A numerical simulation measurement method for impact data of composite structures that can be used for shell elements taking into account strain rate effects

Abstract

The present invention discloses a numerical simulation measurement method for impact data of composite material structures that can be used for shell elements taking strain rate effects into account, which belongs to the technical field of impact resistance measurement of composite material structures, and solves the problem that the existing numerical simulation technology cannot consider the impact strain rate effect when using shell elements, and the impact damage criterion is single, which leads to inaccurate measurement of the response of composite material structures under impact loads. The present invention establishes a shell element VUMAT subroutine containing anisotropic strain rate effects, constructs an Euler grid domain that considers fluid-solid coupling effects and defines the form of impact loads, and calls the subroutine to realize impact simulation measurement when performing display dynamics calculation analysis using finite element software. The present invention can improve the accuracy of impact simulation measurement, accurately determine damage, is suitable for complex shell element structures, considers strain rate and fluid-solid coupling effects, is compatible with existing technologies, reduces costs, provides reliable support for composite material structure research and application, and promotes the development of related fields.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material structure impact resistance measurement, and relates to a composite material structure impact data numerical simulation measurement method which can be used for shell elements taking into account strain rate effects and multiple damage criteria. Background Art

[0002] Advanced fiber composite materials have unique properties such as light weight, non-magnetic, high specific strength, and high sound transmittance, which can meet the current development needs of marine vehicles for non-magnetic and weight reduction. Therefore, they are increasingly used in the structure of current marine vehicles. Due to their good large curvature formability, they are widely favored by various countries in the design of shell structures. However, with the development of various weapons, the possibility of structures being impacted by contact explosions or collisions is increasing. Therefore, the measurement and research of the impact response of composite structures has important practical significance.

[0003] At present, there are many difficulties in measuring the impact response of composite structures: the physical experiment method faces the problems of high processing cost of composite experimental structure, difficulty in loading experimental impact load, and poor experimental repeatability. The numerical simulation method faces the problems that some existing secondary development composite constitutive VUMAT programs are only applicable to three-dimensional solid units, but the aircraft composite structure is mostly a large-size and large-curvature rotating shell structure, which is difficult to accurately model using solid units, and solid modeling will have problems such as long analysis time and numerical instability when the structure is greatly deformed; using shell unit modeling can avoid the above problems when using solid units, but the commonly used composite analysis software including ABAQUS, DYNA and other built-in calculation methods have the shortcomings of not considering the anisotropic strain rate effect of composite materials, resulting in large structural impact response measurement errors, and the inaccurate identification of structural damage caused by the simplification of damage judgment criteria; at the same time, there is the problem of difficulty in simulating the fluid-solid coupling effect of near-field explosion and impact. According to existing research, for impact problems, the strain rate effect will have a significant impact on both material stiffness and strength. Therefore, due to the lack of relevant methods, there are very few impact measurement data on composite structures of underwater vehicles. It is urgent to design a numerical simulation measurement method for composite structure impact data that can be used for shell units to take into account the strain rate effect, so as to realize the inclusion of the material strain rate effect during the numerical simulation measurement of impact data, and combine a variety of damage criterion determination methods to accurately calculate the damage state of the measured structure. Support shell unit modeling and analysis to avoid the problem of using solid units that are difficult to apply to numerical simulation measurement of impact data of large-size and large-curvature structures, and at the same time consider the fluid-solid coupling effect during near-field explosion and impact. Summary of the invention

[0004] The invention proposes a numerical simulation measurement method for impact data of composite material structures which can be used for shell elements and takes strain rate effect into account, so as to solve the problems existing in the prior art.

[0005] A method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects, the method comprising the following steps:

[0006] S1. Establish the shell element VUMAT subroutine including the anisotropic strain rate effect;

[0007] S2. Construct an Euler mesh domain according to the impact measurement conditions, cover the target structure, reasonably allocate Euler domain materials to simulate the impact environment and take into account the fluid-structure interaction effect, and define the impact load form;

[0008] S3. Use finite element software to perform display dynamics calculation analysis and call the VUMAT subroutine to achieve numerical simulation measurement of structural impact data under structural impact load.

[0009] Furthermore, in S1, the VUMAT subroutine is established using Fortran language.

[0010] Further, S1 includes the following steps:

[0011] S101, reading in parameters from the finite element analysis pre-processing interface, defining the physical meaning of each parameter read in the VUMAT program, and defining the integration point state variables for storing the solution variable information;

[0012] S102. Construct an initial stiffness matrix based on the constitutive characteristics of the shell element. The initial stiffness matrix describes the stiffness of the material when it is not subjected to external force. The linear elasticity assumption is used, that is, the relationship between stress and strain is linear when the material is not damaged. The first step stress response is calculated according to the current stress condition.

