Efficient Analysis Method for Material Plastic Deformation Based on Large-Span Double-Cycle Algorithm

Abstract

The present application discloses an efficient analysis method for material plastic deformation based on a large-span double-loop algorithm, which combines a small-time-step loop and a large-time-step loop through an adaptive time-step scheme. Among them, the small-time-step loop uses a constant time increment step to simulate the pinning and release of dislocations at obstacles, and finally obtains the equilibrium structure of dislocation pile-ups; on the basis of the small-time-step reaching equilibrium, the large-time-step loop introduces an increment factor to reasonably expand the step size, reduce redundant calculations, and evaluate dislocation escape or activation through a normalization parameter, and real-time monitor dislocation escape or new dislocation nucleation events. Once the trigger condition is reached, it will return to the small-time-step loop to ensure the accurate capture of key physical processes. This method takes into account both efficiency and accuracy, and significantly improves the computational performance of material plastic deformation simulation.

Description

Technical Field

[0001] The present application relates to the field of material science and technology, and in particular to an efficient material plastic deformation analysis method based on a large-span double-loop algorithm. Background Art

[0002] In the field of materials science, it is of vital importance to deeply understand and accurately simulate the plastic deformation behavior of materials. The plastic deformation of materials not only determines their forming properties during processing, but also directly affects the mechanical properties and service life of materials in practical engineering applications. For example, in high-end manufacturing industries such as aerospace, automobile manufacturing, and mechanical engineering, the strength, toughness, and fatigue performance of materials are extremely high. Accurately grasping the plastic deformation mechanism of materials helps optimize material design, improve processing technology, and ensure product reliability and safety.

[0003] At present, the simulation method based on dislocation dynamics is one of the important means to study the plastic deformation behavior of materials. As a kind of crystal defect in the material, the movement, proliferation and interaction of dislocations are the microscopic root causes of plastic deformation of the material. The introduction of the discrete dislocation dynamics (DDP) model of thermal activation and slip transfer can more carefully consider the interaction between dislocations and the internal microstructure of the material (such as obstacles, grain boundaries, etc.) and the influence of the thermal activation process on the movement of dislocations, thereby providing a more accurate physical model for simulating the plastic deformation behavior of materials.

[0004] However, existing simulation methods face many challenges in practical applications. On the one hand, the DDP model needs to consider different computational frameworks, involving complex physical processes and a large number of microscopic variables, with huge computational complexity and low computational efficiency. In the simulation process, traditional fixed time step algorithms often need to use extremely small time steps to ensure computational accuracy, which significantly increases the computational time. Especially for long time scales and large-scale simulation problems, the computational cost becomes unaffordable. On the other hand, the movement and interaction of dislocations inside the material are highly nonlinear and random. Under different loading conditions and microstructures, the behavior of dislocations varies greatly. Existing algorithms are difficult to accurately capture key physical processes such as the pinning and release of dislocations at obstacles and the nucleation of new dislocations, resulting in a certain deviation between the simulation results and the actual situation.

[0005] In actual engineering applications, due to the lack of efficient and accurate simulation methods, we can only rely on experience and a large number of experiments to optimize materials and processes, which not only consumes a lot of time and resources, but also makes it difficult to obtain the optimal design solution. Therefore, there is an urgent need to develop an algorithm that can quickly and accurately simulate the plastic deformation behavior of materials. Summary of the invention

[0006] This application provides an efficient analysis method for material plastic deformation based on a large-span double-loop algorithm, which significantly improves the calculation efficiency while ensuring the calculation accuracy.

