Friction stir welding simulation method and system with in-situ force parameter constraint

Abstract

The invention discloses an in-situ force parameter constrained friction stir welding simulation method and system, and the method comprises the steps: building a finite element model corresponding to an actual welding component according to an actual geometric structure, material parameters and a technological process of the welding component; a force sensor is used for collecting three-way force parameters of a stirring needle on a weld joint in the welding component welding process and collecting torque; the collected three-way force is converted into a heat source model simulating heat source distribution in the welding process; a finite element model containing the heat source model is established; performing heat transfer simulation on the welding process and the cooling process of the friction stir welding to obtain a temperature field of the friction stir welding; the obtained three-way force parameters and torque are calculated and converted into a mechanical load of the stirring head to a welding seam; and the obtained mechanical loads of the shaft shoulder acting area and the stirring needle acting area serve as input conditions, the obtained temperature field is coupled and guided into a stress field finite element model, and stress field distribution of the welding component is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace welding, and in particular to an in-situ force parameter constrained friction stir welding simulation method and system. Background Art

[0002] With the rapid development of the aerospace industry, the demand for lightweight and high-strength structural components is increasing. Friction stir welding, as an advanced solid-state joining technology, effectively avoids metallurgical defects such as porosity and cracks found in traditional fusion welding, significantly improving joint quality and gradually gaining widespread application in the aerospace field. However, the residual stress generated during friction stir welding can seriously affect the performance and stability of welded structures, potentially leading to fatigue crack initiation and structural failure. Therefore, the accurate prediction and effective control of welding residual stresses are of great engineering significance.

[0003] However, as structural parts in the aerospace field develop towards larger and more complex shapes, traditional experimental verification methods have limitations such as long cycles and high costs. Analysis methods based on numerical simulation have gradually become an important means of studying the distribution of residual stress in welding. This numerical method can not only provide full-field stress distribution information, but also achieve rapid optimization of process parameters, significantly reducing R&D costs. Existing finite element simulation calculation methods for stir friction welding mainly estimate the energy input of the welding process based on the output power of the equipment or the torque of the stirring head, and determine the heat generation ratio of the shoulder and the stirring needle through trial and error. Because this simplified model fails to truly reflect the physical process of stir friction welding, the accuracy and scope of its prediction results are severely limited.

[0004] Furthermore, numerous studies have demonstrated the existence of a complex "thermal-mechanical" coupling during friction stir welding: on the one hand, the temperature field distribution directly influences the formation of residual stress; on the other hand, the mechanical force exerted by the stirrer on the weld significantly affects the magnitude and distribution of residual stress, with this coupling effect having a more pronounced impact on joint performance. However, existing simulation techniques are often limited to simply adding a heat source to the weld area, ignoring the influence of the mechanical force exerted by the stirrer, which compromises the accuracy and reliability of simulation results. Summary of the Invention

[0005] The present invention aims to overcome the defects of the prior art and provide a stir friction welding simulation method and system with in-situ force parameter constraints. The method and system can realize high-precision simulation calculation of the stir friction welding temperature field and residual stress, thereby improving the generalization ability of the model.

[0006] The present invention aims to provide an in-situ force parameter constrained friction stir welding simulation method, comprising:

[0007] Step 1: Establish a finite element model corresponding to the actual welded component based on its actual geometry, material parameters, and process.

[0008] Step 2: Use force sensors to collect the three-dimensional force parameters of the stir needle on the weld during the welding process of the welded component, including the forward resistance Fx, the lateral force Fy, and the downward force Fz. Use the friction stir welding machine to collect the torque M. Convert the collected three-dimensional forces into a heat source model that simulates the heat source distribution during the welding process: apply the obtained shoulder heat source and stir needle heat source to the weld of the finite element model, and establish a finite element model including the heat source model.

