Evolutionary flow stress-strain model determination method and related equipment

Abstract

The invention discloses an evolutionary flow stress-strain model determination method and related equipment, and relates to the technical field of plate stamping forming, and the method comprises the steps: constructing an initial flow stress-strain model; a strain hardening index relational expression is determined, and the strain hardening index relational expression is determined based on the corresponding relation between the strain hardening index and the real strain data; and an evolutionary flow stress-strain model is determined based on the strain hardening index relational expression and the initial flow stress-strain model, and the evolutionary flow stress-strain model is used for fitting a metal material flow stress and strain relation curve.

Description

Technical Field

[0001] This application relates to the technical field of sheet metal stamping forming, and particularly to a method for determining an evolutionary flow stress-strain model and related equipment. Background Art

[0002] In the field of metal sheet stamping forming, the flow stress-strain characteristics of materials are the core parameters for evaluating their plastic deformation ability and forming performance. Usually, the construction of the flow stress-strain curve depends on mathematical models with fixed strain hardening exponents (such as the Hollomon model). These traditional models have been widely adopted in engineering applications due to their simplicity and ease of use. However, since the dynamic evolution characteristics of the strain hardening exponent during the deformation process are not considered, these models are difficult to accurately describe the hardening behavior of metal materials within the true strain range, resulting in low fitting accuracy, especially showing significant limitations when dealing with complex materials such as high-strength steel and aluminum alloy.

[0003] In addition, with the continuous emergence of new metal materials, their hardening behaviors often exhibit non-linear and complex characteristics, and traditional fixed-parameter models are no longer able to meet the characterization requirements of these materials. In engineering practice, ignoring the dynamic changes in the hardening behavior may lead to an increase in the prediction error of the stamping process, thus affecting the accuracy of process design and quality control. Therefore, there is an urgent need for a method for determining an evolutionary flow stress-strain model that can accurately capture the change law of the hardening behavior of metal sheets. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further elaborated in the Detailed Description section. The Summary of the Invention section of this application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] In a first aspect, this application provides a method for determining an evolutionary flow stress-strain model, including:

[0006] Construct an initial flow stress-strain model;

[0007] Determine a strain hardening exponent relationship, where the strain hardening exponent relationship is determined based on the correspondence between the strain hardening exponent and true strain data;

[0008] Determine an evolutionary flow stress-strain model based on the strain hardening exponent relationship and the initial flow stress-strain model, where the evolutionary flow stress-strain model is used to fit the curve of the relationship between the flow stress and strain of the metal material.

[0009] In a feasible implementation manner, the above initial flow stress-strain model includes the Hollomon model, the Swift model, and the Voce model.

[0010] In a feasible implementation manner, the above determination of the strain hardening exponent relationship includes:

[0011] Construct an engineering data curve;

[0012] Based on the above engineering data curve, determine the true data curve;

[0013] Based on the above true data curve, determine the logarithmic true data curve;

[0014] Based on the strain hardening exponent and the above true strain data, determine the strain hardening exponent relationship, where the above strain hardening exponent is the slope of the above logarithmic true data curve.

[0015] In a feasible implementation manner, the above strain hardening exponent relationship is determined according to the fitting operation of the evolution law of the above strain hardening exponent with respect to the above true strain data, where the fitting relationship corresponding to the above evolution law fitting operation includes a linear function, a polynomial function, a power function, and an exponential function.

[0016] In a feasible implementation manner, the above engineering data curve is a curve of the corresponding relationship between engineering stress data and engineering strain data, where the above engineering stress data and the above engineering strain data are obtained by performing a uniaxial tensile test on the metal material to be characterized.

[0017] In a feasible implementation manner, the above true data curve is a curve of the corresponding relationship between true stress data and true strain data, and the above logarithmic true data curve is a curve of the corresponding relationship between logarithmic true stress data and logarithmic true strain data.

[0018] In a feasible implementation manner, it further includes:

[0019] Perform long-term tracking and monitoring on the hardening behavior of the metal material, and update the model parameters of the above evolution flow stress-strain model based on the true stress data and true strain data measured at different time points;

[0020] According to the updated model parameters, draw an evolution curve of the hardening behavior to provide a dynamic characterization result.

[0021] In a second aspect, the present application proposes an evolution flow stress-strain model determination device, including:

[0022] An initial model construction unit for constructing an initial flow stress-strain model;

[0023] An evolution relationship determination unit is configured to determine a strain hardening index relationship formula, where the strain hardening index relationship formula is determined based on the correspondence between the strain hardening index and the true strain data;

[0024] An evolution model determination unit is configured to determine an evolution flow stress-strain model based on the strain hardening index relationship formula and the initial flow stress-strain model, where the evolution flow stress-strain model is used to fit the curve of the flow stress and strain relationship of the metal material.

