Welding tool for thin-wall part

Abstract

The invention relates to the technical field of machine manufacturing and welding, in particular to a welding tool for a thin-wall part. The base supporting module is used for providing a rigid physical reference of the welding tool; the in-plane floating clamping module is configured to vertically apply rigid pressing force and has a moving freedom degree in the parallel direction; the two-way elastic tensioning module is connected with the base and the clamping module and allows displacement deviating from the center through elastic deformation in the heating stage so as to release hot pressing stress; applying restoring tension in the cooling stage to counteract welding seam shrinkage stress; the follow-up heat dissipation module is arranged on the back part and moves along with the clamping module so as to maintain a contact heat conduction state; according to the method, the composite constraint system is constructed, rigid confrontation is converted into elastic dredging, and the root of welding deformation of the thin-wall part is eliminated.

Description

Technical Field

[0001] This invention relates to the fields of mechanical manufacturing and welding technology, specifically to a welding fixture for thin-walled parts. Background Technology

[0002] In the existing thin-walled parts welding manufacturing technology, the welding fixture system mainly includes a rigid base platform and a fixed clamping assembly. The thin-walled parts are positioned on the rigid base platform by mechanical connection and are clamped by the fixed clamping assemblies distributed on both sides of the weld to maintain the geometric position required for welding. The fixed clamping assembly typically uses a spiral clamp or pneumatic clamp, configured to apply a high-strength locking force in a direction perpendicular to the surface of the part, pressing the thin-walled part tightly against the fixed heat dissipation pad at the bottom. This rigid constraint prevents the part from moving, and the fixed heat dissipation pad removes the heat generated during welding through contact heat conduction.

[0003] However, this rigid clamping method forces the in-plane expansion displacement of thin-walled parts caused by heating during the welding heating stage to be restricted, resulting in a sharp increase in the thermal compressive stress inside the material and exceeding the material's yield limit. This leads to irreversible plastic buckling deformation of the thin-walled parts. At the same time, the fixed heat dissipation pad cannot adjust with the local deformation of the parts, causing the parts to detach from the pad when they deform and bulge. This results in heat dissipation failure on the back of the weld and local overheating and burn-through, ultimately leading to severe warping deformation and substandard dimensional accuracy in the final welded components. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a welding fixture for thin-walled parts. Specifically, the technical solution of the present invention includes: The base support module is used to provide a rigid physical reference for the welding fixture; The in-plane floating clamping module is configured to apply a rigid clamping force in a direction perpendicular to the surface of the thin-walled part to establish a clamping connection, and to have a degree of freedom of movement relative to the base support module in a direction parallel to the surface of the thin-walled part; A bidirectional elastic tensioning module connects the base support module and the in-plane floating clamping module, and is configured to provide an elastic connection to allow the in-plane floating clamping module to move relative to the base support module; The bidirectional elastic tensioning module is configured to, during the welding heating stage, respond to the thermal expansion of the thin-walled part through elastic deformation, allowing the in-plane floating clamping module to generate a follow-up displacement away from the welding center direction to release thermal stress. The bidirectional elastic tensioning module is also configured to apply a restoring force to the in-plane floating clamping module in the direction of the welding center or away from the welding center during the welding cooling stage, so as to counteract the weld shrinkage stress. A follow-up heat dissipation module is disposed on the back of the thin-walled part, which supports the thin-walled part and is configured to move along with the in-plane floating clamping module to maintain contact and heat conduction with the thin-walled part.

[0005] Preferably, the in-plane floating clamping module includes: A pressure plate unit is used to contact the upper surface of the thin-walled part; A floating connection unit is disposed between the pressure plate unit and the base support module; The floating connection unit employs a linear guide rail mechanism or an elastic hinge mechanism to limit the vertical displacement of the pressure plate unit and release the horizontal displacement constraint of the pressure plate unit.

[0006] Preferably, the bidirectional elastic tensioning module includes: The pretension force generating unit is connected at one end to the base support module and at the other end to the in-plane floating clamping module; The pre-tension force generating unit is configured to apply a preset initial tensile force to the thin-walled part before welding, so that the thin-walled part is in an elastic taut state.

[0007] Preferably, the pretension force generating unit includes: A mechanical spring assembly is configured to absorb the displacement caused by thermal expansion using elastic deformation potential energy and to provide the restoring tension using restoring force.

[0008] Preferably, the pretension force generating unit includes: Shape memory alloy actuator, configured to respond to temperature changes during the welding process; The shape memory alloy actuator is configured to undergo a martensitic inverse phase transformation or reduce stiffness by utilizing the thermoelasticity of the material when the temperature rises, so as to accommodate the expansion displacement of the thin-walled part. The shape memory alloy actuator is also configured to restore a high stiffness state or generate contraction deformation when the temperature decreases, in order to provide the restoring tensile force.