[0009] Step 3: Based on the conditions determined in step 2, the finite element model including the heat source model determined in step 2 is used to perform heat transfer simulation on the friction stir welding process and the cooling process, and the temperature field results at each moment during the friction stir welding and cooling process are obtained. The temperature field results are used as one of the initial conditions for the subsequent stress field finite element model simulation calculation;

[0010] Step 4: The three-axis force parameters F of the welding seam collected in step 2 are x 、F y and F z And the torque M is calculated and converted into the mechanical load of the stirring head on the weld, which is applied to the stress field finite element model;

[0011] Step 5: Take the mechanical loads of the shoulder action area and the stirring needle action area obtained in step 4 as input conditions, couple the temperature field obtained in step 3, import the stress field finite element model obtained in step 4, and perform stress field simulation calculations on the welding process and cooling process of the stir friction welding; after the welding process is completed, gradually release the constraints, and finally obtain the stress field distribution of the welded component; wherein, the mechanical load includes the circumferential shear stress τ of the shoulder on the upper surface of the weld area x and τ y The uniform surface force P of the shoulder on the weld area and the forward resistance F of the stirring force on the weld area x and lateral force F y ;

[0012] Step 6: Based on the simulation results, the residual stress of the welded component under different welding parameters is compared and analyzed to determine the welding parameters with the lowest residual stress, thereby optimizing the welding process parameters. This optimized welding process is then used in actual component welding, resulting in excellent service stability for the welded component, which can be widely used in aerospace, rail transportation, and other fields, further promoting the use of friction stir welding technology.

[0013] Furthermore, step one specifically includes:

[0014] S11: Use modeling software to perform three-dimensional modeling based on the actual geometric structure of the welded component, and then import it into the finite element analysis software to establish a finite element geometric model of the welded component;

[0015] S12: assigning geometric model material parameters to the established finite element model and setting the ambient temperature before welding and the initial temperature of the test plate;

[0016] S13: Establish simulation analysis steps consistent with the actual welding process, including pressing down, stabilizing welding and cooling process. The analysis step time setting is the same as the actual welding time.

[0017] S14: Mesh the constructed geometric model.

[0018] Furthermore, step 2 specifically includes:

[0019] S21: The friction stir welding machine collects torque M and uses a force sensor to collect three-dimensional force parameters during the welding process: forward resistance Fx, lateral force Fy, and downward force Fz;

[0020] S22: Use thermocouples and pyrometers to measure and obtain the thermal cycle curve of the weld area during the actual welding process, which is used for the accuracy verification of the subsequent temperature field simulation model;

[0021] S23: Based on the three-axis force parameters and torque M obtained in step S21, calculate the heat source Q1 of the shoulder part and the heat source Q2 of the stirring needle applied to the stirring needle action area:

[0022]

[0023] Where ω is the stirring head speed, μ is the friction coefficient, R s is the shoulder radius, R d 、R u are the end and root radii of the stirring needle respectively, H represents the height of the stirring needle, K is the force generated by the action between the shoulder and the workpiece, and the axial pressure F measured by the three-axis force sensor is z The ratio of α is the taper of the stirring needle;

[0024] S24: Apply the shoulder heat source Q1 and the stirring needle heat source Q2 obtained in step S23 to the weld of the finite element model, wherein the shoulder heat source Q1 is added to the weld surface in the form of a surface heat source, and the stirring needle heat source Q2 is added to the stirring needle action area in the form of a body heat source; the heat source movement path is set according to the welding path of the stirring head during the actual welding process, and the distance the heat source moves is also consistent with the actual welding specimen.

[0025] Furthermore, step three also includes: selecting the same characteristic point as the thermocouple measurement position in step S22 in the temperature field simulation model in step three, and comparing the thermal cycle curve obtained in step S22 with the thermal cycle curve simulated in step three; if the simulation result is within 10% of the simulation result of step S22, continue to step four; otherwise, return to step one and re-perform the simulation calculation.

[0026] Furthermore, the step 4 further includes: the downward pressure of the shoulder on the weld area is considered to be a uniformly distributed surface force P, and F z Calculation shows that the circumferential shear stress τ on the upper surface of the weld area is x and τ y From the torque M we get:

[0027]

[0028] Where P, τ x and τ y is the mechanical force applied to the surface of the weld area in the simulation model, F z and M are the down force and torque measured during welding, both obtained in step 2; P is the down force F z The calculated uniform surface force of the shoulder on the weld area, the circumferential shear stress τ of the shoulder on the upper surface of the weld area x and τ y The tangential force of the shaft shoulder on the test plate surface is taken into account, r is the distance from the integration point to the center of the stirring head, R0 is the radius of the shaft shoulder, x and y are the coordinate values of the integration point; In addition, considering the mechanical load of the stirring head on the weld area, F x and F y Added to the area of the stirring needle inside the weld.

