Elastic-plastic damage fatigue life simulation method for metal components based on secondary development of ABAQUS

Abstract

The present invention discloses a metal component elastic-plastic damage fatigue life simulation method based on ABAQUS secondary development, comprising the following steps: 1) establishing a metal component geometric model, and importing the metal component geometric model into ABAQUS simulation software; 2) using ABAQUS simulation software to pre-process the metal component geometric model; 3) based on the pre-processed metal component geometric model, using the metal component elastic-plastic damage fatigue life subroutine to determine whether the metal component has plastic deformation, if so, proceed to step 4); 4) using the metal component elastic-plastic damage fatigue life subroutine to calculate the component elastic-plastic damage and life. The present invention uses a coupled damage Newton iteration algorithm to calculate the plastic strain increment, calculates the plastic stress and strain by the J2 plastic flow criterion, and updates the material parameters according to the degree of damage, thereby ensuring the accuracy of the stress / strain calculation in the plastic deformation stage of the metal component.

Description

Technical Field

[0001] The present invention relates to the field of elastoplastic damage fatigue life prediction of metal components, and in particular to a simulation method for elastoplastic damage fatigue life of metal components based on secondary development of ABAQUS. Background Art

[0002] Metal components are widely used in aerospace, nuclear power, wind power, rail transit and many other industries due to their compact structure, high strength, strong bearing capacity and long life. In particular, some key metal components will directly determine the service life of major equipment. These key metal components usually experience complex load conditions during service, such as tensile and compressive loads, bending and torsion loads, etc., and even stress concentration due to unreasonable structural design, processing and manufacturing errors or defects.

[0003] Based on actual load conditions and stress concentration factors, metal components may suffer elastic damage or elastoplastic damage, which may further cause crack initiation, expansion, and even fracture, leading to equipment failure. Under the action of alternating loads, the fatigue life of components cannot be effectively obtained only through structural strength design and simulation, because the damage process of components is often accompanied by the degradation of material mechanical properties; and prototype experiments will consume huge manpower and material resources and delay the production cycle. Therefore, it is of great significance to propose a metal component elastoplastic damage fatigue life prediction software.

[0004] There are many methods for calculating fatigue life at present, but they fail to fully consider the damage caused by the elastic-plastic deformation of the material, nor the weakening effect of the damage on the component material. Moreover, these methods are only applicable to certain working conditions or certain areas of the component and do not have good universality. Therefore, it is necessary to find a fatigue life simulation method that takes into account the elastic-plastic damage of the material and is generally applicable to most metal components. Summary of the invention

[0005] The purpose of the present invention is to provide a simulation method for elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS, comprising the following steps:

[0006] 1) Establishing a geometric model of a metal component and importing the geometric model of the metal component into ABAQUS simulation software;

[0007] 2) Use ABAQUS simulation software to pre-process the geometric model of metal components;

[0008] 3) Based on the geometric model of the metal component after pre-processing, use the metal component elastoplastic damage fatigue life subroutine to determine whether the metal component has plastic deformation. If so, proceed to step 4);

[0009] 4) Use the metal component elastoplastic damage fatigue life subroutine to calculate the component elastoplastic damage and life.

[0010] Furthermore, the geometric model of the metal component is drawn by three-dimensional modeling software.

[0011] Furthermore, the steps of pre-processing the geometric model of the metal component using ABAQUS simulation software include:

[0012] 2-1) Use ABAQUS simulation software to define the material properties of the metal component geometry model;

[0013] 2-2) Use ABAQUS simulation software to mesh the metal component model;

[0014] 2-3) Assemble and position the geometric model of the metal component after meshing;

[0015] 2-4) Create analysis steps and required output variables according to the load cycle of the metal component, and specify the number of cycles;

[0016] 2-5) Set constraints and contacts according to the motion characteristics of metal components;

[0017] 2-6) Set boundary conditions and apply loads according to the geometric model of the metal component.

[0018] Further, the step of using the metal component elastoplastic damage fatigue life subroutine to determine whether the metal component has plastic deformation includes:

[0019] 3-1) Use ABAQUS simulation software to calculate the elastic strain and stiffness matrix of the current metal component mesh unit;

[0020] 3-2) Calculate the test stress according to the elastic strain and stiffness matrix of the current metal component mesh unit;

[0021] 3-3) Determine whether the test stress is greater than the yield limit. If so, the current metal component mesh unit undergoes plastic deformation, and jump to step 3-5); if not, the current metal component mesh unit does not undergo plastic deformation, and enter step 3-4);

[0022] 3-4) Update the material stiffness matrix, return to step 3-1), and calculate the elastic strain and stiffness matrix of the next metal component mesh unit;

[0023] 3-5) Calculate the plastic damage increment of the current metal component mesh unit according to the Newton iteration rule, and then calculate the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit under plastic deformation according to the plastic flow rule;

[0024] According to the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit, the material plastic damage parameter is updated, and the Jacobian matrix of the material is calculated using the consistent tangent modulus algorithm. Return to step 3-1) to calculate the elastic strain and stiffness matrix of the next metal component mesh unit.

[0025] Further, the test stress is as follows:

[0026]

[0027] Where λ is the Lame constant; G is the shear modulus; D is the damage variable; α ij is the back stress; ij is the test stress; ii and ε ij is the elastic strain; i and j are the stress directions;

[0028] Parameter δ ij As shown below:

[0029]

[0030] Furthermore, the updated material plastic damage parameters are as follows:

[0031]

[0032] In the formula, is the elastic modulus of the damaged unit, is the plastic damage parameter of the damaged unit; is the yield limit of the damaged unit. E is the elastic modulus; C k , γ k is the plastic damage parameter; σ y , represent the yield limit and damage variable respectively.

