Background
The rubber product has the advantages of small volume, light weight, multidimensional nonlinear rigidity and the like, and is widely applied to damping and vibration isolation of engineering equipment. As an important component of an engineering equipment system, a rubber product needs to have good static nonlinear rigidity characteristic, creep resistance and stress relaxation resistance, and the rubber product mainly plays roles of supporting, vibration isolating and shock absorbing in the system. In order to ensure the safety and reliability of the actual service state, a modern finite element numerical simulation technology is adopted, and the mechanical property prediction (such as quasi-static superelasticity analysis, long-time creep analysis and stress relaxation analysis) of the rubber product under different working conditions is necessary.
At present, operators generally perform geometric modeling on rubber products according to structural characteristics during simulation analysis, and can only perform mechanical property analysis on rubber products with fixed sizes; in the product updating design, an operator needs to modify key geometric parameters of rubber products one by one, and manually repeats the operation processes of geometric modeling, grid division, boundary/load/contact condition setting and the like, so that the increase of labor cost and time cost is caused. Therefore, the rubber product is subjected to parametric modeling work (namely, key geometric parameters are extracted, and an automatic input modification model is realized), so that the design cost can be greatly saved, and the rubber product has important practical application value. In addition, when the existing commercial finite element software is applied to analyze the rubber product, the creep deformation and stress relaxation analysis of the rubber product cannot be directly carried out because the commercial software built-in material model library mainly comprises a superelastic material model and a viscoelastic material model of the rubber material. In order to meet the requirements of engineering application, commercial finite element software is subjected to secondary development and compilation, the compiling and warehousing of constitutive models of creep deformation, stress relaxation and the like of rubber materials are realized, and the complete time-varying characteristic analysis is performed on rubber products.
In addition, with the rapid development of modern computer technology, a numerical simulation technology combining a finite element method and an optimization theory is necessary for analyzing, predicting and optimizing actual equipment. For rubber products, through simulation and optimization calculation, the optimal geometric parameter combination of the structure under the condition of meeting the mechanical property requirement can be expected to be determined, and the work has obvious application value for delivery upgrade of the rubber products, shortening of research and development period and saving of design cost.
In conclusion, the commercial finite element software is secondarily developed and compiled, a rubber product mechanical property prediction and optimization design software platform integrating parametric modeling, a constitutive model development module, solution result analysis and multi-parameter optimization analysis is provided, a necessary simulation calculation means is provided for the actual mechanical state analysis of the rubber product, and the method has important engineering application significance. However, a software platform for analyzing and optimizing rubber products with the functions is not available at present, and operation and analysis personnel cannot accurately predict the mechanical property and subsequent integrated optimization design of the rubber products, so that the actual application process of the rubber products is influenced.
Disclosure of Invention
In order to solve the technical problems, the invention provides a software platform for analyzing and optimally designing the mechanical properties of rubber products, which integrates a plurality of modules such as a parametric modeling module, a constitutive model development module, a solution result analysis module, a multi-parameter optimization module and the like, can perform quasi-static superelasticity characteristic analysis, long-term creep analysis and stress relaxation analysis on the rubber products, has higher accuracy, effectively provides the mechanical property prediction results and the optimal design scheme of the rubber products, and has wide practical application value.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a software platform for mechanical property analysis and optimal design of rubber products comprises the following modules:
firstly, a parameterized modeling module: the method realizes automatic modeling of key design parameter change of the rubber product, realizes generation and updating of a geometric model and a finite element model by taking a reference geometric model as a reference sample and changing parameter variables, and drives parameter linkage among the parameter variables, the geometric model and a grid model so that the geometric model and the grid model of an analysis object are automatically generated along with the change of input parameters;
secondly, a constitutive model development module: the method is used for developing a constitutive model suitable for rubber products, constructing a plurality of constitutive model material libraries of the rubber products, identifying constitutive model parameters and realizing nesting calling of constitutive model sub-modules in finite element numerical simulation;
thirdly, a solution result analysis module: on the basis of a parametric modeling module and a constitutive model development module, providing multi-working-condition numerical simulation for predicting and evaluating the mechanical property of the rubber product;
fourthly, a multi-parameter optimization module: on the basis of a parametric modeling module, a constitutive model development module and a solution result analysis module, a multidisciplinary optimization mechanism is introduced, an ABAQUS and Isight optimization integrated operation module is built, and creep resistance and stress relaxation resistance optimization design analysis of the rubber product is realized.
