Fatigue simulation analysis method considering heat affected zone of welding seam

Abstract

The invention relates to a fatigue simulation analysis method considering a heat affected zone of a welding seam. The method comprises the following steps: S1, preparing a fatigue pattern and carrying out a fatigue test; s2, processing test data: fitting the data according to the fatigue test data; s3, creating a fatigue material card; s4, performing finite element simulation; and S5, verifying and optimizing. Through systematic experimental design, accurate data processing and complete simulation integration, accurate prediction of the fatigue life of the welding structure can be realized.

Description

Technical Field

[0001] This invention relates to the field of computer-aided engineering (CAE) technology, and particularly to the field of fatigue life prediction technology for welded structures, specifically to a fatigue simulation analysis method that considers the heat-affected zone of the weld. Background Technology

[0002] Welded structures are widely used in critical components such as automotive chassis and powertrain suspension systems. These components are subjected to complex random loads during service, and localized plastic deformation often occurs at stress concentration points. Traditional stress-life (SN) methods are based on nominal elasticity assumptions and cannot accurately describe the damage accumulation process in localized plastic deformation regions, leading to significant discrepancies between predicted and actual lifespans.

[0003] Currently, the fatigue simulation analysis methods used in engineering have the following technical defects: most are based on standard material databases and lack specific material parameters for the heat-affected zone of welded joints; because the microstructure and mechanical properties of the heat-affected zone change significantly during the welding process, its cyclic elastoplastic behavior is fundamentally different from that of the base material. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a fatigue simulation analysis method that considers the heat-affected zone of welds. Through systematic experimental design, precise data processing, and complete simulation integration, it enables accurate prediction of the fatigue life of welded structures.

[0005] The technical solution adopted in this invention is as follows: The fatigue simulation analysis method considering the heat-affected zone of welds proposed in this invention includes the following steps: S1. Prepare fatigue specimens and conduct fatigue tests; S2. Processing test data: Based on the fatigue test data, perform data fitting processing, including: Plastic strain curve fitting: ; Elastic strain curve fitting: ; Total strain curve fitting: ; Cyclic stress-strain curve fitting: ; Where Δσ / 2 is the stress amplitude, in MPa; Δε p / 2 represents the plastic strain amplitude; K' is the cyclic strength coefficient in MPa; n' is the cyclic strain hardening exponent; Δε t / 2 represents the total strain amplitude; σ f ' represents the fatigue strength coefficient, in MPa; b represents the fatigue strength index; ε f' is the fatigue ductility coefficient; c is the fatigue ductility index; E is the elastic modulus, in MPa; 2N f The number of reverse iterations; S3. Create fatigue material cards; S4, Finite Element Simulation; S5. Verification and Optimization.

[0006] Furthermore, step S1 includes: S1.1 Cut the heat-affected zone to be tested and process it into a specimen for fatigue testing; S1.2. Perform low-cycle fatigue tests on the specimens to obtain low-cycle fatigue test data.

[0007] Furthermore, step S3 includes: establishing a fatigue card for the heat-affected zone of the weld in the fatigue finite element simulation software, inputting the fatigue characteristic parameters of the heat-affected zone, and establishing a fatigue material card for the fatigue heat-affected zone for subsequent simulation calculations.

[0008] Furthermore, the fatigue characteristic parameters of the heat-affected zone include: (1) basic material properties: elastic modulus, Poisson's ratio, and density; (2) strain life parameters of the material: fatigue strength coefficient σ. f ', Fatigue strength index b, Fatigue ductility coefficient ε f 'and fatigue ductility index c; (3) material cyclic characteristic parameters: cyclic strength coefficient K' and cyclic strain hardening index n'.

[0009] Furthermore, step S4 includes: S4.1 Establish a finite element model, mesh the model, and establish the boundary conditions of the model; S4.2 Set material properties: Assign the material properties established in step S3 to the divided finite element mesh within the specified area, and define the material properties of the heat-affected zone separately. S4.3 Perform fatigue finite element simulation calculations.