[0029] The present invention also discloses an in-situ force parameter constrained friction stir welding simulation system, comprising:

[0030] Finite element model building module, used to build a finite element model corresponding to the actual welded component based on its actual geometric structure, material parameters, and process;

[0031] The force data acquisition and coupled model building module is used to collect the three-dimensional force parameters and torque of the stirring force on the weld during the welding process of the welded component; convert the collected three-dimensional force into a heat source model that simulates the heat source distribution during the welding process; and apply the heat source model to the weld of the finite element model to establish a finite element model that includes the heat source model.

[0032] The simulation first condition acquisition module is used to simulate the heat transfer of the friction stir welding process and the cooling process based on the finite element model including the heat source model obtained by the force data acquisition and coupling model establishment module, and obtain the temperature field result of the friction stir welding;

[0033] The simulation module for obtaining the second condition is used to obtain the mechanical loads in the shoulder action area and the stirring needle action area;

[0034] A simulation module is used to input the temperature field obtained by the simulation first condition acquisition module and the mechanical load obtained by the simulation second condition acquisition module into the finite element model, perform stress field simulation calculations on the welding process and cooling process of the friction stir welding, and obtain the stress field distribution of the welded component; and

[0035] The parameter optimization module compares and analyzes the residual stress of samples under different welding parameters to obtain welding parameters with smaller residual stress, optimize welding process parameters, and use them for welding actual components.

[0036] The beneficial effects of the present invention are as follows: the in-situ force parameter constrained friction stir welding simulation method and system of the present invention applies the force parameters measured during the welding process to the simulation model in the form of a heat source to calculate the temperature field;

[0037] In addition, the mechanical load effect of the stirring head on the weld is incorporated into the simulation calculation, so that the thermal-mechanical coupling of the stir friction welding process can be reflected in the simulation calculation, thereby improving the simulation accuracy and increasing the generalization ability of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the force data acquisition device in step 2 of the in-situ force parameter constrained friction stir welding simulation method of the present invention;

[0039] Figure 2 is a flow chart of the in-situ force parameter constrained friction stir welding simulation method of the present invention;

[0040] Figure 3 This is a comparison chart of simulation results and test results obtained by the stir friction welding simulation method using the in-situ force parameter constraint of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions, beneficial effects and significant improvements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings provided in the examples of the present invention. Obviously, all the described embodiments are only partial embodiments of the present invention, rather than all embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] In the description of this application, unless otherwise expressly specified or limited, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; the term "plurality" refers to two or more; unless otherwise specified or explained, the terms "connected" and "fixed" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, an integral connection, or an electrical connection; "connected" can mean a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0043] like Figure 2 As shown, a friction stir welding simulation method with in-situ force parameter constraint includes:

[0044] Step 1: Build a finite element model

[0045] S11: Based on the actual geometric structure of the welded component, perform 3D modeling using modeling software (such as Pro / Engineer, Solidworks, CATIA, UG, etc.). Import the created 3D model into finite element analysis software to create a finite element geometric model of the welded component. The finite element analysis software used includes but is not limited to LUSAS, MSC.Nastran, MACMarc, Ansys, Abaqus, LMS-Samtech, Algor, Femap / NX Nastran, Hypermesh, COMSOL Multiphysics, FEPG, etc.

[0046] S12: Assign geometric model material parameters to the established finite element model, including density, thermal conductivity, and specific heat. These thermophysical parameters will change with temperature and need to be measured through experiments or calculated with the material performance calculation software JMatPro. The convection heat transfer coefficient needs to be set according to the corresponding actual working conditions and the boundary conditions defined according to the contact between the workpiece and the air and the workbench during the actual welding process. Before welding, set the ambient temperature and the initial temperature of the test plate to 20°C.

[0047] S13: Establish simulation analysis steps consistent with the actual welding process, including pressing down, stabilizing welding and cooling process. The analysis step time setting is the same as the actual welding time.