[0025] In a third aspect, an electronic device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program stored in the memory, the steps of the evolution flow stress-strain model determination method according to any one of the first aspects are implemented.

[0026] In a fourth aspect, the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the evolution flow stress-strain model determination method according to any one of the first aspects is implemented.

[0027] In summary, through the introduction of the evolution law of the strain hardening index, the embodiments of the present application establish a more accurate flow stress-strain model, significantly improving the characterization ability of the hardening behavior of metal materials. Compared with the traditional fixed strain hardening index model, the present invention can dynamically fit the relationship between the strain hardening index and the true strain, making the flow stress-strain model closer to the actual deformation characteristics of the material, thereby greatly improving the fitting accuracy and characterization accuracy of the model. In addition, the present invention is compatible with a variety of flow stress-strain models, has strong flexibility and applicability, and can meet the characterization requirements of the hardening behavior of different metal materials. Through experimental verification of new metal materials such as high-strength steel and aluminum alloy, it is shown that the method can effectively reduce the model fitting error, further improve the description ability of the hardening behavior of complex materials, provide a scientific basis for the optimization of the metal sheet stamping forming process and quality control, and has important engineering application value and promotion potential. Description of the Drawings

[0028] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this specification. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0029] Figure 1 It is a schematic flow chart of an evolution flow stress-strain model determination method provided by an embodiment of the present application;

[0030] Figure 2Schematic diagram of the true stress-true strain curve of DC56D provided by the embodiment of the present application;

[0031] Figure 3 Schematic diagram of the logarithmic true stress-logarithmic true strain curve of DC56D provided by the embodiment of the present application;

[0032] Figure 4 Schematic diagram of the comparison between the evolution behavior of the strain hardening index of DC56D material predicted based on the mathematical expression and the test provided by the embodiment of the present application;

[0033] Figure 5 Schematic diagram of the characterization of the hardening behavior of DC56D material by different flow stress-strain models provided by the embodiment of the present application;

[0034] Figure 6 Schematic diagram of the true stress-true strain curve of DP980 provided by the embodiment of the present application;

[0035] Figure 7 Schematic diagram of the logarithmic true stress-logarithmic true strain curve of DP980 provided by the embodiment of the present application;

[0036] Figure 8 Schematic diagram of the comparison between the evolution behavior of the strain hardening index of DP980 material predicted based on the mathematical expression and the test provided by the embodiment of the present application;

[0037] Figure 9 Schematic diagram of the characterization of the hardening behavior of DP980 material by different flow stress-strain models provided by the embodiment of the present application;

[0038] Figure 10 Schematic diagram of the structure of a device for determining an evolutionary flow stress-strain model provided by the embodiment of the present application;

[0039] Figure 11 Schematic diagram of the structure of an electronic device for determining an evolutionary flow stress-strain model provided by the embodiment of the present application. Detailed implementation manners

[0040] In the description and claims of this application and the above-mentioned drawings, terms such as "first", "second", "third", "fourth", etc. (if any) are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices. The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments.

[0041] Please refer to Figure 1 , which is a schematic flowchart of a method for determining an evolutionary flow stress-strain model provided by an embodiment of this application, and specifically may include:

[0042] S110. Construct an initial flow stress-strain model;

[0043] Exemplarily, the selection of the initial flow stress-strain model should be based on the deformation characteristics of the material to be characterized and specific application requirements. Common initial models include the Hollomon model, the Swift model, and the Voce model. Among them, the Hollomon model is widely used for its simplicity and computational efficiency and is suitable for characterizing the hardening behavior of various common metal materials.

[0044] The construction of the initial flow stress-strain model is a macroscopic reflection of the internal microstructure changes of metal materials during plastic deformation. When a material is under an external force, it will go through an elastic stage and a plastic stage. In the plastic stage, the stress-strain relationship shows non-linear growth. This non-linear growth is affected by changes in the dislocation density, grain rearrangement, and accumulation of micro-defects within the material. Therefore, the mathematical expression of the initial model is actually a fitting of the changes in the material's microstructure to its macroscopic mechanical behavior.

[0045] When constructing the model, it is necessary to assume that the hardening behavior can be characterized by simple parameters, which reflect the material's resistance to deformation and its changing law. By selecting a suitable initial model, a stable framework can be provided for the improved model that will subsequently incorporate the evolution characteristics of the strain hardening exponent.

