Method for designing a progressive groove on a shoulder and a friction stir welding tool

Abstract

The application provides a design method of a involute type thread on a shaft shoulder and a friction stir welding tool, and comprises the following steps: performing sensitivity analysis on a plurality of parameters of the involute thread, screening out key parameters affecting welding quality, and preliminarily determining a feasible range of the key parameters; according to the determined key parameters and the feasible range, preliminarily processing the involute thread on a to-be-processed stirring tool, and welding a test plate through the processed stirring tool to obtain processing parameters of the stirring tool; based on a Box-Behnken response surface method, taking the screened key parameters as independent variables and taking the processing parameters of the stirring tool as response variables, fitting a second-order polynomial model through a least square method, establishing a mathematical relationship between the involute thread parameters and the response variables, and calculating to obtain optimal involute thread parameters; and performing a process test to determine a stability interval of welding parameters. The application realizes fine design of the involute thread.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a design method for an involute pattern on a shoulder and a friction stir welding tool. Background Technology

[0002] Aluminum-lithium alloys are widely used in aerospace and automotive manufacturing due to their lightweight and high strength properties. These fields have extremely high requirements for material performance, especially in terms of weight and strength, making aluminum-lithium alloys an ideal material choice. However, welding aluminum-lithium alloys presents a series of challenges, and traditional welding methods and tools are insufficient to meet the requirements for high-quality welds.

[0003] In existing technologies, friction stir welding (FSW), as a solid-state joining technique, has been widely used in welding aluminum alloys. However, when FSW is applied to aluminum-lithium alloys, several problems still arise during the welding process. First, due to the high thermal conductivity of aluminum-lithium alloys, uneven heat input during welding easily leads to uneven temperature distribution in the weld area, thus affecting the material's fluidity. Poor material fluidity directly results in surface defects in the weld, such as grooves and peeling, which not only affects the aesthetics of the weld but also severely weakens the joint's mechanical properties and service life.

[0004] Secondly, traditional friction stir welding tools, due to design flaws, cannot effectively agitate and mix materials when welding aluminum-lithium alloys, resulting in uneven internal structure of the weld and welding defects. Furthermore, the shoulder design of traditional welding tools is mostly a smooth surface or a simple groove design. This design cannot provide sufficient agitation during welding, resulting in poor material flow in the weld area and poor weld surface quality.

[0005] Existing solutions for welding aluminum-lithium alloys largely focus on adjusting welding parameters and using improved welding techniques, but these approaches do not fundamentally address the issue of welding tool design. Since welding tools are the key component that directly contacts the material and influences the welding process, optimizing their design is crucial for improving weld quality.

[0006] Currently, there is a lack of friction stir welding tools on the market that can significantly improve the welding quality of aluminum-lithium alloys. Existing technologies urgently need an innovative tool design that optimizes the structure and surface texture of the welding tool to improve material flow during welding, uniformly distribute heat, thereby improving welding quality, reducing weld surface defects, and enhancing the mechanical properties and durability of the joint. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a design method for involute patterns on shaft shoulders and a friction stir welding tool.

[0008] The present invention provides a design method for an involute pattern on a shoulder, comprising the following steps:

[0009] Sensitivity analysis steps: Perform sensitivity analysis on multiple parameters of the involute pattern to screen out the key parameters that affect the welding quality and preliminarily determine the feasible range of the key parameters; Based on the determined key parameters and feasible range, preliminarily process the involute pattern on the stirring tool to be processed, and weld a test plate through the processed stirring tool to obtain the processing parameters of the stirring tool;

[0010] Response surface optimization steps: Based on the Box-Behnken response surface method, the selected key parameters are used as independent variables, and the processing parameters of the mixing tool are used as response variables. The second-order polynomial model is fitted by the least squares method to establish the mathematical relationship between the involute texture parameters and the response variables, and the optimal involute texture parameters are calculated.

[0011] Process window verification steps: Based on the obtained optimal involute pattern parameters, conduct process experiments to determine the stability range of welding parameters.