[0013] S103, updating and storing the strain response of each display dynamics iteration step for subsequent calculation;

[0014] S104, calculating effective stress according to the "strain response" and the "initial stiffness matrix";

[0015] S105, calculating the rate of change of strain over time, i.e., the strain rate, updating the dynamic enhancement factor according to the value of the strain rate, and using the updated dynamic enhancement factor to correct the stiffness and strength parameters;

[0016] S106. The true stress value is obtained according to the strain response and the stiffness matrix after taking into account the strain rate effect and damage stiffness degradation, which provides more reliable data for subsequent judgment of material state and damage analysis;

[0017] S107, determine the damage criterion to be adopted according to the parameters input by the pre-processing, and judge whether the material is damaged according to the material state obtained by the current calculation, if it is damaged, execute S108; otherwise, execute S110;

[0018] S108, when it is determined that the material is damaged, damage evolution calculation is performed based on the definition of fracture energy, the damage development process is determined by calculating the fracture energy, and the damage criterion coefficient after damage evolution is updated. The coefficient is used to measure the degree of damage and perform stiffness reduction. The unit distortion degree is also calculated to control the deletion of large distortion meshes;

[0019] S109, establishing a mesh deletion determination module, which comprehensively considers three aspects of information, namely, maximum strain, stress-related damage criterion coefficient, and unit distortion degree, to determine whether the unit needs to be deleted, so as to more accurately simulate the actual fracture condition of the material after damage;

[0020] S110, update the material point state variable data, and pass the updated material point state variable data to the finite element software solution main program to determine whether the calculation is completed, if completed, end; otherwise continue to loop S104-S110 until the calculation is completed.

[0021] Furthermore, in S1, the establishment process of the VUMAT subroutine is based on the constitutive properties of three-dimensional shell elements to achieve the purpose of supporting shell element modeling and analysis.

[0022] Furthermore, in the construction process of the VUMAT subroutine of S1, an anisotropic strain rate calculation module is established, and the strain rate to composite material stiffness correction module and the strain rate to composite material strength correction module in the VUMAT subroutine are established by introducing the dynamic enhancement factor, so as to achieve the purpose of considering the anisotropic strain rate effect in the impact measurement process. Among them, the dynamic enhancement factor considers three aspects of 1 direction, 2 directions and 12 directions respectively, and the calculation formula is as follows:

[0023]

[0024] In the above formula is the dynamic enhancement factor, is the reference strain rate, is the strain rate of the current calculation increment, A is the correction parameter which can usually be obtained from material tests, where ij is 11, 22, and 12, representing the 1st, 2nd, and 12th directions, respectively.

[0025] Furthermore, the VUMAT subroutine embeds multiple impairment criteria, including HASHIN, PUCK and CHANGCHANG.

[0026] Furthermore, in the construction process of the VUMAT subroutine of S1, the VUMAT subroutine performs damage evolution calculation based on the fracture energy theory, defines shear damage based on the progressive damage theory and associates it with shear stiffness degradation, where the shear damage determination factor is calculated as follows:

[0027]

[0028] In the above formula, stateNew(k,4) is the fiber tensile damage factor; stateNew(k,5) is the fiber compressive damage factor; stateNew(k,6) is the matrix tensile damage factor; stateNew(k,7) is the matrix compressive damage factor; stateNew(k,8) is the shear damage factor, and the shear stiffness degradation is carried out as follows:

[0029]

[0030] In the above formula represents the shear stiffness after degradation; is the shear stiffness corrected for strain rate; Represents the shear damage factor of the previous increment.

[0031] Furthermore, in S1, the VUMAT subroutine established a comprehensive damage determination module based on maximum strain, stress and unit distortion to improve the measurement accuracy of impact damage. The operation method of the comprehensive damage determination module includes three parts:

[0032] First, compare the tensile and compressive strains of the current incremental step with the tensile and compressive strains at fracture. When the ratio is greater than 1, the material is theoretically fractured and the element definition is deleted.

[0033] Secondly, when the damage criterion coefficient of the current incremental step is greater than 1, the material is theoretically damaged, the unit definition is deleted, and the three built-in damage criteria of the VUMAT program used in S1 are all stress-related criteria;

[0034] Finally, the stress matrix eigenvalues ​​are calculated and the unit distortion coefficients are calculated based on the eigenvalues. When the unit distortion coefficient is greater than 1.0 or less than -0.8, the unit distortion is too large and has affected the accuracy of the finite element calculation, so the unit definition is deleted.

[0035] A storage medium stores a computer program, which, when executed by a processor, implements the above-mentioned numerical simulation measurement method for impact data of composite material structures that can be used for shell elements and takes strain rate effects into account.

[0036] A computer device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the program to implement the above-mentioned numerical simulation measurement method for impact data of composite material structures that can be used for shell elements and takes strain rate effects into account.

[0037] Beneficial effects of the present invention

[0038] Beneficial effects of the present invention:

[0039] 1. The present invention can be used for numerical simulation measurement of impact data of composite material structures subjected to explosion, collision and other impacts in water or air. It is suitable for shell unit modeling and calculation, and is suitable for numerical simulation of impact measurement of curved surface structures. By introducing dynamic enhancement factors and establishing anisotropic strain rate effect modules, high-precision numerical simulation measurement of structural impact response under high-speed impact loads can be achieved.

[0040] 2. The present invention embeds a variety of damage criterion theories, which makes it easy for users to independently select appropriate damage criteria according to different impact conditions.

[0041] 3. The present invention establishes a comprehensive damage judgment module based on maximum strain, stress, and unit distortion, which can more accurately obtain the impact damage state of the composite material structure.

[0042] 4. The present invention performs damage evolution calculation based on fracture energy theory, and defines shear damage and stiffness degradation based on progressive damage theory, so as to achieve the effect of considering shear damage when calculating using shell elements.