[0007] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0008] In the first aspect, an embodiment of the present invention provides an efficient material plastic deformation analysis method based on a large-span dual-loop algorithm, including: obtaining material constants of a target material, the material constants including but not limited to geometric information, elastic modulus, Poisson's ratio, and dislocation mobility; simultaneously obtaining computational information required for simulation, the computational information including but not limited to deformation, load type, and accuracy requirements; constructing a dislocation dynamics geometric model according to the material constants and the computational information, and defining a slip plane in the geometric model according to the crystallographic characteristics of the target material, and randomly distributing dislocation sources and obstacles on the slip plane; initializing a matrix for storing dislocation motion trajectories, stress-strain data, and dislocation nucleation and escape time data in a main loop; setting a time for solving dislocation dynamics. The time step is used to simulate the pinning and release of dislocations at obstacles in a small time step cycle with a constant time increment. The dislocation is restricted from skipping or overlapping the previous dislocation, otherwise the dislocation movement speed is reduced according to the preset rules. When the dislocation reaches the free surface of the sample, it is moved to an effective infinity away from the sample. At the end of each small time step increment, it is checked whether the number of dislocations is the same as the previous increment, and whether the maximum dislocation movement increment is less than the threshold distance of the Burgers vector magnitude. If so, a large time step cycle is entered. After entering the large time step cycle, the time step is adjusted by introducing an increasing factor to keep the dislocation position unchanged. The shear stress on the front dislocation of the pile-up dislocation is calculated, and the thermal activation process is analyzed using the defined normalized parameter, which is expressed as:

[0009] ;

[0010] in, is the time it takes for the dislocation to be pinned and the stress to meet the pinning barrier condition, is the total time required for a dislocation to escape from an obstacle; when the normalized parameter reaches 1 or a dislocation source is activated, the main loop switches back to the small time step loop; during the small time step loop and the large time step loop, the dislocation nucleation and dislocation escape are continuously monitored to obtain the dislocation nucleation and escape time series; based on the obtained dislocation nucleation and escape time series, combined with the dislocation density change and stress-strain curve data obtained during the simulation process, the plastic deformation mechanism of the target material at different loading stages is analyzed.

[0011] In some possible implementations, in each incremental step of the small time step cycle, the dislocation velocity is calculated according to the mobility law of the target material, and the dislocation position is updated according to the calculated velocity.

[0012] In some possible implementations, when determining dislocation nucleation, dislocation nucleation is determined to have occurred after the shear stress in a local area of ​​the material exceeds the critical shear stress of the dislocation and the duration exceeds a dislocation nucleation time threshold.

[0013] In some possible implementations, when judging whether a dislocation has escaped, if the stress concentration factor around the dislocation exceeds a preset critical value and the normalized parameter is greater than 1, it is determined that the dislocation has escaped from the obstacle.

[0014] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0015] In the embodiment of the present invention, an adaptive time step scheme is used to combine a small time step cycle and a large time step cycle. Among them, the small time step cycle uses a constant time increment to simulate the pinning and release of dislocations at obstacles, and finally obtains a balanced structure of dislocation accumulation; the large time step cycle introduces an incremental factor to reasonably expand the step size on the basis of achieving equilibrium in the small time step, reduces redundant calculations, and evaluates dislocation escape or activation through normalized parameters, monitors dislocation escape or new dislocation nucleation events in real time, and falls back to the small time step cycle once the trigger condition is met, ensuring accurate capture of key physical processes. This method takes into account both efficiency and accuracy, and significantly improves the computational performance of material plastic deformation simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0017] Figure 1 A schematic flow chart of an embodiment of an efficient material plastic deformation analysis method based on a large-span double-loop algorithm provided for the implementation of the present invention;

[0018] Figure 2 4 is a flow chart of a large-span double-loop algorithm in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the relevant description of this embodiment, the terms "including, containing, having" and the like are open terms and are generally understood to include but not be limited to; the term "at least one" is generally understood to mean one or more, where "plurality" refers to two or more; the term "at least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items, for example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively; the symbol "A / B" is used to describe the selection relationship of associated objects, generally indicating an "or" relationship before and after.

[0021] In the following description of the present embodiment, the terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0022] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as also specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0024] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to these may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0026] In the field of materials science, it is of vital importance to deeply understand and accurately simulate the plastic deformation behavior of materials. The plastic deformation of materials not only determines their forming properties during processing, but also directly affects the mechanical properties and service life of materials in practical engineering applications. For example, in high-end manufacturing industries such as aerospace, automobile manufacturing, and mechanical engineering, the strength, toughness, and fatigue performance of materials are extremely high. Accurately grasping the plastic deformation mechanism of materials helps optimize material design, improve processing technology, and ensure product reliability and safety.