[0012] Preferably, in the parameter sensitivity analysis step:

[0013] The key parameters selected are the starting radius r0, unfolding angle θ, helix angle α, and texture depth h of the involute pattern;

[0014] The obtained processing parameters are the tensile strength σb, elongation δ, and surface forming factor h of the mixing tool. def ;

[0015] Establish a four-factor, three-level orthogonal experimental table.

[0016] Preferably, the tensile strength σb, the elongation δ, and the surface forming factor h def The specific data acquisition method is as follows:

[0017] The method for obtaining the tensile strength σb is as follows: the welded test plate is stretched to fracture using a universal testing machine, and the maximum load is recorded.

[0018] The method for obtaining the elongation δ is as follows: measuring the rate of change of the gauge length of the test plate after fracture;

[0019] The surface forming coefficient h def Data acquisition method: The weld surface of the test plate is scanned using an optical profilometer to quantify the groove depth and undulation.

[0020] Preferably, in the response surface optimization step:

[0021] A four-factor, three-level experimental matrix was constructed, with the initial radius r0, unfolding angle θ, helix angle α, and texture depth h selected as independent variables, and tensile strength σb, elongation δ, and surface forming coefficient h selected as independent variables. def As a response variable.

[0022] Preferably, the mathematical relationship between the involute texture parameters and the response variable is as follows:

[0023] σb=β0+ + 2 + +ε

[0024] δ=γ0+ + 2 + +ε

[0025] h def =η0+ + 2 + +ε

[0026] in, 1. 2. 3. 4 corresponds to the standardized values ​​of r0, θ, α, and h, respectively. The set of standardized values ​​is (-1, 0, 1), representing the low, medium, and high levels of the parameter in the experimental design. The standardized values ​​are calculated using the following formula:

[0027]

[0028] , , These are the constant terms for each model; , , Each of the corresponding models The regression coefficients of the first-order term, i=1, 2, 3, 4; , , Each of the corresponding models 2 The quadratic regression coefficient; , , Each of the corresponding models The interaction term regression coefficients, j=1, 2, 3, 4; ε is the error value;

[0029] The calculated values ​​of σb, δ, and h will be obtained. def Substitute into the objective function:

[0030] Q = 0.85σb + 0.10δ - 0.05h def ;

[0031] The optimal parameter combination is determined by solving for the extrema of the objective function Q.

[0032] Preferably, in the process window verification step, the welding parameters include: rotational speed tolerance, welding speed window, and pressure compensation coefficient.

[0033] Preferably, the specific method for determining the stability range of the speed tolerance is as follows: welding is performed within the speed range of 750 rpm to 850 rpm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

[0034] Preferably, the specific method for determining the stability range of the welding speed window is as follows: welding is performed within the welding speed range of 280 mm / min to 320 mm / min, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

[0035] Preferably, the specific method for determining the stability range of the pressure compensation coefficient is as follows: welding is performed within the pressure range of 0.18mm to 0.23mm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

[0036] The present invention also provides a friction stir welding tool, which uses the above-mentioned design method for involute patterns on the shoulder to process involute patterns on the shoulder.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The involute pattern used in this invention significantly improves the surface quality of aluminum-lithium alloy welds, reduces defects, and increases the tensile strength of the joint to over 85%. It effectively widens the process window (speed tolerance ±50 rpm) and adapts to complex working conditions. The method of this invention is simple, economical, efficient, and easy to implement.

[0039] 2. This invention proposes a friction stir welding tool with involute patterns added to the shoulder. By designing specific involute patterns on the tool surface, the starting radius and development angle of the involute are optimized to guide the spiral flow of the material, reduce local overheating, and distribute heat evenly. By optimizing the helix angle and depth of the involute, the flow of the material in the vertical direction is enhanced, surface defects are eliminated, and the mechanical properties and durability of the weld joint are improved. This innovative design provides a brand-new solution for high-quality welding of aluminum-lithium alloys and has significant application prospects and commercial value. Attached Figure Description

[0040] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0041] Figure 1 This is a schematic diagram of the welding tool.