[0010] Furthermore, step S5 includes: comparing the fatigue risk location predicted by simulation with the results of physical tests; controlling the life prediction error within ±10%; if the deviation exceeds the range, returning to step S2 to check the material parameter fitting quality and refitting.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Improve the accuracy of simulation calculations: Based on real heat-affected zone material data, systematic errors are eliminated, and the direct connection between experimental data and simulation models ensures physical authenticity and calculation accuracy; 2. Outstanding technological innovation: A method for obtaining specific material parameters of the heat-affected zone was established; a conversion process from experimental data to simulation material cards was developed, realizing a deep integration of physical experiments and digital simulation; 3. Strong engineering applicability: It provides a complete solution from experiment to simulation, which is convenient for practical engineering applications; it can handle fatigue problems under complex working conditions such as random loads and impact loads. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating a fatigue simulation analysis method considering the heat-affected zone of a weld, as proposed in this invention. Figure 2 This is a schematic diagram of a fatigued sample. Figure 3 This is a schematic diagram of the plastic strain curve fitting for a fatigued sample. Figure 4 This is a schematic diagram of fitting the elastic strain curve of a fatigued sample. Figure 5 A schematic diagram of the total strain curve fitting for the fatigue sample; Figure 6 This is a schematic diagram of the stress-strain curve fitting for a fatigued sample. Figure 7 This is a schematic diagram of the finite element mesh for a fatigued sample. Figure 8 This is a schematic diagram of the fatigue simulation results; Figure 9 This is a schematic diagram of a bench test. Detailed Implementation

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] See appendix Figure 1 The fatigue simulation analysis method considering the heat-affected zone of the weld proposed in this invention includes the following steps: S1. Prepare fatigue specimens and conduct fatigue tests, including: S1.1 Cut the heat-affected zone to be tested and process it into a specimen for fatigue testing; S1.2. Perform low-cycle fatigue tests on the specimens to obtain low-cycle fatigue test data.

[0015] S2. Processing test data: Based on the fatigue test data, perform data fitting processing, including: Plastic strain curve fitting: ; Elastic strain curve fitting: ; Total strain curve fitting: ; Cyclic stress-strain curve fitting: ; Where Δσ / 2 is the stress amplitude, in MPa; Δε p / 2 represents the plastic strain amplitude; K' is the cyclic strength coefficient in MPa; n' is the cyclic strain hardening exponent; Δε t / 2 represents the total strain amplitude; σ f ' represents the fatigue strength coefficient, in MPa; b represents the fatigue strength index; ε f ' is the fatigue ductility coefficient; c is the fatigue ductility index; E is the elastic modulus, in MPa; 2N f This represents the number of reverse iterations.

[0016] S3. Create fatigue material card: In the fatigue finite element simulation software, create a fatigue card for the heat-affected zone of the weld, input the fatigue characteristic parameters of the heat-affected zone, and create a fatigue material card for the fatigue heat-affected zone for subsequent simulation calculations.

[0017] Among them, the fatigue characteristic parameters of the heat-affected zone include: (1) the basic properties of the material: elastic modulus, Poisson's ratio and density, etc.; (2) the strain life parameters of the material: fatigue strength coefficient σ. f ', Fatigue strength index b, Fatigue ductility coefficient ε f 'and fatigue ductility index c; (3) material cyclic characteristic parameters: cyclic strength coefficient K' and cyclic strain hardening index n'.

[0018] S4, Finite Element Simulation, including: S4.1 Establish a finite element model, mesh the model, and establish the boundary conditions of the model; S4.2 Set material properties: Assign the material properties established in step S3 to the divided finite element mesh within the specified area, and define the material properties of the heat-affected zone separately. S4.3 Perform fatigue finite element simulation calculations.

[0019] S5. Verification and Optimization: Compare the fatigue risk locations predicted by simulation with the results of physical tests; control the life prediction error within ±10%; if the deviation exceeds the range, return to step S2 to check the material parameter fitting quality and refit.

[0020] The failure mode of weld fatigue is not the formation of cracks in the weld itself, but rather the destruction of the heat-affected zone (HAZ) surrounding the weld. Current weld fatigue analysis sets fatigue properties for the weld itself, but no longer sets separate material properties for the HAZ; instead, it examines the HAZ's lifespan after simulation calculations. The method of this invention does not examine the weld itself, but rather the fatigue life of the HAZ. During simulation calculations, the material parameters of the HAZ obtained through fatigue tests are directly assigned to the HAZ mesh, and the calculation results directly examine the fatigue life of the HAZ. This method is more direct, accurate, and consistent with reality.

