A method for calculating stress intensity factor of gap defect solder joint under tensile shear load

Abstract

The present application belongs to the technical field of welded structure reliability evaluation, and particularly relates to a calculation method of stress intensity factor of gap defect weld under tensile shear load, comprising: selecting an automobile sheet part as a research object, and constructing a strip two-dimensional model of a gap defect weld containing an initial gap; based on the linear elastic superposition principle, the load borne by the gap defect weld is decomposed into multiple load types; based on the strip two-dimensional model of the gap defect weld containing the initial gap, the analytical solution of the stress intensity factor under the load generation mode corresponding to different load types is calculated respectively, and the analytical solution of the stress intensity factor under different load generation modes is calculated; a finite element model of the gap defect weld is constructed and finite element analysis is carried out, and the finite element solution of the stress intensity factor under different load generation modes is calculated; the analytical solution and the finite element solution of the stress intensity factor under different load generation modes are compared, and the accuracy of the analytical solution of the stress intensity factor is verified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welded structure reliability evaluation, and particularly relates to a calculation method of stress intensity factor of a gap defect welding point under tensile shear load. BACKGROUND

[0002] As the main way of connecting the automobile body-in-white, the welding point bears various complex load conditions during service, among which, the welding point fatigue failure is the most significant failure mode during the service of the automobile body-in-white structure, and the welding point fatigue strength is crucial to the performance of the whole vehicle. The stress intensity factor at the key position of the welding point is often used to predict the welding point fatigue strength and is associated with the fatigue life under cyclic load.

[0003] However, in actual application, the comprehensive deviation caused by the fluctuation of welding conditions, the stamping deviation of the automobile body-in-white thin plate structure, and the process clamping error and other errors will cause the initial gap before welding of the thin plate structure and the gap defect welding point after welding. The existence of the initial gap changes the mechanical balance of the stress intensity factor around the welding point, and further affects the welding point fatigue strength. In the prior art, only the stress intensity factor of the crack is accurately calculated by constructing a finite element model to evaluate the fatigue crack life of the steel structure weld, and the average stress intensity of the welding point is calculated by constructing a modular welding point finite element model and using the stress and strain of each node of the welding point. The solving of the stress intensity factor of the welding point without gap is not applicable to the solving of the stress intensity factor of the welding point with initial gap. SUMMARY

[0004] The application provides a calculation method of stress intensity factor of a gap defect welding point under tensile shear load, which can form a general calculation method by calculating the analytical solution of the stress intensity factor under different load generation modes, and is applicable to various welding points containing initial gap defects, and is thus applicable to different types of welding point structures, and has strong applicability. The accuracy of the analytical solution of the stress intensity factor can be ensured by comparing and verifying the finite element solution and the analytical solution of the stress intensity factor. The method can provide a basis for accurately predicting the fatigue strength and life of the welding point.

[0005] A calculation method of stress intensity factor of a gap defect welding point under tensile shear load, comprising:

[0006] An automobile thin plate part is selected as the research object, and an idealized strip-shaped two-dimensional model of a welding point without initial gap is constructed;

[0007] Based on the strip-shaped two-dimensional model of the welding point without initial gap, a strip-shaped two-dimensional model of a gap defect welding point containing initial gap is constructed;

[0008] Based on the linear elastic superposition principle, the load borne by the gap defect weld point is decomposed into multiple load types; the load types include reverse bending load, center bending load, tensile load and shear load;

[0009] Based on the strip-shaped two-dimensional model of the gap defect weld point containing the initial gap, the analytical solutions of the stress intensity factors under different load generation modes corresponding to different load types are calculated respectively, and the analytical solutions of the stress intensity factors under different load generation modes are calculated;

[0010] The finite element model of the gap defect weld point is constructed and finite element analysis is carried out, and the finite element solutions of the stress intensity factors under different load generation modes are calculated;

[0011] The analytical solutions and the finite element solutions of the stress intensity factors under different load generation modes are compared to verify the accuracy of the analytical solutions of the stress intensity factors.