[0027] At present, the simulation method based on dislocation dynamics is one of the important means to study the plastic deformation behavior of materials. As a kind of crystal defect in the material, the movement, proliferation and interaction of dislocations are the microscopic root causes of plastic deformation of the material. The introduction of the discrete dislocation dynamics (DDP) model of thermal activation and slip transfer can more carefully consider the interaction between dislocations and the internal microstructure of the material (such as obstacles, grain boundaries, etc.) and the influence of the thermal activation process on the movement of dislocations, thereby providing a more accurate physical model for simulating the plastic deformation behavior of materials.

[0028] However, existing simulation methods face many challenges in practical applications. On the one hand, the DDP model needs to consider different computational frameworks, involving complex physical processes and a large number of microscopic variables, with huge computational complexity and low computational efficiency. In the simulation process, traditional fixed time step algorithms often need to use extremely small time steps to ensure computational accuracy, which significantly increases the computational time. Especially for long time scales and large-scale simulation problems, the computational cost becomes unaffordable. On the other hand, the movement and interaction of dislocations inside the material are highly nonlinear and random. Under different loading conditions and microstructures, the behavior of dislocations varies greatly. Existing algorithms are difficult to accurately capture key physical processes such as the pinning and release of dislocations at obstacles and the nucleation of new dislocations, resulting in a certain deviation between the simulation results and the actual situation.

[0029] In actual engineering applications, due to the lack of efficient and accurate simulation methods, we can only rely on experience and a large number of experiments to optimize materials and processes, which not only consumes a lot of time and resources, but also makes it difficult to obtain the optimal design solution. Therefore, there is an urgent need to develop an algorithm that can quickly and accurately simulate the plastic deformation behavior of materials.

[0030] Based on this, an embodiment of the present invention provides an efficient analysis method for material plastic deformation based on a large-span double-loop algorithm, which significantly improves the calculation efficiency while ensuring the calculation accuracy.

[0031] Figure 1 A schematic diagram of an embodiment of an efficient material plastic deformation analysis method based on a large-span double-loop algorithm provided for the implementation of the present invention is shown in FIG. Figure 1 As shown, the above method may include:

[0032] S101, obtaining material constants of the target material, including but not limited to geometric information, elastic modulus, Poisson's ratio, and dislocation mobility; and obtaining calculation information required for simulation, including but not limited to deformation, load type, and accuracy requirements;

[0033] Among them, geometric information can include the overall shape and size specifications of the target material, and can also go deep into the geometric characteristics of the internal microstructure of the material, such as the size, shape and distribution of grains. These micro-geometric characteristics can provide a deeper characterization of the internal stress transfer and dislocation movement path of the material. The elastic modulus is an indicator of the material's ability to resist elastic deformation. The elastic modulus of different materials varies greatly, which determines the difficulty of the material to produce elastic deformation under the same external force. Poisson's ratio reflects the proportional relationship between the lateral strain and the longitudinal strain of the material when it is subjected to stress, which is of great significance for analyzing the deformation behavior of the material under complex stress states. The numerical value of the dislocation mobility reflects the speed and ease of dislocation movement in the material lattice, which directly affects the rate and degree of plastic deformation of the material.

[0034] In addition, in the calculation information, the deformation refers to the quantitative characterization of the shape, size or structural changes of the target material under the action of external force or environment. There are many types of loads, the most common of which are tensile loads, compressive loads, bending loads and shear loads. Different types of loads applied to the material will cause completely different stress distributions and deformation patterns. For example, tensile loads will cause the material to stretch along the loading direction, compressive loads will cause the material to shorten, bending loads will cause the material to bend and deform, and shear loads will cause the material to shift between layers. The accuracy requirements are flexibly set according to the specific application scenarios and research depth of the simulation. For example, in fields such as aerospace and automobile manufacturing that have extremely high requirements for material performance, in order to ensure the safety and reliability of the product, higher accuracy requirements need to be set to capture subtle changes in the material deformation process; in some basic research or preliminary exploratory simulation work, the accuracy requirements can be appropriately relaxed to improve the calculation efficiency and reduce the calculation cost while ensuring the correct research direction.