[0021] The invention will be further illustrated below with specific examples: A fatigue simulation analysis method considering the heat-affected zone of the weld, taking the connecting rod of a certain vehicle model as an example, includes the following steps: S1. Prepare fatigue test specimens for the heat-affected zone of the weld; According to the dimensional requirements for fatigue testing, fatigue test specimens for the heat-affected zone of the weld were prepared, with the specimen dimensions as follows: Figure 2 As shown.

[0022] S2. Processing experimental data; such as... Figure 3-6 As shown, based on the fatigue test data, data fitting was performed, and the fitted data is shown in the table below:

[0023] S3. Create a fatigue card. Output the fitted experimental data parameters from step S2 to the fatigue finite element simulation software to obtain the fatigue properties of the heat-affected zone and create a fatigue card for the heat-affected zone, as shown in the table below.

[0024]

[0025] S4. Establish a finite element model, such as Figure 7 As shown. Using the fatigue card from step S3, fatigue properties are assigned to the heat-affected zone individually, and fatigue finite element simulation is performed. A load of 9.2 kN is applied along the axial direction, with 80,000 loading cycles constituting one cycle.

[0026] S5. Verify the results and perform post-processing on the simulation results, such as... Figure 8 As shown, the fatigue life in the heat-affected zone of the weld is 1.019 cycles (80,000 * 1.019 = 81,520 cycles). The fatigue test results show that the heat-affected zone of the weld fractured at 80,000 cycles, which is highly consistent with the test results. The error between the predicted life and the bench test results is within ±10%, proving the effectiveness and engineering value of the invention.

[0027] All matters not covered in this invention are common knowledge.

[0028] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A fatigue simulation analysis method considering the heat-affected zone of a weld, characterized in that, The method includes the following steps: S1. Prepare fatigue samples and conduct fatigue tests; S2. Processing test data: Based on the fatigue test data, perform data fitting processing, including: Plastic strain curve fitting: ; Elastic strain curve fitting: ; Total strain curve fitting: ; Cyclic stress-strain curve fitting: ; Where Δσ / 2 is the stress amplitude, in MPa; Δε p / 2 represents the plastic strain amplitude; K' is the cyclic strength coefficient in MPa; n' is the cyclic strain hardening exponent; Δε t / 2 represents the total strain amplitude; σ f ' represents the fatigue strength coefficient, in MPa; b represents the fatigue strength index; ε f ' is the fatigue ductility coefficient; c is the fatigue ductility index; E is the elastic modulus, in MPa; 2N f The number of reverse iterations; S3. Create fatigue material cards; S4, Finite Element Simulation; S5. Verification and Optimization.

2. The fatigue simulation analysis method considering the heat-affected zone of the weld as described in claim 1, characterized in that: Step S1 includes: S1.1 Cut the heat-affected zone to be tested and process it into a specimen for fatigue testing; S1.

2. Perform low-cycle fatigue tests on the specimens to obtain low-cycle fatigue test data.

3. The fatigue simulation analysis method considering the heat-affected zone of the weld as described in claim 1, characterized in that: Step S3 includes: creating a fatigue card for the heat-affected zone of the weld in the fatigue finite element simulation software, inputting the fatigue characteristic parameters of the heat-affected zone, and creating a fatigue material card for the fatigue heat-affected zone for subsequent simulation calculations.

4. The fatigue simulation analysis method considering the heat-affected zone of the weld as described in claim 3, characterized in that: The fatigue characteristic parameters of the heat-affected zone include: (1) basic material properties: elastic modulus, Poisson's ratio, and density; (2) material strain life parameters: fatigue strength coefficient σ. f ', Fatigue strength index b, Fatigue ductility coefficient ε f 'and fatigue ductility index c; (3) material cyclic characteristic parameters: cyclic strength coefficient K' and cyclic strain hardening index n'.

5. The fatigue simulation analysis method considering the heat-affected zone of the weld as described in claim 1, characterized in that: Step S4 includes: S4.1 Establish a finite element model, mesh the model, and establish the boundary conditions of the model; S4.2 Set material properties: Assign the material properties established in step S3 to the divided finite element mesh within the specified area, and define the material properties of the heat-affected zone separately. S4.3 Perform fatigue finite element simulation calculations.

6. The fatigue simulation analysis method considering the heat-affected zone of the weld according to claim 1, characterized in that: Step S5 includes: comparing the fatigue risk location predicted by simulation with the results of physical tests; controlling the life prediction error within ±10%; if the deviation exceeds the range, returning to step S2 to check the material parameter fitting quality and refitting.

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