[0012] By calculating the analytical solutions of the stress intensity factors under different load generation modes, a general calculation method can be formed, which is suitable for various weld points containing initial gap defects, and is suitable for various types of weld point structures, and has strong applicability; by comparing the finite element solutions and the analytical solutions of the stress intensity factors, the accuracy of the analytical solutions of the stress intensity factors can be ensured; and the foundation for subsequent accurate prediction of the fatigue strength and life of the weld point can be provided.

[0013] Further, the strip-shaped two-dimensional model of the gap defect weld point containing the initial gap, respectively calculates the analytical solutions of the stress intensity factors under different load generation modes corresponding to different load types, and calculates the analytical solutions of the stress intensity factors under different load generation modes, including:

[0014] Based on the reverse bending load, the load generation mode is determined, and the analytical solution of the stress intensity factor under the corresponding generation mode is calculated in combination with the structural stress of the reverse bending load;

[0015] Based on the center bending load, the load generation mode is determined, and the analytical solution of the stress intensity factor under the corresponding generation mode is calculated in combination with the structural stress of the center bending load;

[0016] Based on the tensile load, the load generation mode is determined, and the analytical solution of the stress intensity factor under the corresponding generation mode is calculated in combination with the structural stress of the tensile load;

[0017] Based on the shear load, the load generation mode is determined, and the analytical solution of the stress intensity factor under the corresponding generation mode is calculated in combination with the structural stress of the shear load;

[0018] The stress intensity factor of the reverse bending load in the load generation mode I is calculated according to the analytical solution of the stress intensity factor of different load types in the corresponding load generation mode.

[0019] Further, the load generation mode of the reverse bending load is I type, and the expression of the analytical solution of the stress intensity factor of the reverse bending load in the load generation mode I is:

[0020] ;

[0021] In the formula, K I represents the analytical solution of the stress intensity factor of the reverse bending load in the load generation mode I; P represents the loading load at the gap defect welding point; t represents the thickness of the plate; D represents the diameter of the gap defect welding point.

[0022] Further, the load generation mode of the center bending load is II type, and the expression of the analytical solution of the stress intensity factor of the center bending load in the load generation mode II is:

[0023] ;

[0024] ;

[0025] In the formula, K II represents the analytical solution of the stress intensity factor of the center bending load in the load generation mode II; A represents an influence factor; θ represents the angle formed between the upper plate and the lower plate.

[0026] Further, the tensile load includes a transverse tensile load and a vertical tensile load;

[0027] When the tensile load type is the transverse tensile load, it has no contribution to the stress intensity factor;

[0028] When the tensile load type is the vertical tensile load, the load generation mode is I type, and the expression of the analytical solution of the stress intensity factor of the vertical tensile load in the load generation mode I is:

[0029] ;

[0030] In the formula, K I represents the analytical solution of the stress intensity factor of the vertical tensile load in the load generation mode I.

[0031] Further, the shear load includes a transverse shear load and a vertical shear load;

[0032] When the shear load type is the lateral shear load, the load generation mode is mode II, and the expression of the analytical solution of the stress intensity factor of the lateral shear load under the load generation mode II is:

[0033] ;

[0034] In the formula, represents the analytical solution of the stress intensity factor of the lateral shear load under the load generation mode II;

[0035] When the shear load type is the vertical shear load, the load generation mode is mode III, and the expression of the analytical solution of the stress intensity factor of the vertical shear load under the load generation mode III is:

[0036] ;

[0037] In the formula, represents the analytical solution of the stress intensity factor of the vertical shear load under the load generation mode III.

[0038] Further, the analytical solution of the stress intensity factor under different load generation modes under the tensile shear load is calculated by combining the analytical solutions of the stress intensity factors under the load generation modes corresponding to different load types, and the analytical solution of the stress intensity factor under different load generation modes under the tensile shear load is calculated by combining the analytical solutions of the stress intensity factors under the load generation modes corresponding to different load types.