[0035] S102, constructing a dislocation dynamics geometric model according to material constants and calculation information, defining a slip plane in the geometric model according to crystallographic characteristics of the target material, and randomly distributing dislocation sources and obstacles on the slip plane;

[0036] First, the model can be finely meshed according to the geometric information of the material. For materials with complex shapes, adaptive meshing technology can be used to encrypt the mesh in stress concentration areas or key locations, such as notches and corners of the material, to improve calculation accuracy; and in areas where stress changes are relatively gentle, the mesh density can be appropriately relaxed to balance calculation efficiency and accuracy. The elastic modulus and Poisson's ratio, as parameters of the material constitutive relationship, can be embedded in the mechanical calculation module of the dislocation dynamics geometry model to describe the elastic deformation behavior of the material when subjected to force, ensuring that the model can accurately simulate the elastic response of the material.

[0037] After the geometric model is constructed, the slip plane can be defined according to the crystallographic characteristics of the target material. The crystallographic characteristics are the embodiment of the atomic arrangement law inside the material. Different crystal structures have specific slip planes. By accurately analyzing the crystal structure of the target material, its slip plane is determined, and this information is accurately input into the constructed dislocation dynamics geometric model.

[0038] After defining the slip plane, dislocation sources and obstacles can be randomly distributed on the slip plane to more realistically simulate the complexity of the internal microstructure of the material. Among them, the dislocation source is the source of dislocation generation, and its random distribution simulates the uncertainty of the dislocation generation position during the actual production and processing of the material. Obstacles are used to simulate various factors that hinder the movement of dislocations inside the material, such as impurity atoms, second phase particles, grain boundaries, etc. By reasonably setting the distribution density, size and other parameters of dislocation sources and obstacles, the finite element model is closer to the microstructure of the real material, thereby improving the reliability of the simulation results. For example, for materials containing more impurities, the distribution density of obstacles can be appropriately increased; for materials that have been specially treated and have relatively concentrated dislocation sources, the distribution range and frequency of dislocation sources can be adjusted.

[0039] S103, in the main loop, initializing a matrix for storing dislocation motion trajectories, stress-strain data, and dislocation nucleation and escape time data;

[0040] Specifically, for the dislocation motion trajectory, a two-dimensional matrix can be created, with the number of rows preset to the maximum number of possible dislocations and the number of columns determined based on the total simulation time step. Each matrix element is used to record the three-dimensional coordinates of the corresponding dislocation at each time step to accurately track the movement path of the dislocation.

[0041] The matrix storing stress and strain data can be constructed in three dimensions. The first dimension corresponds to the nodes or units of the finite element model, which is used to distinguish different locations inside the material; the second and third dimensions represent the components of the stress-strain tensor respectively. During the simulation process, the stress-strain data calculated at each time step can be stored in the corresponding position of the matrix in a timely manner to record the changes of stress and strain at various locations of the material over time.

[0042] Two one-dimensional matrices can be initialized for dislocation nucleation and escape time data, respectively. The matrix lengths are set according to the estimated maximum number of dislocations. During the simulation, once a dislocation nucleation or escape event is detected, the corresponding time is recorded at the position of the corresponding dislocation in each matrix, thus providing time series data for subsequent studies of the microscopic mechanism of plastic deformation.

[0043] S104, setting the time step for solving the dislocation dynamics, simulating the pinning and release of the dislocation at the obstacle with a constant time increment in the small time step loop; wherein, the dislocation is restricted from skipping or overlapping the previous dislocation, otherwise the dislocation movement speed is reduced according to the preset rules; when the dislocation reaches the free surface of the sample, it is moved to an effective infinite distance away from the sample; at the end of each small time step increment, checking whether the number of dislocations is the same as the previous increment, and whether the maximum dislocation movement increment is less than the threshold distance of the Burgers vector magnitude, if satisfied, entering the large time step loop;

[0044] Specifically, the time step for solving the dislocation dynamics should be small enough to accurately capture the microscopic behavior details of the dislocation at the obstacle, but not too small to cause excessive computation and low computational efficiency. The specific time step can be set based on experience and a comprehensive consideration of the accuracy and efficiency of the algorithm. For example, the time step for solving the dislocation dynamics can be set to 0.5×10 -9 By setting an appropriate time step, it is possible to accurately simulate key processes such as the pinning and release of dislocations at obstacles while balancing the consumption of computing resources to a certain extent, thus ensuring the feasibility and efficiency of the entire simulation process.

