CN-121765819-B - Rail fatigue crack simulation method and system based on fracture phase field fatigue model

Abstract

The invention provides a method and a system for simulating fatigue cracks of a steel rail based on a fracture phase field fatigue model, which relate to the technical field of rail traffic structure safety and computational mechanics and comprise the steps of obtaining geometric, material and wheel-load parameters of the steel rail; the method comprises the steps of constructing a three-dimensional steel rail finite element model according to basic data, setting local encryption grids in key areas such as wheel-rail contact and the like, building a fracture phase field model capable of describing natural initiation and expansion of cracks on the basis of the local encryption grids, further integrating a fatigue degradation model, simulating crack resistance attenuation caused by fatigue to form a phase field fatigue coupling model, finally simulating mobile wheel load through envelope loading, and applying a cyclic transition strategy to perform efficient calculation to achieve accurate simulation of the initiation position, the expansion path and the damage field distribution of the fatigue cracks of the steel rail. The invention can naturally predict crack evolution and remarkably improve high cycle fatigue analysis efficiency.

Inventors

• XU JINGMANG
• YANG JIAN
• WANG KAI
• WANG PING
• Bai Taoshuo
• GAO WENFENG
• ZHU HUI

Assignees

• 西南交通大学

Dates

Publication Date

20260512

Application Date

20260305

Claims (6)