[0039] When the load generation mode is mode I, the analytical solution of the corresponding stress intensity factor is calculated;

[0040] The expression of the analytical solution of the stress intensity factor under the load generation mode I is:

[0041] ;

[0042] In the formula, represents the analytical solution of the stress intensity factor under the load generation mode I;

[0043] When the load generation mode is mode II, the analytical solution of the corresponding stress intensity factor is calculated;

[0044] The expression of the analytical solution of the stress intensity factor under the load generation mode II is:

[0045] ;

[0046] In the formula, represents the analytical solution of the stress intensity factor under the load generation mode II;

[0047] When the load generation mode is mode III, the analytical solution of the corresponding stress intensity factor is calculated;

[0048] The analytical solution for the stress intensity factor under the load generation mode of Type III is expressed as follows:

[0049] ;

[0050] In the formula, This represents the analytical solution of the stress intensity factor under load generation mode III.

[0051] Furthermore, the construction of a finite element model of the gap defect weld joint and the performance of finite element analysis, calculating the finite element solution of the stress intensity factor under different load generation modes, includes:

[0052] Under tensile and shear loads, a finite element model of the gap defect weld joint is constructed, and finite element analysis is performed.

[0053] When the load generation mode is type I, calculate the finite element solution of the corresponding stress intensity factor;

[0054] The finite element solution for the stress intensity factor under the type I load generation mode is expressed as follows:

[0055] ;

[0056] In the formula, This represents the finite element solution for the stress intensity factor under type I load generation mode. This indicates the stress on the inner surface of the upper plate; This indicates the stress on the outer surface of the upper plate; This indicates the stress on the inner surface of the lower plate; This indicates the stress on the outer surface of the lower plate;

[0057] When the load generation mode is type II, calculate the finite element solution of the corresponding stress intensity factor;

[0058] The finite element solution expression for the stress intensity factor under the type II load generation mode is:

[0059] ;

[0060] In the formula, This represents the finite element solution for the stress intensity factor under type II load generation mode;

[0061] When the load generation mode is type III, calculate the finite element solution of the corresponding stress intensity factor;

[0062] The finite element solution for the stress intensity factor under the load generation mode of Type III is expressed as follows:

[0063] ;

[0064] In the formula, This represents the finite element solution for the stress intensity factor under load generation mode III. This represents the shear stress in the upper plate; This represents the shear stress in the lower plate.

[0065] Furthermore, the comparison of analytical solutions and finite element solutions for the stress intensity factor under different load generation modes to verify the accuracy of the analytical solutions for the stress intensity factor includes:

[0066] The maximum error is calculated by combining the analytical and finite element solutions of the stress intensity factor under different load generation modes;

[0067] By comparing the maximum error with the preset error threshold, the accuracy of the analytical solution of the stress intensity factor is determined and verified.

[0068] The beneficial effects of this invention are as follows:

[0069] This invention calculates analytical solutions for the stress intensity factor under different load generation modes, enabling the formation of a universal calculation method applicable to various weld joints containing initial gap defects. This facilitates its application to different types of weld joint structures, demonstrating strong applicability. By comparing and verifying the finite element solution and analytical solution of the stress intensity factor, the accuracy of the analytical solution can be ensured. This provides a foundation for accurate prediction of the fatigue strength and life of weld joints. Attached Figure Description

[0070] Figure 1 This is a flowchart of the present invention;

[0071] Figure 2 Schematic diagram of a tensile shear test specimen for a weld joint with gap defects;

[0072] Figure 3 A schematic diagram showing the tensile-shear load, equivalent tensile-shear load, and stress under different load types at the weld joint;

[0073] Figure 4 A schematic diagram of the finite element model of a weld joint with gap defects;

[0074] Figure 5 This is a schematic diagram comparing the analytical and finite element solutions of the stress intensity factor for different load generation modes under different loading loads, with the weld joint being of type I.