[0048] S14: Mesh the geometric components constructed above. To improve numerical simulation accuracy and computational efficiency, meshes in key areas, such as welds, are refined using transitional meshing techniques. The minimum mesh size can be set to 1 mm × 1 mm × 1 mm. During the temperature field simulation, the mesh type is set to eight-node linear heat transfer hexahedral elements (DC3D8).

[0049] Step 2: Collect force data and thermal cycle curve of welding process

[0050] S21: Fix the components to be welded in the following way: Figure 1 The friction stir welding platform shown includes a three-axis force testing system. The three-axis force testing system includes four force sensors evenly distributed on the workbench, and the sampling frequency can reach 7800 Hz.

[0051] Among them, the three-axis force testing system can collect the three-axis force parameters Fx (forward resistance), Fy (lateral force), and Fz (downward force) during the welding process. It is electrically connected to the computer through wires. In order to avoid abnormal signal fluctuations caused by electromagnetic interference during the collection process, the three-axis force signal collection device needs to be protected against electromagnetic interference. The torque collection during the welding process is completed by the stir friction welding machine.

[0052] S22: Before the welding test, a 1.1mm diameter hole was prefabricated at a distance from the weld seam of the specimen. A 1mm diameter WRNK-191 armored K-type thermocouple was fixed in the hole. An AT4532 thermometer was used to measure the thermal cycle curve of the area around the weld seam during welding. This was used to verify the accuracy of the subsequent temperature field simulation model. The thermocouple's temperature measurement range was 0-1200°C; the thermometer had a resolution of 0.1°C and a sampling frequency of 10Hz.

[0053] S23: The computer receives the three-dimensional force parameters (forward resistance Fx, lateral force Fy and downward force Fz) and torque M transmitted in step S21, and converts the collected three-dimensional force into a heat source model that simulates the heat source distribution during welding. The heat source model is a composite heat source composed of the heat source on the shoulder surface and the heat source on the stirring needle body. Among them, the heat generated by the shoulder part is Q1, which is mainly related to F z As shown in formula (1), the heat source of the shoulder mainly acts on the weld surface and is added to the simulation model in the form of a surface heat source; the heat generated by the stirring needle is Q2, which is mainly related to F x As shown in formula (2), the heat source of the stirring needle is set as a volume heat source and applied to the stirring needle action area:

[0054]

[0055] Where ω is the stirring head speed, μ is the friction coefficient, R s is the shoulder radius, R d 、R u are the end and root radii of the stirring needle respectively, H represents the height of the stirring needle, K is the force generated by the action between the shoulder and the workpiece, and the axial pressure F measured by the three-axis force sensor is z The ratio of α to the stirring needle.

[0056] S24: The heat sources Q1 and Q2 obtained in step S23 are applied to the weld of the finite element model through the dynamic heat source subroutine (DFLUX), wherein the shoulder heat source Q1 is added to the weld surface in the form of a surface heat source, and the stirring needle heat source Q2 is added to the stirring needle action area in the form of a body heat source. The heat source movement path is set according to the welding path of the stirring head during the actual welding process, and the distance the heat source moves is also consistent with the actual welding specimen. The starting coordinates of the heat source need to be set in the DFLUX subroutine. When setting the coordinates of the starting positions of the Q1 and Q2 heat sources, they need to be determined based on the starting position of the stirring needle during the actual welding process, so as to ensure the consistency between the actual welding process and the numerical simulation calculation.

[0057] Step 3: Based on the conditions determined in step 2, use the finite element model including the heat source model determined in step 2 to simulate the heat transfer of the friction stir welding process and the cooling process, and obtain the temperature field results at each moment during the friction stir welding and cooling process. The temperature field results are used as one of the initial conditions for the subsequent stress field simulation calculation, and are used to couple the temperature field of the welding process with the welding mechanical force during the welding process to calculate the stress field. Before performing the stress field calculation, it is necessary to select the same feature point as the thermocouple measurement position in the temperature field simulation model, and compare the thermal cycle curves of the two during the welding process. The error between the simulation results and the test results is required to be within 10%, so as to verify the accuracy of the temperature field calculation model. Figure 3 To maximize computational efficiency while ensuring accuracy, a mesh sensitivity analysis can be performed on the temperature field model. This involves continuously refining the mesh until the simulation results no longer change significantly. At this point, the mesh size meets the accuracy requirements without incurring computational inefficiency due to an excessively large number of meshes.