[0046] S120. Determine the strain hardening exponent relationship, where the strain hardening exponent relationship is determined based on the corresponding relationship between the strain hardening exponent and the true strain data;

[0047] Exemplarily, the strain hardening index is an important parameter describing the hardening behavior of materials, reflecting the sensitivity of true stress to the change in true strain. Specifically, the strain hardening index is defined as the slope of the true stress-true strain relationship in the logarithmic coordinate system, representing the response strength of the material to the strain hardening effect during the plastic deformation stage. At different true strain stages, the microstructure of the material (such as dislocation density, grain orientation, etc.) evolves, resulting in dynamic changes in the hardening behavior. Therefore, the strain hardening index is no longer a fixed value but a dynamic function that changes with true strain.

[0048] The determination of the strain hardening index relationship depends on the true stress-true strain data obtained from experiments and the logarithmic true stress-logarithmic true strain data processed based on these data. Through experimental methods such as uniaxial tensile tests, engineering stress and engineering strain data are first obtained and further converted into true stress and true strain data. Then, the logarithmic true stress and logarithmic true strain curves are plotted in the logarithmic coordinate system, and the strain hardening index at different true strains is calculated according to the trend of the curve slope change.

[0049] S130. Determine the evolving flow stress-strain model based on the above strain hardening index relationship and the above initial flow stress-strain model, where the evolving flow stress-strain model is used to fit the curve of the flow stress and strain relationship of metallic materials.

[0050] Exemplarily, the evolving flow stress-strain model is a model constructed by dynamically adjusting the hardening parameters in combination with the strain hardening index relationship on the basis of the initial flow stress-strain model. Traditional initial models usually assume that the strain hardening index is a fixed value, while the evolving model can dynamically adapt to the changes in the hardening behavior of materials within the true strain range by introducing the evolution law of the strain hardening index.

[0051] The hardening behavior of metallic materials refers to the phenomenon that the strength of the material gradually increases with the increase of deformation during the plastic deformation process. The hardening behavior is affected by the evolution of the internal microstructure (such as dislocation multiplication, grain rearrangement, precipitation strengthening, etc.), and has a direct impact on the forming performance and mechanical properties of the material. Through the evolving flow stress-strain model, it is possible to quantitatively describe the change law of true stress with true strain; analyze the hardening mechanism of the material at different strain stages, such as linear hardening, exponential hardening or saturation hardening; provide mechanical property prediction, providing a basis for process optimization and quality control in the material forming process.

[0052] The characterization results are the product of fitting the evolutionary flow stress-strain model to experimental data, usually including model parameters determined by fitting the experimental data, which can quantitatively reflect the hardening characteristics of the material; evaluating the accuracy of the model through the correlation between the fitting curve and the experimental data; and the true stress-true strain curve plotted based on the evolutionary model, intuitively showing the whole process of the material's hardening behavior.

[0053] In summary, in the embodiments of the present application, by introducing the evolutionary law of the strain hardening exponent, a more accurate flow stress-strain model is established, significantly improving the characterization ability of the hardening behavior of metallic materials. Compared with the traditional fixed strain hardening exponent model, the present invention can dynamically fit the relationship between the strain hardening exponent and the true strain, making the flow stress-strain model closer to the actual deformation characteristics of the material, thereby greatly improving the fitting accuracy and characterization accuracy of the model. In addition, the present invention is compatible with a variety of flow stress-strain models, has strong flexibility and applicability, and can meet the characterization requirements of the hardening behavior of different metallic materials.

[0054] In some examples, the above initial flow stress-strain model includes, but is not limited to, the Hollomon model, the Swift model, and the Voce model.

[0055] Exemplarily, the initial flow stress-strain model is a basic tool for characterizing the hardening behavior of metallic materials, and its core role is to describe the relationship between the true stress and the true strain of the material in the plastic deformation stage. According to the specific material characteristics and application requirements, classical models that are suitable for the material characteristics of metallic materials and have strong applicability are usually selected, such as the Hollomon model, the Swift model, and the Voce model. These models describe the hardening characteristics of the material through different mathematical forms and adapt to the deformation behaviors of different types of materials.

[0056] The Hollomon model assumes that the stress-strain relationship of the material in the entire plastic deformation stage conforms to the power function law, and is applicable to ordinary metallic materials with relatively simple hardening behaviors and relatively stable strain hardening exponents (such as low-carbon steel and certain aluminum alloys). Due to its simple mathematical form and clear physical meaning of the parameters, it is widely used in engineering applications. The Hollomon model does not consider the initial plastic deformation stage or strain saturation behavior, so there may be deviations when characterizing some high-strength metallic materials or complex hardening behaviors.

[0057] The Swift model effectively describes the mechanical behavior of metallic materials in the initial plastic deformation stage by introducing the initial strain. It is particularly applicable to some materials that need to consider the pre-strain effect (such as steel with a certain amount of plastic deformation during the rolling process). At the same time, it can more accurately describe the hardening behavior of high-strength metallic materials. The Swift model is suitable for characterizing the hardening behavior of materials from initial loading to high strain ranges, but the model complexity increases relatively, and the fitting process may require more experimental data support.