[0075] Figure 6 This is a schematic diagram comparing the analytical solution and the finite element solution of the stress intensity factor for different load generation modes under different loading loads for weld joints of type II.

[0076] Figure label:

[0077] 1. Weld nugget; 2. Upper plate; 21. Upper plate - base material area; 22. Upper plate - heat-affected zone; 3. Upper plate spacer; 4. Lower plate; 41. Lower plate - base material area; 42. Lower plate - heat-affected zone; 5. Lower plate spacer; 6. Weld nugget area. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0080] In addition, specific details are provided in the following description to facilitate a thorough understanding of the examples, and those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0081] Example 1

[0082] Figure 1 This paper presents a method for calculating the stress intensity factor of a weld joint with a gap defect under tensile-shear load. By calculating the analytical solutions of the stress intensity factor under different load generation modes, a general calculation method is developed, applicable to various weld joints containing initial gap defects. This facilitates its application to different types of weld joint structures, demonstrating strong applicability. The accuracy of the analytical solution is ensured by comparing the finite element solution with the analytical solution, providing a foundation for accurate prediction of the fatigue strength and life of the weld joint. The specific steps include:

[0083] S1: Select thin automotive sheet metal parts as the research object and construct an idealized strip-shaped two-dimensional model with no initial gap weld points;

[0084] S2: Based on the strip-shaped two-dimensional model of the weld point without initial gap, construct a strip-shaped two-dimensional model of the weld point with gap defect that includes the initial gap;

[0085] In this embodiment, Figure 2 The diagram shows a tensile-shear test specimen of a weld joint with gap defects. Weld nugget 1 is a rigid body. The upper plate 2 receives external tensile-shear load through upper plate pad 3, and the lower plate 4 receives external tensile-shear load through lower plate pad 5. The initial gap between the upper plate 2 and the lower plate 3 is set to... The thickness of the sheet metal is set to The diameter of the gap defect weld point is set to .

[0086] S3: Based on the principle of linear elastic superposition, the load borne by the gap defect weld joint is decomposed into multiple load types;

[0087] In this embodiment, the tensile-shear load is decomposed into reverse bending load, central bending load, tensile load, and shear load. The tensile load includes transverse tensile load and vertical tensile load; the shear load includes transverse shear load and vertical shear load.

[0088] Figure 3 The diagram shows the tensile-shear load, equivalent tensile-shear load, and stress under different load types at the weld joint. The tensile-shear load A is equivalent to the equivalent tensile-shear load B, equivalent tensile-shear load C, and the sum of the reverse bending load D1, the central bending load D2, the tensile load D3, and the shear load D4.

[0089] S4: Based on the strip-shaped two-dimensional model of the gap defect weld point containing the initial gap, calculate the analytical solution of the stress intensity factor under the load generation mode corresponding to different load types, and calculate the analytical solution of the stress intensity factor under different load generation modes.

[0090] S41: Based on the reverse bending load, determine its load generation mode, and combine the structural stress of the reverse bending load to calculate the analytical solution of the stress intensity factor of the reverse bending load under the corresponding generation mode.

[0091] Among them, the load generation mode of the reverse bending load is Type I, and the analytical solution expression of the stress intensity factor of the reverse bending load under the Type I load generation mode is:

[0092] ;

[0093] In the formula, This represents the analytical solution of the stress intensity factor under the type I load generation mode of the reverse bending load; This indicates the applied load at the gap defect weld joint; Indicates the thickness of the sheet material; This indicates the diameter of the weld joint with gap defects.

[0094] S42: Based on the central bending load, determine its load generation mode, and in combination with the structural stress of the central bending load, calculate the analytical solution of the stress intensity factor under the corresponding generation mode of the central bending load.