[0043] 5. The present invention adopts the Euler Lagrangian method to display the dynamic calculation and solve to obtain the impact measurement data, wherein the impacted structure is established using the Lagrangian shell unit, and the Euler domain is established using the Euler unit to completely include the impact measurement target structure. The material settings of the Euler domain are allocated according to demand, and the fluid-solid coupling effects in various impact scenarios such as water or air can be simulated. It has strong applicability and is suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A main flow chart of a method of a specific embodiment of a method for numerical simulation measurement of impact data of a composite material structure taking into account strain rate effect of shell elements according to the present invention;

[0045] Figure 2 It is an execution diagram of a composite material VUMAT subroutine that can be used for three-dimensional shell elements taking into account strain rate effects and multiple damage determination methods in a specific embodiment of the present invention;

[0046] Figure 3 A schematic diagram of a composite material coordinate system of a specific embodiment of the present invention;

[0047] Figure 4 is a schematic diagram of a finite element model of Example 1 of the present invention;

[0048] Figure 5 This is a schematic diagram of the finite element model of Example 2 of the present invention.

[0049] Among them, 1 is the air Euler domain, 2 is the composite material flat plate, 3 is the impact punch, 4 is the water Euler domain, 5 is the composite material cylindrical shell, and 6 is the TNT spherical explosive. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] A method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects, the method comprising the following steps:

[0052] S1. Establish the shell element VUMAT subroutine including the anisotropic strain rate effect;

[0053] S2. Construct an Euler mesh domain according to the impact measurement conditions, cover the target structure, reasonably allocate Euler domain materials to simulate the impact environment and take into account the fluid-structure interaction effect, and define the impact load form;

[0054] S3. Use finite element software to perform display dynamics calculation analysis and call the VUMAT subroutine to achieve numerical simulation measurement of structural impact data under structural impact load.

[0055] Specifically, refer to Figure 1 , Figure 3 As shown, Figure 1 A specific embodiment of the method of the present invention is shown in FIG. Figure 3 1 is a schematic diagram of a composite material coordinate system of a specific embodiment of the present invention, wherein direction 1 is the fiber direction, direction 2 is the transverse direction, and direction 3 is the thickness direction, that is, the ply stacking direction, corresponding to the coordinate system definition in the VUMAT program created by this method.

[0056] S1, using Fortran language to establish the VUMAT subroutine used;

[0057] S2. The Euler-Lagrangian method is used in the finite element analysis software. The Lagrangian shell element is used to establish the target structure of the impact measurement study. The Euler mesh is used to establish the Euler domain to completely contain the impacted structure, and the relevant loads and contact properties are defined.

[0058] S3. Establish display dynamic analysis, set the calling relationship between the finite element main program and the established VUMAT subroutine, and submit the calculation to complete the numerical simulation measurement process of impact data.

[0059] The present invention establishes a VUMAT subroutine in S1 that includes the influence of anisotropic strain rate effect, and establishes a strain rate correction module and a strength correction module for composite material stiffness by introducing a dynamic enhancement factor. This makes it possible to fully consider the anisotropic strain rate effect of the composite material structure during the impact measurement process, and to correct the stiffness and strength aspects of multiple angles, thereby improving the numerical simulation measurement accuracy of the structural impact response under high-speed impact loads. The entire method flow is based on shell unit modeling and analysis, avoiding the problem of being difficult to apply to the numerical simulation measurement of impact data of large-size and large-curvature structures caused by the use of solid units, so that the method is particularly suitable for the numerical simulation measurement of impact data of large and complex curved composite material structures, and has stronger applicability. The VUMAT subroutine embeds a variety of existing and commonly used damage criteria, and the user can select a suitable damage criterion by setting input parameters in the finite element pre-processing stage. The VUMAT subroutine also establishes a comprehensive damage judgment module based on maximum strain, stress, and unit distortion. These measures can more accurately obtain the impact damage state of the composite structure and improve the accuracy of damage judgment. The VUMAT subroutine calculates damage evolution based on fracture energy theory, defines shear damage based on progressive damage theory and associates it with shear stiffness degradation, so as to achieve the effect of still being able to calculate and consider shear damage using shell elements. This further improves the simulation of composite material structure damage, making the simulation results more in line with actual conditions. When constructing the Euler grid domain in S2, the Euler domain materials are reasonably allocated to simulate the environment and take into account the fluid-solid coupling effect. The fluid-solid coupling effect is also considered when the impact measurement data is obtained by displaying dynamics calculations in S3. This enables the method of the present invention to simulate the fluid-solid coupling effect in a variety of impact scenarios such as water or air, more realistically reflects the actual impact scenario, and improves the authenticity and reliability of the simulation. The numerical simulation measurement method of the present invention avoids the problems of high cost and poor repeatability brought about by the physical experimental method. At the same time, compared with the method using solid elements, the calculation cost can be greatly reduced, and the economy and practicality of the method are improved.

[0060] Furthermore, in S1, the VUMAT subroutine is established using Fortran language.

[0061] Specifically, the use of Fortran language to establish the VUMAT subroutine has many beneficial effects, including its efficient computing performance can reduce computing time and improve efficiency, good compatibility with existing technologies to facilitate integration and use of related resources to reduce development costs, and good code readability and maintainability, which is conducive to subsequent program modification, optimization and debugging.