[0058] Step 4: Conversion of force parameters and torque in welding process

[0059] S41: Considering the mechanical load of the shoulder action area, the three-axis force parameters F of the welding seam collected during the welding process (i.e., step S21) are used again. x 、F y and F z And the torque M, where the downward pressure of the shoulder on the weld area is considered to be a uniform surface force P, which is given by F z Calculation shows that the circumferential shear stress τ on the upper surface of the weld area is x and τ y From the torque M we get:

[0060]

[0061] Where P, τ x and τ y The mechanical force applied to the weld of the stirring head in the simulation model, Fz and M are the downward force and torque measured during welding, both measured in step S21; P is the downward force F z The calculated uniform surface force of the shoulder on the weld area, τ x and τ y The tangential force of the shoulder on the test plate surface is taken into account, r is the distance from the integration point to the center of the stirring head, R0 is the shoulder radius, and x and y are the coordinate values of the integration point.

[0062] Step 5: The mechanical load P and τ of the shoulder action area obtained in step 4 are x and τ y Import the finite element model, in which the uniform surface force P of the shoulder on the weld area is added to the upper surface of the weld in the form of surface force, and the circumferential shear stress τ of the shoulder on the upper surface of the weld area is x and τ y The shoulder action area is added in the form of body force; in addition, considering the mechanical load of the stirring pin on the weld area, F x and F y It is added to the stirring needle action area inside the weld in the form of body force, and a finite element model including the mechanical load relationship is obtained.

[0063] Step 6: Add the mechanical properties parameters required for stress analysis to the geometric model of stress analysis, such as Poisson's ratio, elastic modulus, thermal expansion coefficient, and yield strength. Considering the change of material flow stress with temperature and strain rate, the Johnson-Cook constitutive model can be used to describe the material constitutive structure, as shown in Equation (7):

[0064]

[0065] Where A is the yield strength of the material; B is the strain hardening coefficient of the material; C is the strain rate sensitivity; m is the thermal sensitivity; n is the strain hardening exponent; ε is the equivalent plastic strain; is the test strain rate, is the reference strain rate; T melt is the melting temperature; T room is room temperature. In the actual modeling process, the constitutive parameters of the material should be set according to the specific type of the material to be welded. Taking the 2219 aluminum alloy commonly used in aerospace as an example, the yield strength of the material at room temperature is about 345MPa, the strain hardening coefficient is 1100MPa, and the strain rate sensitivity is generally selected as 0.015. In addition, the simulation calculation of the temperature field and the stress field in the present invention adopts the sequential thermomechanical coupling method, so the stress field calculation model needs to maintain the same mesh division as the temperature field model, and only the geometric model unit type needs to be modified to an eight-node linear hexahedron unit (C3D8R). During the calculation process, the unit adopts the reduced integration method and hourglass control.

[0066] Step 7: Use the DLOAD subroutine in ABAQUS to load the mechanical load of the above stirring head on the weld, such as the uniform surface force P and shear stress τ acting on the weld surface by the shoulder. x and τ y and F in the stirring area x and F y As input conditions, the temperature field obtained in step three is coupled, and the finite element model obtained in step six is used to simulate the stress field of the welding process and cooling process of the stir friction welding. Similarly, the starting position of the mechanical load needs to be set in the DLOAD subroutine to synchronize it with the movement of the heat source in the temperature field model, thereby ensuring the consistency between the actual welding process and the numerical simulation calculation. In addition, during the stress analysis calculation process, boundary conditions need to be set for the simulation model to limit its displacement. After the welding process is completed, the constraints are gradually released to finally obtain the stress field distribution of the welded component.

