CN115204003B - Method for constructing nonlinear creep-type viscoelastic constitutive model of polymer material - Google Patents
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Abstract
A method for constructing a nonlinear creep-type viscoelastic constitutive model of a polymer material belongs to the field of polymer materials and is characterized in that: the process of establishing the nonlinear creep-type viscoelastic constitutive model of the polymer material takes ageing, temperature, stress level and damage factors into consideration; the parameter solving and model verification process of the nonlinear creep-type viscoelastic constitutive model of the polymer material takes aging, temperature, stress level and damage factors into consideration. The method can effectively reflect the influence of aging, ambient temperature and stress level on the creep deformation process and damage behavior, further can describe and predict the creep deformation mechanical response of polymer materials such as plastics, solid propellant, explosive and the like which are subjected to different storage periods, wide-temperature use environments and bearing different fixed load ranges, and has a wider application range.
Description
Technical Field
The invention belongs to the field of polymer materials, and particularly relates to a method for constructing a nonlinear creep-type viscoelasticity constitutive model of a polymer material.
Background
In general, structural members or devices made of polymer materials such as plastics, solid propellants, explosives and the like undergo different storage periods before use, and the interior of the polymer materials is generally provided with a large number of polymer chains, so that the structural morphology and physical properties of the materials during storage change with the storage time, namely, physical aging effects occur, and further the performance of the manufactured structural members in actual use is affected. Secondly, the polymer materials such as plastics, solid propellant, explosive and the like have obvious rheological properties, namely the mechanical properties of the polymer materials are obviously influenced by time, temperature, stress level and the like, the polymer materials exhibit viscoelasticity properties, and creep deformation under the constant loading effect of different environmental temperatures is one of the main characteristics of the viscoelasticity properties of the materials. With prolonged loading or increased stress levels, the formation and expansion of molecular chain breaks or micro-porosity or other microscopic structural defects may occur within the polymeric material, i.e., damage may occur within the material and structure and accumulate. The build-up of this damage can cause polymeric materials such as plastics, solid propellants, explosives, etc. to exhibit non-linear characteristics upon deformation, even causing eventual failure to fracture.
At present, a large number of nonlinear viscoelastic constitutive model building methods based on relaxation mechanical response are proposed by researchers at home and abroad aiming at the deformation characteristics of polymer materials under the conditions of constant-rate stretching and compression at different ambient temperatures. In the deformation process of the material, aiming at nonlinear characteristics caused by the generation and accumulation of mesostructure damage, researchers focus on establishing a plurality of damage evolution functions from a macro-micro perspective. In order to describe the influence of aging effect on the mechanical properties of polymer materials such as solid propellant, explosive and the like, some researchers propose a method of adopting the cross-linking density and gel percentage as characterization parameters and a method of characterizing the parameters of a poisson ratio and the like as an aging time function, but the constructed model does not effectively consider the influence of aging factors on the damage characteristics of the polymer materials such as solid propellant, explosive and the like when the polymer materials are greatly deformed, and especially does not consider the influence of multi-factor coupling on the damage characteristics. In addition, since the relaxation mechanical response of the polymeric material differs significantly from the creep mechanical response characteristics, the method of building a nonlinear viscoelastic constitutive model based on the relaxation mechanical response is not necessarily suitable for describing creep deformation, especially when significant damage characteristics occur. For creep deformation of polymer materials such as plastics, solid propellants and the like, partial researchers propose a method for referencing a creep constitutive model of a metal material and a method for constructing a relaxation type viscoelastic constitutive model without damage, and the constitutive model established based on the methods cannot effectively describe and predict the damage characteristics of the polymer materials during creep deformation, and also cannot fully reflect the influences of storage aging effects, environmental temperature and other factors on the creep deformation of the polymer materials. Thus, there are significant errors in performing structural integrity analyses of structural members made of polymeric materials such as plastics, solid propellants, explosives and the like.
Disclosure of Invention
The invention aims to solve the problems and provides a method for constructing a nonlinear creep-type viscoelastic constitutive model of a polymer material, which fully considers the influence of multiple factors.
According to the method for constructing the nonlinear creep-type viscoelastic constitutive model of the polymer material, aging, temperature, stress level and damage factors are considered in the process of constructing the nonlinear creep-type viscoelastic constitutive model of the polymer material; the parameter solving and model verification process of the nonlinear creep-type viscoelastic constitutive model of the polymer material takes aging, temperature, stress level and damage factors into consideration.