1. 1. A rail fatigue crack simulation method based on a fracture phase field fatigue model is characterized by comprising the following steps: Acquiring basic data of a railway steel rail, wherein the basic data comprises geometric parameters, material properties and wheel-load parameters of the steel rail, and the material properties are physical property test values of steel rail materials; Carrying out three-dimensional steel rail finite element model construction processing according to the basic data, and obtaining an optimized three-dimensional steel rail finite element model by establishing a three-dimensional finite element model comprising a steel rail head, a rail web and a rail bottom and setting local encryption grids in a wheel rail contact area and a potential crack initiation area; Performing fracture phase field model construction treatment according to the optimized three-dimensional steel rail finite element model to obtain a fracture phase field model capable of describing natural crack initiation and propagation; performing fatigue degradation model integration treatment according to the fracture phase field model, and obtaining a phase field fatigue coupling model containing a fatigue degradation mechanism by simulating the degradation of the cracking resistance caused by fatigue; carrying out rail fatigue crack evolution simulation treatment according to the phase field fatigue coupling model to obtain the initiation position, the propagation path and the damage field distribution result of the rail fatigue crack; The fatigue degradation model integration processing is performed according to the fracture phase field model, and the phase field fatigue coupling model containing a fatigue degradation mechanism is obtained by simulating the degradation of the cracking resistance caused by fatigue, and the fatigue degradation model integration processing comprises the following steps: carrying out fatigue accumulation variable initialization processing according to the fracture phase field model, introducing local fatigue life variable at each grid point of the phase field model, initializing to zero life variable to indicate no accumulated damage, and obtaining an initial phase field model containing the fatigue accumulation variable; Performing fracture toughness degradation function definition processing according to the initial phase field model containing the fatigue accumulation variables, and defining a fracture toughness degradation function by fatigue experiment data based on railway steel rail materials to obtain a phase field model with the degradation function; Carrying out fatigue degradation mechanism integration treatment according to the phase field model with the degradation function, enabling the evolution of the phase field variable to be modulated by a fatigue accumulation variable through embedding the fracture toughness degradation function into a fracture energy item in a phase field evolution equation, and simulating the damage progressive process of the steel rail under the cyclic load to obtain a phase field fatigue coupling model containing the fatigue degradation mechanism; the method for carrying out the rail fatigue crack evolution simulation processing according to the phase field fatigue coupling model comprises the following steps: carrying out rail movement wheel load simulation processing according to the phase field fatigue coupling model containing the fatigue degradation mechanism to obtain complete load historical data of single wheel set passing; Performing fatigue acceleration calculation processing according to the complete load historical data passing through the single wheel set, and performing transition for a preset number of cycles in a constant damage increment by applying a cycle transition strategy in a fatigue accumulation stable stage, and automatically reducing a preset transition step length when the difference value between a damage variable or a phase field variable and a preset failure threshold value is smaller than 0.1 to obtain accumulated damage field and phase field evolution results of the steel rail under the action of the cycle load; And carrying out crack evolution result extraction processing according to the accumulated damage field and the phase field evolution result, updating the fatigue accumulated variable and the historical field by solving the field variable of the displacement field and the phase field, and extracting the spatial distribution and the evolution process of the phase field variable to obtain the initiation position, the corresponding cycle number, the crack propagation path and the damage field distribution result of the fatigue crack of the steel rail.
2. 2. The method for simulating rail fatigue cracks based on a fracture phase field fatigue model according to claim 1, wherein the three-dimensional rail finite element model construction process is performed according to the basic data, and the method comprises the following steps: Carrying out construction processing on a steel rail geometric model according to the basic data, and obtaining an initial three-dimensional steel rail geometric model by extracting geometric parameters in the actual size measurement value of the steel rail and defining three-dimensional geometric shapes of the steel rail head, the rail web and the rail bottom based on the geometric parameters; Performing finite element mesh division processing according to the initial three-dimensional steel rail geometric model, and obtaining a three-dimensional steel rail finite element model with local encryption meshes by identifying special wheel rail contact areas and potential crack initiation areas of railway steel rails and arranging the local encryption meshes in the areas; And carrying out grid size optimization treatment according to the three-dimensional steel rail finite element model with the local encryption grid, and matching the size of the local encryption grid with the phase field length scale parameter to ensure that the grid size is less than or equal to one third of the phase field length scale parameter, thereby obtaining the three-dimensional steel rail finite element model with optimized grid size.
3. 3. The method for simulating the fatigue crack of the steel rail based on the fracture phase field fatigue model according to claim 1, wherein the fracture phase field model construction process is performed according to the optimized three-dimensional steel rail finite element model, and the method comprises the following steps: performing definition processing on phase field variables and driving functions according to the optimized three-dimensional steel rail finite element model, introducing phase field variables to represent the damage state of materials according to the wheel-rail contact stress distribution characteristics of the railway steel rail, and setting a driving function to be defined based on elastic strain energy density or a tensioning part thereof to obtain an initial phase field model; Performing threshold control mechanism integration processing according to the initial phase field model, and setting a driving function threshold by combining a railway steel rail high-cycle fatigue scene, wherein the phase field evolution is performed only when a local driving function is larger than the driving function threshold, so as to obtain a phase field model with threshold control; And carrying out historical field loading processing according to the phase field model with the threshold control, recording the maximum value of the driving function from the analysis start to the current moment through a preset historical field, and loading the historical field to the phase field model with the threshold control to obtain a fracture phase field model describing natural crack initiation and propagation.