[0058] The Voce model can well describe the phenomenon that the hardening behavior of some metal materials tends to be stable in the high-strain stage by introducing the concept of saturation stress. It is widely used in superalloys and some metal materials with significant stress saturation characteristics. The Voce model is suitable for describing complex hardening behaviors, but it has more parameters and a complex mathematical form, usually requiring high-precision experimental data support.

[0059] In some embodiments, determining the strain hardening exponent relationship includes:

[0060] Construct an engineering data curve, where the engineering data curve is a curve of the correspondence between engineering stress data and engineering strain data, and the engineering stress data and the engineering strain data are obtained by performing a uniaxial tensile test on the metal material to be characterized;

[0061] Based on the above engineering data curve, determine the true data curve;

[0062] Based on the above true data curve, determine the logarithmic true data curve, where the true data curve is a curve of the correspondence between true stress data and true strain data, and the logarithmic true data curve is a curve of the correspondence between logarithmic true stress data and logarithmic true strain data;

[0063] Based on the strain hardening exponent and the above true strain data, determine the strain hardening exponent relationship, where the strain hardening exponent is the slope of the above logarithmic true data curve.

[0064] Exemplarily, determining the strain hardening exponent relationship is a key link in the method for determining the evolving flow stress-strain model. The purpose is to analyze and extract the dynamic evolution law of the strain hardening exponent from the stress and strain data obtained through experiments, and establish a relationship between the strain hardening exponent and the true strain through mathematical fitting.

[0065] The engineering stress data and the engineering strain data are obtained by a uniaxial tensile test. This test is a standardized test method that measures the deformation behavior of a metal material by applying a tensile load. The engineering stress recorded in the test is the ratio of the force acting on the cross-sectional area of the material to the original cross-sectional area, and the engineering strain is the ratio of the change in the tensile length to the original length. The engineering data curve is a curve of the relationship between engineering stress and engineering strain, which reflects the overall behavior of the metal material from elastic deformation to plastic deformation during the tensile process. This curve serves as the initial basis for data analysis and cannot be directly used for modeling because its stress and strain are based on the original dimensions of the material rather than the instantaneous deformation state.

[0066] After converting the engineering data curve into a true data curve, it can more accurately reflect the mechanical behavior of metal materials during plastic deformation. The true stress-true strain curve describes the corresponding relationship between stress and strain in the instantaneous deformation state and is the basis for characterizing the material's hardening behavior. In a logarithmic coordinate system, taking the logarithms of the true stress and true strain respectively gives the logarithmic true stress and logarithmic true strain. This can linearize the originally non-linear relationship and facilitate the analysis of the changing trend of the strain hardening index. The slope of the logarithmic true data curve is the strain hardening index, which represents the dynamic change of the hardening rate of the material during deformation. Through this curve, the evolution law of the strain hardening index with the true strain can be observed, providing a data basis for establishing a mathematical relationship.

[0067] The strain hardening index is the derivative of the logarithmic true stress with respect to the logarithmic true strain. By differentiating or piecewise linearly fitting the logarithmic true data curve, the strain hardening index at different true strain values can be obtained. Based on the corresponding relationship between the strain hardening index and the true strain, a suitable mathematical form (such as a linear function, polynomial function, power function, or exponential function) is selected for fitting. The fitted mathematical relationship can accurately describe the dynamic change of the strain hardening index with the true strain.

[0068] In some examples, the above strain hardening index relationship is determined according to the above evolution law fitting operation of the strain hardening index with respect to the above true strain data, where the fitting relationship corresponding to the above evolution law fitting operation includes a linear function, polynomial function, power function, and exponential function.

[0069] Exemplarily, linear function fitting is applicable to materials where the strain hardening index varies linearly with true strain, and is generally suitable for metallic materials with simple hardening behavior and a relatively slow change in the hardening index. Linear fitting describes the evolution of the hardening index through a simple linear change, can quickly provide an approximate hardening law. The initial parameter can approximately reflect the hardening strength in the initial plastic stage, while the slope reflects the linear trend of the hardening rate of the material during deformation. Polynomial function fitting is applicable to materials with complex non-linear evolution trends of the hardening index, and can capture the subtle changes in the hardening behavior of the material during multi-stage deformation. Polynomial fitting improves the fitting flexibility by increasing the number of terms and can more accurately describe the complex change law of the hardening index. It is particularly applicable to scenarios where the strain hardening index exhibits obvious non-linear changes, such as the presence of inflection points or multi-stage trends. Power function fitting is applicable to materials where the hardening index increases or decreases exponentially with true strain, and is commonly used to characterize high-strength metallic materials with a rapid change in the strain hardening index. Power function fitting can capture the rapid change trend of the hardening index in the initial stage of strain, and can also reflect the behavior that tends to be stable in the high-strain stage. This model is particularly effective when dealing with materials with strong non-linear characteristics. Exponential function fitting is applicable to materials where the change rate of the hardening index gradually decreases and tends to saturation, and is commonly used to describe the process where the hardening behavior of the material tends to be stable in a large strain range. Exponential function fitting can effectively describe the behavior that the strain hardening index rapidly increases in the initial stage and gradually tends to be stable or saturated. This model plays an important role in the deformation analysis of high-strength materials because it can capture the saturation phenomenon of the hardening behavior.