[0033] Further, the steps of calculating the elastic-plastic damage and life of a component using the elastic-plastic damage fatigue life subroutine of a metal component include:

[0034] 4-1) When the remaining time of the current load cycle is less than 2 increments, if the unit of the component only experiences elastic deformation, only the elastic damage growth rate of the unit is calculated and stored in the state variable. If the unit undergoes plastic deformation, the elastic damage growth rate and the plastic damage growth rate need to be calculated separately, and the total damage growth rate is the sum of the elastic damage growth rate and the plastic damage growth rate, and the state variable is updated;

[0035] 4-2) At the first incremental step of the next load cycle, according to the jump cycle algorithm, the number of cycles ΔN represented by the current load cycle is calculated through the damage increment of the custom load cycle and the total damage growth rate. The number of cycles ΔN obtained for each load cycle is accumulated to obtain the total number of cycles, and the calculation result is stored in the corresponding state variable;

[0036] 4-3) The damage growth rate of each unit is multiplied by the number of cycles ΔN to obtain the damage increment ΔD caused by the current load cycle. The damage increment ΔD obtained in each load cycle is added together to obtain the total damage of the unit. The calculation result is stored in the state variable;

[0037] 4-4) When the total damage of one of the units reaches the set critical damage value, it is considered that the crack has initiated and the simulation calculation ends. The total number of cycles experienced by the component is the fatigue life.

[0038] Further, in step 4-1), when the component unit undergoes only elastic deformation, the elastic damage rate calculation formula is As shown below:

[0039]

[0040] Where D e It is the damage caused by elastic deformation; M0, b2, β, η are elastic damage parameters, which need to be obtained by consulting the data of specific metal materials or through fatigue tests;

[0041] Among them, the octahedral shear stress amplitude A II As shown below:

[0042]

[0043] Where: S ij,max and S ij,min They represent the maximum and minimum values ​​of the deviatoric stress under a load cycle respectively;

[0044] Mean hydrostatic pressure σ H,mean As shown below:

[0045]

[0046] In the formula, σ H,max , σ H,min Respectively represent the maximum and minimum values ​​of hydrostatic pressure;

[0047] The parameter η is as follows:

[0048]

[0049]

[0050] In the formula, σ l0 , a, σ u , b1 is the elastic damage parameter, which can be obtained by referring to the material manual or fatigue test according to the specific metal material; is the intermediate parameter;

[0051] When the component unit undergoes plastic deformation, the plastic damage growth rate As shown below:

[0052]

[0053] Where D p Damage caused by plastic deformation; is the maximum equivalent stress; m and S are plastic damage parameters, which can be obtained by referring to the material manual or fatigue test according to the specific metal material;

[0054] The cumulative plastic strain rate is As shown below:

[0055]

[0056] Where D is the damage variable; is the plastic strain rate; represents the plastic flow rate;

[0057] The plastic strain rate As shown below:

[0058]

[0059] Wherein, the subscript "eq" represents equivalent stress; σ is the stress tensor; α is the back stress tensor; S is the deviatoric stress tensor; F is the plastic yield function;

[0060] The plastic yield function F is as follows:

[0061]

[0062] In the formula, σ y is the yield limit of the material.

[0063] Furthermore, the total number of load cycles N of the jth unit of the component i+1 As shown below:

[0064] N i+1 =N i +ΔN i (13)

[0065] Where N i is the cycle number corresponding to the last load cycle;

[0066] Among them, the number of cycles represented by one load cycle is ΔN i As shown below:

[0067]

[0068] In the formula, i represents the number of load cycles, and ΔD represents the maximum damage increment of one load cycle;

[0069] Among them, the critical damage growth rate As shown below:

[0070]

[0071] Where j is the unit number;

[0072] The damage growth rate As shown below:

[0073]

[0074] In the formula, n is the number of component units.

[0075] Furthermore, in step 4-3), the total damage of unit j is As shown below:

[0076]

[0077] The damage increment under one load cycle is As shown below:

[0078]

[0079] Where, ΔN i The number of cycles represented by one load cycle.

[0080] Furthermore, the material properties include elastic modulus, Poisson's ratio, yield limit, and plasticity parameters of the material.

[0081] Furthermore, the stress / strain conditions, damage and lifespan of metal components can be visualized.

[0082] The technical effect of the present invention is undoubted, and the beneficial effects of the present invention are:

[0083] 1. The present invention is applicable to most metal components and is not limited to a certain working condition or a certain position of the component, and has good versatility;

[0084] 2. The present invention adopts the Newton iteration algorithm with coupled damage to calculate the plastic strain increment, calculates the plastic stress and strain by the J2 plastic flow criterion, adopts the consistent tangent modulus algorithm with damage to calculate the Jacobian matrix of the component material under the plastic deformation condition, and updates the material parameters according to the degree of damage, thereby ensuring the accuracy of the stress / strain calculation in the plastic deformation stage of the metal component;

[0085] 3. The present invention adopts a skip cycle algorithm, which reasonably considers that one load cycle in simulation is ΔN load cycles in reality, effectively reducing the calculation cost and improving the calculation efficiency;

[0086] 4. The present invention extends Chaboche's damage evolution model to multiaxial stress conditions, making the calculation results of elastic damage growth rate more accurate;

[0087] 5. The present invention considers the total damage growth rate as the sum of the elastic damage growth rate and the plastic damage growth rate, avoiding the disadvantage of overestimating or underestimating the fatigue life of the component by a single damage growth rate, and the life calculation result is more accurate