[0042] Figure 2 This is a schematic diagram of the involute pattern structure;

[0043] Figure 3 A flowchart illustrating the design steps for an involute pattern on a shaft shoulder.

[0044] The diagram shows:

[0045] 1. Welding tool; 2. Shoulder; 3. Involute pattern. Detailed Implementation

[0046] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0047] Example 1

[0048] like Figures 1 to 3 As shown, this embodiment provides a design method for involute patterns on a shoulder, including the following steps:

[0049] Sensitivity analysis steps: Perform sensitivity analysis on multiple parameters of the involute pattern to screen out the key parameters that affect the welding quality and preliminarily determine the feasible range of the key parameters; Based on the determined key parameters and feasible range, preliminarily process the involute pattern on the stirring tool to be processed, and weld a test plate through the processed stirring tool to obtain the processing parameters of the stirring tool;

[0050] In the parameter sensitivity analysis phase, a four-factor, three-level orthogonal experimental design was first employed. A small number of experiments were conducted to systematically change combinations of parameters such as the initial radius, development angle, helix angle, and weld depth, and the corresponding welding quality indicators (such as tensile strength and elongation) were measured. Subsequently, range analysis was used to calculate the range of the influence of each parameter on the quality indicators at different levels. Parameters with large ranges (i.e., those with significant impact on the welding results) were identified as critical parameters. Finally, the feasible range of the critical parameters was determined by comprehensively considering geometric constraints, processing feasibility, and the performance change trends revealed by the orthogonal experiments, ensuring that this range was both engineering-feasible and covered the potential optimal performance range.

[0051] The key parameters selected are the starting radius r0, unfolding angle θ, helix angle α, and texture depth h of the involute pattern;

[0052] The obtained processing parameters are the tensile strength σb, elongation δ, and surface forming factor h of the mixing tool. def ;

[0053] Establish a four-factor, three-level orthogonal experimental table;

[0054] Method for obtaining tensile strength σb: The welded test plate is stretched to fracture using a universal testing machine, and the maximum load is recorded;

[0055] Method for obtaining elongation δ: Measure the rate of change of gauge length of the test plate after fracture;

[0056] Surface forming factor h def Data acquisition method: The weld surface of the test plate is scanned using an optical profilometer to quantify the groove depth and undulation.

[0057] Response surface optimization steps: Based on the Box-Behnken response surface method, the selected key parameters are used as independent variables, and the processing parameters of the mixing tool are used as response variables. The second-order polynomial model is fitted by the least squares method to establish the mathematical relationship between the involute texture parameters and the response variables, and the optimal involute texture parameters are calculated.

[0058] A four-factor, three-level experimental matrix was constructed, with the initial radius r0, unfolding angle θ, helix angle α, and texture depth h selected as independent variables, and tensile strength σb, elongation δ, and surface forming coefficient h selected as independent variables. def As a response variable;

[0059] The specific mathematical relationship between the involute texture parameters and the response variable is as follows:

[0060] σb=β0+ + 2 + +ε

[0061] δ=γ0+ + 2 + +ε

[0062] h def =η0+ + 2 + +ε

[0063] in, 1. 2. 3. 4 corresponds to the standardized values ​​of r0, θ, α, and h, respectively. The set of standardized values ​​is (-1, 0, 1), representing the low, medium, and high levels of the parameter in the experimental design. The standardized values ​​are calculated using the following formula:

[0064]

[0065] , , These are the constant terms for each model; , , Each of the corresponding models The regression coefficients of the first-order term, i=1, 2, 3, 4; , , Each of the corresponding models 2 The quadratic regression coefficient; , , Each of the corresponding models The interaction term regression coefficients, j=1, 2, 3, 4; ε is the error value;

[0066] The calculated values ​​of σb, δ, and h will be obtained. def Substitute into the objective function:

[0067] Q = 0.85σb + 0.10δ - 0.05h def ;

[0068] The optimal parameter combination is determined by solving for the extrema of the objective function Q.