[0070] In some examples, the above-mentioned evolution flow stress-strain model is used to characterize the hardening behavior of metallic materials, and the characterization results include:

[0071] Based on the above-mentioned evolution flow stress-strain model, fitting is performed on the true data curve to obtain the model parameters of the above-mentioned evolution flow stress-strain model;

[0072] Based on the above-mentioned model parameters, a flow stress-strain curve is plotted to characterize the hardening behavior of metallic materials, and the characterization results are obtained.

[0073] Exemplarily, the true stress-true strain curve is obtained by converting experimental data (engineering stress and strain), and it is closer to the actual mechanical behavior of metallic materials, capable of reflecting the change in the instantaneous resistance of the material during the deformation process. The evolution model is a mathematical model established based on the initial flow stress-strain model by combining the dynamic strain hardening exponent relationship. By fitting the true stress-true strain curve obtained from experiments with the evolution model, the key parameters in the model can be determined. These parameters not only describe the hardening characteristics of the material but also provide a basis for plotting the flow stress-strain curve. The fitting process usually adopts numerical optimization algorithms (such as the least squares method), and by adjusting the model parameters, the stress values calculated by the model are made as close as possible to the experimental data. The quality of the fitting can be evaluated by the correlation coefficient index.

[0074] In some examples, it also includes:

[0075] According to the comparison between the above characterization results and the fitting results of the above initial flow stress-strain model, the fitting accuracy of the above evolution flow stress-strain model is evaluated.

[0076] Exemplarily, the hardening behavior of metallic materials is complex and dynamic. Traditional initial flow stress-strain models usually assume that the hardening exponent is a fixed value. Although this assumption simplifies the calculation, significant errors may occur when dealing with the dynamic hardening behavior of complex materials (such as high-strength steel).

[0077] The evolution flow stress-strain model can more accurately describe the evolution characteristics of the hardening behavior within different true strain ranges by introducing the dynamic strain hardening exponent relationship. However, this improvement needs to be compared with the fitting results of the initial model to evaluate the improvement in accuracy and applicability of the evolution model.

[0078] The fitting curve of the fixed hardening exponent based on the initial flow stress-strain model can describe the basic hardening trend but may deviate from the experimental data within complex strain ranges. The fitting curve of the evolution model combined with the dynamic hardening exponent can better fit the experimental data within the true strain range. By comparing the coincidence degrees of the two fitting curves with the experimental data curve, the improvement effect of the evolution model can be visually observed.

[0079] The correlation coefficient is a commonly used fitting accuracy evaluation index, indicating the degree of interpretation of the fitting model to the experimental data. The closer the correlation coefficient is to 1, the better the model fitting. By comparing the correlation coefficients of the initial model and the evolution model, the degree of model improvement can be quantified. By plotting the experimental data curve, the fitting curve of the initial model, and the fitting curve of the evolution model, the fitting advantages of the evolution model can be visually displayed.

[0080] The comparison results show that the evolutionary flow stress-strain model can significantly improve the fitting accuracy by dynamically adjusting the hardening index, especially showing better fitting effects in complex deformation stages (such as high strain ranges). The initial model usually can only describe fixed hardening characteristics, while the evolutionary model can capture the dynamic changes of hardening behavior during the deformation process, thus more comprehensively reflecting the mechanical properties of materials. Comparative analysis can verify the wide applicability of the evolutionary model and whether it can handle different types of metallic materials (such as ordinary steel, high-strength steel, aluminum alloy, etc.).

[0081] In some instances, it also includes:

[0082] Conduct long-term tracking and monitoring of the hardening behavior of metallic materials, and update the model parameters of the above evolutionary flow stress-strain model based on the true stress data and true strain data measured at different time points;

[0083] According to the updated model parameters, plot the evolution curve of the hardening behavior to provide dynamic characterization results.