[0088] 6. The present invention conducts secondary development through the UMAT port of ABAQUS software. Through the calculation results such as state variable storage, transmission damage and life, users can directly view them in the Visualization module of ABAQUS, avoiding tedious plug-in installation, data integration, programming and drawing. The simulation results provide a good reference for the optimization design of metal components. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is the overall flow chart of the simulation method of the present invention;

[0090] Figure 2 Create meshes for metal components;

[0091] Figure 3 It is the damage distribution map of metal components;

[0092] Figure 4 Plastic strain distribution diagram of metal components. DETAILED DESCRIPTION

[0093] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0094] Embodiment 1:

[0095] See also Figures 1 to 4The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development includes the following steps:

[0096] 1) Establishing a geometric model of a metal component and importing the geometric model of the metal component into ABAQUS simulation software;

[0097] 2) Use ABAQUS simulation software to pre-process the geometric model of metal components;

[0098] 3) Based on the geometric model of the metal component after pre-processing, use the metal component elastoplastic damage fatigue life subroutine to determine whether the metal component has plastic deformation. If so, proceed to step 4);

[0099] 4) Use the metal component elastoplastic damage fatigue life subroutine to calculate the component elastoplastic damage and life.

[0100] Embodiment 2:

[0101] The method for simulating the elastoplastic damage fatigue life of metal components based on secondary development of ABAQUS has the same technical content as that of Example 1. Furthermore, the geometric model of the metal component is drawn by three-dimensional modeling software.

[0102] Embodiment 3:

[0103] The elastoplastic damage fatigue life simulation method of metal components based on ABAQUS secondary development has the same technical content as any one of Embodiments 1-2. Further, the step of pre-processing the geometric model of the metal component using ABAQUS simulation software includes:

[0104] 2-1) Use ABAQUS simulation software to define the material properties of the metal component geometry model;

[0105] 2-2) Use ABAQUS simulation software to mesh the metal component model;

[0106] 2-3) Assemble and position the geometric model of the metal component after meshing;

[0107] 2-4) Create analysis steps and required output variables according to the load cycle of the metal component, and specify the number of cycles;

[0108] 2-5) Set constraints and contacts according to the motion characteristics of metal components;

[0109] 2-6) Set boundary conditions and apply loads according to the geometric model of the metal component.

[0110] Embodiment 4:

[0111] The method for simulating the elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS has the same technical content as any one of Embodiments 1 to 3. Further, the step of using the elastic-plastic damage fatigue life subroutine of the metal component to determine whether plastic deformation occurs to the metal component includes:

[0112] 3-1) Use ABAQUS simulation software to calculate the elastic strain and stiffness matrix of the current metal component mesh unit;

[0113] 3-2) Calculate the test stress according to the elastic strain and stiffness matrix of the current metal component mesh unit;

[0114] 3-3) Determine whether the test stress is greater than the yield limit. If so, the current metal component mesh unit undergoes plastic deformation, and jump to step 3-5); if not, the current metal component mesh unit does not undergo plastic deformation, and enter step 3-4);

[0115] 3-4) Update the material stiffness matrix, return to step 3-1), and calculate the elastic strain and stiffness matrix of the next metal component mesh unit;

[0116] 3-5) Calculate the plastic damage increment of the current metal component mesh unit according to the Newton iteration rule, and then calculate the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit under plastic deformation according to the plastic flow rule;

[0117] According to the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit, the material plastic damage parameter is updated, and the Jacobian matrix of the material is calculated using the consistent tangent modulus algorithm. Return to step 3-1) to calculate the elastic strain and stiffness matrix of the next metal component mesh unit.

[0118] Embodiment 5:

[0119] The elastoplastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same technical content as any one of Embodiments 1 to 4. Furthermore, the test stress is as follows:

[0120]

[0121] Where λ is the Lame constant; G is the shear modulus; D is the damage variable; α ij is the back stress; ij is the test stress; ii and ε ij is the elastic strain; i and j are the stress directions;

[0122] Parameter δ ij As shown below:

[0123]

[0124] Embodiment 6:

[0125] The elastic-plastic damage fatigue life simulation method of metal components based on secondary development of ABAQUS has the same technical content as any one of Embodiments 1 to 5. Furthermore, the updated material plastic damage parameters are as follows:

[0126]

[0127] In the formula, is the elastic modulus of the damaged unit, is the plastic damage parameter of the damaged unit; is the yield limit of the damaged unit. E is the elastic modulus; C k , γ k is the plastic damage parameter; σ y , represent the yield limit and damage variable respectively.

[0128] Embodiment 7:

[0129] The method for simulating the elastic-plastic damage fatigue life of a metal component based on secondary development of ABAQUS has the same technical content as any one of Embodiments 1 to 6. Further, the steps of calculating the elastic-plastic damage and life of a component using the elastic-plastic damage fatigue life subroutine of a metal component include:

[0130] 4-1) When the remaining time of the current load cycle is less than 2 increments, if the unit of the component only experiences elastic deformation, only the elastic damage growth rate of the unit is calculated and stored in the state variable. If the unit undergoes plastic deformation, the elastic damage growth rate and the plastic damage growth rate need to be calculated separately, and the total damage growth rate is the sum of the elastic damage growth rate and the plastic damage growth rate, and the state variable is updated;

[0131] 4-2) At the first incremental step of the next load cycle, according to the jump cycle algorithm, the number of cycles ΔN represented by the current load cycle is calculated through the damage increment of the custom load cycle and the total damage growth rate. The number of cycles ΔN obtained for each load cycle is accumulated to obtain the total number of cycles, and the calculation result is stored in the corresponding state variable;

[0132] 4-3) The damage growth rate of each unit is multiplied by the number of cycles ΔN to obtain the damage increment ΔD caused by the current load cycle. The damage increment ΔD obtained in each load cycle is added together to obtain the total damage of the unit. The calculation result is stored in the state variable;

[0133] 4-4) When the total damage of one of the units reaches the set critical damage value, it is considered that the crack has initiated and the simulation calculation ends. The total number of cycles experienced by the component is the fatigue life.