In the above solution, the method for implementing the parameterized modeling module includes the following steps:
(1) extracting key geometric characteristic parameters of the structure according to the geometric model of the rubber product, and establishing a parameterized geometric model;
(2) constructing a grid division plug-in, carrying out numerical simulation environment setting, unit type setting and material model setting, comprehensively considering grid convergence consistency and calculation cost, and providing grid division schemes with different densities;
(3) according to the practical application working condition, the interaction relation among all components in the rubber product analysis is set, and the method comprises the following analysis option settings: contact friction conditions, boundary constraints and load conditions are defined.
In the above solution, the implementation method of the constitutive model development module includes the following steps:
(1) according to the national standard and the industrial specification, carrying out a mechanical test on the rubber product material;
(2) developing a constitutive model submodule material library of rubber product materials by adopting a FORTRAN language based on a user self-defined subprogram interface provided by ABAQUS;
(3) carrying out computer language integrated programming through Python, applying an intelligent optimization algorithm, and carrying out the parameter identification of the constitutive model of the rubber product material based on the test result of the mechanical test;
(4) and establishing a guide type material input module, establishing a self-compiling user subprogram plug-in, and realizing the nested calling of the constitutive model submodule in the finite element numerical simulation.
In the above scheme, the mechanical test includes quasi-static uniaxial tension, equibiaxial tension, plane tension test, long-term creep test and long-term stress relaxation test.
In a further technical scheme, the developing a material library of the constitutive model submodule of the rubber product material comprises the following steps:
firstly, an ABAQUS built-in superelastic material constitutive model is used, and a superelastic constitutive model submodule is established;
secondly, comprehensively considering nonlinear superelasticity characteristics and a time-variable-containing degradation mechanism, and establishing time-varying stress relaxation and creep constitutive model submodules;
and finally, introducing a plastic damage effect on the basis of the established time-varying stress relaxation and creep constitutive model, and establishing a time-varying relaxation-damage and time-varying creep-damage constitutive model submodule considering the damage residual deformation effect.
In the above scheme, the implementation method of the solution result analysis module includes the following steps:
(1) compiling and calling an ABAQUS kernel solution command stream plug-in according to the mechanical characteristics of rubber products under different working conditions to complete a static solution module, dynamic stress relaxation and dynamic creep solution;
(2) establishing a mechanical characterization system under different working conditions, analyzing a post-processing result through a Python language, extracting a quasi-static superelasticity load-displacement analysis result, outputting a time-varying creep deformation main curve, outputting a time-varying stress relaxation degradation main curve, and displaying a stress/strain cloud picture and a time-varying deformation animation process at any moment.
In the above scheme, the method for implementing the multi-parameter optimization module includes the following steps:
(1) establishing a data exchange mechanism from a rubber product parameterized modeling module to a solution result analysis module, creating a multidisciplinary optimization flow based on data flow, generating an optimization input file, and providing a file interface for optimization design;
(2) determining an objective function and constraint conditions of creep and stress relaxation optimization analysis of the rubber product and key geometric parameters extracted from a rubber product parametric modeling module, and establishing an optimized mathematical model of the rubber product;
(3) utilizing Isight integrated ABAQUS software to complete input and output file analysis and compiling of a program plug-in, and realizing parameter sensitivity analysis of the structure size and the mechanical property of the rubber product; and selecting a proper optimization algorithm to perform iterative optimization calculation on the model to obtain the optimized structural design parameters of the rubber product.