[0084] Exemplarily, in an actual engineering environment, the mechanical properties of metallic materials may change due to various factors (such as time, environmental conditions, processing technology, etc.). For example, high-strength steel may show attenuation of hardening characteristics during long-term service, while new alloys may exhibit strengthening of hardening characteristics under certain processes. Therefore, long-term monitoring of the hardening behavior of metallic materials can dynamically capture these changes, providing an accurate basis for predicting the performance of materials under complex working conditions. Long-term tracking and monitoring are also applicable to evaluating the performance evolution of metallic materials under multiple loading or cyclic loading conditions, helping to analyze the long-term stability and applicability of materials.

[0085] Collect true stress and true strain data through experiments at different time points to form multiple sets of data sets, which can reflect the mechanical behavior of materials under different loading histories or service conditions. Based on the newly collected data sets, conduct fitting analysis through the evolutionary flow stress-strain model to dynamically update the model parameters. By regularly updating the model parameters, the evolutionary flow stress-strain model can maintain an accurate description of the current hardening behavior of materials, providing support for subsequent analysis and prediction.

[0086] Use the updated model parameters to recalculate the stress within the entire true strain range and plot the evolution curve of the material's hardening behavior. By plotting multiple curves at different time points, the time-dependence of the material's hardening behavior can be visually displayed.

[0087] Dynamic characterization results can reveal the strengthening and hardening mechanisms of metallic materials at different deformation stages, loading conditions, or service times. For example, it can analyze how the proliferation rate of dislocation density decreases over time, or the gradual decline of grain boundary strengthening during long-term service. Through the evolution curve of the hardening behavior, the mechanical life of the material under complex working conditions can be predicted. For example, by observing the trend of the weakening hardening ability, the time when the material reaches the failure or deformation limit can be estimated. The dynamic characterization results can provide data support for the real-time adjustment of processing technologies. For example, adjusting the forming process parameters according to the current hardening state to ensure the stability of material properties during the production process. This method is applicable to the performance analysis of various metallic materials. Whether it is ordinary low-carbon steel, high-strength steel, or new composite metallic materials, their performance evolution laws can be understood through dynamic characterization.

[0088] The technical solutions of this application will be further described in detail through specific embodiments below.

[0089] This application takes the Hollomon flow stress-strain model as an example, and its expression is: σ = K·ε m . It should be noted that in this application, the hardening models that can be selected include but are not limited to Hollomon, Swift, Voce, etc. Among them, the Hollomon model is the most widely used in actual engineering. The flow stress-strain models considering the evolution of strain hardening index are respectively established using the commonly used DC56D material for automotive deep drawing inner panel parts and the commonly used advanced high-strength steel DP980 material for automotive reinforcement parts. On the one hand, it evaluates the feasibility of the proposed method for determining the evolution flow stress-strain model, and on the other hand, it verifies the applicability of the proposed method for materials with different strengths.

[0090] Example 1

[0091] Taking the commonly used DC56D material for automotive deep drawing inner panel parts as an example, according to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", on the test steel plate, a "dumbbell-shaped" specimen with a gauge length of 80 mm is taken along the rolling direction, and a quasi-static tensile test is carried out using a Zwick-Z100 type testing machine, with a tensile rate of 0.001 s -1 . According to formulas (1) and (2), the engineering stress-strain curve obtained from the tensile test is converted into the true stress-true strain curve of the DC56D material in the rolling direction, as Figure 2 shown.

[0092] ε T = ln(1 + ε nom ) (1)

[0093] σ T = σ nom (1 + ε nom ) (2)

[0094] Wherein, ε nom is the engineering strain, σ nom is the engineering stress, ε T is the true strain, and σ T is the true stress.

[0095] The true stress-true strain curve is transformed to obtain the logarithmic true stress-logarithmic true strain curve as shown in Figure 3 . According to the mechanical definition of the strain hardening index n = d(lnσ T ) / d(lnε T ), the strain hardening index is the slope of the tensile curve in the logarithmic true stress-logarithmic true strain coordinate system. The evolution relationship of the strain hardening index with the true strain is obtained, and a matching mathematical relationship between the strain hardening index and the true strain is established as shown in formula (3). The comparison between the evolution relationship of the strain hardening index of DC56D material predicted based on formula (3) and the experimental values is shown in Figure 4 .

[0096]

[0097] Substitute formula (3) into the initially selected Hollomon flow stress-strain model to establish a flow stress-strain model considering the evolution of the strain hardening index as shown in formula (4). Combining with mathematical analysis software, the true stress-true strain curve of DC56D material is fitted based on formula (4), and the parameters of the flow stress-strain model considering the evolution of the strain hardening index are obtained as shown in Table 1. The hardening behavior of DC56D material is characterized based on the flow stress-strain model considering the evolution of the strain hardening index, as shown in Figure 5 , and compared with the initial Hollomon model. The correlation coefficient R 2 of the characterization accuracy is improved from 0.9888 to 0.9918.