[0062] Further, see Figure 2 As shown, S1 includes the following steps:

[0063] S101, reading in parameters from the finite element analysis pre-processing interface, defining the physical meaning of each parameter read in the VUMAT program, and defining the integration point state variables for storing the solution variable information;

[0064] S102. Construct an initial stiffness matrix based on the constitutive characteristics of the shell element. The initial stiffness matrix describes the stiffness of the material when it is not subjected to external force. The linear elasticity assumption is used, that is, the relationship between stress and strain is linear when the material is not damaged. The first step stress response is calculated according to the current stress condition.

[0065] S103, updating and storing the strain response of each display dynamics iteration step for subsequent calculation;

[0066] S104, calculating effective stress according to the "strain response" and the "initial stiffness matrix";

[0067] S105, calculating the rate of change of strain over time, i.e., the strain rate, updating the dynamic enhancement factor according to the value of the strain rate, and using the updated dynamic enhancement factor to correct the stiffness and strength parameters;

[0068] S106. The true stress value is obtained according to the strain response and the stiffness matrix after taking into account the strain rate effect and damage stiffness degradation, which provides more reliable data for subsequent judgment of material state and damage analysis;

[0069] S107, determine the damage criterion to be adopted according to the parameters input by the pre-processing, and judge whether the material is damaged according to the material state obtained by the current calculation, if it is damaged, execute S108; otherwise, execute S110;

[0070] S108, when it is determined that the material is damaged, damage evolution calculation is performed based on the definition of fracture energy, the damage development process is determined by calculating the fracture energy, and the damage criterion coefficient after damage evolution is updated. The coefficient is used to measure the degree of damage and perform stiffness reduction. The unit distortion degree is also calculated to control the deletion of large distortion meshes;

[0071] S109, establishing a mesh deletion determination module, which comprehensively considers three aspects of information, namely, maximum strain, stress-related damage criterion coefficient, and unit distortion degree, to determine whether the unit needs to be deleted, so as to more accurately simulate the actual fracture condition of the material after damage;

[0072] S110, update the material point state variable data, and pass the updated material point state variable data to the finite element software solution main program to determine whether the calculation is completed, if completed, end; otherwise continue to loop S104-S110 until the calculation is completed.

[0073] Specifically, the use of Fortran language in S1 to establish the VUMAT subroutine and the series of steps involved have many significant beneficial effects. First, the Fortran language has outstanding advantages in the field of scientific computing. It is known for its efficient computing performance, especially when dealing with large-scale numerical calculations. For tasks such as numerical simulation measurement of composite structure impact data involving a large number of complex calculations, Fortran can significantly reduce the calculation time and improve the efficiency of the entire simulation process. At the same time, the Fortran language has good compatibility with the existing technology ecosystem. In related fields such as finite element analysis, it has a wide range of application history and rich technical resources. The use of Fortran language to establish the VUMAT subroutine can be easily integrated with existing finite element software and related algorithm libraries, tools, etc. This not only reduces the difficulty and cost of development, but also enables developers to make full use of existing mature technologies and accelerate the development process of the subroutine. From the specific steps, S101 reads in parameters from the finite element analysis pre-processing interface and clarifies their physical meanings and defines the integration point state variables, which provides an accurate data basis and clear variable definitions for subsequent calculations, ensuring the accuracy and traceability of data throughout the simulation process. S102 constructs the initial stiffness matrix based on the constitutive characteristics of the shell element and calculates the first step stress response. Combined with the linear elastic assumption, it can accurately describe the mechanical response of the material in the initial state, laying the foundation for the subsequent consideration of stress-strain changes under complex working conditions. S103 updates and stores the strain response of each dynamic iteration step for subsequent calculations, ensuring the consistency and availability of the data, so that the strain data can be called at any time for further analysis in subsequent calculations. S104 calculates the effective stress based on the "strain response" and the "initial stiffness matrix". S105 calculates the strain rate and updates the dynamic enhancement factor to correct the stiffness and strength parameters, fully considering the characteristic changes of the material at different strain rates, so that the simulation can more realistically reflect the mechanical behavior of the material under dynamic impact loads. S106 obtains the true stress value based on the strain response and the stiffness matrix after taking into account the strain rate effect and damage stiffness degradation, providing more reliable data for subsequent judgment of material state and damage analysis. S107 determines the damage criterion and judges the damage situation based on the pre-processing input parameters, providing a clear basis and triggering conditions for subsequent damage analysis and processing. After determining the material damage, S108 calculates the damage evolution based on the fracture energy definition, updates the damage criterion coefficient, performs stiffness reduction and calculates the unit distortion, comprehensively considering various factors in the damage development process, and can accurately simulate the performance changes and structural deformation of the material after damage. S109 comprehensively considers the maximum strain, stress-related damage criterion coefficient and unit distortion to determine whether the unit needs to be deleted, more accurately simulating the actual situation of the material after damage, and improving the authenticity and accuracy of the simulation.S110 updates the material point state variable data and passes it to the finite element software solution main program, as well as determines whether the calculation is completed and performs a loop, ensuring the continuity and integrity of the entire simulation process, allowing the program to continuously iterate the calculation until the calculation requirements are met, thereby obtaining accurate and reliable simulation results.

[0074] Furthermore, in S1, the establishment process of the VUMAT subroutine is based on the constitutive properties of three-dimensional shell elements to achieve the purpose of supporting shell element modeling and analysis.

