Method for carrying out fatigue damage evolution analysis on engineering structure by utilizing Abaqus software

Abstract

The invention provides a method for carrying out fatigue damage evolution analysis on an engineering structure by utilizing Abaqus software. The method comprises the following steps: constructing a material constitutive relation model capable of reflecting a material fatigue damage evolution behavior of an engineering structure, and compiling a VUMAT program of the material constitutive relation model based on a material subprogram interface provided by Abaqus software; designing an acceleration strategy for accelerating material fatigue damage analysis; establishing a finite element analysis model of the engineering structure in Abaqus software, and generating a reference INP file by using the finite element analysis model; modifying the reference INP file by using an acceleration strategy, and generating a fatigue damage analysis task of the engineering structure based on the VUMAT program; and executing a fatigue damage analysis task by using the acceleration strategy until the engineering structure fails, and obtaining a fatigue damage analysis result of the engineering structure. According to the method, the fatigue damage evolution process of the engineering structure is analyzed by utilizing the Abaqus software, and the problem of non-convergence of calculation in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue damage analysis of structures, and particularly to a method for analyzing fatigue damage evolution of engineering structures by using Abaqus software. Background Art

[0002] Fatigue damage refers to the cumulative damage generated in materials under cyclic loading. In actual engineering, many structures such as bridges and airplanes are at risk of fatigue failure due to cyclic loading. In essence, the fatigue failure of a structure is the result of the evolution of its fatigue damage to a certain extent. Therefore, carrying out the analysis of fatigue damage evolution of structures is an important means to achieve its anti-fatigue optimal design. At the same time, since the fatigue life of a structure is usually counted in millions or tens of millions, the time consumed by its numerical analysis is usually unacceptable. Therefore, a specific acceleration strategy is generally adopted to accelerate the analysis process.

[0003] At present, a method for analyzing the whole process of fatigue damage of a wind turbine foundation on the road in the prior art includes: carrying out an accelerated analysis of fatigue damage evolution of the wind turbine structure in Abaqus / Standard (i.e., the Abaqus standard module). The disadvantages of this method include: this method relies on the Abaqus / Standard platform and has the problem of non-convergence in calculation. Summary of the Invention

[0004] The present invention provides a method for analyzing fatigue damage evolution of engineering structures by using Abaqus software to effectively analyze the fatigue damage evolution process of engineering structures.

[0005] To achieve the above object, the present invention adopts the following technical solutions.

[0006] A method for analyzing fatigue damage evolution of engineering structures by using Abaqus software includes:

[0007] Constructing a material constitutive relation model that can reflect the fatigue damage evolution behavior of materials of an engineering structure, and compiling a VUMAT program of the material constitutive relation model based on the material subroutine interface provided by Abaqus software;

[0008] Designing an acceleration strategy for accelerating the analysis of material fatigue damage;

[0009] Establishing a finite element analysis model of an engineering structure in Abaqus software, using the path of the VUMAT program as a parameter for the finite element analysis model to generate a fatigue damage analysis task of the engineering structure, and the Abaqus software executing the fatigue damage analysis task to generate a reference INP file;

[0010] Modify the reference INP file based on the result of the previous analysis using the acceleration strategy, generate an analysis task based on the modified INP file, execute the analysis task to obtain an analysis result, and then modify the reference INP file based on the analysis result and the acceleration strategy, and so on until the engineering structure fails, to obtain the fatigue damage analysis result of the engineering structure.

[0011] Preferably, the construction of a material constitutive relation model that can reflect the material fatigue damage evolution behavior of the engineering structure, and the preparation of the VUMAT program of the material constitutive relation model based on the material subroutine interface provided by Abaqus software, includes:

[0012] For various materials that make up the engineering structure, select a material constitutive relation model that can reflect the material fatigue damage evolution behavior. The material constitutive relation model includes the relationship between stress and strain, the evolution law of the damage variable, and the evolution law of the plastic strain. The relationship between stress and strain is:

[0013] Stress = (I - damage) * elastic stiffness * (strain - plastic strain)

[0014] where I is the unit tensor;

[0015] Prepare the VUMAT subroutine of the material constitutive relation model based on the material subroutine interface provided by Abaqus software.