[0095] Among them, the load generation mode of the central bending load is Type II, and the analytical solution expression of the stress intensity factor of the central bending load under the Type II load generation mode is:

[0096] ;

[0097] ;

[0098] In the formula, This represents the analytical solution of the stress intensity factor under the load generation mode II of the central bending load; Indicates the impact factor; This indicates the angle formed between the upper plate 2 and the lower plate 4.

[0099] S43: Based on the tensile load, determine its load generation mode, and in combination with the structural stress of the tensile load, calculate the analytical solution of the stress intensity factor under the corresponding generation mode of the tensile load.

[0100] Tensile loads include transverse tensile loads and longitudinal tensile loads;

[0101] Specifically, when the tensile load type is transverse tensile load, it does not contribute to the stress intensity factor.

[0102] Specifically, when the tensile load type is longitudinal tensile load, its load generation mode is Type I, and the analytical solution expression for the stress intensity factor of the vertical tensile load under the Type I load generation mode is:

[0103] ;

[0104] In the formula, This represents the analytical solution of the stress intensity factor under a vertical tensile load with load generation mode I.

[0105] S44: Based on the shear load, determine its load generation mode, and in conjunction with the structural stress of the shear load, calculate the analytical solution of the stress intensity factor under the corresponding generation mode of the shear load.

[0106] The shear load includes transverse shear load and longitudinal shear load;

[0107] Specifically, when the shear load type is transverse shear load, its load generation mode is Type II, and the analytical solution expression for the stress intensity factor of transverse shear load under load generation mode II is:

[0108] ;

[0109] In the formula, This represents the analytical solution of the stress intensity factor under transverse shear load with load generation mode II.

[0110] Specifically, when the shear load type is vertical shear load, its load generation mode is Type III, and the analytical solution expression for the stress intensity factor of vertical shear load under load generation mode III is:

[0111] ;

[0112] In the formula, This represents the analytical solution of the stress intensity factor under load generation mode III for vertical shear load.

[0113] S45: Calculate the analytical solutions of the stress intensity factor under different load generation modes under tension-shear load by combining the analytical solutions of the stress intensity factor under different load generation modes corresponding to different load types.

[0114] S451: When the load generation mode is Type I, calculate the analytical solution of the corresponding stress intensity factor;

[0115] The analytical solution for the stress intensity factor under load generation mode I is expressed as follows:

[0116] ;

[0117] In the formula, This represents the analytical solution of the stress intensity factor under type I load generation mode;

[0118] S452: When the load generation mode is type II, calculate the analytical solution of the corresponding stress intensity factor;

[0119] The analytical solution for the stress intensity factor under load generation mode II is expressed as follows:

[0120] ;

[0121] In the formula, This represents the analytical solution for the stress intensity factor under type II load generation mode;

[0122] S453: When the load generation mode is Type III, calculate the analytical solution of the corresponding stress intensity factor;

[0123] The analytical solution for the stress intensity factor under load generation mode III is expressed as follows:

[0124] ;

[0125] In the formula, This represents the analytical solution of the stress intensity factor under load generation mode III.

[0126] S5: Construct a finite element model of the gap defect weld and perform finite element analysis to calculate the finite element solution of the stress intensity factor under different load generation modes under different loading loads;

[0127] In this embodiment, as Figure 4 As shown, a finite element model of a weld joint with initial gap defects is constructed under tensile and shear loads to simulate the mechanical behavior of such weld joints under tensile and shear loads. Weld nugget 1 is a rigid body, upper plate 2 is the loading end, with external tensile and shear loads applied via upper plate pads 3, and lower plate 4 is the fixed end, with fixed constraints via lower plate pads 5. The initial gap between upper plate 2 and lower plate 3 is set to... It also includes the upper plate_base material area 21 and the lower plate_base material area 41, the upper plate_heat affected area 22 and the lower plate_heat affected area 42, and the weld nugget area 6.

