springs is connected to a connecting rod, and the connecting rod is raised or lowered during the deformation of the first spring.

[0014] As a preferred option, copper is used for all parts that come into contact with the test sample.

[0015] To achieve the above objectives, in a second aspect, the present invention proposes a method for preparing fatigue crack propagation samples in the weld heat-affected zone, using the aforementioned heat dissipation fixture, comprising the following steps:

[0016] S1. Select a long strip-shaped object to be tested, and use the heat dissipation fins of the object to be tested to test the flatness. Select an object to be tested that meets the flatness requirements.

[0017] S2. Machining the teeth onto the test object that meets the requirements;

[0018] S3. The processed test object is clamped in the testing machine using a heat dissipation fixture, and the testing machine is evacuated.

[0019] 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.

[0020] 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;

[0021] S6. Process the heat-treated test material into a compact tensile specimen.

[0022] 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.

[0023] 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:

[0024] 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.

[0025] 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 heat dissipation is also better.

[0026] 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.

[0027] 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

[0028] Figure 1 This is a schematic diagram of the structure of a sample according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of a sample and a corresponding fixture in an embodiment of the present invention.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Figure 6 This is a schematic diagram of the structure for processing CT samples according to an embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of the structure of another sample according to an embodiment of the present invention.

[0035] Figure 8 This is a schematic diagram of the structure of the present invention with added heat dissipation fins.

[0036] 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.

[0037] Figure 10 This is a schematic diagram of the installation structure of the clamping device according to an embodiment of the present invention.

[0038] Figure 11 This is a schematic diagram of the clamping device in an embodiment of the present invention during clamping.

[0039] in:

[0040] 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

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Example 1:

[0046] 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.

[0047] Welding thermal simulation (see) Figure 5 This includes sample loading and sealing, thermocouple arrangement and function, and temperature field monitoring.

[0048] 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.

[0049] Thermocouple arrangement and function: At the geometric center of the side of the sample with a width of 40mm, a group A thermocouple is precisely welded using a capacitor discharge spot welder. 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Example 2:

[0055] 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.

[0056] 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:

[0057] S1. Select a long strip-shaped object to be tested (e.g., ... Figure 1 The 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.

[0058] 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.

[0059] 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).

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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: The flatness test uses a heat dissipation fixture; 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); 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); When the object under test moves horizontally below the heat dissipation fins (2), if the surface of the object under test is horizontal, the height of each fin (22) is the same. If the surface of the object under test has a protrusion or a depression, the height of one or more fins (22) will be different from the others.

2. The 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.

3. A heat dissipation clamp as described in claim 1, 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.

4. A heat dissipation clamp as described in claim 3, 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).

5. A heat dissipation clamp as described in claim 4, 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.

6. A heat dissipation clamp as described in claim 5, 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.

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

8. 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 1-7, 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.

9. The method for preparing a fatigue crack propagation sample in the weld heat-affected zone as described in claim 8, characterized in that: 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 points monitored by the B and C groups of thermocouples 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 the B and C groups and the A group should be controlled at 50°C.

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