[0075] Specifically, in S1, the VUMAT subroutine is established based on the constitutive characteristics of three-dimensional shell elements, so that the subroutine can fully adapt to the needs of shell element modeling and analysis, and accurately simulate the mechanical behavior of composite structures in three-dimensional space. By establishing a subroutine based on this characteristic, it is possible to more accurately describe the stress and deformation of shell elements under various working conditions, taking into account the particularity of the shell element structure, such as complex mechanical responses such as bending and torsion, thereby providing a more reliable basis for the numerical simulation measurement of impact data of composite structures. It helps to improve the precision and accuracy of the simulation, making the simulation results closer to the actual situation, and providing strong support for studying the performance changes, damage evolution and structural response of composite structures under impact loads, and thus providing more valuable reference for related engineering design and analysis.

[0076] Furthermore, in the construction process of the VUMAT subroutine of S1, an anisotropic strain rate calculation module is established, and the strain rate to composite material stiffness correction module and the strain rate to composite material strength correction module in the VUMAT subroutine are established by introducing the dynamic enhancement factor, so as to achieve the purpose of considering the anisotropic strain rate effect in the impact measurement process. Among them, the dynamic enhancement factor considers three aspects of 1 direction, 2 directions and 12 directions respectively, and the calculation formula is as follows:

[0077]

[0078] In the above formula is the dynamic enhancement factor, is the reference strain rate, is the strain rate of the current calculation increment, A is the correction parameter which can usually be obtained from material tests, where ij is 11, 22, and 12, representing the 1st, 2nd, and 12th directions, respectively.

[0079] Specifically, in the construction process of the VUMAT subroutine of S1, the establishment of anisotropic strain rate calculation module and related correction modules has important and rich beneficial effects. By introducing the dynamic enhancement factor and considering it from three aspects of 1, 2 and 12 directions respectively, a correction module for strain rate on the stiffness and strength of composite materials is established, which can accurately incorporate the anisotropic strain rate effect in the impact measurement process. This allows the subroutine to more realistically simulate the mechanical response characteristics of composite materials under complex impact conditions. Specifically, the determination of the dynamic enhancement factor based on a clear calculation formula provides a scientific basis for accurately correcting the stiffness and strength of composite materials. This precise correction can significantly improve the accuracy and reliability of the numerical simulation measurement of impact data, making the simulation results more in line with the actual performance changes of composite structures under the action of strain rates in different directions in actual engineering.

[0080] Furthermore, the VUMAT subroutine embeds multiple impairment criteria, including HASHIN, PUCK and CHANGCHANG.

[0081] Specifically, the present invention embeds multiple damage criteria (including HASHIN, PUCK and CHANGCHANG) in the VUMAT subroutine, providing a comprehensive and rich damage assessment method for the impact analysis of composite materials. Different damage criteria start from different theories and perspectives, and can more carefully capture and describe various damage modes and mechanisms that may occur in composite materials during the impact process. The HASHIN damage criterion may have unique advantages in the assessment of fiber tensile and compression damage of fiber-reinforced composite materials, and can accurately judge the force damage in the fiber direction; the PUCK damage criterion may be more effective in the damage of the matrix material and the interface damage analysis between the fiber and the matrix, which helps to deeply understand the interaction and damage propagation between different components in the composite material; the CHANGCHANG damage criterion may have excellent performance in comprehensively considering a variety of complex stress states and damage development paths, and provides a new perspective for comprehensively evaluating the overall damage degree of composite materials. By integrating these multiple damage criteria, the VUMAT subroutine can more accurately predict the occurrence, development and distribution of damage when simulating the impact of composite materials, providing a more accurate and reliable basis for structural design optimization, reliability analysis and life prediction.

[0082] Furthermore, in the construction process of the VUMAT subroutine of S1, the VUMAT subroutine performs damage evolution calculation based on the fracture energy theory, defines shear damage based on the progressive damage theory and associates it with shear stiffness degradation, where the shear damage determination factor is calculated as follows:

[0083]

[0084] In the above formula, stateNew(k,4) is the fiber tensile damage factor; stateNew(k,5) is the fiber compressive damage factor; stateNew(k,6) is the matrix tensile damage factor; stateNew(k,7) is the matrix compressive damage factor; stateNew(k,8) is the shear damage factor, and the shear stiffness degradation is carried out as follows:

[0085]

[0086] In the above formula represents the shear stiffness after degradation; is the shear stiffness corrected for strain rate; Represents the shear damage factor of the previous increment.

[0087] Specifically, in the construction process of the VUMAT subroutine of S1, by calculating the damage evolution based on the fracture energy theory, the energy absorption and release of the material during the damage process can be more accurately simulated, so as to have a deep understanding of the development process and trend of the damage, so as to predict the evolution path and degree of its internal damage when the composite material structure is impacted, and provide a key basis for the safety assessment and life prediction of the structure. At the same time, based on the progressive damage theory to define shear damage and in combination with a specific shear damage determination factor for calculation, it is possible to carefully consider the damage factors under different conditions such as fiber tension, compression and matrix tension, compression, and comprehensively and accurately describe the shear damage characteristics of the composite material under complex stress state. Moreover, through the association with the degradation of shear stiffness, a clear calculation formula is used to realize the reasonable correction of shear stiffness, taking into account the influence of strain rate and damage factor, so that the mechanical property changes of the material after damage can be more truly reflected in the simulation process. This comprehensive processing method of the present invention improves the accuracy and reliability of the VUMAT subroutine for composite structure damage simulation.