4. 4. A rail fatigue crack simulation system based on a fracture phase field fatigue model, comprising: The system comprises an acquisition unit, a control unit and a control unit, wherein the acquisition unit is used for acquiring basic data of a railway steel rail, the basic data comprise geometric parameters, material properties and wheel-load parameters of the steel rail, and the material properties are physical property test values of steel rail materials; The construction unit is used for carrying out three-dimensional steel rail finite element model construction processing according to the basic data, and obtaining an optimized three-dimensional steel rail finite element model by establishing a three-dimensional finite element model comprising a steel rail head, a rail web and a rail bottom and setting local encryption grids in a wheel-rail contact area and a potential crack initiation area; the processing unit is used for constructing a fracture phase field model according to the optimized three-dimensional steel rail finite element model to obtain a fracture phase field model capable of describing natural initiation and expansion of cracks; The integration unit is used for carrying out fatigue degradation model integration treatment according to the fracture phase field model, and obtaining a phase field fatigue coupling model containing a fatigue degradation mechanism through simulating the degradation of the cracking resistance caused by fatigue; the simulation unit is used for carrying out rail fatigue crack evolution simulation treatment according to the phase field fatigue coupling model to obtain the initiation position, the propagation path and the damage field distribution result of the rail fatigue crack; wherein the integrated unit comprises: The first integration subunit is used for carrying out fatigue accumulation variable initialization processing according to the fracture phase field model, introducing local fatigue life variables into each grid point of the phase field model, initializing to zero life variables to indicate no accumulated damage, and obtaining an initial phase field model containing the fatigue accumulation variables; the second integrated subunit is used for carrying out fracture toughness degradation function definition processing according to the initial phase field model containing the fatigue accumulation variable, and defining the fracture toughness degradation function based on fatigue experimental data of the railway steel rail material to obtain a phase field model with the degradation function; The third integration subunit is used for carrying out fatigue degradation mechanism integration treatment according to the phase field model with the degradation function, enabling the evolution of the phase field variable to be modulated by a fatigue accumulation variable through embedding the fracture toughness degradation function into a fracture energy item in a phase field evolution equation, and simulating the damage progressive process of the steel rail under the cyclic load to obtain a phase field fatigue coupling model containing the fatigue degradation mechanism; wherein the simulation unit includes: The first simulation subunit is used for carrying out rail movement wheel load simulation processing according to the phase field fatigue coupling model containing the fatigue degradation mechanism to obtain complete load historical data of single wheel set passing; The second simulation subunit is used for performing fatigue acceleration calculation processing according to the complete load historical data passed by the single wheel set, performing transition for a preset number of cycles in a constant damage increment by applying a cycle transition strategy in a fatigue accumulation and stabilization stage, and automatically reducing a preset transition step length when the difference value between a damage variable or a phase field variable and a preset failure threshold value is smaller than 0.1, so as to obtain accumulated damage field and phase field evolution results of the steel rail under the action of the cycle load; And the third simulation subunit is used for extracting and processing crack evolution results according to the accumulated damage field and the phase field evolution results, updating the fatigue accumulated variable and the historical field by solving the field variables of the displacement field and the phase field, and extracting the spatial distribution and the evolution process of the phase field variable to obtain the initiation position, the corresponding cycle number, the crack propagation path and the damage field distribution result of the fatigue crack of the steel rail.
5. 5. The rail fatigue crack simulation system based on the fracture phase field fatigue model according to claim 4, wherein the construction unit comprises: The first construction subunit is used for carrying out construction processing on the geometric model of the steel rail according to the basic data, and obtaining an initial three-dimensional geometric model of the steel rail by extracting geometric parameters in the actual dimension measurement value of the steel rail and defining three-dimensional geometric shapes of the head part, the web and the bottom of the steel rail based on the geometric parameters; The second construction subunit is used for carrying out finite element mesh division processing according to the initial three-dimensional steel rail geometric model, and obtaining a three-dimensional steel rail finite element model with local encryption meshes by identifying special wheel rail contact areas and potential crack initiation areas of the railway steel rail and arranging the local encryption meshes in the areas; and the third construction subunit is used for carrying out grid size optimization processing according to the three-dimensional steel rail finite element model with the local encryption grid, and matching the size of the local encryption grid with the phase field length scale parameter to ensure that the grid size is less than or equal to one third of the phase field length scale parameter so as to obtain the three-dimensional steel rail finite element model with optimized grid size.
6. 6. The rail fatigue crack simulation system based on a fracture phase field fatigue model according to claim 4, wherein the processing unit comprises: The first processing subunit is used for defining and processing phase field variables and driving functions according to the optimized three-dimensional steel rail finite element model, introducing phase field variable representation material damage states according to wheel-rail contact stress distribution characteristics of the railway steel rail, and setting a driving function to be defined based on elastic strain energy density or tensioning parts of the driving function to obtain an initial phase field model; The second processing subunit is used for carrying out threshold control mechanism integration processing according to the initial phase field model, setting a driving function threshold value by combining a railway steel rail high-cycle fatigue scene, wherein the phase field evolution is carried out only when the local driving function is larger than the driving function threshold value, and a phase field model with threshold value control is obtained; And the third processing subunit is used for carrying out historical field loading processing according to the phase field model with the threshold control, recording the maximum value of the driving function from the analysis start to the current moment through a preset historical field, and loading the historical field to the phase field model with the threshold control to obtain a fracture phase field model describing the natural initiation and the expansion of the crack.