[0009] Preferably, the follow-up heat dissipation module includes: The segmented heat-conducting unit consists of multiple independent heat-conducting blocks arranged along the weld seam direction, and the heat-conducting blocks are used to directly contact the back of the thin-walled part; Thermally insulating elastic filling units are filled between adjacent thermally conductive blocks; The thermally insulating elastic filling unit is configured to allow relative micro-displacement between adjacent thermally conductive blocks to maintain the segmented thermally conductive unit as a whole as it deforms with the thin-walled part.

[0010] Preferably, the in-plane floating clamping module and the follow-up heat dissipation module are connected by a synchronous connection mechanism; The synchronous connection mechanism is configured to transfer the horizontal displacement of the in-plane floating clamping module to the follow-up heat dissipation module, ensuring that the relative position between the follow-up heat dissipation module and the thin-walled part remains unchanged when the thin-walled part undergoes thermal expansion or cold contraction displacement.

[0011] Preferably, the stiffness characteristics provided by the bidirectional elastic tensioning module are configured to satisfy the following conditions: During the welding heating stage, the equivalent stiffness of the bidirectional elastic tensioning module is set to be less than the critical stiffness corresponding to the thermal expansion yield strength of the thin-walled part, so as to prevent the thin-walled part from undergoing compressive plastic deformation. During the welding cooling stage, the recovery tension provided by the bidirectional elastic tensioning module is set to be no less than the residual shrinkage stress of the thin-walled part, so as to block the accumulation path of residual stress.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. This system constructs a composite constraint system of rigid normal clamping and elastic in-plane boundary. The in-plane floating clamping module applies rigid clamping force in the vertical direction to prevent the part from falling off. At the same time, it releases displacement constraint in the direction parallel to the surface of the thin-walled part. Combined with the elastic deformation capability of the bidirectional elastic tensioning module, the tooling is allowed to respond to the thermal expansion of the thin-walled part during the welding heating stage and generate a follow-up displacement away from the welding center. This effectively releases thermal compressive stress, avoids peak compressive stress, and prevents the thin-walled part from plastic buckling deformation due to thermal compression. 2. This system provides restoring tension during the welding cooling stage through a bidirectional elastic tensioning module. By utilizing the elastic potential energy release of the mechanical spring assembly or the phase transformation recovery characteristics of the shape memory alloy actuator, a tension opposite to the direction of weld shrinkage force is applied to the in-plane floating clamping module, thereby offsetting the weld shrinkage stress, blocking the accumulation path of residual stress, eliminating the root cause of welding deformation of thin-walled parts in terms of physical mechanism, and significantly improving the post-weld dimensional accuracy of large thin-walled structural parts in aerospace and other fields. 3. This system, by setting up a follow-up heat dissipation module and a synchronous connection mechanism, adopts a design that combines segmented heat conduction units with heat insulation elastic filling units. This allows the back heat dissipation pad to move and deform along with the thin-walled parts like a chain. This ensures that even if the workpiece moves during thermal expansion and contraction, the heat dissipation pad always maintains a tight contact with the thin-walled parts for heat conduction. This effectively solves the problem of local overheating, burn-through, or oxidation caused by the workpiece arching and detaching in traditional fixed pads, and ensures uniform heat dissipation throughout the entire process. 4. This system achieves strict limitation of the Z-axis displacement and controlled release of the XY-axis displacement of the pressure plate unit by adopting a precision linear guide mechanism or a parametrically designed elastic hinge mechanism, thus resolving the contradiction between clamping force and degree of freedom of movement. Combined with the thermo-mechanical coupling characteristics of the shape memory alloy actuator, an adaptive intelligent tensioning system is constructed, which can achieve intelligent stress management without external sensors, by reducing stiffness during heating to accommodate expansion and restoring stiffness during cooling to provide tension. Attached Figure Description

[0013] The present invention will be further explained below with reference to the accompanying drawings and embodiments: Figure 1 This is a structural diagram of the system of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0015] Example 1: Please see Figure 1 A welding fixture for thin-walled parts, comprising: The base support module is used to provide a rigid physical reference for the welding fixture; The in-plane floating clamping module is configured to apply a rigid clamping force in a direction perpendicular to the surface of the thin-walled part to establish a clamping connection, and has a degree of freedom of movement relative to the base support module in a direction parallel to the surface of the thin-walled part. A bidirectional elastic tensioning module connects the base support module and the in-plane floating clamping module, and is configured to provide an elastic connection to allow the in-plane floating clamping module to move relative to the base support module; Among them, the bidirectional elastic tensioning module is configured to respond to the thermal expansion of the thin-walled part through elastic deformation during the welding heating stage, allowing the in-plane floating clamping module to generate a follow-up displacement away from the welding center direction to release the thermal stress. The bidirectional elastic tensioning module is also configured to apply a restoring force to the in-plane floating clamping module in the direction of the welding center or away from the welding center during the welding cooling stage to counteract the weld shrinkage stress. The follow-up heat dissipation module is located on the back of the thin-walled part. It supports the thin-walled part and is configured to move with the in-plane floating clamping module to maintain contact and heat conduction with the thin-walled part.