[0098]

[0099] Table 1 Parameters of different flow stress-strain models for DC56D material

[0100]

[0101] Exemplarily, the mathematical analysis software in the embodiments of the present application helps to import, organize, and clean experimental data, making the data more standardized and easier to analyze. By selecting appropriate mathematical models (such as linear models, polynomial models, exponential models, etc.), the software can perform curve fitting on the data. The fitting process usually involves algorithms such as the least squares method to find the optimal model parameters, so that the fitting curve is as close as possible to the experimental data. During the fitting process, the software will automatically calculate the parameters of the model and provide information such as the confidence interval and standard error of these parameters to evaluate the accuracy of the fitting. The software can visualize the fitting results and experimental data to generate charts, enabling researchers to intuitively observe the fitting effect and data trends. The software can handle complex mathematical operations, including differentiation, integration, and solving nonlinear equations, which is very important for establishing and analyzing the mathematical relationship between the strain hardening index and the true strain evolution. The mathematical analysis software used in this embodiment is Python (NumPy, SciPy), and these libraries in Python can perform numerical calculations, data processing, and visualization, which are suitable for scientific computing.

[0102] Embodiment 2

[0103] Taking the commonly used advanced high-strength steel DP980 material for automotive reinforcement parts as an example, according to the calculation process of the method for determining the evolution flow stress-strain model given above, the true stress-true strain curve of the DP980 material (such as Figure 6 ) is transformed to obtain the logarithmic true stress-logarithmic true strain curve as shown in Figure 7 . A mathematical relationship between the strain hardening index and the true strain that matches is established as shown in formula (5). The evolution relationship of the strain hardening index predicted based on formula (5) with respect to the true plastic strain is compared with the experimental values as shown in Figure 8 .

[0104]

[0105] Substitute formula (5) into the initially selected Hollomon flow stress-strain model to establish a flow stress-strain model considering the evolution of the strain hardening index as shown in formula (6). Combining with the mathematical analysis software, based on formula (6), the true stress-true strain curve of the DP980 material is fitted, and the flow stress-strain model parameters considering the evolution of the strain hardening index are obtained as shown in Table 2. Characterize the hardening behavior of the DP980 material based on the flow stress-strain model considering the evolution of the strain hardening index, as shown in Figure 9 , and compare it with the initial Hollomon model. The correlation coefficient R 2 of the characterization accuracy is improved from 0.8969 to 0.9989.

[0106]

[0107] Table 2 DP980 material different flow stress-strain model parameters

[0108]

[0109] Please refer to Figure 10 , which is a schematic structural diagram of an evolution flow stress-strain model determination device provided by an embodiment of the present application, including:

[0110] An initial model construction unit 21, configured to construct an initial flow stress-strain model;

[0111] An evolution relationship determination unit 22, configured to determine a strain hardening index relationship formula, where the strain hardening index relationship formula is determined based on the corresponding relationship between the strain hardening index and the true strain data;

[0112] An evolution model determination unit 23, configured to determine an evolution flow stress-strain model based on the strain hardening index relationship formula and the initial flow stress-strain model, where the evolution flow stress-strain model is used to fit the curve of the flow stress and strain relationship of the metal material.

[0113] Please refer to Figure 11 , an embodiment of the present application also provides an electronic device 300, including a memory 310, a processor 320, and a computer program 311 stored in the memory 310 and executable on the processor. When the processor 320 executes the computer program 311, the steps of any method for determining an evolution flow stress-strain model as described above are implemented.

[0114] Since the electronic device introduced in this embodiment is the device used to implement an evolution flow stress-strain model determination device in an embodiment of the present application, based on the method introduced in an embodiment of the present application, those skilled in the art can understand the specific implementation manners and various variations of the electronic device in this embodiment. Therefore, the specific implementation of how this electronic device implements the method in an embodiment of the present application will not be described in detail here. As long as the device used by those skilled in the art to implement the method in an embodiment of the present application belongs to the scope of protection of the present application.

[0115] In the specific implementation process, when the computer program 311 is executed by the processor, it can implement any implementation manner in the corresponding embodiment of the first aspect.

[0116] It should be noted that in the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailedly described in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0117] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-readable program code.

[0118] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or multiple flows and / or blocks

[0119] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in Figure 1 one or more of the flows Figure 1 or multiple flows and / or blocks

[0120] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or multiple flows and / or blocks

[0121] The embodiments of the present application also provide a computer program product, which includes computer software instructions. When the computer software instructions run on a processing device, the processing device is caused to execute Figure 1 the process of a method for determining an evolution flow stress-strain model in a corresponding embodiment.