[0088] Furthermore, in S1, the VUMAT subroutine established a comprehensive damage determination module based on maximum strain, stress and unit distortion to improve the measurement accuracy of impact damage. The operation method of the comprehensive damage determination module includes three parts:

[0089] First, compare the tensile and compressive strains of the current incremental step with the tensile and compressive strains at fracture. When the ratio is greater than 1, the material is theoretically fractured and the element definition is deleted.

[0090] Secondly, when the damage criterion coefficient of the current incremental step is greater than 1, the material is theoretically damaged, the unit definition is deleted, and the three built-in damage criteria of the VUMAT program used in S1 are all stress-related criteria;

[0091] Finally, the stress matrix eigenvalues ​​are calculated and the unit distortion coefficient is calculated based on the eigenvalues. When the unit distortion coefficient is greater than 1.0 or less than -0.8, the unit distortion is too large and has affected the accuracy of the finite element calculation. The unit definition is deleted and the unit distortion coefficient is only a reference value, which is determined according to the specific material parameters of the current experiment.

[0092] Specifically, in S1, the VUMAT subroutine establishes a comprehensive damage judgment module based on maximum strain, stress and unit distortion, which brings many significant and important beneficial effects. The maximum strain reflects the degree of local deformation and can capture the damage that may be caused by excessive deformation of the material; the stress combined with the current damage criterion theory can accurately determine whether the material has reached the damage limit under the external load; the unit distortion takes into account the non-uniformity of mesh deformation during numerical analysis, which can avoid the calculation error caused by large mesh distortion. By combining these three aspects for damage judgment, the precision and accuracy of impact damage measurement are greatly improved, making the simulation results closer to the actual situation. This helps engineers and researchers to more accurately understand the damage mechanism and development process of composite structures under impact loads, and provides a more reliable basis for the optimization design, reliability assessment and life prediction of the structure, thereby effectively improving the safety and durability of composite structures, reducing the risk of structural failure due to impact damage in practical applications, and promoting the wider and safer application of composite materials in many fields such as aerospace, automotive industry, and construction engineering.

[0093] A storage medium stores a computer program, which, when executed by a processor, implements the above-mentioned numerical simulation measurement method for impact data of composite material structures that can be used for shell elements and takes strain rate effects into account.

[0094] Specifically, first, the storage medium of the present invention provides a convenient storage and execution carrier for the numerical simulation measurement method of impact data of composite material structures that can be used for shell elements taking into account strain rate effects. By storing the complex simulation measurement method in the medium in the form of a computer program, the method can be efficiently called and run, greatly improving the utilization efficiency of computing resources and the stability of the computing process. In practical applications, this storage medium and program can accurately simulate various mechanical behaviors and responses of composite material structures under impact loads. By accurately considering the strain rate effect, the performance changes of materials under different loading rates can be truly reflected, providing a reliable analysis method for the study of materials under complex working conditions such as high-speed impact. The applicability of shell elements enables the method to better handle composite material structures with complex shapes such as large size and large curvature, broadening the application scope of the simulation. At the same time, the various functional modules contained in the program, such as the embedding of multiple damage criteria, damage calculation and judgment based on fracture energy and progressive damage theory, etc., can comprehensively and meticulously analyze the damage of composite material structures, and improve the precision and accuracy of impact damage measurement. This helps engineers and researchers gain a deeper understanding of the damage mechanism and development process of the structure, so as to carry out structural design optimization in a more targeted manner, improve the safety and reliability of composite structures, reduce the risk of structural failure, and promote the widespread application and innovative development of composite materials in many fields such as aerospace, automobile manufacturing, civil engineering, etc., providing strong technical support and decision-making basis for related engineering practices.

[0095] A computer device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the program to implement the above-mentioned numerical simulation measurement method for impact data of composite material structures that can be used for shell elements and takes strain rate effects into account.

[0096] Specifically, the computer device of the present invention provides a powerful and efficient tool for numerical simulation measurement of impact data of composite material structures in scientific research and engineering applications. By accurately implementing a simulation measurement method that can be used for shell elements to account for strain rate effects, the complex mechanical behavior of composite materials under impact loads can be simulated and measured with high accuracy. The efficient execution of the program by the processor allows researchers to deeply explore the response of composite material structures under different impact conditions, including the distribution and change of stress and strain, as well as the initiation, development and final damage state of damage. This is of key significance for optimizing the design and performance of composite materials, and can help develop composite material structures with better impact resistance and reliability, promote the innovative application of composite materials in high-end fields such as aerospace, automotive industry, and shipbuilding, and improve the safety and durability of products. From the perspective of practical operation, the computer device is convenient and flexible. The memory storage program facilitates the management and call of data, and the fast running ability of the processor ensures the efficient conduct of simulation calculations. Whether it is a small-scale experimental simulation or a large-scale engineering analysis, accurate results can be obtained quickly, greatly shortening the research and development cycle and cost. At the same time, the equipment can be flexibly adjusted and parameterized according to different research needs and working conditions, adapting to various complex practical application scenarios, providing engineers and researchers with a powerful technical platform, and promoting the continuous development and progress of composite material structure research and application. In the field of education and talent training, this computer equipment is also of great value. It can be used as a teaching tool to help students more intuitively understand the mechanical principles and impact response characteristics of composite material structures, cultivate students' practical ability and innovative thinking, and provide strong support for the cultivation of high-quality professionals in related fields.