[0016] This embodiment discloses a welding fixture for thin-walled parts, which aims to solve the problem that traditional rigid clamps cause plastic deformation of thin-walled parts due to thermal compression during the welding process, resulting in warping after welding. The welding fixture is mainly composed of four core modules working together: a base support module, an in-plane floating clamping module, a bidirectional elastic tensioning module, and a follow-up heat dissipation module. The base support module serves as the physical reference system for the entire system, providing a rigid physical benchmark for the welding fixture. In this embodiment, the base support module employs a high-rigidity cast iron or steel structure platform, with its upper surface precision-ground, defining the absolute coordinate system of the fixture. ; The in-plane floating clamping module constructs a clamping mechanism with anisotropic constraint characteristics, which enables the Z-axis locking and controlled XY-axis release of thin-walled parts. In this embodiment, the module is configured to apply a rigid clamping force in the direction perpendicular to the surface of the thin-walled part, i.e., the Z-axis direction. This can be achieved through a helical clamping mechanism, a quick-release toggle clamp, or a miniature hydraulic cylinder set on the floating module. These force-applying elements move together with the floating module to establish a stable clamping connection and prevent the part from detaching from the tooling. At the same time, it has a degree of freedom of movement relative to the base support module in the direction parallel to the surface of the thin-walled part, i.e., the XY plane direction. The bidirectional elastic tensioning module connects the base support module and the in-plane floating clamping module, configured to provide an elastic connection to construct dynamic boundaries. During the welding heating phase, in response to the thermal expansion of the thin-walled part caused by the heat source of the welding torch, the bidirectional elastic tensioning module, through its own elastic deformation, such as spring compression or extension, allows the in-plane floating clamping module to drive the thin-walled part to produce a follow-up displacement away from the welding center direction. This yielding mechanism effectively releases the thermal stress and prevents the internal stress of the material from exceeding the yield limit. During the welding cooling phase, in response to the weld solidification and the beginning of contraction, the bidirectional elastic tensioning module applies a restoring force to the in-plane floating clamping module pointing towards the welding center direction or away from the direction set according to the pre-tension setting. This force is opposite to or counteracts the contraction force of the weld, thereby counteracting the weld contraction stress and blocking the accumulation path of residual stress. The follow-up heat dissipation module is located on the back of the thin-walled part to support it. Its key feature is its follow-up function, which means it is configured to move along with the in-plane floating clamping module. This ensures that even if the workpiece moves during thermal expansion and contraction, the heat dissipation pad on the back always maintains a tight contact with the thin-walled part to conduct heat, preventing local overheating and burn-through caused by contact loss. This embodiment constructs a composite constraint system of rigid normal clamping and elastic in-plane boundary, transforming the traditional rigid confrontation of welding stress into elastic conduction. During the heating expansion period, the tooling actively yields to avoid the peak compressive stress and prevent plastic buckling of thin-walled parts. During the cooling contraction period, the tooling provides elastic restoring force to compensate for contraction strain, thereby eliminating the root cause of welding deformation of thin-walled parts in terms of physical mechanism and significantly improving the post-weld dimensional accuracy of large thin-walled structural parts in aerospace and other fields.

[0017] Example 2: The in-plane floating clamping module includes: Pressure plate unit, used to contact the upper surface of thin-walled parts; A floating connection unit is disposed between the pressure plate unit and the base support module; The floating connection unit uses a linear guide rail mechanism or an elastic hinge mechanism to limit the vertical displacement of the pressure plate unit and release the horizontal displacement constraint of the pressure plate unit.

[0018] The follow-up heat dissipation module includes: The segmented heat-conducting unit consists of multiple independent heat-conducting blocks arranged along the weld seam direction. The heat-conducting blocks are used to directly contact the back of thin-walled parts. Thermally insulating elastic filler units are filled between adjacent thermally conductive blocks; The thermally insulating elastic filler unit is configured to allow relative micro-displacement between adjacent thermally conductive blocks, so as to keep the segmented thermally conductive unit as a whole deforming with the thin-walled part.

[0019] The in-plane floating clamping module and the follow-up heat dissipation module are connected by a synchronous connection mechanism; The synchronous connection mechanism is configured to transfer the horizontal displacement of the in-plane floating clamping module to the follow-up heat dissipation module, ensuring that the relative position between the follow-up heat dissipation module and the thin-walled part remains unchanged when the thin-walled part undergoes thermal expansion or cold contraction displacement.