[0122] A computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the processes or functions according to the embodiments of the present application are all or partially generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from a website, a computer, a server, or a data center to another website, a computer, a server, or a data center by wire (such as coaxial cable, optical fiber, digital subscriber line) or by wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium may be any available medium that can be stored by a computer or a data storage device such as a server or a data center that includes one or more integrated available media. The available medium may be a magnetic medium, an optical medium, or a semiconductor medium (such as a solid-state drive), etc.

[0123] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the systems, devices, and units described above may refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0124] In several embodiments provided in the present application, it should be understood that the disclosed devices, apparatuses, and methods may be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Another point is that the displayed or discussed couplings, direct couplings, or communication connections to each other may be indirect couplings or communication connections through some interfaces, devices, or units, and may be in electrical, mechanical, or other forms.

[0125] The units described as separate components may or may not be physically separated, and the components displayed 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 units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0126] In addition, each functional unit in the various embodiments of the present application may be integrated in a processing unit, or each unit may exist physically alone, or two or more units may be integrated in one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0127] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of this application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories, random access memories, magnetic disks, or optical discs.

[0128] The above embodiments are only used to illustrate the technical solution of this application, rather than to limit it; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of various embodiments of this application.

[0129] Although the preferred embodiments of this specification have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications that fall within the scope of this specification.

[0130] Obviously, those skilled in the art can make various changes and modifications to this specification without departing from the spirit and scope of this specification. In this way, if these modifications and variations of this specification fall within the scope of the claims of this specification and their equivalent technologies, this specification is also intended to include these modifications and variations.

Claims

1. A method for determining an evolution flow stress-strain model, characterized in that The method includes: Constructing an initial flow stress-strain model; Determining a strain hardening exponent relationship, where the strain hardening exponent relationship is determined based on the correspondence between the strain hardening exponent and true strain data; Determining an evolving flow stress-strain model based on the strain hardening exponent relationship and the initial flow stress-strain model, where the evolving flow stress-strain model is used to fit the curve of the flow stress and strain relationship of the metal material.

2. The method for determining the evolutionary flow stress-strain model according to claim 1, characterized in that The initial flow stress-strain model includes the Hollomon model, the Swift model, and the Voce model.

3. The method for determining the evolutionary flow stress-strain model according to claim 1, characterized in that The determining of the strain hardening exponent relationship includes: Constructing an engineering data curve; Determining a true data curve based on the engineering data curve; Determining a logarithmic true data curve based on the true data curve; Determining a strain hardening exponent relationship based on the strain hardening exponent and the true strain data, where the strain hardening exponent is the slope of the logarithmic true data curve.

4. The method for determining the evolutionary flow stress-strain model according to claim 1, characterized in that, The strain hardening exponent relationship is determined by performing a fitting operation on the evolution law of the strain hardening exponent with respect to the true strain data, where the fitting relationship corresponding to the evolution law fitting operation includes a linear function, a polynomial function, a power function, and an exponential function.

5. The method for determining the evolutionary flow stress-strain model according to claim 3, characterized in that, The engineering data curve is a curve of the correspondence between engineering stress data and engineering strain data, where the engineering stress data and the engineering strain data are obtained by performing a uniaxial tensile test on the metal material to be characterized.

6. The method for determining the evolutionary flow stress-strain model according to claim 3, wherein The true data curve is a curve of the correspondence between true stress data and true strain data, and the logarithmic true data curve is a curve of the correspondence between logarithmic true stress data and logarithmic true strain data.

7. The method for determining the evolution flow stress-strain model according to claim 1, characterized in that It further includes: Performing long-term tracking and monitoring on the hardening behavior of the metal material, and updating the model parameters of the evolving flow stress-strain model based on the true stress data and true strain data measured at different time points; Drawing an evolution curve of the hardening behavior according to the updated model parameters to provide a dynamic characterization result.

8. An apparatus for determining an evolutionary flow stress-strain model, characterized in that It includes: An initial model construction unit for constructing an initial flow stress-strain model; An evolution relationship determination unit for determining a strain hardening exponent relationship, where the strain hardening exponent relationship is determined based on the correspondence between the strain hardening exponent and true strain data; An evolving model determination unit for determining an evolving flow stress-strain model based on the strain hardening exponent relationship and the initial flow stress-strain model, where the evolving flow stress-strain model is used to fit the curve of the flow stress and strain relationship of the metal material.

9. An electronic device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that when the processor executes the computer program stored in the memory, it implements the steps of the evolving flow stress-strain model determination method according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the evolving flow stress-strain model determination method according to any one of claims 1-7.

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