[0069] Process window verification steps: Based on the obtained optimal involute pattern parameters, conduct process experiments to determine the stability range of welding parameters;

[0070] Welding parameters include: rotational speed tolerance, welding speed window, and downward pressure compensation coefficient;

[0071] The specific method for determining the stability range of speed tolerance is as follows: Welding is carried out in the speed range of 750rpm to 850rpm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is judged to be stable.

[0072] The specific method for determining the stability range of the welding speed window is as follows: Weld within the welding speed range of 280 mm / min to 320 mm / min, and detect the strength fluctuation of the stirring tool joint. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is judged to be stable.

[0073] The specific method for determining the stability range of the pressure compensation coefficient is as follows: Welding is carried out within the pressure range of 0.18mm to 0.23mm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is judged to be stable.

[0074] This embodiment provides a friction stir welding tool, which uses the above-mentioned design method for involute patterns on the shoulder to process involute patterns on the shoulder.

[0075] Example 2

[0076] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0077] To address the problems existing in the prior art, this embodiment provides a welding tool for friction stir welding of aluminum-lithium alloys. This tool significantly improves material flowability and weld surface quality during welding by adding involute patterns to the shoulder. Compared to existing involute designs, this embodiment refines the design parameter range. Existing designs often use fixed parameters; this embodiment proposes a dynamic parameter range through orthogonal experiments and response surface methodology optimization. Composite objective optimization is implemented; existing methods focus on a single performance (such as tensile strength), while the objective function used in this embodiment integrates mechanical properties and surface quality.

[0078] This embodiment is implemented by the following technical solution, and includes the following specific steps:

[0079] Step 1: Design involute patterns on the shoulder of the friction stir welding tool.

[0080] The involute pattern refers to grooves or protrusions that form an involute shape along the surface of the tool shoulder. This design helps to evenly distribute heat and agitate the material during welding, thus improving weld quality. Taking the design of a stirring tool for welding 4mm 2195 aluminum alloy sheets as an example, the optimization steps for the involute pattern design are as follows:

[0081] Step 1: Parameter Sensitivity Analysis

[0082] Screening involute parameters that significantly affect welding quality, identifying key design variables, reducing optimization complexity, and then determining the order of parameters and the preliminary feasible range.

[0083] Based on previous experience in designing mixing tools, the influencing parameters and their approximate range of variation were determined. A four-factor, three-level orthogonal experimental table was established. The corresponding involute-shaped mixing tool was fabricated, and test plates were welded to obtain tensile strength, elongation, and surface forming coefficient. The surface forming coefficient is a relative evaluation value of the surface forming quality of different mixing tools.

[0084]

[0085] The methods for obtaining tensile strength, elongation, and surface forming coefficient data include:

[0086] Tensile strength (σb): The maximum load is recorded when the specimen is stretched to fracture using a universal testing machine.

[0087] Elongation (δ): The rate of change of gauge length after fracture.

[0088] Surface form factor (h) def ): An optical profilometer is used to scan the weld surface to quantify the depth and undulation of the groove.

[0089] Step 2: Response Surface Optimization

[0090] Based on the Box-Behnken design, a four-factor, three-level experimental matrix was constructed. The involute texture parameters r0, θ, α, and h were selected as independent variables, along with the tensile strength σb, elongation δ, and surface finish coefficient h of the welded joint. def As the response variable. The experimental design includes 29 trials (including 5 center-point replicates), with the following parameter ranges:

[0091]

[0092] By fitting a second-order polynomial model using the least squares method, the mathematical relationship between the parameters and the response variable is established.

[0093] σb=β0+ + 2 + +ε

[0094] δ=γ0+ + 2 + +ε

[0095] hdef=η0+ + 2 + +ε

[0096] in: 1. 2. 3. 4 corresponds to the standardized values ​​of r0, θ, α, and h, respectively. The set of standardized values ​​is (-1, 0, 1), representing the low, medium, and high levels of the parameter in the experimental design. The standardized values ​​are calculated using the following formula:

[0097]

[0098] , , These are the constant terms for each model; , , Each of the corresponding models The regression coefficients of the first-order term, i=1, 2, 3, 4; , , Each of the corresponding models 2 The quadratic regression coefficient; , , Each of the corresponding models The interaction term regression coefficients are j=1, 2, 3, 4; ε is the error value.