[0020] This embodiment further refines the specific implementation of the mechanical structure based on Embodiment 1, especially the optimization of the floating mechanism and heat dissipation consistency; Regarding the specific structure of the in-plane floating clamping module, the module includes a pressure plate unit and a floating connection unit. The pressure plate unit is made of high-temperature resistant alloy steel and directly contacts the upper surface of the thin-walled part. The floating connection unit is located between the pressure plate unit and the base support module. In this embodiment, a precision linear guide mechanism is used. The guide rail slider is connected to the pressure plate unit, and the guide rail track is fixed to the base support module. This mechanism strictly limits the displacement of the pressure plate unit in the vertical direction, i.e., the Z-axis, with the error controlled within 0.01mm. At the same time, it completely removes the displacement constraint of the pressure plate unit in the horizontal direction, i.e., along the weld seam normal. The friction coefficient is extremely low, ensuring that a small thermal expansion force can drive the clamp to move. Regarding the specific structure of the follow-up heat dissipation module, in order to solve the problem of the traditional integral copper pad restricting workpiece deformation, this embodiment adopts a segmented follow-up design; the segmented heat conduction unit is composed of multiple independent copper heat conduction blocks arranged along the weld direction; the length of each heat conduction block is 20mm to 50mm, used to directly contact the back of the thin-walled part for heat absorption; the heat-insulating elastic filling unit fills the gaps between adjacent heat conduction blocks; in this embodiment, high-temperature resistant silicone rubber or ceramic fiber felt is used; its function is to allow relative micro-displacement between adjacent heat conduction blocks, such as a gap change of 0.1mm to 0.5mm, so that the segmented heat conduction unit as a whole can deform with the thin-walled part like a chain, avoiding interference of the rigid pad on the in-plane displacement of the workpiece; To ensure the consistency of movement between the fixture and the heat dissipation pad, the in-plane floating clamping module and the follow-up heat dissipation module are connected by a synchronous connection mechanism. In this embodiment, the mechanism adopts a rigid connecting rod or integrated frame design to rigidly lock the upper pressure plate unit and the lower heat-conducting block together. In order to avoid interference with thin-walled parts, the synchronous connection mechanism adopts a C-shaped external cross-connection structure to bypass the edge of the part or to connect through the pre-set process hole of the part, so as to achieve synchronous floating up and down without obstructing the welding path. This embodiment solves the contradiction between clamping force and freedom of movement in traditional tooling by combining linear guide rails and segmented heat sinks. The linear guide rails provide a movement path with extremely low friction, so that the thermal expansion thrust of the thin-walled parts is sufficient to overcome the resistance of the tooling. With the flexible connection of the segmented heat sink unit, it is ensured that the heat dissipation conditions on the back do not change when the workpiece undergoes large in-plane deformation, avoiding the problem of weld burn-through or oxidation caused by the workpiece arching and detaching from the pad, and ensuring uniform heat dissipation throughout the process. Furthermore, regarding the elastic hinge mechanism mentioned in the embodiments as another implementation method, in order to ensure that its stiffness characteristics meet the anisotropic requirements of vertical rigidity and horizontal flexibility, and to solve the problem of unclear design parameter sources, this embodiment provides a parametric design logic based on the critical load of the workpiece; the elastic hinge mechanism adopts a double parallel four-bar flexible hinge structure, and its dimensional design must meet the following stiffness boundary conditions: The first step is to calculate the upper limit of the target horizontal stiffness. To prevent buckling of thin-walled parts when thermal expansion pushes the hinge, the reaction force of the hinge must be less than the Euler critical load of the part. Therefore, the following settings are made: in, To obtain to The safety factor is mainly used to cover the effects of assembly errors and nonlinear geometric effects. The more complex the structure or the lower the assembly precision, the smaller the value should be. The coefficient of static friction between the in-plane floating clamping module and the base support module is taken as the coefficient of friction for the linear guide rail. to To ensure the calculation results cover the maximum resistance during startup, it is recommended to use a larger value for conservative calculations. If the operating conditions involve high