[0045] After setting the time step, a small time step loop is entered, in which the pinning and release of dislocations at obstacles can be simulated with constant time increments.

[0046] It is understandable that the movement of dislocations inside the material is not unconstrained and free, but is affected by various factors, among which the interaction with the previous dislocation and the obstacles encountered have a limiting effect on its movement trajectory. In order to simulate this physical phenomenon more realistically, the algorithm can explicitly restrict dislocations from skipping or overlapping previous dislocations.

[0047] It should be noted that, since there are mutually repulsive or attractive forces between dislocations in actual materials, skipping or overlapping the previous dislocation is physically inconsistent with the actual situation. Once a dislocation is detected that violates this rule, the movement speed of the dislocation can be reduced according to the preset rules. The preset rules can be formulated based on the physical principles of dislocation interaction and a large amount of simulation experimental experience. The unreasonable movement of dislocations can be corrected by reducing the speed to make their movement state more consistent with the actual situation. For example, according to the theoretical model of dislocation interaction, when it is detected that dislocations have a tendency to skip or overlap, a new, lower speed value is calculated according to a formula related to the current speed and dislocation spacing, thereby ensuring the rationality of dislocation movement.

[0048] When dislocations move inside the material, it is also necessary to consider the situation where the dislocations reach the free surface of the specimen. In real materials, when dislocations reach the free surface, their behavior changes and affects the overall performance of the material. In order to accurately simulate this process, it can be stipulated in the algorithm that when dislocations reach the free surface of the specimen, they are moved to an effective infinity away from the sample. In this way, the interference caused by dislocations that disappear due to annihilation or escape from the free surface can be eliminated. By removing the dislocations that reach the free surface, the behavior of dislocations inside the material can be more clearly observed and analyzed, ensuring that the simulation results can accurately reflect the real situation inside the material.

[0049] In some embodiments, in each incremental step of the small time step cycle, the dislocation velocity may be calculated according to the mobility law of the target material, and the dislocation position may be updated according to the calculated velocity.

[0050] In the small time step cycle, at the end of each small time step increment, a key check operation must be performed. It mainly includes two aspects: one is to check whether the number of dislocations is the same as the previous increment, and the other is to check whether the maximum dislocation movement increment is less than the threshold distance of the Burgers vector magnitude. The change in the number of dislocations reflects the complex processes of dislocation proliferation and annihilation inside the material, while the maximum dislocation movement increment reflects the activity of the dislocation in the time step. The Burgers vector is an important physical quantity that describes the characteristics of dislocations. By comparing the maximum dislocation movement increment with the threshold distance of the Burgers vector magnitude, it can be determined whether the movement of the dislocation tends to be stable. If the number of dislocations is the same as the previous increment, and the maximum dislocation movement increment is less than the threshold distance of the Burgers vector magnitude, it means that under the current simulation conditions, the movement of dislocations at the obstacle has reached a relatively stable state, that is, the dislocations accumulate to form an equilibrium structure. At this point, it is considered that the simulation in the small time step cycle has completed a phased goal, and then enters the large time step cycle to further analyze the behavior of dislocations and the plastic deformation process of the material on a larger time scale. By combining this small time step cycle with a large time step cycle, we can not only accurately simulate the complex behavior of dislocations at the microscopic scale, but also grasp the overall trend of the plastic deformation of the material at the macroscopic scale, thereby achieving efficient and accurate simulation of the plastic deformation behavior of the material.