Through the technical scheme, the software platform for mechanical property analysis and optimal design of the rubber product provided by the invention has the following beneficial effects:
1. the software platform for mechanical property analysis and optimization design of rubber products, which is developed and provided by the invention, is convenient to operate, has a clear analysis purpose, can predict various mechanical properties (quasi-static superelasticity, long-term creep and stress relaxation characteristics) of the rubber products, and has comprehensive analysis results;
2. the parameterized modeling module in the software platform developed by the invention provides an automatic modeling function of the geometric model of the rubber product, namely, the rapid geometric modeling of the rubber product can be realized by inputting the key geometric parameters of the rubber product, the numerical modeling work of repeated operation caused by the change of the key parameters is avoided, and the labor and time cost is effectively saved. Through the operation test, the following results are obtained: when a parameterized modeling module is not used, the geometric modeling of the rubber product is completed in 2 hours; after the parameterized modeling module is used, the establishment of the geometric model can be completed quickly within 3 minutes, and the analysis efficiency is greatly improved.
3. The software platform rubber material constitutive model development module developed by the invention realizes compiling and warehousing of various superelastic constitutive models; a time-varying creep and stress relaxation constitutive model is provided for creep and stress relaxation behaviors of rubber, and is integrated into a software platform based on a Fortran language and a UHYPER subprogram, so that a proper constitutive model module is provided for realizing creep and stress relaxation analysis of a rubber product.
4. The software platform rubber product multi-parameter optimization module developed by the invention integrates the ABAQUS finite element model and the Isight optimization mathematical model, takes the minimum creep deformation or stress relaxation degradation rate of the rubber product as an optimization target, obtains the corresponding optimal structure model size, and provides favorable theoretical and numerical guidance for practical engineering application.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
The invention provides a software platform for mechanical property analysis and optimization design of rubber products, which carries out secondary development and compilation on commercial finite element software (ABAQUS), applies Python language, Fortran language and UHYPER self-defined programs and integrates Isight optimization design software to complete a parameterized modeling module, a constitutive model development module, a solution analysis module and a multi-parameter optimization module.
In this embodiment, taking a rubber damper as an example, as shown in fig. 1, the following steps are specifically included:
step one, building a main interface
Through secondary development, the rubber shock absorber mechanical property analysis and optimization design software platform provided by the patent is integrated into commercial finite element software ABAQUS. The method specifically comprises the following steps:
first, a kernel file xxxfunction.py file is written, which contains definitions of execution operation steps and related parameters in the respective modules in ABAQUS/CAE.
Secondly, compiling a graphic interface file XXXDB.py, wherein the XXXDB.py file is a way for compiling a graphic user interface, and compiling the interface, key parameter words and the like can be realized in the XXXDB.py file; at the same time, xxxxdb.
Finally, writing a xxxform. Meanwhile, the xxxform.
The three types of files (XXXfunction. py, XXXDB. py, XXXform. py) are connected with each other, but are not all in the same way; the three files are put into a main interface folder, and then the mechanical property analysis and optimization design software platform developed by the patent can be associated and registered into commercial finite element analysis software ABAQUS.
The main interface of the rubber shock absorber mechanical property analysis and optimization design software platform provided by the invention is shown in figure 2 and comprises the following functions:
"1. Structural analysis" (structure selection), "2. Material models" (Material model), "3. Contact setting" (Contact setting), "4. Boundary condition)," 5.Loading setting "(load setting)," 6. shifting setting "(grid setting)," 7.Job analysis "(submission analysis)," 8.Post process "(Post-processing display)," 9. isolation optimization "(isolation integration optimization analysis)," 10. sensing analysis Sensitivity "(analysis).