[0134] Embodiment 8:

[0135] The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development has the same technical content as any one of embodiments 1-7. Further, in step 4-1), when the component unit undergoes only elastic deformation, the elastic damage rate calculation formula is As shown below:

[0136]

[0137] Where D e It is the damage caused by elastic deformation; M0, b2, β, η are elastic damage parameters, which need to be obtained by consulting the data of specific metal materials or through fatigue tests;

[0138] Among them, the octahedral shear stress amplitude A II As shown below:

[0139]

[0140] Where: S ij,max and S ij,min They represent the maximum and minimum values ​​of the deviatoric stress under a load cycle respectively;

[0141] Mean hydrostatic pressure σ H,mean As shown below:

[0142]

[0143] In the formula, σ H,max , σ H,min Respectively represent the maximum and minimum values ​​of hydrostatic pressure;

[0144] The parameter η is as follows:

[0145]

[0146]

[0147] In the formula, σ l0 , a, σ u , b1 is the elastic damage parameter, which can be obtained by referring to the material manual or fatigue test according to the specific metal material; is the intermediate parameter;

[0148] When the component unit undergoes plastic deformation, the plastic damage growth rate As shown below:

[0149]

[0150] Where D p Damage caused by plastic deformation; is the maximum equivalent stress; m and S are plastic damage parameters, which can be obtained by referring to the material manual or fatigue test according to the specific metal material;

[0151] The cumulative plastic strain rate is As shown below:

[0152]

[0153] Where D is the damage variable; is the plastic strain rate; represents the plastic flow rate;

[0154] The plastic strain rate As shown below:

[0155]

[0156] Wherein, the subscript "eq" represents equivalent stress; σ is the stress tensor; α is the back stress tensor; S is the deviatoric stress tensor; F is the plastic yield function;

[0157] The plastic yield function F is as follows:

[0158]

[0159] In the formula, σ y is the yield limit of the material.

[0160] Embodiment 9:

[0161] The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development has the same technical content as any one of embodiments 1-8. Furthermore, the total number of load cycles N of the jth unit of the component is i+1 As shown below:

[0162] N i+1 =N i +ΔN i (13)

[0163] Where N i is the cycle number corresponding to the last load cycle;

[0164] Among them, the number of cycles represented by one load cycle is ΔN i As shown below:

[0165]

[0166] In the formula, i represents the number of load cycles, and ΔD represents the maximum damage increment of one load cycle;

[0167] Among them, the critical damage growth rate As shown below:

[0168]

[0169] Where j is the unit number;

[0170] The damage growth rate As shown below:

[0171]

[0172] In the formula, n is the number of component units.

[0173] Embodiment 10:

[0174] The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development has the same technical content as any one of embodiments 1-9. Further, in step 4-3), the total damage of unit j is As shown below:

[0175]

[0176] The damage increment under one load cycle is As shown below:

[0177]

[0178] Where, ΔN i The number of cycles represented by one load cycle.

[0179] Embodiment 11:

[0180] The method for simulating the elastic-plastic damage fatigue life of metal components based on the secondary development of ABAQUS has the same technical content as any one of Examples 1-10. Furthermore, the material properties include the elastic modulus, Poisson's ratio, yield limit, plasticity parameters, elastic damage parameters and plastic damage parameters of the material.

[0181] Embodiment 12:

[0182] The elastic-plastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same technical content as any one of Examples 1-11. Furthermore, the stress / strain condition, damage and life of the metal components can be visualized.

[0183] Embodiment 13:

[0184] The simulation method of elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS is as follows:

[0185] 1) Establish the geometric model of the metal component: Use 3D modeling software to draw the 3D model of the metal component and save it in STEP format, and import it into ABAQUS simulation software;

[0186] 2) Complete the pre-processing settings of the metal component model through ABAQUS simulation software:

[0187] 2-1) Define the material properties of the metal component model through ABAQUS simulation software;

[0188] 2-2) Meshing the metal component model using ABAQUS simulation software;

[0189] 2-3) Assemble and position the meshed metal component model;

[0190] 2-4) creating an analysis step and required output variables according to the load cycle of the metal component; wherein the number of cycles is given when creating the analysis step;

[0191] 2-5) Set constraints and contacts based on the motion characteristics between metal components;

[0192] 2-6) Set boundary conditions and apply loads according to the geometric model of the metal component;

[0193] 2-7) In the Job Manager module, select the metal component elastic-plastic damage fatigue life analysis subroutine Dmage_and_fatigue_life_analysis.for written in Fortran through the User subroutine file option;

[0194] 3) Determine whether the component has plastic deformation through the metal component elastoplastic damage fatigue life subroutine and update the material stiffness matrix:

[0195] 3-1) Submit the job in ABAQUS to calculate the stress / strain of the component;

[0196] 3-2) Read the finite element calculation results through the subroutine and calculate the test stress based on the elastic strain and stiffness matrix;

[0197] 3-3) Determine whether plastic deformation occurs in the unit by comparing the test stress and the yield limit;

[0198] 3-4) If the element does not become plastic, the material stiffness matrix is ​​updated according to the element damage and the next analysis step is performed;