[0051] S105, after entering the large time step cycle, the time step is adjusted by introducing an increasing factor to keep the dislocation position unchanged; the shear stress on the front dislocation of the pile-up dislocation is calculated, and the thermal activation process is analyzed using the defined normalized parameter, which is expressed as:

[0052] ;

[0053] in, is the time that the dislocation is pinned and the stress meets the conditions for crossing the pinning barrier (for example, the stress magnitude meets the conditions required for the dislocation to escape), is the total time required for the dislocation to escape from the obstacle; when the normalized parameter reaches 1 or a dislocation source is activated, the main loop switches back to the small time step loop;

[0054] Specifically, after entering the large time step cycle, the time step can be adjusted by introducing an increasing factor. The increasing factor can be an empirical value obtained by a large number of simulation experiments or theoretical analysis in advance. By selecting an appropriate range of values ​​for the increasing factor, the time step can be significantly expanded, the amount of calculation can be reduced, and key information will not be lost due to excessive step size, which will affect the simulation accuracy.

[0055] While adjusting the time step, the dislocation position is kept unchanged. This is because the dislocation has reached a relatively stable state in the small time step cycle. Keeping its position unchanged at this time is conducive to focusing on analyzing the possibility of dislocation escaping from obstacles under thermal activation at the new time step without being disturbed by the change of dislocation position.

[0056] Next, calculate the shear stress on the front dislocation of the pileup dislocation. A pileup dislocation is a structure formed by multiple dislocations piled up in front of an obstacle. The shear stress on the front dislocation plays a key role in determining whether the dislocation can escape from the obstacle. When calculating the shear stress, it is necessary to comprehensively consider factors such as the crystal structure of the material, dislocation distribution, external stress field, and the nature of the obstacle.

[0057] Then, the thermal activation process was analyzed using the defined normalization parameters. The time starts from when the dislocation is pinned by the obstacle in the small time step cycle, and accumulates as the large time step cycle progresses; It is related to many factors such as the material's microstructure, temperature, stress state, etc. It is usually a characteristic time obtained through theoretical calculation or experimental data fitting. Normalized parameter The introduction of provides a quantitative indicator for judging the escape state of dislocation.

[0058] During the large time step cycle, the value of the normalized parameter and the activation of the dislocation source are continuously monitored. When the normalized parameter reaches 1, it means that the time after the dislocation is pinned has reached the total time required to escape from the obstacle. At this time, the dislocation has a high probability of being released from the obstacle, which will break the current equilibrium state of dislocation accumulation. In addition, if a dislocation source is activated during this process, the equilibrium state will also be broken. The activation of the dislocation source may be caused by factors such as thermal fluctuations and stress concentration. It will generate new dislocations and change the dislocation distribution and stress state inside the material.

[0059] Once dislocation nucleation or dislocation escape occurs, in order to accurately simulate the behavior after dislocation escape or dislocation source activation, it is necessary to trace back to the increment before the equilibrium is broken. This is because at the moment the equilibrium is broken, the state of the system changes suddenly, and the previous calculation based on the equilibrium state is no longer applicable. That is, within a large time step cycle, once dislocation nucleation or dislocation escape is detected, it can be traced back to a small time step cycle. By backtracking, you can return to a known stable state and re-simulate the behavior changes of dislocations in a small time step cycle. The main loop also switches back to the small time step cycle, and again uses a smaller time step to simulate in detail the microscopic processes such as the pinning and release of dislocations at obstacles, the movement of dislocations, and the interaction with other dislocations and obstacles, to ensure that the changes in dislocation behavior can be accurately captured, providing accurate data support for in-depth research on the plastic deformation mechanism of materials.

[0060] S106, during the small time step cycle and the large time step cycle, continuously monitor the dislocation nucleation and dislocation escape to obtain the dislocation nucleation and escape time series;

[0061] In some embodiments, when determining dislocation nucleation, when determining that the shear stress in a local area of ​​the material exceeds the critical shear stress of the dislocation and satisfies the crystallographic dislocation Burgers vector conservation and slip plane orientation conditions, it is determined that dislocation nucleation occurs;

[0062] In some embodiments, when judging dislocation escape, if the stress concentration factor around the dislocation exceeds a preset critical value, the normalized parameter is greater than a preset threshold, and the obstacle is of a weak pinning type, then the dislocation is judged to have escaped from the obstacle.

[0063] S107, analyzing the plastic deformation mechanism of the target material at different loading stages based on the obtained dislocation nucleation and escape time series and the dislocation density change and stress-strain curve data obtained during the simulation process.