Step two, establishing a parameterized modeling module
And developing a rubber shock absorber parameterized modeling module based on ABAQUS by applying Python language to create a user interaction interface. The rubber shock absorber parametric modeling module needs to use a reference geometric model as a reference sample, realize the generation and the update of the geometric model and a finite element model by changing parameter variables, and realize the automatic generation of the geometric model and the grid model of an analysis object along with the change of the input geometric parameters of a main interface. The automatic modeling of the change of the key design parameters of the rubber shock absorber can be realized through the parametric modeling module. The operation steps comprise:
extracting key geometric characteristic parameters of a structure according to a geometric model of the rubber shock absorber, and establishing a parameterized geometric model:
firstly, a user inputs key geometric parameter values (such as height h, distance d and included angle a), a system automatically searches parameter tags by using mark letters of the key geometric parameters, and the positions of the parameter tags in a XXXfunction.
Then, after finding the location, replacing the marked letter parameter tags in the xxxfunction.py file with the parameter values entered by the user to create a new re-encoded xxxfunction.py file;
and finally, running the recoded XXXfunction. The completed model is built as shown in fig. 3 a.
Contacting setting of rubber damper model (contact setting): and connecting the upper end of the rubber shock absorber with the analytic rigid body according to the practical application condition. In order to prevent interpenetration of the rigid body and the rubber material, a surface-to-surface contact is provided at the contact area. And (3) integrating the contact relation into a mechanical property analysis and optimization design software platform of the rubber shock absorber by using Python language. The model for setting the completed contact is shown in fig. 3 b.
Boundary condition setting (boundary setting) of the rubber shock absorber model: according to the practical application working condition, the bottom of the rubber shock pad is set to be a full constraint condition, and the upper end of the rubber shock pad is a free boundary (namely, a displacement boundary condition is not required to be designed). According to the symmetry of the model, in order to improve the calculation efficiency, only a quarter of the model is established in the embodiment, and symmetric constraints are applied in the X and Z directions. And (3) integrating the boundary conditions into a rubber damper mechanical property analysis and optimization design software platform by using Python language. The model for setting the completion boundary conditions is shown in fig. 3 c.
Setting the load condition of the rubber shock absorber model (loading setting): according to the practical application working condition, the load acts on the analytic rigid body along the vertical direction and is transmitted to the rubber shock absorber through the degree of freedom coupling. And (3) integrating the load conditions into a mechanical property analysis and optimization design software platform of the rubber shock absorber by using Python language. Using creep analysis load as an example, a model for setting the complete load condition is shown in fig. 3 d.
Fifthly, mesh division setting of the rubber shock absorber model (meshing setting): after the rubber shock absorber is subjected to numerical simulation environment setting, unit type setting and material model setting, the grid convergence consistency characteristic and the calculation cost are comprehensively considered, and grid division schemes with different densities are provided: coarse grid, Medium grid, Fine grid. In this embodiment, a 4-DOF-8-node three-dimensional solid unit is adopted. A Meshing setting model of the rubber product under the specified Fine Meshing density scheme is shown in fig. 3 e.
Step three, establishing a constitutive model development module
In order to analyze the quasi-static superelasticity characteristics and creep deformation and stress relaxation of the rubber shock absorber, a rubber material constitutive model for corresponding mechanical characteristic analysis needs to be established, and a plurality of constitutive model material libraries of rubber materials are established in a rubber shock absorber mechanical property analysis and optimization design software platform. The material parameters of each constitutive model can be obtained by identification according to rubber mechanical test data. The operation steps comprise:
mechanical tests of the rubber shock absorber material, such as quasi-static uniaxial tension, equibiaxial tension, plane tension tests, long-term creep tests and long-term stress relaxation tests, are carried out according to national standards.
Secondly, developing a constitutive model submodule material library of the rubber material by adopting a FORTRAN language based on a user self-defined subprogram interface provided by ABAQUS.