[0199] 3-5) If the unit undergoes plastic deformation, the plastic damage increment is calculated according to the Newton iteration rule, and then the actual elastic stress / strain and plastic stress / strain of the unit under plastic deformation are calculated according to the plastic flow law, and the state variables are updated. Further, according to the plastic calculation results, the plastic damage parameters are updated, and the Jacobian matrix of the material is calculated using the generalized consistent tangent modulus algorithm, and the next analysis step is calculated;

[0200] 4) Calculate the elastic-plastic damage and life of components through the elastic-plastic damage fatigue life subroutine of metal components:

[0201] 4-1) When the remaining time of the current load cycle is less than 2 increments, if the unit of the component only experiences elastic deformation, only the elastic damage growth rate of the unit is calculated and stored in the state variable. If the unit undergoes plastic deformation, the elastic damage growth rate and the plastic damage growth rate need to be calculated separately. The total damage growth rate is the sum of the elastic damage growth rate and the plastic damage growth rate, and the state variable is updated;

[0202] 4-2) At the first incremental step of the next load cycle, according to the jump cycle algorithm, the number of cycles ΔN represented by the current load cycle is obtained through the damage increment of a custom load cycle and the total damage growth rate. The number of cycles ΔN obtained for each load cycle is accumulated to obtain the total number of cycles, and the calculation result is stored in the corresponding state variable;

[0203] 4-3) The damage growth rate of each unit is multiplied by the number of cycles ΔN to obtain the damage increment ΔD caused by the current load cycle. The damage increment ΔD obtained in each load cycle is added to obtain the total damage of the unit, and the calculation result is stored in the state variable;

[0204] 4-4) When the total damage of one unit reaches the set critical damage value, it is considered that the crack has initiated and the simulation calculation ends. The total number of cycles experienced by the component is the fatigue life;

[0205] 5) The stress / strain condition of metal components can be viewed through the Visualization module of ABAQUS. Its damage and life can also be intuitively obtained by reading the state variables.

[0206] Step 2-1) When customizing the material properties of metal components, you need to define the elastic modulus, Poisson's ratio, yield limit, plasticity parameters, etc. of the material through User Material, and you need to define the number of state variables through Depvar.

[0207] In step 2-7), the elastic-plastic damage and fatigue life simulation program is coupled to the UMAT subroutine, which needs to be called through the User subroutine file when submitting the job in ABAQUS.

[0208] In step 3-2), when calculating the test stress based on the strain calculated by ABAQUS and the stiffness matrix of the material, it is necessary to restore the stress to the undamaged state and then compare it with the yield limit that has not been weakened by damage. The calculation formula used is as follows:

[0209]

[0210] Where: λ is the Lame constant, G is the shear modulus, D is the damage variable, ε ij is the strain calculated by ABAQUS, α ij is the back stress, i and j are the stress directions, δ ij It can be calculated as follows:

[0211]

[0212] Step 3-5) When the element of the component undergoes plastic deformation, the following damage-coupled yield function is used:

[0213]

[0214] Where: the subscript "eq" represents equivalent stress; σ is the stress tensor; α is the back stress tensor; S is the deviatoric stress tensor; F is the plastic yield function; the plastic strain rate can be calculated by the following formula:

[0215]

[0216] in represents the plastic flow rate, and the cumulative plastic strain rate can be calculated using the following formula:

[0217]

[0218] The material parameters of the damaged element can be updated using the following formula:

[0219]

[0220] In the formula, is the elastic modulus of the damaged unit, is the plastic damage parameter of the damaged unit; is the yield limit of the damaged unit.

[0221] Step 4-1) When the component unit undergoes only elastic deformation, the elastic damage rate calculation formula is as follows:

[0222]

[0223] Where: D eis the damage caused by elastic deformation; M0, b2, β, η are elastic damage parameters, which need to be obtained by consulting data or through fatigue tests based on specific metal materials; A II represents the octahedral shear stress amplitude and can be calculated using the following formula:

[0224]

[0225] Where: S ij,max and S ij,min represent the maximum and minimum values ​​of the deviatoric stress under a load cycle, σ H,mean represents the mean hydrostatic pressure and can be calculated using the following formula:

[0226]

[0227] In the formula, σ H,max , σ H,min Respectively represent the maximum and minimum values ​​of hydrostatic pressure;

[0228] According to the sinusoidal fatigue limit criterion, the parameters η and It can be calculated by the following formula:

[0229]

[0230]

[0231] When the component unit undergoes plastic deformation, its plastic damage growth rate can be calculated using the following formula:

[0232]

[0233] Where D p Damage caused by plastic deformation; is the maximum equivalent stress; m and S are plastic damage parameters, which can be obtained by referring to the material manual or fatigue test according to the specific metal material;

[0234] Step 4-2) The number of cycles represented by one load cycle can be calculated using the following formula:

[0235]

[0236] Where: i represents the number of load cycles, ΔD represents the maximum damage increment of a load cycle, which needs to be defined by the user. It represents the critical damage growth rate and can be calculated using the following formula:

[0237]

[0238] Where j is the unit number, and the damage growth rate It can be calculated by the following formula:

[0239]

[0240] The total number of load cycles for the jth unit of the component can be calculated using the following formula:

[0241] N i+1 =N i +ΔN i (16)

[0242] Step 4-3) The damage increment under one load cycle can be calculated by the following formula:

[0243]

[0244] The total damage of unit j can be calculated using the following formula:

[0245]

[0246] Step 4-4) When the total damage value of a unit reaches the set total damage value, it is considered that crack initiation occurs and the simulation ends. The total number of load cycles experienced by the current component is the fatigue life of the component.