[0099] σb, δ, h def Substitute into the objective function:

[0100] Q = 0.85σb + 0.10δ - 0.05h def

[0101] Weighting criteria: Tensile strength σb has the highest weight (0.85) because it has the greatest impact on street performance; surface form factor h... def With a negative weight (-0.05), the defect needs to be minimized.

[0102] The optimal parameter combination is determined by solving for the extrema of the objective function Q:

[0103] By eliminating insignificant terms, a simplified model is obtained. Partial derivatives of Q are taken, and by setting = 0, the system of equations is solved. 1. 2. 3. 4. The specific process is as follows:

[0104] Model simplification: First, an analysis of variance was performed on the initially fitted complete second-order polynomial model to test the statistical significance of each coefficient. Term with a p-value greater than 0.10 was identified as insignificant and its coefficient was set to zero, thereby eliminating redundant terms and obtaining a simplified and more accurate regression model for σb, δ, and h~def~.

[0105] Constructing the objective function: Substituting the simplified regression model above into the composite objective function Q=0.85σb+0.10δ-0.05h~def~, we obtain a purely objective function concerning the four standardized parameters ( 1, 2, 3, 4) The simplified second-order polynomial function.

[0106] Differentiation to establish a system of equations: To find the maximum point of the objective function Q, respectively... 1, 2, 3, 4. Find the first-order partial derivatives. According to the multivariable function extremum theorem, set all four partial derivative equations equal to zero, thus obtaining a first-order partial derivative. 1, 2, 3, A system of four linear equations with four unknowns.

[0107] Solving the system of equations: Convert the system of linear equations into matrix form and solve it using linear algebra methods to find the inverse matrix. The solution that maximizes the Q value can be found directly. 1, 2, 3, The standardized value of 4.

[0108] Denormalization: Finally, the optimal normalized parameter values ​​obtained by the solution are converted back to the actual physical parameter range through denormalization calculation, that is, the final optimal involute texture parameter combination is obtained: r0=2.5mm, θ=47.3°, α=7.2°, h=0.22mm.

[0109] Finally, the optimal parameters can be calculated as follows: r0 = 2.5 mm, θ = 47.3°, α = 7.2°, h = 0.22 mm.

[0110] Step 3: Process window verification

[0111] Verify the stability of the involute design under different welding parameters to ensure that the design adapts to actual production fluctuations (such as changes in rotational speed) and determine the stable range of welding parameters.

[0112] Using the involute structure design optimization parameters determined in step three, conduct process window experiments to optimize and establish the stability range of welding parameters:

[0113] Speed ​​tolerance: ±50rpm, critical value 750rpm~850rpm. Welding within the range of 750rpm~850rpm, the joint strength fluctuation is ≤5% and the weld surface is well formed, which is judged as stable.

[0114] Welding speed window: 280 mm / min to 320 mm / min (peak efficiency at 305 mm / min). Welding within the range of 280 mm / min to 320 mm / min, with joint strength fluctuation ≤5% and good weld surface formation, is considered stable.

[0115] The pressure compensation coefficient is 0.18mm to 0.23mm. If the joint strength fluctuation is ≤5% and the weld surface is well formed when welding within the pressure range of 0.18mm to 0.23mm, it is judged as stable.

[0116] Step two: Select appropriate welding parameters and conduct welding experiments.

[0117] The welding experiment refers to a comparative experiment using traditional tools or other textured welding tools and involute textured welding tools.

[0118] Step 3: Through quality inspection and performance testing, determine the involute pattern as the optimal solution.

[0119] The quality inspection refers to visually inspecting the weld surface for defects such as grooves and peeling, and using X-ray inspection to check for internal defects in the weld.