temperatures or no lubrication, it is recommended to use high-temperature grease and adjust the temperature correction factor according to the manufacturer's specifications. Make corrections, typically using a correction factor of [value missing]. to ; For the quality of the floating clamping module, The mass of the follow-up heat dissipation module, where mass is... and The total mass of all components involved in the follow-up motion should be clearly included, including connecting bolts, force-applying mechanism components, and sensor accessories; in the preliminary design stage, if a detailed model is unavailable, the mass can be calculated by multiplying the geometric volume of each component by its material density. The estimate is multiplied to include the weight of standard parts; For gravitational acceleration, take the standard value. ; The formula explicitly deducts the parasitic frictional resistance caused by the device's own weight, ensuring that the remaining thrust allowance is sufficient to overcome the elastic resistance of the flexible hinge. The elastic modulus of the part. Let the moment of inertia of the cross section of the part be , The effective length of the part under compression is taken as the actual span for simply supported boundaries and 0.5 times the span for fixed supported boundaries. For parts with stiffeners or irregular cross-sections, The effective length should be obtained directly through the section property analysis tool in CAD software, or by summing the moments of inertia of each section block to the neutral axis using the parallel axis theorem. For other complex boundary conditions, such as elastic supports, half the wavelength of the buckling mode can be taken as the effective length. ; To estimate thermal expansion; and to enable those skilled in the art to perform this accurately, it is clearly stated herein. The calculation formula is: in, The coefficient of thermal expansion of the part material. The ambient temperature during assembly. The average temperature of the parts during the welding process can be taken as 30% to 40% of the material's melting point; this range is based on empirical data on the average heat accumulation of common metallic materials in the welding thermal cycle: for materials with high thermal conductivity, the upper limit is recommended. For materials with low thermal conductivity, it is recommended to use the lower limit. To ensure the uniqueness of the calculation parameters, in this embodiment... Defined as: in, The melting point of the part material. The first step is to set the room temperature as the reference temperature; the second step is to calculate the lower limit of the target's vertical stiffness. To ensure clamping reliability, the hinge is operated at the rated clamping force. The deformation under the action must be less than the allowable error. For example, 0.01mm: The third step is to solve for the hinge dimensions using structural mechanics formulas; based on the fixed-guide beam mechanical model of double parallel leaf springs, the following is defined: The width of the flexible hinge. The thickness of a single spring sheet. The effective length of the spring is usually preset according to the overall dimensions of the tooling module. For example, take The above formula derivation is based on the mechanical model of two leaf springs connected in parallel: the lateral stiffness of a single leaf spring is... Based on the cantilever beam subjected to end lateral forces model, the tensile stiffness is... Because of the symmetrical arrangement of two plates, the total stiffness is multiplied by . ; Solve the above inequalities and The thickness of the reed can then be accurately calculated. and length The feasible domain; Fourthly, to prevent the flexible hinge from undergoing plastic yielding failure during large-scale deformation, this embodiment adds static strength verification logic based on material mechanics; due to the thermal expansion displacement of thin-walled parts... The stress is entirely borne by the bending deformation of the flexible hinge; therefore, the maximum stress at the hinge root must be verified. Is it less than the allowable stress of the material? The verification formula is constructed as follows: The first item is forced displacement. The resulting bending normal stress, the second term is the clamping force. The resulting tensile / compressive stress, For example, the yield strength of hinge materials such as spring steel 65Mn. A safety factor of 1.5 to 2.0 is used here; For static strength design under a single welding thermal cycle, if the tooling needs to be reused multiple times, considering fatigue cumulative damage and material property degradation, it is recommended to... Increase to The above; if the above inequality does not hold, the program will execute a parameter iterative optimization loop: maintain The ratio remains unchanged, but increases synchronously. and The values ​​are calculated to reduce the bending stress term until the strength constraint condition is met, thus outputting the final engineering parameters that can be used for manufacturing. .