Firstly, an ABAQUS built-in superelastic material constitutive model is used, and a superelastic constitutive model submodule is established;
secondly, comprehensively considering the nonlinear superelasticity characteristic and a time variable-containing degradation effect mechanism, and establishing a time-varying stress relaxation and creep constitutive model submodule;
and finally, introducing a plastic damage effect on the basis of the established time-varying stress relaxation and creep constitutive model, and establishing a time-varying relaxation-damage and time-varying creep-damage constitutive model submodule considering the damage residual deformation effect.
The ultra-elastic constitutive model follows the ABAQUS built-in material constitutive model, and comprises a Mooney-Rivlin model, a Neo-Hookean model, an Odgen model, a Van-DER-Waals model and an ARUUDA-BOYCE model. A schematic diagram of a superelastic constitutive model development module shown in fig. 4 a.
Time-varying relaxation constitutive model
The superelastic constitutive model can describe the nonlinear large deformation characteristics of the rubber material, but cannot describe the time-dependent stress relaxation behavior. Aiming at the problem, the invention introduces a strain energy function containing a time variable on the basis of the super-elastic strain energy constitutive relation of the rubber material, and provides a stress relaxation constitutive model considering the time-varying degradation effect. A time-varying relaxation constitutive model development module schematic diagram as shown in fig. 4 b. For the convenience of engineering application, the superelastic part adopts a Mooney-Rivlin constitutive model. The established time-varying relaxation constitutive model is as follows:
in the formula, t is the time of stress relaxation deformation of the rubber material; k is a radical of
rThe amplitude degradation coefficient is used for representing the amplitude degradation degree of the relaxation stress; r is
rFor relaxing the damping coefficient, for characterizing the gradual stress damping over time, C
10,C
01,D
10Is the super-elastic parameter of the rubber material;
is a strain invariant; j is the elastic volume ratio.
Time-varying creep constitutive model
The stress relaxation and the creep are macroscopic expressions of time-varying mechanical properties of the rubber material, and the two have correspondingEquivalent relation, therefore, the creep property of the rubber material is described by using the time-varying relaxation constitutive model; however, at this time kcThe creep amplitude degradation coefficient is used for representing the amplitude degradation degree of creep deformation; r iscThe creep deformation attenuation coefficient is used for characterizing the creep deformation attenuation degree changing along with time. A schematic diagram of a time-varying creep constitutive model development module as shown in fig. 4 c. The time-varying creep constitutive model is as follows:
time-varying relaxation-Damage constitutive model
On the basis of the stress relaxation constitutive model, in order to further describe the damage residual deformation effect of the rubber material after relaxation unloading, on the basis of the time-varying relaxation constitutive model, a yield flow criterion and a plasticity function are adopted to construct the time-varying relaxation-damage constitutive model. A schematic diagram of a time-varying relaxation-damage constitutive model development module as shown in fig. 4 d. The incremental constitutive relation in each time step is:
wherein f is a yield function, K is a strengthening function,
in order to be equivalent to the plastic strain,
in increments of equivalent plastic strain, S
ijAs a result of the amount of the stress deflection,
is the equivalent yield stress; the damage during plastic flow of rubber materials can be expressed in stages,
for equivalent plastic strains at different loading stages,
for equivalent stress at different loading stages, when n is 0, the initial equivalent yield stress can be obtained
d
ijIn order to increase the total strain,
increase in plastic strain for damage σ
ijIs the strain energy stress component of the rubber material,
for superelastic and relaxation strain increments, W
r-eThe constitutive model is relaxed for the modified time-varying superelastic.
Time-varying creep-damage constitutive model
Similarly, on the basis of the creep constitutive model, a time-varying creep-damage constitutive model is constructed, which is in the form of formula (3), but the physical meanings of the key constitutive parameters are different at the moment. A schematic diagram of a time-varying creep-damage constitutive model development module as shown in fig. 4 e.