Description

Rail fatigue crack simulation method and system based on fracture phase field fatigue model Technical Field The invention relates to the technical field of rail transit structure safety and computational mechanics, in particular to a rail fatigue crack simulation method and system based on a fracture phase field fatigue model. Background In the fields of rail traffic structure safety and computational mechanics, the accurate prediction of fatigue cracks of a steel rail serving as a key component for directly bearing train wheel load is always a core difficult problem for guaranteeing operation safety. Because the rail bears high-frequency cyclic movement load in the long-term service process, fatigue cracks are easy to initiate and expand in the rail, and the damage behavior has the complex characteristics of no-to-no, uncertain path and multiple occurrence on the subsurface. The traditional crack simulation method mainly depends on fracture mechanics of preset initial cracks or numerical technology requiring grid repartition, when the method is used for coping with complex three-dimensional structures such as steel rails, the crack initiation process is difficult to naturally describe, topological changes such as path bifurcation which possibly occurs in crack propagation cannot be effectively processed, meanwhile, the existing method is difficult to meet the actual solving requirement of engineering due to low calculation efficiency in face of huge cycle times involved in high-cycle fatigue analysis. Therefore, development of a rail fatigue crack simulation method capable of naturally describing crack initiation and propagation and efficiently treating high-cycle fatigue problems becomes a technical bottleneck to be broken through in the field. Disclosure of Invention The invention aims to provide a rail fatigue crack simulation method and system based on a fracture phase field fatigue model, so as to solve the problems. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: in a first aspect, the application provides a method for simulating fatigue cracks of a steel rail based on a fracture phase field fatigue model, comprising the following steps: Acquiring basic data of a railway steel rail, wherein the basic data comprises geometric parameters, material properties and wheel-load parameters of the steel rail, and the material properties are physical property test values of steel rail materials; Carrying out three-dimensional steel rail finite element model construction processing according to the basic data, and obtaining an optimized three-dimensional steel rail finite element model by establishing a three-dimensional finite element model comprising a steel rail head, a rail web and a rail bottom and setting local encryption grids in a wheel rail contact area and a potential crack initiation area; Performing fracture phase field model construction treatment according to the optimized three-dimensional steel rail finite element model to obtain a fracture phase field model capable of describing natural crack initiation and propagation; performing fatigue degradation model integration treatment according to the fracture phase field model, and obtaining a phase field fatigue coupling model containing a fatigue degradation mechanism by simulating the degradation of the cracking resistance caused by fatigue; And carrying out rail fatigue crack evolution simulation processing according to the phase field fatigue coupling model to obtain the distribution results of the initiation position, the propagation path and the damage field of the rail fatigue crack. In a second aspect, the present application also provides a rail fatigue crack simulation system based on a fracture phase field fatigue model, including: The system comprises an acquisition unit, a control unit and a control unit, wherein the acquisition unit is used for acquiring basic data of a railway steel rail, the basic data comprise geometric parameters, material properties and wheel-load parameters of the steel rail, and the material properties are physical property test values of steel rail materials; The construction unit is used for carrying out three-dimensional steel rail finite element model construction processing according to the basic data, and obtaining an optimized three-dimensional steel rail finite element model by establishing a three-dimensional finite element model comprising a steel rail head, a rail web and a rail bottom and setting local encryption grids in a wheel-rail contact area and a potential crack initiation area; the processing unit is used for constructing a fracture phase field model according to the optimized three-dimensional steel rail finite element model to obtain a fracture phase field model capable of describing natural initiation and expansion of cracks; The integration unit is used for carrying out fatigue degradation model integration treatment according to the fra