[0016] Preferably, the acceleration strategy designed to accelerate the material fatigue damage analysis includes:

[0017] The acceleration strategy designed to accelerate the material fatigue damage analysis, which includes the number of cycle jumps. The number of cycle jumps represents the time interval between the current analysis and the next analysis. Each extrapolation represents a jump in the structural performance state. The number of cycles = time * the frequency of load application.

[0018] Preferably, the establishment of a finite element analysis model of the engineering structure in Abaqus software and the generation of a reference INP file using the finite element analysis model include:

[0019] Establish a finite element analysis model of the engineering structure in Abaqus software, including the following steps: (1) Establish all components included in the finite element analysis model; (2) Establish the material properties of all components; (3) Assemble each component; (4) Set the analysis parameters; (5) Establish the contact method between each component; (6) Complete the setting of the model boundary conditions; (7) Complete the element division of each component of the model;

[0020] Generate a fatigue damage analysis task for the engineering structure using the finite element analysis model, call the compiled VUMAT subroutine to complete the verification of the correctness of the finite element model. After executing the current fatigue damage analysis task, generate a reference INP file for the fatigue damage analysis of the engineering structure. The reference INP file contains the basic information of a fatigue damage analysis task.

[0021] Preferably, the reference INP file is modified based on the results of the previous analysis using the acceleration strategy, an analysis task is generated based on the modified INP file, the analysis task is executed to obtain the analysis results, and then the reference INP file is modified based on the analysis results and the acceleration strategy, and so on until the engineering structure fails to obtain the fatigue damage analysis results of the engineering structure, including:

[0022] The Abaqus software modifies the reference INP file based on the results of the previous analysis using the acceleration strategy to obtain the INP file for the current analysis, calls the VUMAT program and the INP file to generate an analysis task, submits and executes the analysis task to generate an ODB (output database) result file containing the analysis results. The ODB result file includes the damage evolution information of the engineering structure at the current time node;

[0023] Calculate the overall cyclic jump number of the structure and the values of the state variables of the material elements after the jump according to the acceleration strategy, set the calculated values of the state variables of the material elements after the jump as the initial values of the state variables of the material elements, generate a new fatigue damage analysis task for the next execution, and then modify the reference INP file based on the analysis results and the acceleration strategy. Repeat the above processing process until the engineering structure fails to trigger the stop condition of the fatigue damage analysis task. Take the finally obtained ODB result file as the fatigue damage analysis result of the engineering structure, and splice the stress analysis results of the engineering structure at different time points to obtain the fatigue damage evolution process of the engineering structure.

[0024] As can be seen from the technical solutions provided by the embodiments of the present invention above, the present invention proposes an implementation method for accelerating the fatigue damage evolution analysis of engineering structures in the Explicit module of Abaqus, which solves the problem of non-convergence in the prior art calculations.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description, and these will become obvious from the following description or be understood through the practice of the present invention. Description of the Drawings

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is a processing flow chart of a method for carrying out engineering structure fatigue damage evolution analysis by using the Explicit module of Abaqus provided by the embodiments of the present invention. Specific embodiments

[0028] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention.

[0029] Those skilled in the art of the present technology can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The phrase "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0030] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here.

[0031] For the convenience of understanding the embodiments of the present invention, the following will further explain with several specific embodiments as examples in conjunction with the drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0032] An embodiment of the present invention proposes a method for accelerating the analysis of fatigue damage evolution of engineering structures in the Explicit module of Abaqus, which solves the problem of non-convergence in existing technologies.

[0033] The processing flow chart of the method for analyzing the fatigue damage evolution of engineering structures using the Explicit module of Abaqus provided by the embodiment of the present invention is as Figure 1 shown, and includes the following processing steps;

[0034] Step S10: Compile the VUMAT subroutine.

[0035] The VUMAT subroutine is a material subroutine interface provided by the Abaqus software. Given the input, calculations are performed to obtain the output. It is similar to a function y = f(x), except that x is given by the software and f(·) is defined by the user himself.