[0247] Embodiment 14:

[0248] The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development is used to simulate the fatigue damage process of Ti-6Al-4V metal plate with a central circular hole under alternating tensile load. The steps are as follows:

[0249] 1) Establish the geometric model of metal components: The structure of this case is simple, so the modeling is completed in ABAQUS through two steps of stretching and cutting.

[0250] 2) Complete the pre-processing settings of the metal component model through ABAQUS simulation software:

[0251] 2-1) Define the material properties of the metal component model through ABAQUS simulation software; the default unit used in this embodiment is mm-N-MPa, add User Material in Edit Material, input the Ti-6Al-4V material parameters shown in Table 1 in sequence, and add Depvar to input the number of state variables 75 (this value needs to be consistent with Dmage_and_fatigue_life_analysis.for);

[0252] Table 1 Ti-6Al-4V material parameters

[0253]

[0254] 2-2) Use ABAQUS simulation software to mesh the metal component model; in the "Mesh" function of ABAQUS software, set the unit type to An 8-node linear brick, reduced integration, hourglass control (C3D8R), set the hourglass control in Element Controls to Enhanced, set the global grid to 0.5mm, and the precision grid to 0.3mm. The component mesh is divided as follows: Figure 2 As shown;

[0255] 2-3) Assemble and position the meshed metal component model; create a metal component assembly, and set fixed constraints on the bottom surface of the metal component;

[0256] 2-4) Create the metal component analysis step and the required output variables; the metal component is only subjected to tensile alternating loads during the movement, so create a time step Step-1: turn on large deformation, set the Time period to 1.56s, the Initial increment size to 0.02s, and the Maximum increment size to 0.02s; in addition to the default variables, the history output "Field output requests manager" also needs to add the STATUS variable, select "Every n increments" for the output frequency, and the value is 1, the field variable "History Output" output is set to the default value, and the output frequency is also 1;

[0257] 2-5) Set constraints and contacts according to the motion characteristics between metal components; since the assembly is an independent component, no other constraints and contacts are involved;

[0258] 2-6) Apply load according to the load conditions of the metal component; create Pressure through Load Manager, select Create Amplitude to create a Tabular type load, the load amplitude is 200MP, and the cycle period is 0.12s;

[0259] 2-7) Edit the job Job, select Fortran in User subroutine file to write the metal component elastoplastic damage fatigue life calculation subroutine "Dmage_and_fatigue_life_analysis.for", set the Ti-6Al-4V damage parameters shown in Table 2 in the subroutine, and set the maximum damage increment of a load cycle to 0.1, the critical damage value to 0.99, and the load cycle period to 0.12s.

[0260] Table 2 Damage parameters of Ti-6Al-4V

[0261]

[0262] 3) Determine whether the component has plastic deformation through the metal component elastoplastic damage fatigue life subroutine and update the material stiffness matrix:

[0263] a) Submit a job through ABAQUS to calculate the stress / strain of the component in one increment;

[0264] b) Read the ABAQUS calculation results through the subroutine, calculate each stress component according to the elastic strain and stiffness matrix, and each stress component needs to be restored to a lossless state. The following formula can be used for calculation:

[0265]

[0266] Where λ is the Lame constant, G is the shear modulus, D is the damage variable, and ε ii and ε ij is the strain calculated by ABAQUS, α ij is the back stress, i and j are the stress directions, δ ij It can be calculated as follows:

[0267]

[0268] c) Calculate the test stress based on the stress components and with reference to the Von Mises stress calculation formula, compare the test stress with the yield limit, and determine whether plastic deformation occurs in the unit;

[0269] d) If the unit does not undergo plastic deformation, the material stiffness matrix is ​​updated according to the unit damage and the next analysis step is calculated. The stiffness matrix can be expressed as follows:

[0270]

[0271] Among them, λ and G are calculated from the elastic modulus E. The elastic modulus of the damaged unit can be calculated by the following formula:

[0272] E=E0(1-D) (3)

[0273] Among them, E0 is the elastic modulus of the metal material when it is lossless;

[0274] e) If the unit undergoes plastic deformation, the plastic damage increment is calculated according to the Newton iteration rule, and then the actual elastic stress / strain and plastic stress / strain of the unit under plastic deformation are calculated according to the plastic flow law, and the state variables are updated. Further, according to the plastic calculation results, the plastic damage parameters are updated, and the Jacobian matrix of the material is calculated using the generalized consistent tangent modulus algorithm, and the next analysis step is calculated; when judging whether plastic yield occurs, the following damage-coupled yield function can be used:

[0275]

[0276] Among them, σ y is the yield limit, the subscript "eq" represents the equivalent stress; the plastic strain rate can be calculated by the following formula:

[0277]

[0278] in represents the plastic flow rate, σ is the stress tensor, α is the back stress tensor, S is the deviatoric stress tensor, and F is the plastic yield function; the cumulative plastic strain rate can be calculated using the following formula:

[0279]

[0280] The material parameters of the damaged element can be updated using the following formula:

[0281]

[0282] Where i represents the number of load cycles, j is the component unit number, is the elastic modulus of the damaged unit, is the plastic damage parameter of the damaged element, is the yield limit of the damaged unit; the consistent tangent modulus algorithm with damage can be calculated using the following formula:

[0283]

[0284]

[0285] 4) Calculate the elastic-plastic damage and life of components through the elastic-plastic damage fatigue life subroutine of metal components:

[0286] I) When the remaining time of the current load cycle is less than 2 increments, if the unit of the component only undergoes elastic deformation, only the elastic damage growth rate of the unit is calculated and stored in the state variable. If the unit undergoes plastic deformation, the elastic damage growth rate and the plastic damage growth rate need to be calculated separately. The total damage growth rate is the sum of the elastic damage growth rate and the plastic damage growth rate. The state variable is updated. The elastic damage growth rate can be calculated using the following formula:

[0287]

[0288] Where: D e is the damage caused by elastic deformation; M0, b2, β, η are elastic damage parameters, see Table 2; A II represents the octahedral shear stress amplitude and can be calculated using the following formula:

[0289]

[0290] Where: S ij,max and S ij,min represent the maximum and minimum values ​​of the deviatoric stress under a load cycle, σ H,mean represents the mean hydrostatic pressure and can be calculated using the following formula:

[0291]

[0292] In the formula, σ H,max , σ H,min Represent the maximum and minimum values ​​of the hydrostatic pressure respectively; according to the sinusoidal fatigue limit criterion, the parameters η and It can be calculated by the following formula:

[0293]

[0294]

[0295] In the formula, σ l0 , a, σ u , b1 is the elastic damage parameter, see Table 2;

[0296] When the component unit undergoes plastic deformation, its plastic damage growth rate can be calculated using the following formula:

[0297]

[0298] Where D p Damage caused by plastic deformation; is the maximum equivalent stress; m and S are plastic damage parameters, see Table 2;

[0299] II) In the early stage of the next load cycle, according to the jump cycle algorithm, the number of cycles ΔN represented by the current load cycle is obtained through the damage increment and the total damage growth rate under a custom load cycle. The number of cycles ΔN obtained for each load cycle is accumulated to obtain the total number of cycles. The calculation result is stored in the corresponding state variable. The number of cycles represented by one load cycle can be calculated using the following formula:

[0300]

[0301] Where: ΔD represents the maximum damage increment of a load cycle, which needs to be defined by the user. It represents the critical damage growth rate and can be calculated using the following formula:

[0302]

[0303] The damage growth rate It can be calculated by the following formula:

[0304]

[0305] The total number of load cycles for the jth unit of the component can be calculated using the following formula:

[0306] N i+1 =N i +ΔN i (19)

[0307] III) The damage increment ΔD caused by the current load cycle is obtained by multiplying the damage growth rate of each unit by the number of cycles ΔN. The total damage of the unit is obtained by adding the damage increment ΔD obtained for each load cycle. The calculation result is stored in the state variable. The damage increment under one load cycle can be calculated by the following formula:

[0308]

[0309] The total damage of unit j can be calculated using the following formula:

[0310]

[0311] IV) When the total damage of one of the units reaches the set maximum damage value, it is considered that crack initiation has occurred and the simulation calculation ends. The total number of load cycles experienced by the current component is the fatigue life of the component.

[0312] 5) Use the Visualization module of ABAQUS to view the stress / strain of metal components. The crack initiation life can be viewed through SDV75, and the damage and plastic deformation can also be intuitively obtained by reading the state variables, such as Figures 3-4 In addition, you can also query the ODB field output through Create XY Data to export state variable data and analyze the critical unit damage and life evolution process.

[0313] Embodiment 15:

[0314] The elastic-plastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same main steps as Example 14. Furthermore, the Ti-6Al-4V metal plate with a central circular hole in step 1) can be replaced by metal components of other shapes, and the material can also be replaced with other metal materials.

[0315] Embodiment 16:

[0316] The elastic-plastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same main steps as Example 14. Furthermore, step 1) can first complete the modeling in three-dimensional software such as Solidworks, then save it in STEP format, and then import it into ABAQUS for pre-processing.

[0317] Embodiment 17:

[0318] The elastic-plastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same main steps as Example 14. Furthermore, in step 2-2), a mesh independence analysis of the metal components is required to ensure the accuracy of the calculation results.

[0319] Embodiment 18:

[0320] The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development has the same main steps as Example 14. Furthermore, in step 2-7), the maximum damage increment of a load cycle is set to 0.01, the critical damage value is 0.99, and the load cycle period is determined according to the actual working conditions.

[0321] Embodiment 19:

[0322] The elastic-plastic damage fatigue life simulation method of metal components based on the secondary development of ABAQUS has the same main steps as Example 14. Furthermore, the total damage growth rate described in step II) can be taken as the maximum value of the elastic damage growth rate and the plastic damage growth rate.