And thirdly, carrying out computer language integrated programming through Isight and Python, applying an intelligent optimization algorithm, establishing an evaluation fitness target based on a mechanical test result, and identifying constitutive model parameters of the rubber material. Specifically, the method comprises the following steps: identifying a superelastic parameter based on a stress-strain curve tested by a superelastic mechanical test; identifying time-varying relaxation constitutive model and time-varying relaxation-damage constitutive model parameters by using numerical difference of time-stress curves and relaxation unloading residual deformation difference values of stress relaxation test and simulation calculation as fitness targets; and identifying parameters of the time-varying creep constitutive model and the time-varying creep-damage constitutive model by taking the numerical difference of time-deformation curves of creep test and simulation calculation and the creep unloading residual deformation difference value as fitness targets.
Establishing a guide type material input module, constructing a self-compiling user subprogram plug-in, and realizing the nesting calling of the constitutive model submodule in the finite element numerical simulation. Firstly, defining a constitutive model library (a superelastic constitutive model, a time-varying relaxation constitutive model, a time-varying creep constitutive model, a time-varying relaxation-damage constitutive model and a time-varying creep-damage constitutive model); secondly, selecting a certain constitutive model by using the judgment condition statement.
Step four, establishing a solution result analysis module
On the basis of a parametric modeling module and a constitutive model development module, a multi-working-condition numerical simulation solving and result analyzing module is provided and can be used for predicting and evaluating the mechanical property of the rubber shock absorber. The operation steps comprise:
firstly, compiling and solving a command stream program aiming at the mechanical characteristics of the rubber shock absorber under different working conditions, calling an ABAQUS built-in solver, and completing static solving, dynamic stress relaxation and dynamic creep solving.
Firstly, defining five analysis types (namely, superelasticity analysis, time-varying relaxation analysis, time-varying creep analysis, time-varying relaxation damage analysis and time-varying creep damage analysis) corresponding to the constitutive model library of the patent software platform;
secondly, the judgment conditional statement is used for realizing the selection of a certain analysis type.
Secondly, establishing a mechanical characterization system under different working conditions: analyzing the post-processing result through Python language, and extracting a quasi-static superelastic load-displacement analysis result, as shown in FIG. 5 a; outputting a time-varying creep deformation amount main curve as shown in FIG. 5 b; outputting a time-varying stress relaxation degradation main curve, as shown in FIG. 5 c; and displaying a stress/strain cloud picture at any moment, a time-varying deformation animation process and the like.
Step five, establishing a multi-parameter optimization module
Based on a multidisciplinary optimization mechanism, an ABAQUS and Isight optimization integrated operation module is set up, and optimization design analysis of the rubber shock absorber is achieved. The operation steps comprise:
establishing a data exchange mechanism from a rubber shock absorber parameterized modeling module to a solving and result analyzing module, establishing a multidisciplinary optimization flow based on data flow, generating an optimization input file, and providing a file interface for optimization design;
determining an objective function (minimum creep deformation amount or minimum stress relaxation degradation rate) of creep and stress relaxation optimization analysis of the rubber shock absorber, constraint conditions (shock absorber rigidity limit range) and design variables (key geometric parameters in rubber shock absorber parametric modeling, namely height h, distance d and included angle a), and establishing an optimized mathematical model of the rubber shock absorber;
thirdly, input/output file analysis and program realization plug-in are completed by utilizing Isight integrated ABAQUS software, an optimized model file and a sensitivity analysis file path are defined by utilizing Python language, the selection is realized through functions, the parameter sensitivity analysis of the structural size and the mechanical property of the rubber shock absorber is realized, and the analysis result is shown in figure 6a, so that the geometric parameter combination which influences the creep deformation and the stress relaxation degradation rate of the shock absorber most obviously is obtained; the time-stress curve comparison of the optimized model of the rubber product obtained by using the minimum stress relaxation degradation rate as the optimization target and the original model is shown in FIG. 6 b.
Establishing an optimization model based on ABAQUS and Isight integration, and performing iterative optimization calculation on the established model to obtain the optimized structural design parameters of the rubber shock absorber.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.