[0064] Wherein, the dislocation nucleation and escape time series are obtained by the above-mentioned step S106, and in the process of simulating using the above-mentioned dislocation dynamics geometric model, the corresponding dislocation density change, stress-strain curve and other data can also be obtained. The dislocation nucleation and escape time series records the specific time of each dislocation nucleation and escape of the target material during the simulation process. By analyzing these time points, the generation and movement of dislocations at different times can be understood, such as whether there are a large number of dislocation nucleations at the initial stage of loading, and which time periods during the loading process dislocation escapes more frequently. Dislocation density refers to the total length of dislocation lines per unit volume. During the simulation process, as loading proceeds, dislocation density changes. An increase in dislocation density may mean that the nucleation rate of dislocations is greater than the annihilation rate, while a decrease in dislocation density may indicate that the annihilation of dislocations dominates. The stress-strain curve intuitively reflects the relationship between stress and strain of the material during the loading process. Different loading stages are represented by different slopes and characteristic points on the curve, such as elastic stage, yield point, strengthening stage and necking stage.

[0065] The following combination Figure 2 The above steps S101 to S107 are described in detail.

[0066] Figure 2 This is a flow chart of a large-span double-loop algorithm in an embodiment of the present invention, see Figure 2 As shown in the figure, first, input the material constants of the target material and the required calculation information to construct the dislocation dynamics geometric model. In the constructed combined model, define the slip plane and randomly distribute the dislocation sources and obstacles on the slip plane. Then, initialize the matrix used to store the dislocation motion trajectory, stress-strain data, and dislocation nucleation and escape time data, where: Figure 2 Zhongwei Current time, The total time required for plastic deformation.

[0067] First of all Initialize, Figure 2 In the expression: ;judge , a small time step loop is entered. Within the small time step loop, the pinning and release of dislocations at obstacles are simulated with constant time increments. For example, represents a constant time increment in a small time step cycle, expressed as:

[0068] ;

[0069] In each cycle of the small time step loop, the process described in step S104 is executed, and at the end of each small time step increment, it is determined whether there is a sudden change in stress and strain to determine whether it is balanced. If it is balanced, enter the large time step loop.

[0070] After entering the large time step cycle, the time step is adjusted by introducing an increasing factor. For a constant time increment in a large time step cycle, the current Assign value to , then Zoom in by a preset factor. Figure 2 middle express The magnification factor, It can be an empirical value or determined based on the needs of actual applications, expressed as:

[0071] .

[0072] In a large time step cycle, the new time step is expressed as:

[0073] ;

[0074] During the small time step cycle and the large time step cycle, the existence of dislocation nucleation and dislocation escape is continuously monitored to obtain the dislocation nucleation and escape time series.

[0075] Specifically, when dislocation nucleation or obstacle escape is detected, , the loop re-enters the small time step loop, otherwise, it is determined whether t is less than or equal to , if so, re-execute the large time step cycle, otherwise output the obtained dislocation nucleation and escape time series.

[0076] In the embodiment of the present invention, an adaptive time step scheme is used to combine a small time step cycle and a large event step cycle. The small time step cycle uses a constant time increment to simulate the pinning and release of dislocations at obstacles, and finally obtains a balanced structure of dislocation accumulation; the large time step cycle introduces an incremental factor to reasonably expand the step size on the basis of achieving equilibrium in the small time step, reduce redundant calculations, and improve calculation efficiency.

[0077] After obtaining the above data, the plastic deformation mechanism of the target material at different loading stages can be analyzed based on these data. Specifically, it may include:

[0078] In the initial stage of loading, the target material is in the elastic deformation region, and the stress and strain maintain a linear relationship. Plastic deformation has not yet occurred significantly at this stage because the external force has not yet reached a level sufficient to trigger the nucleation and movement of a large number of dislocations. The dislocation density remains relatively stable, indicating that the microstructure inside the material has not changed significantly. The plastic deformation mechanism at this stage is mainly the accumulation of elastic strain, and the direct cause of plastic deformation (i.e., significant activity of dislocations) has not yet appeared.