[0067] Step 8: Use X-ray diffraction or blind hole method to detect the residual stress distribution of the sample after welding. Before using the X-ray diffractometer to measure the residual stress, it is necessary to calibrate the equipment with aluminum alloy powder in a stress-free state. In addition, the measuring point position on the surface of the test plate to be tested needs to be electropolished to remove the surface oxide layer and contaminants, thereby improving the clarity of the diffraction signal and the measurement accuracy. Similarly, before using the blind hole method to detect the residual stress, it is also necessary to clean the surface of the specimen and paste the strain gauge at the position to be measured. The residual stress is measured by drilling a hole with a depth of not less than 1.2 times the aperture on the strain gauge. The blind hole method calculates the residual stress by collecting the strain difference before and after the stress release at the target position, as shown in formula (8):

[0068] σ1=C1(△ε1+C2△ε3) (8)

[0069] Where C1 and C1 are parameters related to the strain release coefficient, and ε is the strain. After the test is completed, the residual stress at the same position in the stress field simulation model is extracted and compared to ensure the accuracy of the simulation model. If the simulation model accuracy meets the requirements, proceed to step nine. If not, return to step one to re-divide the mesh or return to step five to further improve the boundary condition settings, so that the boundary conditions of the model during the stress field calculation process are as consistent as possible with the constraint method of the actual welding process component until the accuracy requirements are met;

[0070] Step 9: Based on the above simulation model, the welding process parameters (spindle speed, welding speed, and downward pressure, etc.) are adjusted. The optimized welding process parameters are applied to the actual component welding process, ensuring that the welded component has good service stability, reducing residual stress levels, and improving structural stability and safety. This can be widely used in many fields such as aerospace and rail transportation, further promoting the use of friction stir welding technology.

[0071] Figure 3 The simulation results of friction stir welding based on the force parameters described in this invention are compared with experimental results. The results show good consistency with the experimental results, with an error of less than 10%. The simulation results for residual stress show an abnormal increase in the weld end region, which is related to the unstable welding phase in this area. Because the present invention uses the welding process force parameters as input and couples the mechanical load of the stir head in the residual stress calculation process, it has good generalization capabilities.

[0072] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A friction stir welding simulation method with in-situ force parameter constraint, characterized in that: include: Step 1: Establish a finite element model corresponding to the actual welded component based on its actual geometry, material parameters, and process. Step 2: Use force sensors to collect the three-dimensional force parameters of the stir needle on the weld during the welding process of the welded component, including the forward resistance Fx, the lateral force Fy, and the downward force Fz. Use the friction stir welding machine to collect the torque M. Convert the collected three-dimensional forces into a heat source model that simulates the heat source distribution during the welding process: apply the obtained shoulder heat source and stir needle heat source to the weld of the finite element model to establish a finite element model including the heat source model. Step 3: Based on the conditions determined in step 2, the finite element model including the heat source model determined in step 2 is used to perform heat transfer simulation on the friction stir welding process and the cooling process, and the temperature field results at each moment during the friction stir welding and cooling process are obtained. The temperature field results are used as one of the initial conditions for the subsequent stress field simulation calculation; Step 4: Calculate and convert the three-axis force parameters of the stirring head on the weld and the torque M collected in step 2 into the mechanical load of the stirring head on the weld and apply it to the finite element model; Step 5: Using the mechanical loads in the shoulder action area and the stirring needle action area obtained in step 4 as input conditions, coupled with the temperature field obtained in step 3, the finite element model obtained in step 4 is imported to perform stress field simulation calculations on the welding process and cooling process of the friction stir welding; After the welding process is completed, the constraints are gradually released, and finally the stress field distribution of the welded component is obtained; among them, the mechanical load includes the circumferential shear stress τ of the upper surface of the shoulder to the weld area x and τ y The uniform surface force P of the shoulder on the weld area and the forward resistance F of the stirring force on the weld area x and lateral force F y ; Step 6: Based on the simulation results, the residual stress of the welded components under different welding parameters is compared and analyzed to obtain welding parameters with smaller residual stress for use in welding actual components.

2. The in-situ force parameter constrained friction stir welding simulation method according to claim 1, characterized in that: Step 1 specifically includes: S11: Use modeling software to perform three-dimensional modeling based on the actual geometric structure of the welded component, and then import it into the finite element analysis software to establish a finite element geometric model of the welded component; S12: assigning geometric model material parameters to the established finite element model and setting the ambient temperature before welding and the initial temperature of the test plate; S13: Establish simulation analysis steps consistent with the actual welding process, including pressing down, stabilizing welding and cooling process. The analysis step time setting is the same as the actual welding time. S14: Mesh the constructed geometric model.