Claims

1. The elastic-plastic damage fatigue life simulation method of metal components based on ABAQUS secondary development is characterized by: The following steps are involved: 1) Establishing a geometric model of a metal component and importing the geometric model of the metal component into ABAQUS simulation software; 2) Use ABAQUS simulation software to pre-process the geometric model of metal components; 3) Based on the geometric model of the metal component after pre-processing, use the metal component elastoplastic damage fatigue life subroutine to determine whether the metal component has plastic deformation. If so, proceed to step 4); 4) Calculate the elastic-plastic damage and life of components using the elastic-plastic damage fatigue life subroutine of metal components; The steps of using the elastoplastic damage fatigue life subroutine of metal components to determine whether plastic deformation occurs in the metal components include: 3-1) Use ABAQUS simulation software to calculate the elastic strain and stiffness matrix of the current metal component mesh unit; 3-2) Calculate the test stress according to the elastic strain and stiffness matrix of the current metal component mesh unit; 3-3) Determine whether the test stress is greater than the yield limit. If so, the current metal component mesh unit undergoes plastic deformation, and jump to step 3-5); if not, the current metal component mesh unit does not undergo plastic deformation, and enter step 3-4); 3-4) Update the material stiffness matrix, return to step 3-1), and calculate the elastic strain and stiffness matrix of the next metal component mesh unit; 3-5) Calculate the plastic damage increment of the current metal component mesh unit according to the Newton iteration rule, and then calculate the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit under plastic deformation according to the plastic flow rule; According to the actual elastic stress / strain and plastic stress / strain of the current metal component mesh unit, the material plastic damage parameter is updated, and the Jacobian matrix of the material is calculated using the consistent tangent modulus algorithm, and then return to step 3-1) to calculate the elastic strain and stiffness matrix of the next metal component mesh unit; The steps of calculating the elastic-plastic damage and life of a component using the elastic-plastic damage fatigue life subroutine of a metal component include: 4-1) When the remaining time of the current load cycle is less than 2 increments, if the unit of the component only experiences elastic deformation, only the elastic damage growth rate of the unit is calculated and stored in the state variable. If the unit undergoes plastic deformation, the elastic damage growth rate and the plastic damage growth rate need to be calculated separately, and the total damage growth rate is the sum of the elastic damage growth rate and the plastic damage growth rate, and the state variable is updated; 4-2) At the first incremental step of the next load cycle, according to the jump cycle algorithm, the number of cycles ΔN represented by the current load cycle is calculated through the damage increment of the custom load cycle and the total damage growth rate. The number of cycles ΔN obtained for each load cycle is accumulated to obtain the total number of cycles, and the calculation result is stored in the corresponding state variable; 4-3) The damage growth rate of each unit is multiplied by the number of cycles ΔN to obtain the damage increment ΔD caused by the current load cycle. The damage increment ΔD obtained in each load cycle is added together to obtain the total damage of the unit. The calculation result is stored in the state variable; 4-4) When the total damage of one unit reaches the set critical damage value, it is considered that the crack has initiated and the simulation calculation ends. The total number of cycles experienced by the component is the fatigue life; Step 4-1) When the component unit undergoes only elastic deformation, the elastic damage growth rate calculation formula is: As shown below: Where D e is the damage caused by elastic deformation; M0, b2, β, η are elastic damage parameters; Among them, the octahedral shear stress amplitude A II As shown below: Where: S ij,max and S ij,min They represent the maximum and minimum values ​​of the deviatoric stress under a load cycle respectively; Mean hydrostatic pressure σ H,mean As shown below: In the formula, σ H,max , σ H,min Respectively represent the maximum and minimum values ​​of hydrostatic pressure; The parameter η is as follows: In the formula, σ l0 , a, σ u , b1 is the elastic damage parameter; is the intermediate parameter; When the component unit undergoes plastic deformation, the plastic damage growth rate As shown below: Where D p Damage caused by plastic deformation; is the maximum equivalent stress; m and S are plastic damage parameters; The cumulative plastic strain rate is As shown below: Where D is the damage variable; is the plastic strain rate; represents the plastic flow rate; The plastic strain rate As shown below: Wherein, the subscript "eq" represents equivalent stress; σ is the stress tensor; α is the back stress tensor; S is the deviatoric stress tensor; F is the plastic yield function; The plastic yield function F is as follows: In the formula, σ y is the yield limit of the material.

2. The elastoplastic damage fatigue life simulation method of metal components based on ABAQUS secondary development according to claim 1 is characterized in that: The geometric model of the metal component is drawn by three-dimensional modeling software.

3. The elastoplastic damage fatigue life simulation method of metal components based on ABAQUS secondary development according to claim 1 is characterized in that: The steps of pre-processing the geometric model of metal components using ABAQUS simulation software include: 2-1) Use ABAQUS simulation software to define the material properties of the metal component geometry model; 2-2) Use ABAQUS simulation software to mesh the metal component model; 2-3) Assemble and position the geometric model of the metal component after meshing; 2-4) Create analysis steps and required output variables according to the load cycle of the metal component, and specify the number of cycles; 2-5) Set constraints and contacts according to the motion characteristics of metal components; 2-6) Set boundary conditions and apply loads according to the geometric model of the metal component.

4. The method for simulating the elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS according to claim 1 is characterized in that: The test stress is as follows: Where λ is the Lame constant; G is the shear modulus; D is the damage variable; α ij is the back stress; ij To test stress; ε ii and ε ij is the elastic strain; i and j are the stress directions; Parameter δ ij As shown below:

5. The method for simulating the elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS according to claim 1 is characterized in that: The updated material plastic damage parameters are as follows: In the formula, is the elastic modulus of the damaged unit; is the plastic damage parameter of the damaged unit; is the yield limit of the damaged unit; E is the elastic modulus; C k , γ k is the plastic damage parameter; σ y , represent the yield limit and damage variable respectively.

6. The method for simulating the elastoplastic damage fatigue life of metal components based on secondary development of ABAQUS according to claim 1 is characterized in that: The total number of load cycles N for the j'th unit of the component i+1 As shown below: N i+1 =N i +ΔN i (13) Where N i is the cycle number corresponding to the last load cycle; Among them, the number of cycles represented by one load cycle is ΔN i As shown below: In the formula, i represents the number of load cycles, and ΔD represents the maximum damage increment of one load cycle; Among them, the critical damage growth rate As shown below: Where j' is the unit number; The damage growth rate As shown below: In the formula, n is the number of component units.

7. The method for simulating the elastic-plastic damage fatigue life of metal components based on secondary development of ABAQUS according to claim 6 is characterized in that: In step 4-3), the total damage of unit j' As shown below: The damage increment under one load cycle is As shown below: Where, ΔN i The number of cycles represented by one load cycle.

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