[0079] As stress increases, when the yield point is reached, the target material begins to enter the plastic deformation stage. At this point, dislocations begin to nucleate in large numbers and move rapidly along the slip plane, causing a sharp increase in dislocation density and forming plastic deformation. After yielding, as strain increases, the material enters the strengthening stage, and the interaction between dislocations becomes complex, forming structures such as dislocation entanglements and dislocation networks, which further hinder the movement of dislocations, thereby increasing the strength of the material. The formation mechanism of plastic deformation at this stage is mainly the proliferation, movement and interaction of dislocations, which together lead to significant changes in the internal microstructure of the material and the manifestation of macroscopic plasticity.

[0080] In the later stages of loading, as the strain continues to increase, necking begins to occur inside the material, indicating that the material is about to reach its plastic deformation limit. At this point, the dislocation density may reach a peak and begin to decline, as a large number of dislocations are annihilated in the necking region, which is usually accompanied by the formation and expansion of cracks. Eventually, when the crack runs through the entire material, the material breaks. The formation mechanism of plastic deformation at this stage is mainly the annihilation of dislocations, the initiation and expansion of cracks, which together lead to the failure of the material.

[0081] In summary, by analyzing the plastic deformation mechanism of the target material at different loading stages, we can not only reveal how the plastic deformation is gradually formed with the change of external load, but also gain an in-depth understanding of its microscopic mechanism (i.e., the nucleation, movement, interaction and annihilation of dislocations), thereby providing theoretical support for the performance optimization and application of materials.

[0082] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0083] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. An efficient material plastic deformation analysis method based on a large-span double-loop algorithm, characterized in that: include: Obtain material constants of the target material, including but not limited to geometric information, elastic modulus, Poisson's ratio, and dislocation mobility; and simultaneously obtain calculation information required for simulation, including but not limited to deformation, load type, and accuracy requirements; Constructing a dislocation dynamics geometric model according to the material constants and the calculated information, defining a slip plane in the geometric model according to the crystallographic characteristics of the target material, and randomly distributing dislocation sources and obstacles on the slip plane; In the main loop, the matrix used to store dislocation motion trajectory, stress-strain data, dislocation nucleation and escape time data is initialized; Set the time step for dislocation dynamics solution. In the small time step cycle, simulate the pinning and release of dislocations at obstacles with constant time increments. The dislocation is restricted from skipping or overlapping the previous dislocation, otherwise the dislocation movement speed is reduced according to the preset rules. When the dislocation reaches the free surface of the sample, it is moved to an effective infinity away from the sample. At the end of each small time step increment, check whether the number of dislocations is the same as the previous increment, and whether the maximum dislocation movement increment is less than the threshold distance of the Burgers vector magnitude. If so, enter the large time step cycle. After entering the large time step cycle, the time step is adjusted by introducing an increasing factor to keep the dislocation position unchanged; the shear stress on the front dislocation of the pile-up dislocation is calculated, and the thermal activation process is analyzed using the defined normalized parameter, which is expressed as: ； in, is the time it takes for the dislocation to be pinned and the stress to meet the pinning barrier condition, is the total time required for the dislocation to escape from the obstacle; when the normalized parameter reaches 1 or a dislocation source is activated, the main loop switches back to the small time step loop; During the small time step cycle and the large time step cycle, the dislocation nucleation and dislocation escape are continuously monitored to obtain the dislocation nucleation and escape time series; According to the obtained dislocation nucleation and escape time series, combined with the dislocation density change and stress-strain curve data obtained during the simulation process, the plastic deformation mechanism of the target material at different loading stages is analyzed.

2. The method according to claim 1, characterized in that In each incremental step of the small time step cycle, the dislocation velocity is calculated according to the mobility law of the target material, and the dislocation position is updated according to the calculated velocity.

3. The method according to claim 2, characterized in that When judging dislocation nucleation, when the shear stress in a local area of ​​the material exceeds the critical shear stress of the dislocation and the duration exceeds the dislocation nucleation time threshold, it is determined that dislocation nucleation occurs.

4. The method according to claim 3, characterized in that When judging the dislocation escape, if the stress concentration factor around the dislocation exceeds a preset critical value and the normalized parameter is greater than 1, it is determined that the dislocation escapes from the obstacle.

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