[0097] In view of the above method, the present invention establishes two typical impact measurement specific embodiments:

[0098] Example 1: Reference Figure 4 As shown, Figure 4 : is a schematic diagram of the finite element model of Example 1, and the calculation scenario is the impact measurement of a composite material flat plate structure in the air under high-speed impact. The composite material flat plate 1 is fixed on all sides, the Euler domain is set to be air that completely contains the impacted structure, the Euler domain boundary is set to be non-reflective to simulate an infinite domain, the overall system applies gravity, and the initial atmospheric pressure is applied in the form of ground stress, and the impact punch 3 vertically impacts the composite material structure at a speed of 50m / s.

[0099] Specifically, the VUMAT subroutine is established according to the method in step S1, and the composite plate 2 is established by using the Lagrangian shell unit. The composite plate 2 is rigidly fixed on all sides and placed in the air Euler domain 1 set as air material. The boundary condition of the air Euler domain 1 is set to be non-reflective to simulate an infinite domain. Gravity is applied to the entire system, and the initial atmospheric pressure is applied in the form of ground stress. The impact punch 3 vertically impacts the composite structure at a speed of 50 m / s. The working condition is the impact measurement of the composite plate 2 under high-speed impact in the air. The schematic diagram of the impact model is shown in Figure 4 As shown. The calculation time is 10ms, and the 6-core CPU is used for parallel calculation, and the total time is 1 hour. It can be seen from the calculation results that the strain rate of the severely impacted area of ​​the composite plate 2 exceeds the reference strain rate of 1000s-1 set in this example. It has been verified that under the action of high-speed impact, the material stiffness and strength of the composite plate 2 in the area corresponding to the strain rate higher than the reference strain rate are improved according to the equations in the VUMAT program, and are updated in real time as the strain rate response of the impacted structure changes. Since the damage judgment of this method integrates factors such as strain, stress, and unit distortion, the numerical simulation measurement results using this method show that the mesh with excessive distortion has been successfully deleted. In summary, this method has achieved the expected effect and is suitable for numerical simulation measurement of impact of composite structures under high-speed impact loads.

[0100] Example 2: According to the method of step S1, a VUMAT subroutine is established, and a composite cylindrical shell 5 is established using Lagrangian shell elements. The composite cylindrical shell 5 is composed of a steel material and a fiber composite material laminate. The four sides are freely supported and placed in a water Euler domain 4 set as a water material. The boundary condition of the water Euler domain 4 is set to be non-reflective to simulate an infinite domain. Gravity is added to the overall system, and initial water pressure is applied in the form of ground stress. The TNT spherical explosive 6 has an equivalent of 150g and is attached to the middle of the column shell structure and detonated. The working condition is the impact measurement of the composite cylindrical shell 5 in water under the action of contact explosion load. The impact model is as follows: Figure 5As shown. The calculation time is 10ms, and it takes 6 hours to calculate in parallel using a 10-core CPU. It can be seen from the calculation results that the structure has obvious impact deformation and damage in the area affected by the explosion shock wave. The damage morphology of the pure steel column shell structure under the explosion impact load presents a typical approximate cross crack; the damage of the composite cylindrical shell 5 under the explosion impact load is due to the official built-in program calculation. The shell unit does not take into account the strain rate effect, and the damage judgment is single, resulting in the mesh of the composite cylindrical shell 5 has significantly produced a large distortion but cannot present a reasonable crack; the impact measurement is performed using this method, and the results show that the crack morphology of the composite cylindrical shell 5 is clear, and the impact crack of the composite cylindrical shell 5 is slightly smaller than that of the pure steel structure, and the impact measurement law is reasonable. In summary, compared with the built-in method of the existing finite element software, this method can support the case of shell unit modeling, take into account the strain rate effect in the impact simulation numerical measurement, and more accurately capture the impact response of materials and structures. At the same time, factors such as strain, stress and unit distortion can be taken into account to comprehensively calculate the rupture damage under impact. The calculation results are more reasonable than the existing methods, which verifies the applicability of this method for impact numerical simulation measurement of underwater composite structures under explosive impact loads.

[0101] The method of the present invention introduces a dynamic enhancement factor, establishes an anisotropic strain rate calculation module and a strain rate stiffness and strength correction module, thereby improving the numerical simulation measurement accuracy under high-speed impact loads; embeds a variety of damage criterion theories, so that users can choose appropriate damage criteria according to different impact conditions; establishes a comprehensive damage judgment module based on maximum strain, stress, and unit distortion, which can more accurately obtain the impact damage state; and adopts the Euler Lagrangian method to take into account the fluid-solid coupling effect. Through typical examples, it is verified that this method can be well used for numerical simulation measurement of impact data of composite material structures subjected to explosions, collisions, etc. in water or air, has strong applicability and is suitable for promotion, and has high engineering practical value.

[0102] In the above description, the classical algorithms and theories that may be involved are all existing technologies and will not be elaborated here.