[0128] S51: When the load generation mode is type I, calculate the finite element solution of the corresponding stress intensity factor;

[0129] The expression for the stress intensity factor under type I load generation mode is:

[0130] ;

[0131] In the formula, This represents the finite element solution for the stress intensity factor under type I load generation mode. Represents the stress on the inner surface of upper plate 2; This indicates the stress on the outer surface of the upper plate 2; This indicates the stress on the inner surface of the lower plate 4; This indicates the stress on the outer surface of the lower plate 4;

[0132] S52: When the load generation mode is type II, calculate the finite element solution of the corresponding stress intensity factor;

[0133] The expression for the stress intensity factor under type II load generation mode is as follows:

[0134] ;

[0135] In the formula, This represents the finite element solution for the stress intensity factor under type II load generation mode;

[0136] S53: When the load generation mode is Type III, calculate the finite element solution of the corresponding stress intensity factor;

[0137] The expression for the stress intensity factor under load generation mode III is as follows:

[0138] ;

[0139] In the formula, This represents the finite element solution for the stress intensity factor under load generation mode III. This represents the shear stress in the upper plate 2; This represents the shear stress in the lower plate 4.

[0140] S6: Compare the analytical solution and finite element solution of the stress intensity factor under different load generation modes to verify the accuracy of the analytical solution of the stress intensity factor.

[0141] S61: Calculate the maximum error by combining the analytical and finite element solutions of the stress intensity factor under different load generation modes;

[0142] S62: Compare the maximum error with the preset error threshold to determine the accuracy of the analytical solution of the stress intensity factor;

[0143] In this embodiment, the preset error threshold is 10%, that is, the maximum error is acceptable if it is within 10%, which means that the analytical solution of the stress intensity factor of the gap defect weld under tensile and shear load conditions has good accuracy.

[0144] Example 2

[0145] Based on the same design concept, this embodiment provides a method for calculating the stress intensity factor of a gap defect weld joint under tensile-shear load, specifically including the following steps:

[0146] T1: Select thin automotive sheet metal parts as the research object and construct an idealized strip-shaped two-dimensional model with no initial gap weld points;

[0147] In this embodiment, low-carbon steel, commonly used in automotive sheet metal parts, is taken as an example, and the research object is a shear tensile specimen.

[0148] T2: Based on the strip-shaped two-dimensional model of the weld point without initial gap, construct a strip-shaped two-dimensional model of the weld point with gap defect that includes the initial gap;

[0149] Since the standard value for the positioning welding of thin body panels in domestically produced cars is 0.55cm, the initial gap between the upper plate 2 and the lower plate 3 is selected within 5mm. In this embodiment, the initial gap... Select 0mm, 3mm, and 5mm thicknesses respectively, and on a sheet thickness of... The diameter of the weld nugget is The first type of solder joint and the thickness of the plate are The diameter of the weld nugget is The second type of weld joint was analyzed based on different loading loads, and the lengths of the upper plate pad 3 and the lower plate pad 5 were both 26mm.

[0150] T3: Based on the principle of linear elastic superposition, the tensile and shear loads borne by the gap defect weld joint are decomposed into multiple load types;

[0151] T4: Based on the strip-shaped two-dimensional model of the gap defect weld point including the initial gap, the analytical solutions of the stress intensity factor under the load generation modes of reverse bending load, central bending load, vertical tensile load, transverse shear load and vertical shear load are calculated respectively. The analytical solutions of the stress intensity factor under the load generation modes of type I, type II and type III are integrated and calculated respectively.

[0152] T5: Based on tensile and shear loads, a finite element model of the gap defect weld joint is constructed and finite element analysis is performed. The finite element solutions of stress intensity factors for load generation modes of type I, type II, and type III are calculated respectively.

[0153] T6: Compare the analytical solution and finite element solution of the stress intensity factor under different load generation modes to verify the accuracy of the analytical solution of the stress intensity factor.