[0021] Example 3: The bidirectional elastic tensioning module includes: The pretension force generating unit is connected at one end to the base support module and at the other end to the in-plane floating clamping module; The pre-tension force generating unit is configured to apply a preset initial tensile force to the thin-walled part before welding, so that the thin-walled part is in an elastic taut state.

[0022] The pretension force generating unit includes: The mechanical spring assembly is configured to absorb the displacement caused by thermal expansion using elastic deformation potential energy and to provide restoring tension using restoring force.

[0023] The stiffness characteristics provided by the bidirectional elastic tensioning module are configured to meet the following conditions: During the welding heating stage, the equivalent stiffness of the bidirectional elastic tensioning module is set to be less than the critical stiffness corresponding to the thermal expansion yield strength of the thin-walled part, so as to prevent the thin-walled part from undergoing compressive plastic deformation. During the welding cooling stage, the recovery tension provided by the bidirectional elastic tensioning module is set to be no less than the residual shrinkage stress of the thin-walled part, so as to block the accumulation path of residual stress.

[0024] This embodiment focuses on describing the mechanical property settings of the bidirectional elastic tensioning module, which is the key to achieving stress-free welding. The bidirectional elastic tensioning module includes a pre-tension force generating unit, one end of which is anchored to the base support module, and the other end is connected to the in-plane floating clamping module. In this embodiment, a mechanical spring assembly, such as a mold spring or a disc spring assembly, is used. During the pre-welding preparation stage, a preset initial tensile force is applied to the thin-walled part by adjusting the screw to compress the spring. This allows thin-walled parts to be in an elastically taut state before welding; this helps to improve the rigidity of the workpiece and prevent instability in the early stages of welding. Based on this, in order to precisely control stress evolution, this embodiment introduces stiffness matching logic; during the welding heating stage, in order to prevent thin-walled parts from yielding due to excessive restraining force when thermally expanding, the equivalent stiffness of the bidirectional elastic tensioning module is... The following conditions must be met: Considering that the in-plane floating clamping module and the bidirectional elastic tensioning module are mechanically in parallel, the total equivalent stiffness of the system acting on the thin-walled part must be [value missing]. The sum of the two; to prevent the total system reaction force from causing buckling of the parts, the global stability constraint must be satisfied: in, The actual horizontal stiffness of the flexible hinge is determined in Example 2; in this step, the upper limit of the allowable stiffness of the spring assembly needs to be calculated based on this inequality: If the calculation result If so, we need to return to Example 2 and reduce the stiffness design value of the flexible hinge; in, The source is the stiffness coefficient setting of the spring assembly, and its physical meaning is the equivalent stiffness of the bidirectional elastic tensioning module, with the unit being N / mm; The source is a material property handbook; its physical meaning is the yield strength of thin-walled part materials at the peak welding temperature, and the unit is... ; The source is the measurement of the geometric dimensions of the part; its physical meaning is the cross-sectional area of ​​a thin-walled part perpendicular to the direction of force, and the unit is mm². The source is calculated using thermodynamic formulas. It should be noted that here... The melting point temperature of the weld center should not be used, otherwise the calculated expansion will be too large and the stiffness setting will fail. It should be defined as the equivalent volume average temperature of the region between the inner edge of the in-plane floating clamping module and the welding fusion line. In practical engineering operations, if detailed measurements or simulations are not possible, a simplified definition is permitted: the arithmetic mean of the solidus temperature at the weld fusion line and the measured temperature at the inner edge of the clamping module is taken as... The engineering approximation value typically needs to have its error range controlled within a certain range. within; The specific geometric boundary of this area is defined as follows: the thickness direction is the thickness of the part plate, and the planar area is a rectangular strip area enclosed by the weld fusion line and the inner side line of the clamping module; To address the challenge of defining the weld fusion line in actual welding due to the complex temperature field, this embodiment explicitly defines the weld fusion line as the theoretical weld width boundary determined according to the welding procedure specification, i.e., the distance from the weld centerline. This is used as a definite geometric reference line; This refers to the upper limit of weld width specified in the welding procedure specification; at the same time, in order to provide repeatable operational guidance, It is recommended to use the two-point linearization approximation method to determine the temperature: that is, take the arithmetic mean of the solidus temperature of the material at the theoretical fusion line and the measured temperature of the inner edge of the clamping module; in engineering practice, the temperature field distribution of this region can be obtained by thermocouple measurement or finite element simulation, and the integral average value can be taken. If no measured data or simulation conditions are available, empirical formulas can be used. Engineering estimation is performed; the empirical coefficient of 0.3 is a statistical constant derived from the analytical solution of heat conduction of typical aerospace aluminum alloys such as 2219 and stainless steel such as 304 thin plates under conventional TIG / MIG welding heat input based on the Rosenthal moving heat source model and corrected by experiments. It represents the average heat accumulation level outside the heat-affected zone under conditions without forced cooling. The vertical distance between the in-plane floating clamping module and the welding centerline is the effective expansion length, expressed in mm. This formula defines the critical softness of the system; if the tooling stiffness... If the force exceeds the critical value on the right, the reaction force generated by the tooling restricting thermal expansion will exceed the material's yield limit, leading to irreversible plastic deformation. In this embodiment, a low-stiffness spring is used to ensure that the tooling yields. Furthermore, during the welding cooling stage, in order to counteract weld shrinkage, the bidirectional elastic tensioning module provides restoring tension. Must meet: Regarding the original text Regarding the issue of unknown origin, this embodiment clarifies: The formula for calculating the estimated residual shrinkage stress in the weld is set as follows: ;in, The yield strength of the material at room temperature can be obtained from the material handbook. The residual stress coefficient needs to be selected based on the actual restraint level: for unrestrained plate surfacing, take [value missing]. For welding of strongly restrained structures The above The value range is referenced from typical experimental data in literature such as "Numerical Simulation and Control of Residual Stress in Welded Structures"; among them, strong restraint is defined as the width of the plates on both sides of the weld being greater than The plate is twice the thickness and both ends are rigidly fixed; To ensure that the aforementioned restoring tension condition is physically feasible, this embodiment further defines the rules for setting the initial pre-compression of the mechanical spring assembly; restoring tension. Essentially based on Hooke's Law of the spring Decision; taking into account the thermal expansion of the workpiece during the welding process. And with the subsequent contraction, at the end of cooling, the actual deformation of the spring is equal to the initial pre-compression. Add or subtract the residual displacement; to ensure sufficient final tensile force, define... The initial pre-compression displacement of the mechanical spring assembly in the installed state must satisfy the following value: This formula provides a clear adjustment guideline for on-site operators: by adjusting the preload nut, the spring compression distance should reach at least [a certain value]. In this way, no matter how the workpiece deforms during the welding process, the high-stiffness spring assembly can always store enough elastic potential energy, which is actively released and stretched during the cooling stage, thereby blocking the accumulation path of residual stress in a physical mechanism.

[0025] Example 4: The pretension force generating unit includes: Shape memory alloy actuator, configured to respond to temperature changes during the welding process; Among them, the shape memory alloy actuator is configured to: undergo a martensitic inverse phase transformation or reduce stiffness by utilizing the thermoelasticity of the material when the temperature rises, so as to accommodate the expansion displacement of thin-walled parts. The shape memory alloy actuator is also configured to restore a high stiffness state or generate contraction deformation when the temperature decreases, in order to provide restoring tension.