[0036] The format of the VUMAT interface is:

[0037]

[0038]

[0039]

[0040] For various materials that make up the engineering structure, select a constitutive relation model of the material that can correctly reflect the fatigue damage evolution behavior of the material. The material constitutive relation refers to the relationship between the stress and strain of a representative volume element of the material (where stress can be understood as force and strain can be understood as deformation. Therefore, the material constitutive relation is also the relationship between the force on the material unit and the deformation it produces). For an ideal linear elastic material, the relationship between stress and strain is:

[0041] Stress = Elastic stiffness * Strain

[0042] However, there is no ideal linear elastic material in engineering. Under the action of external forces, engineering materials usually produce cracks and irreversible cumulative deformations. Damage is a concept introduced to reflect the influence of cracks on the material properties. At the same time, irreversible cumulative deformations are usually reflected by plastic strain. In this context, the typical expression of the constitutive relation of engineering materials is:

[0043] Stress = (I - Damage) * Elastic stiffness * (Strain - Plastic strain)

[0044] where I is the unit tensor.

[0045] In addition to the above stress-strain equation form, a complete constitutive relation model also includes two other parts. These two parts are the evolution law of the damage variable and the evolution law of the plastic strain, that is, how the damage variable and the plastic strain develop respectively as the stress or strain increases. The establishment of the evolution laws of the damage variable and the plastic strain is a difficult point in the research on the constitutive relations of engineering materials. So far, the vast majority of constitutive relations still establish these two types of evolution laws through experimental experience.

[0046] The material constitutive relation model that correctly reflects the fatigue damage evolution behavior of materials mentioned in the present invention refers to that the damage evolution law adopted by the model can be applied to cyclic loading.

[0047] Compile a computer program of the material constitutive relation model based on the VUMAT interface provided by Abaqus / Explicit; analyze the stress behavior of a material element to complete the unit test of the VUMAT program.

[0048] Step S20: Determine the acceleration strategy. Design an acceleration strategy for accelerating fatigue damage analysis according to the requirements for calculation accuracy and cost.

[0049] Material fatigue refers to the phenomenon that materials are damaged under cyclic stresses lower than their static strength. The fatigue life of engineering materials (i.e., the number of stress cycles that can be endured) is usually several million or tens of millions of load cycles. According to the current computer performance, within an acceptable calculation cost, Abaqus can only handle the stress analysis problems of engineering structures under several to dozens of load cycles. Therefore, if we want to carry out the fatigue damage analysis of engineering structures, we must adopt a certain acceleration strategy. So the role of the acceleration strategy is to reduce the calculation cost, improve the calculation efficiency, and ensure a certain calculation accuracy at the same time. The most effective acceleration strategy for fatigue damage analysis is the cyclic jump acceleration strategy. The core idea of this strategy is: first, conduct the stress analysis of the engineering structure under several load cycles. After the analysis is completed, extract the analysis results to obtain the speed and acceleration of the performance evolution of the engineering structure at the current time node. Based on these results, extrapolate the performance of the engineering structure at the next time node, and repeat the above steps until the engineering structure finally fails due to fatigue. The difference between different acceleration strategies lies in the calculation method of the next time node and the extrapolation method of the performance of the engineering structure.

[0050] The acceleration strategy includes the cyclic jump number. The cyclic jump number represents the time interval between the current analysis and the next analysis. Each extrapolation represents a jump in the structural performance state. The number of cycles = time * the frequency of load application.

[0051] Step S30: Generate a reference INP file (Input file).

[0052] The finite element analysis model of the engineering structure is established in Abaqus / Explicit, which includes the following steps: (1) Establish all components included in the finite element analysis model; (2) Establish the material properties of all components (if user-defined material properties are required, the input parameters of the user material subroutine need to be filled in), and assign them to the corresponding components; (3) Assemble each component; (4) Complete the analysis step settings (select the dynamic explicit (Dynamic, Explicit) process type, set the analysis time based on the determined acceleration strategy, etc.); (5) Establish the contact method between each component; (6) Complete the setting of the model boundary conditions; (7) Complete the element division of each component of the model.