[0154] T61: Calculate the maximum error by combining the analytical and finite element solutions of the stress intensity factor under different load generation modes;

[0155] In this embodiment, Figure 5 This is a schematic diagram comparing the analytical and finite element solutions of the stress intensity factor for different load generation modes under different loading loads, with the weld joint being of type I. Figure 6 This diagram compares the analytical and finite element solutions for the stress intensity factor under different load generation modes for weld joints of type II. Specifically, when the weld joint is type I, the plate thickness is 1.2 mm and the weld nugget diameter is 6.4 mm; when the weld joint is type II, the plate thickness is 1.0 mm and the weld nugget diameter is 6.8 mm; the loads are 500 N, 1000 N, 2000 N, 4000 N, and 8000 N, respectively.

[0156] The maximum error between the analytical solution and the finite element solution for the stress intensity factor is no more than 8.5%.

[0157] T62: Compare the maximum error with the preset error threshold to determine the accuracy of the analytical solution of the stress intensity factor;

[0158] In this embodiment, the preset error threshold is 10%, that is, the maximum calculated error of 8.5% is acceptable within 10%. Therefore, the analytical solution of the stress intensity factor of the gap defect weld under tensile and shear load conditions has good accuracy.

[0159] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0160] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for calculating the stress intensity factor of a weld joint with gap defects under tensile-shear load, characterized in that, include: We selected thin-plate automotive parts as the research object and constructed an idealized strip-shaped two-dimensional model with no initial gap weld points. Based on the strip-shaped two-dimensional model of weld joints without initial gaps, a strip-shaped two-dimensional model of weld joints with gap defects containing initial gaps is constructed. Based on the principle of linear elastic superposition, the load borne by the gap defect weld joint is decomposed into multiple load types; the load types include reverse bending load, central bending load, tensile load and shear load. Based on the strip-shaped two-dimensional model of the gap defect weld point including the initial gap, the analytical solutions of the stress intensity factor under the load generation mode corresponding to different load types are calculated respectively. A finite element model of the gap defect weld joint was constructed and finite element analysis was performed to calculate the finite element solution of the stress intensity factor under different load generation modes. The accuracy of the analytical solution of the stress intensity factor is verified by comparing the analytical solution and the finite element solution under different load generation modes. The strip-shaped two-dimensional model based on the gap defect weld point including the initial gap is used to calculate the analytical solutions of the stress intensity factor under different load types and corresponding load generation modes, including: Based on the reverse bending load, its load generation mode is determined, and combined with the structural stress of the reverse bending load, the analytical solution of the stress intensity factor of the reverse bending load under the corresponding generation mode is calculated. Based on the central bending load, its load generation mode is determined, and combined with the structural stress of the central bending load, the analytical solution of the stress intensity factor under the corresponding generation mode of the central bending load is calculated. Based on the tensile load, its load generation mode is determined, and combined with the structural stress of the tensile load, the analytical solution of the stress intensity factor under the corresponding generation mode of the tensile load is calculated. Based on the shear load, its load generation mode is determined, and combined with the structural stress of the shear load, the analytical solution of the stress intensity factor under the corresponding generation mode of the shear load is calculated. By combining the analytical solutions of the stress intensity factor under different load generation modes corresponding to different load types, the analytical solutions of the stress intensity factor under different load generation modes under tension-shear load are calculated. The load generation mode of the reverse bending load is Type I, and the analytical solution expression for the stress intensity factor of the reverse bending load under the Type I load generation mode is: ； In the formula, This represents the analytical solution of the stress intensity factor under the type I load generation mode of the reverse bending load; This indicates the applied load at the gap defect weld joint; Indicates the thickness of the sheet material; Indicates the diameter of the gap defect weld point; The load generation mode of the central bending load is Type II, and the analytical solution expression for the stress intensity factor of the central bending load under the Type II load generation mode is: ； ； In the formula, This represents the analytical solution of the stress intensity factor under the load generation mode II of the central bending load; Indicates the impact factor; This indicates the angle formed between the upper and lower plates; The tensile load includes transverse tensile load and longitudinal tensile load; When the tensile load type is transverse tensile load, it does not contribute to the stress intensity factor. When the tensile load type is longitudinal tensile load, its load generation mode is Type I. The analytical expression for the stress intensity factor of the vertical tensile load under load generation mode Type I is: ； In the formula, This represents the analytical solution of the stress intensity factor under a vertical tensile load with load generation mode I. The shear load includes transverse shear load and longitudinal shear load; When the shear load type is transverse shear load, its load generation mode is Type II. The analytical solution expression for the stress intensity factor of transverse shear load under load generation mode II is: ； In the formula, This represents the analytical solution of the stress intensity factor under transverse shear load with load generation mode II. When the shear load type is vertical shear load, its load generation mode is Type III. The analytical solution expression for the stress intensity factor of vertical shear load under load generation mode III is: ； In the formula, This represents the analytical solution of the stress intensity factor under load generation mode III for vertical shear load.