[0120] The performance test refers to a tensile test on the joint to test its mechanical properties. The test results show that the tensile strength of the welded joint reaches more than 85% of the strength of the base material, indicating good performance.

[0121] This embodiment describes an improved involute design method for the stirring tool used in friction stir welding of 2195 aluminum alloy. The method optimizes the geometric parameters of the involute pattern to enhance material flowability and heat distribution uniformity. It is applicable to various profiles, and its general steps include:

[0122] Step 1: Parameter definition, determine the range of key parameters for the involute curve.

[0123] Starting radius, adaptable to different profile thicknesses;

[0124] The unfolding angle controls the coverage area of ​​the texture.

[0125] The helix angle adjusts the direction of material flow.

[0126] The depth of the grooves affects the intensity of the agitation.

[0127] Step two, parameter optimization.

[0128] Key parameters were screened through orthogonal experiments, and the optimal combination was determined by combining them with the response surface methodology.

[0129] The objective function should include tensile strength, elongation and surface forming coefficient, balancing mechanical properties and forming quality.

[0130] Step 3, Adaptability Validation.

[0131] For different profiles, adjust the parameter range and verify the stability of the process window.

[0132] This embodiment relates to the field of welding technology, and specifically provides a welding tool for friction stir welding of aluminum-lithium alloys, particularly a method for improving welding quality and surface finish by adding involute patterns.

[0133] The friction stir welding tool for improving the surface forming of aluminum-lithium alloys in this embodiment has an involute pattern added to the shoulder of the tool to enhance the stirring effect and heat distribution on the surface material of aluminum-lithium alloys during the welding process.

[0134] The curve equation of the involute pattern is optimized based on the thickness of the welding material and the welding process requirements.

[0135] The welding tools are made of high-strength, high-temperature resistant materials, including tungsten alloys and molybdenum alloys, to ensure good durability and reliability during high-temperature and high-pressure welding processes.

[0136] This embodiment provides a welding tool for friction stir welding of aluminum-lithium alloys. By adding involute lines to the shoulder of the tool, the material flowability and weld surface quality during welding are significantly improved, eliminating grooves and peeling on the weld surface, and increasing the tensile strength of the joint to over 85%. The method of this embodiment is simple, economical, efficient, and easy to implement, making it suitable for demanding applications in aerospace and automotive manufacturing.

[0137] Example 3

[0138] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0139] The material welded in this embodiment is a 3mm 2195 aluminum-lithium alloy plate, and the welding is performed using a welding tool with involute patterns designed in this invention.

[0140] This embodiment includes the following specific steps:

[0141] Step 1: Design and manufacture involute pattern 3 on the shoulder 2 of welding tool 1. The parameters of involute pattern 3 are optimized according to the material thickness and welding process requirements. The optimized involute structure parameters are: r0=2.0mm, θ=44.1°, α=6.9°, h=0.17mm.

[0142] Step 2: Conduct a welding experiment and set the welding parameters as follows: welding speed 300 mm / min, indentation 0.2 mm, and rotation speed 800 rpm.

[0143] Step 3: Quality inspection and mechanical property testing of the welded joint were carried out. The results showed that there were no defects on the surface and inside of the weld, and the tensile strength reached more than 85% of the material, which was significantly better than the welding effect of traditional friction stir welding tools.

[0144] In this embodiment, the involute pattern significantly improves the surface quality of the aluminum-lithium alloy weld, reduces defects, and increases the tensile strength of the joint to over 85%, effectively widening the process window (speed tolerance ±50 rpm) to adapt to complex working conditions. This embodiment is simple, economical, efficient, and easy to implement.

[0145] This invention achieves a refined design of the involute texture.