[0103] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A numerical simulation measurement method for impact data of composite material structures that can be used for shell elements taking into account strain rate effects, characterized in that: The numerical simulation measurement method for impact data of composite material structures that can be used for shell elements and take strain rate effects into account comprises the following steps: S1. Establish the shell element VUMAT subroutine including the anisotropic strain rate effect. In the process of constructing the VUMAT subroutine of S1, an anisotropic strain rate calculation module is established. The strain rate to composite material stiffness correction module and the strain rate to composite material strength correction module in the VUMAT subroutine are established by introducing the dynamic enhancement factor, so as to achieve the purpose of considering the anisotropic strain rate effect in the impact measurement process. Among them, the dynamic enhancement factor considers three aspects of 1 direction, 2 directions and 12 directions respectively, and the calculation formula is as follows: In the above formula is the dynamic enhancement factor, is the reference strain rate, is the strain rate of the current calculation increment, A is the correction parameter obtained from material test, where ij is 11, 22, 12, representing the 1st, 2nd and 12th directions respectively; S2. Construct an Euler mesh domain according to the impact measurement conditions, cover the target structure, reasonably allocate Euler domain materials to simulate the impact environment and take into account the fluid-structure interaction effect, and define the impact load form; S3. Use finite element software to perform display dynamics calculation analysis and call the VUMAT subroutine to achieve numerical simulation measurement of structural impact data under structural impact load.

2. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 1, characterized in that: In S1, the VUMAT subroutine is established using Fortran language.

3. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 2, characterized in that: S1 includes the following steps: S101, reading in parameters from the finite element analysis pre-processing interface, defining the physical meaning of each parameter read in the VUMAT program, and defining the integration point state variables for storing the solution variable information; S102, constructing an initial stiffness matrix based on the constitutive characteristics of the shell element, wherein the initial stiffness matrix describes the stiffness of the material when it is not subjected to external force, and using the linear elasticity assumption that the stress and strain are linear when the material is not damaged, calculating the first step stress response according to the current stress condition; S103, updating and storing the strain response of each display dynamics iteration step for subsequent calculation; S104, calculating effective stress according to the strain response and the initial stiffness matrix; S105, calculating the rate of change of strain over time, i.e., the strain rate, updating the dynamic enhancement factor according to the value of the strain rate, and using the updated dynamic enhancement factor to correct the stiffness and strength parameters; S106. The true stress value is obtained according to the strain response and the stiffness matrix after taking into account the strain rate effect and damage stiffness degradation, which provides more reliable data for subsequent judgment of material state and damage analysis; S107, determine the damage criterion to be adopted according to the parameters input by the pre-processing, and judge whether the material is damaged according to the material state obtained by the current calculation, if it is damaged, execute S108; otherwise, execute S110; S108, when it is determined that the material is damaged, damage evolution calculation is performed based on the definition of fracture energy, the damage development process is determined by calculating the fracture energy, and the damage criterion coefficient after damage evolution is updated. The coefficient is used to measure the degree of damage and perform stiffness reduction. The unit distortion degree is also calculated to control the deletion of large distortion meshes; S109, establishing a mesh deletion determination module, wherein the mesh deletion determination module comprehensively considers information of maximum strain, stress-related damage criterion coefficient, and unit distortion degree to determine whether a unit needs to be deleted, so as to more accurately simulate the actual fracture condition of the material after damage; S110, update the material point state variable data, and pass the updated material point state variable data to the finite element software solution main program to determine whether the calculation is completed, if completed, end; otherwise continue to loop S104-S110 until the calculation is completed.

4. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 3, characterized in that: In S1, the establishment process of the VUMAT subroutine is based on the constitutive properties of three-dimensional shell elements to achieve the purpose of supporting shell element modeling and analysis.

5. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 1, characterized in that: The VUMAT subroutine embeds multiple impairment criteria including HASHIN, PUCK and CHANGCHANG.

6. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 5, characterized in that: In the construction process of the VUMAT subroutine of S1, the VUMAT subroutine performs damage evolution calculation based on the fracture energy theory, defines shear damage based on the progressive damage theory and associates it with shear stiffness degradation, wherein the shear damage determination factor is calculated as follows: In the above formula, stateNew(k,4) is the fiber tensile damage factor; stateNew(k,5) is the fiber compressive damage factor; stateNew(k,6) is the matrix tensile damage factor; stateNew(k,7) is the matrix compressive damage factor; stateNew(k,8) is the shear damage factor, and the shear stiffness degradation is carried out as follows: In the above formula represents the shear stiffness after degradation; is the shear stiffness corrected for strain rate; Represents the shear damage factor of the previous increment.

7. The method for numerical simulation measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects according to claim 6, characterized in that: In S1, the VUMAT subroutine establishes a comprehensive damage determination module based on maximum strain, stress and unit distortion to improve the measurement accuracy of impact damage. The operation method of the comprehensive damage determination module includes three parts: First, compare the tensile and compressive strains of the current incremental step with the tensile and compressive strains at fracture. When the ratio is greater than 1, the material is theoretically fractured and the element definition is deleted. Secondly, when the damage criterion coefficient of the current incremental step is greater than 1, the material is theoretically damaged, the unit definition is deleted, and the three built-in damage criteria of the VUMAT program used in S1 are all stress-related criteria; Finally, the stress matrix eigenvalue is calculated and the unit distortion coefficient is calculated according to the eigenvalue. When the unit distortion coefficient is greater than 1.0 or less than -0.8, the unit distortion is too large and has affected the accuracy of the finite element calculation. The unit definition is deleted.

8. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for numerical simulation and measurement of impact data of composite material structures that can be used for shell elements taking into account strain rate effects as described in any one of claims 1 to 7 is implemented.

9. A computer device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a numerical simulation measurement method for impact data of a composite material structure that can be used for shell elements taking into account strain rate effects as described in any one of claims 1 to 7.

Images