2. The method for calculating the stress intensity factor of a weld joint with gap defects under tensile-shear load according to claim 1, characterized in that, The analytical solutions for the stress intensity factors under different load generation modes corresponding to different load types are combined to calculate the analytical solutions for the stress intensity factors under different load generation modes under tension-shear loads, including: When the load generation mode is type I, calculate the analytical solution of the corresponding stress intensity factor; The analytical solution for the stress intensity factor under the load generation mode of Type I is expressed as follows: ； In the formula, This represents the analytical solution of the stress intensity factor under type I load generation mode; When the load generation mode is type II, calculate the analytical solution of the corresponding stress intensity factor; The analytical solution for the stress intensity factor under the type II load generation mode is expressed as follows: ； In the formula, This represents the analytical solution for the stress intensity factor under type II load generation mode; When the load generation mode is type III, calculate the analytical solution of the corresponding stress intensity factor; The analytical solution for the stress intensity factor under the load generation mode of Type III is expressed as follows: ； In the formula, This represents the analytical solution of the stress intensity factor under load generation mode III.

3. The method for calculating the stress intensity factor of a weld joint with gap defects under tensile-shear load according to claim 1, characterized in that, The construction of a finite element model of the gap defect weld joint and the performance of finite element analysis, including calculating the finite element solutions of the stress intensity factor under different load generation modes, include: Under tensile and shear loads, a finite element model of the gap defect weld joint is constructed, and finite element analysis is performed. When the load generation mode is type I, calculate the finite element solution of the corresponding stress intensity factor; The finite element solution for the stress intensity factor under the type I load generation mode is expressed as follows: ； In the formula, This represents the finite element solution for the stress intensity factor under type I load generation mode; This indicates the stress on the inner surface of the upper plate; This indicates the stress on the outer surface of the upper plate; This indicates the stress on the inner surface of the lower plate; This indicates the stress on the outer surface of the lower plate; When the load generation mode is type II, calculate the finite element solution of the corresponding stress intensity factor; The finite element solution expression for the stress intensity factor under the type II load generation mode is: ； In the formula, This represents the finite element solution for the stress intensity factor under type II load generation mode; When the load generation mode is type III, calculate the finite element solution of the corresponding stress intensity factor; The finite element solution for the stress intensity factor under the load generation mode of Type III is expressed as follows: ； In the formula, This represents the finite element solution for the stress intensity factor under load generation mode III. This represents the shear stress in the upper plate; This represents the shear stress in the lower plate.

4. The method for calculating the stress intensity factor of a weld joint with gap defects under tensile-shear load according to claim 1, characterized in that, The comparison of analytical and finite element solutions for the stress intensity factor under different load generation modes verifies the accuracy of the analytical solution for the stress intensity factor, including: The maximum error is calculated by combining the analytical and finite element solutions of the stress intensity factor under different load generation modes; By comparing the maximum error with the preset error threshold, the accuracy of the analytical solution of the stress intensity factor is determined and verified.

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