[0146] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0147] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A design method for an involute pattern on a shoulder, characterized in that, Includes the following steps: Sensitivity analysis steps: Perform sensitivity analysis on multiple parameters of the involute pattern to screen out the key parameters that affect the welding quality and preliminarily determine the feasible range of the key parameters; Based on the determined key parameters and feasible range, preliminarily process the involute pattern on the stirring tool to be processed, and weld a test plate through the processed stirring tool to obtain the processing parameters of the stirring tool; Response surface optimization steps: Based on the Box-Behnken response surface method, the selected key parameters are used as independent variables, and the processing parameters of the mixing tool are used as response variables. The second-order polynomial model is fitted by the least squares method to establish the mathematical relationship between the involute texture parameters and the response variables, and the optimal involute texture parameters are calculated. Process window verification steps: Based on the obtained optimal involute pattern parameters, conduct process experiments to determine the stability range of welding parameters.

2. The design method for the involute texture on the shoulder according to claim 1, characterized in that, In the parameter sensitivity analysis step: The key parameters selected are the starting radius r0, unfolding angle θ, helix angle α, and texture depth h of the involute pattern; The obtained processing parameters are the tensile strength σb, elongation δ, and surface forming factor h of the mixing tool. def ; Establish a four-factor, three-level orthogonal experimental table.

3. The design method for the involute texture on the shoulder according to claim 2, characterized in that, The tensile strength σb, the elongation δ, and the surface forming coefficient h def The specific data acquisition method is as follows: The method for obtaining the tensile strength σb is as follows: the welded test plate is stretched to fracture using a universal testing machine, and the maximum load is recorded. The method for obtaining the elongation δ is as follows: measuring the rate of change of the gauge length of the test plate after fracture; The surface forming coefficient h def Data acquisition method: The weld surface of the test plate is scanned using an optical profilometer to quantify the groove depth and undulation.

4. The design method for the involute texture on the shoulder according to claim 2, characterized in that, In the response surface optimization step: A four-factor, three-level experimental matrix was constructed, with the initial radius r0, unfolding angle θ, helix angle α, and texture depth h selected as independent variables, and tensile strength σb, elongation δ, and surface forming coefficient h selected as independent variables. def As a response variable.

5. The design method for the involute texture on the shoulder according to claim 4, characterized in that, The specific mathematical relationship between the involute texture parameters and the response variable is as follows: σb=β0+ + 2 + +e δ=γ0+ + 2 + +e h def =η0+ + 2 + +e in, 1.

2.

3. 4 corresponds to the standardized values ​​of r0, θ, α, and h, respectively. The set of standardized values ​​is (-1, 0, 1), representing the low, medium, and high levels of the parameter in the experimental design. The standardized values ​​are calculated using the following formula: , , These are the constant terms for each model; , , Each of the corresponding models The regression coefficients of the first-order term, i=1, 2, 3, 4; , , Each of the corresponding models 2 The quadratic regression coefficient; , , Each of the corresponding models The interaction term regression coefficients, j=1, 2, 3, 4; ε is the error value; The calculated values ​​of σb, δ, and h will be obtained. def Substitute into the objective function: Q=0.85σb+0.10δ-0.05h def ; The optimal parameter combination is determined by solving for the extrema of the objective function Q.

6. The design method for the involute texture on the shoulder according to claim 1, characterized in that, In the process window verification step, the welding parameters include: rotational speed tolerance, welding speed window, and pressure compensation coefficient.

7. The design method for the involute texture on the shoulder according to claim 6, characterized in that, The specific method for determining the stability range of the speed tolerance is as follows: Welding is performed within the speed range of 750 rpm to 850 rpm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

8. The design method for the involute texture on the shoulder according to claim 6, characterized in that, The specific method for determining the stability range of the welding speed window is as follows: Welding is carried out within the welding speed range of 280 mm / min to 320 mm / min, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

9. The design method for involute patterns on the shoulder according to claim 6, characterized in that, The specific method for determining the stability range of the pressure compensation coefficient is as follows: Welding is performed within the pressure range of 0.18mm to 0.23mm, and the strength fluctuation of the stirring tool joint is detected. If the strength fluctuation of the stirring tool joint is ≤5% and the weld surface is well formed, it is determined to be stable.

10. A friction stir welding tool, characterized in that, The involute pattern on the shoulder is machined using the design method of any one of claims 1 to 9.

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