[0026] Although the phase transformation stress plateau of the material itself decreases with decreasing temperature, the actuator is configured to operate along the unloading path of the stress-strain hysteresis loop to ensure that its unloading stress at the cooling end temperature is still sufficient to overcome the weld resistance. This embodiment provides an advanced implementation based on smart materials for replacing or enhancing traditional mechanical springs; The pretension force generating unit uses a shape memory alloy actuator, such as a nickel-titanium (NiTi) alloy spring or bar; this actuator utilizes the unique thermoelastic martensitic phase transformation properties of SMA material to respond to temperature field changes during the welding process. During the welding heating stage, in order to specifically realize the function of reducing stiffness by utilizing the thermoelasticity of the material, it is necessary to ensure that the SMA actuator operates in the hyperelastic range; therefore, this embodiment proposes strict screening conditions for the phase transformation temperature parameters of the SMA material: the austenite termination temperature of the selected SMA material. The temperature must be lower than the ambient temperature of the actuator during the welding heating stage. ,Right now ; here Specifically referring to the surface temperature of the SMA actuator body, it can be monitored in real time using a type K thermocouple attached to the actuator surface. Care must be taken to avoid direct interference from heat radiation at the measurement point. Under these conditions, when the welding heat transfer causes the actuator temperature to rise to... At this time, SMA is in the fully austenitic phase; at this time, it faces the thermal expansion displacement of thin-walled parts. When the SMA actuator enters the stress plateau region of stress-induced martensitic phase transformation, it exhibits extremely low tangential stiffness, i.e., constant force weak stiffness characteristics. To quantify this characteristic for actuator selection, this embodiment defines the actuator cross-sectional area based on the constitutive model of SMA. Design constraints; to address the temperature-stress coupling effect not considered in the original model, this embodiment introduces the Clausius-Clapeyron equation to dynamically correct the actuator output force to conform to the laws of thermodynamics; considering the upper platform stress of the SMA The hardening effect increases linearly with temperature, leading to increased hardness. To ensure proper welding at peak temperatures... If the reaction force of the lower actuator does not damage the workpiece, the cross-sectional area must be adjusted. Upper limit constraint formula; Define the upper plateau stress function after temperature correction: in, The Clausius-Clapeyron coefficients, Reference temperature The test stress value is specified below. To clarify the source of the above key design parameters and ensure the feasibility of the solution, this embodiment stipulates that the above parameters should be obtained by isothermal tensile-unloading cycle testing of the selected SMA material, such as the commonly used Ni-50.8at.%Ti binary alloy, according to ASTM F2516 "Standard Method for Tensile Testing of Nickel-Titanium Hyperelastic Materials"; the strain rate should be set to [value missing] during the test. to To match the quasi-static loading conditions of the welding process, and must be carried out in a constant temperature chamber, the test temperature should cover at least [temperature range missing]. to The scope; as specific implementation reference data, for typical commercial NiTi wire, The measured value is usually It is recommended to directly use typical engineering experience values. This value represents the statistical median of commonly used materials and does not require separate calculation; select hour, The typical measured range is The constraint condition is modified to: the platform force generated by the actuator. Even at the highest temperature, it must be less than the critical buckling load of the workpiece. By Euler's formula Calculations are required; therefore, the cross-sectional area of ​​the SMA actuator must satisfy: This formula clarifies that: with welding temperature... The increase in allowable SMA cross-sectional area The temperature must be reduced to counteract the stress hardening effect of the material itself; this is safer and more reliable than simply using room temperature parameters. During the welding cooling phase, the SMA actuator unloads as the temperature decreases. Although the phase transformation stress at low temperatures is lower than at high temperatures according to the Clausius-Clapeyron relation, to effectively counteract weld shrinkage, the minimum tensile force provided by the actuator at the end of cooling must still be greater than the residual stress in the weld. Therefore, the cross-sectional area of ​​the actuator... The lower limit requirement must be met: in, This represents the lower plateau stress of the SMA material at the final cooling temperature. This value needs to be determined based on the unloading curve measured according to ASTM F2516 standard. During design, it is crucial to note that this utilizes the characteristic of superelastic materials not returning to zero under unloading, rather than the flawed logic of temperature-induced hardening. For the NiTi alloy example above, its lower plateau stress... Usually located For the interval, the lower limit value of the measured curve should be used during the design to ensure sufficient resilience; The fifth step is to perform a feasibility closed-loop verification of the SMA actuator design domain; Combining the above high-temperature buckling constraints and low-temperature recovery constraints, a dimensionless feasibility determination factor is defined. : During calculation, the formula and Test curves must be taken from the same batch of materials at the corresponding temperature. Data from different batches or different heat treatment states must not be mixed to prevent performance deviations. The numerator represents the coupling index of the maximum safe recovery capability and high-temperature buckling resistance that the SMA actuator can provide during the low-temperature unloading phase, while the denominator represents the stress boundary required by the actual working conditions. This means that the material property space covers the working condition requirement space; Dimensionless factor The physical meaning lies in verifying the match between material properties and structural requirements: it requires that the hysteresis width ratio of the SMA material must be better than the structural strength safety margin of the workpiece; only when Only then can a legal cross-sectional area exist. This allows the tooling to be both soft enough at high temperatures to protect the workpiece from buckling and strong enough at low temperatures to eliminate residual stress. The program executes the following logical branches: like This indicates the existence of a valid solution set, which can be found in... Select within the interval The engineering value; like This indicates that the current SMA material cannot simultaneously meet the dual requirements of protecting the workpiece and relieving stress, i.e., the solution set is empty. In this case, one of the following optimization strategies needs to be implemented: (a) Replace with an SMA alloy material with a wider hysteresis loop, i.e., find (a) Materials with smaller ratios; (b) Adding parallel passive negative stiffness mechanisms to offset some of the high-temperature stiffness; This embodiment utilizes the thermo-mechanical coupling characteristics of shape memory alloys to construct an adaptive intelligent tensioning system; the solution obtained by simultaneously solving the above two inequalities yields... Within this range, engineers can precisely manufacture intelligent tooling that can soften and yield when heated and harden and stretch when cooled, achieving stress management that is naturally synchronized with the welding thermal cycle without the need for external sensors.