3. The in-situ force parameter constrained friction stir welding simulation method according to claim 1, characterized in that: Step 2 specifically includes: S21: The friction stir welding machine collects torque M and uses a force sensor to collect three-dimensional force parameters during the welding process: forward resistance Fx, lateral force Fy, and downward force Fz; S22: Use thermocouples and pyrometers to measure and obtain the thermal cycle curve of the weld area during the actual welding process, which is used for the accuracy verification of the subsequent temperature field simulation model; S23: Based on the three-axis force parameters and torque M obtained in step S21, calculate the heat source Q1 of the shoulder part and the heat source Q2 of the stirring needle applied to the stirring needle action area: (1) (2) Where ω is the stirring head speed, is the friction coefficient, R s is the shoulder radius, R d 、R u are the end and root radii of the stirring needle respectively, H represents the height of the stirring needle, K is the force generated by the action between the shoulder and the workpiece, and the axial pressure F measured by the three-axis force sensor is z The ratio of is the taper of the stirring needle; S24: Apply the shoulder heat source Q1 and the stirring needle heat source Q2 obtained in step S23 to the weld of the finite element model, wherein the shoulder heat source Q1 is added to the weld surface in the form of a surface heat source, and the stirring needle heat source Q2 is added to the stirring needle action area in the form of a body heat source; the heat source movement path is set according to the welding path of the stirring head during the actual welding process, and the distance the heat source moves is also consistent with the actual welding specimen.

4. The in-situ force parameter constrained friction stir welding simulation method according to claim 2, characterized in that: The step three also includes: selecting the same characteristic point as the thermocouple measurement position in step S22 in the temperature field simulation model in step three, and comparing the thermal cycle curve obtained in step S22 with the thermal cycle curve simulated in step three; if the simulation result is within 10% of the simulation result of step S22, continuing to step four; otherwise, returning to step one and re-simulating the calculation.

5. The in-situ force parameter constrained friction stir welding simulation method according to claim 1, characterized in that: The step 4 also includes: considering the downward pressure of the shoulder on the weld area as a uniform surface force P, by F z Calculation shows that the circumferential shear stress τ on the upper surface of the weld area is x and τ y From the torque M we get: (3) (4) (5) (6) Where P, τ x and τ y is the mechanical force applied to the surface of the weld area in the simulation model, F z and M are the down force and torque measured during welding, both obtained in step 2; P is the down force F z The calculated uniform surface force of the shoulder on the weld area, the circumferential shear stress τ of the shoulder on the upper surface of the weld area x and τ y The tangential force of the shaft shoulder on the test plate surface is taken into account, r is the distance from the integration point to the center of the stirring head, R0 is the radius of the shaft shoulder, x and y are the coordinate values of the integration point; In addition, considering the mechanical load of the stirring head on the weld area, F x and F y Added to the area of the stirring needle inside the weld.

6. An in-situ force parameter constrained friction stir welding simulation system, characterized in that: include: Finite element model building module, used to build a finite element model corresponding to the actual welded component based on its actual geometric structure, material parameters, and process; Force data acquisition and coupling model building module, used to collect the three-dimensional force parameters and torque of the welding seam during the welding process of the welded components; The collected three-dimensional forces are converted into a heat source model to simulate the heat source distribution during welding; Applying the heat source model to the weld of the finite element model to establish a finite element model including the heat source model; The simulation first condition acquisition module is used to simulate the heat transfer of the friction stir welding process and the cooling process based on the finite element model including the heat source model obtained by the force data acquisition and coupling model establishment module, and obtain the temperature field result of the friction stir welding; The simulation module for obtaining the second condition is used to obtain the mechanical loads in the shoulder action area and the stirring needle action area; A simulation module is used to input the temperature field obtained by the simulation first condition acquisition module and the mechanical load obtained by the simulation second condition acquisition module into the finite element model, perform stress field simulation calculations on the welding process and cooling process of the friction stir welding, and obtain the stress field distribution of the welded component; as well as The parameter optimization module compares and analyzes the residual stress of samples under different welding parameters to obtain welding parameters with smaller residual stress, optimize welding process parameters, and use them for welding actual components.

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