[0053] After the finite element analysis model is established, the fatigue damage analysis task can be generated and submitted. Since the material subroutine is compiled using the VUMAT interface, when submitting the fatigue damage analysis task, it is necessary to set the user-defined material subroutine used to the compiled VUMAT program. Then, the above-compiled VUMAT subroutine can be called to complete the verification of the correctness of the finite element model. After the fatigue damage analysis task is executed this time, a reference INP file for subsequent formal fatigue damage analysis is generated. The reference INP file contains the complete finite element model information, and its function is to facilitate the generation of the INP file for single fatigue damage analysis, that is, each time only the reference INP file needs to be modified to obtain the INP file for this fatigue damage analysis.

[0054] Step S40: Compile the INP file generation program. When the number of times of submitting the fatigue damage analysis is 1, the reference INP file is directly used as the generated INP file; when the number of analyses is greater than 1, the reference INP file is modified, and the modification result is used as the generated INP file. The process of modifying the reference INP file is as follows:

[0055] ① Read the ODB result file formed during the previous fatigue damage analysis, and extract the damage evolution information of each material element from the ODB result file;

[0056] ② Based on the above-determined acceleration strategy, calculate the overall cyclic jump number of the structure and the values of the state variables of the material elements after the jump; based on the *INITIAL CONDITIONS command built into Abaqus, add an initialization section of the material element state variables to the reference INP file, and set the calculated values of the state variables of the material elements after the jump as the initial values of the material element state variables.

[0057] The Abaqus software modifies the reference INP file based on the results of the previous analysis using an acceleration strategy to obtain the INP file for the current analysis, calls the VUMAT program and the INP file to generate an analysis task, submits and executes the analysis task. The Abaqus software automatically performs the problem-solving calculation to generate an.odb file containing the analysis results, that is, the ODB result file. The ODB result file includes the damage evolution information of the engineering structure at the current time node. The above processing process is repeated until the engineering structure fails, triggering the stop condition of the fatigue damage analysis task. The finally obtained ODB result file is used as the fatigue damage analysis result of the engineering structure, and the stress analysis results of the engineering structure at different time points are spliced together to obtain the fatigue damage evolution process of the engineering structure.

[0058] The fatigue damage finite element analysis of the engineering structure of the present invention relies on the cyclic jump acceleration algorithm. The core idea of this algorithm is to adopt the jump-extrapolation method, that is, to perform the analysis for several cycles first. After obtaining the analysis results, the analysis results are processed to obtain the evolution speed and acceleration of the structural mechanical behavior at the current moment, etc. Then, based on these results, the jump time of the structural performance and the performance of the structure after the jump are calculated. Finally, the mechanical behavior analysis of the structure under several cycles is restarted with the performance after the jump as the starting point, and so on, until the structure fails.

[0059] In summary, the existing engineering structure fatigue damage acceleration analysis method of the embodiments of the present invention is implemented through the Abaqus / Standard platform. Since the Abaqus / Standard platform uses an iterative method to solve the equations, there is a problem of non-convergence in the existing technology. To address this problem, the present invention proposes an implementation method for carrying out the fatigue damage acceleration analysis of engineering structures in Abaqus / Explicit. Abaqus / Explicit does not require an iterative process to solve the equations, but directly calculates the physical quantities of the next time step explicitly using the motion equations based on the known physical quantities at the current time step and the information at the previous time step. Therefore, compared with the existing technology, the advantage of the present invention is that there is no problem of non-convergence in the calculation, and the full-process analysis of the fatigue failure of the engineering structure can be truly realized.

[0060] Those of ordinary skill in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or processes in the drawings are not necessarily essential for implementing the present invention.