[0027] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A welding fixture for thin-walled parts, characterized in that, include: The base support module is used to provide a rigid physical reference for the welding fixture; The in-plane floating clamping module is configured to apply a rigid clamping force in a direction perpendicular to the surface of the thin-walled part to establish a clamping connection, and to have a degree of freedom of movement relative to the base support module in a direction parallel to the surface of the thin-walled part; A bidirectional elastic tensioning module connects the base support module and the in-plane floating clamping module, and is configured to provide an elastic connection to allow the in-plane floating clamping module to move relative to the base support module; The bidirectional elastic tensioning module is configured to, during the welding heating stage, respond to the thermal expansion of the thin-walled part through elastic deformation, allowing the in-plane floating clamping module to generate a follow-up displacement away from the welding center direction to release thermal stress. The bidirectional elastic tensioning module is also configured to apply a restoring force to the in-plane floating clamping module in the direction of the welding center or away from the welding center during the welding cooling stage, so as to counteract the weld shrinkage stress. A follow-up heat dissipation module is disposed on the back of the thin-walled part, which supports the thin-walled part and is configured to move along with the in-plane floating clamping module to maintain contact and heat conduction with the thin-walled part.

2. The welding fixture for thin-walled parts according to claim 1, characterized in that, The in-plane floating clamping module includes: A pressure plate unit is used to contact the upper surface of the thin-walled part; A floating connection unit is disposed between the pressure plate unit and the base support module; The floating connection unit employs a linear guide rail mechanism or an elastic hinge mechanism to limit the vertical displacement of the pressure plate unit and release the horizontal displacement constraint of the pressure plate unit.

3. The welding fixture for thin-walled parts according to claim 1, characterized in that, The bidirectional elastic tensioning module includes: The pretension force generating unit is connected at one end to the base support module and at the other end to the in-plane floating clamping module; The pre-tension force generating unit is configured to apply a preset initial tensile force to the thin-walled part before welding, so that the thin-walled part is in an elastic taut state.

4. A welding fixture for thin-walled parts according to claim 3, characterized in that, The pretension force generating unit includes: A mechanical spring assembly is configured to absorb the displacement caused by thermal expansion using elastic deformation potential energy and to provide the restoring tension using restoring force.

5. A welding fixture for thin-walled parts according to claim 3, characterized in that, The pretension force generating unit includes: Shape memory alloy actuator, configured to respond to temperature changes during the welding process; The shape memory alloy actuator is configured to undergo a martensitic inverse phase transformation or reduce stiffness by utilizing the thermoelasticity of the material when the temperature rises, so as to accommodate the expansion displacement of the thin-walled part. The shape memory alloy actuator is also configured to restore a high stiffness state or generate contraction deformation when the temperature decreases, in order to provide the restoring tensile force.

6. A welding fixture for thin-walled parts according to claim 1, characterized in that, The follow-up heat dissipation module includes: The segmented heat-conducting unit consists of multiple independent heat-conducting blocks arranged along the weld seam direction, and the heat-conducting blocks are used to directly contact the back of the thin-walled part; Thermally insulating elastic filling units are filled between adjacent thermally conductive blocks; The thermally insulating elastic filling unit is configured to allow relative micro-displacement between adjacent thermally conductive blocks to maintain the segmented thermally conductive unit as a whole as it deforms with the thin-walled part.

7. A welding fixture for thin-walled parts according to claim 1, characterized in that, The in-plane floating clamping module and the follow-up heat dissipation module are connected by a synchronous connection mechanism; The synchronous connection mechanism is configured to transfer the horizontal displacement of the in-plane floating clamping module to the follow-up heat dissipation module, ensuring that the relative position between the follow-up heat dissipation module and the thin-walled part remains unchanged when the thin-walled part undergoes thermal expansion or cold contraction displacement.

8. A welding fixture for thin-walled parts according to claim 1, characterized in that, The stiffness characteristics provided by the bidirectional elastic tensioning module are configured to meet the following conditions: During the welding heating stage, the equivalent stiffness of the bidirectional elastic tensioning module is set to be less than the critical stiffness corresponding to the thermal expansion yield strength of the thin-walled part, so as to prevent the thin-walled part from undergoing compressive plastic deformation. During the welding cooling stage, the recovery tension provided by the bidirectional elastic tensioning module is set to be no less than the residual shrinkage stress of the thin-walled part, so as to block the accumulation path of residual stress.

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