[0061] As can be seen from the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention, in essence, or the part that makes a contribution to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0062] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiments. The device and system embodiments described above are only illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0063] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A fatigue damage evolution analysis method for engineering structures using Abaqus software, characterized in that: include: Construct a material constitutive relationship model that can reflect the material fatigue damage evolution behavior of the engineering structure, and compile a VUMAT program of the material constitutive relationship model based on the material subroutine interface provided by the Abaqus software; Design acceleration strategies to accelerate material fatigue damage analysis; Establishing a finite element analysis model of the engineering structure in the Abaqus software, wherein the finite element analysis model uses the path of the VUMAT program as a parameter to generate a fatigue damage analysis task of the engineering structure, and the Abaqus software executes the fatigue damage analysis task to generate a reference INP file; The Abaqus software uses the acceleration strategy to modify the reference INP file based on the results of the previous analysis, generates an analysis task based on the modified INP file, executes the analysis task, obtains the analysis results, and then modifies the reference INP file based on the analysis results and the acceleration strategy, and so on, until the engineering structure fails and the fatigue damage analysis results of the engineering structure are obtained.

2. The method according to claim 1, characterized in that The material constitutive relationship model that can reflect the material fatigue damage evolution behavior of the engineering structure is constructed, and the VUMAT program of the material constitutive relationship model is compiled based on the material subroutine interface provided by the Abaqus software, including: For various materials constituting engineering structures, a material constitutive relationship model that can reflect the fatigue damage evolution behavior of the material is selected. The material constitutive relationship model includes the relationship between stress and strain, the evolution law of damage variables and the evolution law of plastic strain. The relationship between stress and strain is: Stress = (I-damage) * elastic stiffness * (strain-plastic strain) Where I is the unit tensor; A VUMAT subroutine of the material constitutive relationship model is compiled based on the material subroutine interface provided by Abaqus software.

3. The method according to claim 1, characterized in that The acceleration strategy designed to accelerate material fatigue damage analysis includes: An acceleration strategy is designed to accelerate material fatigue damage analysis. The acceleration strategy includes the number of cycle jumps, which represents the time interval between the current analysis and the next analysis. Each extrapolation represents a jump in the structural performance state. The number of cycles = time * frequency of load application.

4. The method according to claim 3, characterized in that The method of establishing a finite element analysis model of the engineering structure in the Abaqus software and generating a reference INP file using the finite element analysis model includes: Establishing a finite element analysis model of an engineering structure in Abaqus software includes the following steps: (1) establishing all components included in the finite element analysis model; (2) establishing the material properties of all components; (3) assembling the components; (4) setting the analysis parameters; (5) establishing the contact mode between the components; (6) completing the setting of the model boundary conditions; (7) completing the unit division of the model components; The finite element analysis model is used to generate a fatigue damage analysis task for the engineering structure, and the VUMAT subroutine is called to complete the verification of the correctness of the finite element model. After executing this fatigue damage analysis task, a reference INP file for engineering fatigue damage analysis is generated, and the reference INP file contains basic information of a fatigue damage analysis task.

5. The method according to claim 4, characterized in that The use of the acceleration strategy to modify the reference INP file based on the results of the previous analysis, generate an analysis task based on the modified INP file, execute the analysis task, obtain the analysis result, and then modify the reference INP file based on the analysis result and the acceleration strategy, and so on, until the engineering structure fails, and the fatigue damage analysis result of the engineering structure is obtained, including: Abaqus software uses the acceleration strategy to modify the reference INP file based on the results of the previous analysis to obtain the INP file for this analysis, calls the VUMAT program and the INP file to generate the analysis task, submits and executes the analysis task, and generates an output database ODB result file containing the analysis results. The ODB result file includes the damage evolution information of the engineering structure at the current time node. According to the acceleration strategy, the number of cyclic jumps of the entire structure and the value of the state variable of the material unit after the jump are calculated, the calculated value of the material unit state variable after the jump is set as the initial value of the material unit state variable, and a new fatigue damage analysis task for the next round of execution is generated. Then, based on the analysis results and the acceleration strategy, the reference INP file is modified, and the above processing is repeated until the engineering structure fails and the stop condition of the fatigue damage analysis task is triggered. The final ODB result file is used as the fatigue damage analysis result of the engineering structure, and the force analysis results of the engineering structure at different time points are spliced ​​together to obtain the fatigue damage evolution process of the engineering structure.

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