Further, the method for constructing the nonlinear creep-type viscoelastic constitutive model of the polymer material comprises the following steps:
the establishment of a creep-type viscoelastic constitutive model of a polymer material taking into account aging, temperature and stress levels;
based on the Boltzmann superposition principle, the integral creep deformation viscoelastic constitutive model without considering the influence of other factors is as follows:
wherein:creep strain under uniaxial tensile loading that is independent of other factors; j (J) 0 And Δj is the initial instantaneous compliance and the time dependent instantaneous creep compliance, respectively; />Is a step load with a value of creep stress level; t is the actual physical time;
the creep-type viscoelastic constitutive model of the polymer material taking into account aging, temperature and stress levels is:
wherein: t is t a Is the aging time; g (t) a ) Describing the influence of different ageing times on the initial instantaneous compliance of the polymeric material for the ageing coefficient; ζ is the reduced loading time associated with stress level, aging time, and ambient temperature; alpha σ 、α ta And alpha T Stress shift factor, aging time shift factor, and ambient temperature shift factor, respectively, and stress level sigma, aging time t, respectively a And an ambient temperature T to describe the effect of stress level, aging time, and ambient temperature on the creep characteristics of the polymer material;
the method comprises the steps of (1) establishing a nonlinear creep-type viscoelastic constitutive model of a polymer material taking ageing, temperature, stress level and damage into consideration;
based on the strain equivalent assumption, the effective stress can be expressed asSecondly, when the mechanical state of the material is analyzed by adopting the damage mechanical theory, the damage state or damage evolution D of the material can be quantified by using macro-micro characterization parameters; because the mesoscopic characterization method relates to the accurate test of mesoscopic structural parameters such as microcracks, pores and the like in the solid propellant, the form of a damage evolution function is complex. Therefore, a macroscopic method based on the accumulated damage concept is adopted to characterize damage evolution D, and a polymer material nonlinear creep type viscoelasticity constitutive model considering aging, temperature, stress level and damage is established as follows:
wherein: d is accumulated damage in the creep deformation process of the polymer material; sigma (sigma) 0 Stress level at creep deformation; beta and N are model parameters affected by aging time and temperature; equation (6) may reflect the effect of aging time, temperature and stress level on the behavior of damage during creep of polymeric materials such as plastics, solid propellants and explosives.
The load when creep deformation is assumed to occur satisfies the constant stress condition, and t=t f When d=1 in formula (6), formula (6) can be further simplified to:
wherein: t is t f The breaking time of creep deformation of the polymer material under the loading of a fixed stress;
and (3) taking the formula (7) into the formula (5) to obtain the nonlinear creep type viscoelastic constitutive model of the polymer material, wherein the aging, the temperature, the stress level and the damage are considered under different constant stress loading.
Further, the polymer material of the invention has nonlinear creep type viscoelasticityThe method for constructing the constitutive model comprises the following steps of: for constant load creep deformation, due to τ>Load at 0 timeNo longer changes; thus, the integral term in equation (2) is integrated only at τ=0; the relaxation modulus and creep compliance of a polymeric material can be described in terms of a Prony series; then at constant load uniaxial tensile creep, formula (2) may be further expressed as:
wherein: j (J) n Is equal to the nth delay time tau n Coefficients of corresponding Prony series; n is the number of Prony series expansion;
at critical damage strain ε th Or critical damage time t th Previously, the damage during creep deformation of polymeric materials was negligible. Thus, first of all based on the reference aging time α ta =1, reference stress level α σ =1 and reference ambient temperature α T Creep strain-time curve data before critical damage strain threshold under the condition of (1), calculating to obtain model parameter J in the formula (8) through a global optimization algorithm 0 、J n And τ n Is a numerical value of (2);
then the obtained model parameter value is carried into the formula (8), and the model parameter alpha in the formula (8) is calculated by a global optimization algorithm based on the aging time, the stress level and the typical creep strain-time curve data before critical damage strain at loading temperature σ 、α ta And alpha T And establish a corresponding mathematical expression alpha σ (σ)、α ta (t a ) And alpha T (T)；
Based on creep mechanical property tests of polymer materials at different environmental temperatures and constant stress levels after different ageing times, the creep time t of material fracture under corresponding conditions is obtained f ；
Based on the determined stress waterThe corresponding relation between the flat creep rupture time and the flat creep rupture time can be determined by adopting a global optimization algorithm, namely, beta (t) under different ageing times and environmental temperatures in the formula (6) and the formula (7) a T) and N (T) a T) numerical value, and then establishing a corresponding mathematical expression;
finally, all parameter values of the non-linear creep-type viscoelastic constitutive model of the polymer material are determined by fitting calculations taking into account aging, temperature, stress level and damage.
Further, the method for constructing the nonlinear creep-type viscoelastic constitutive model of the polymer material comprises the following steps of: and (3) respectively carrying the obtained model parameter values into the formula (5) and the formula (7), and predicting the creep deformation mechanical response and damage behavior of the polymer material under the residual loading condition which does not participate in the model parameter solving, and comparing the prediction result with creep mechanical property test data under the corresponding condition to verify the validity of the built nonlinear creep type viscoelasticity constitutive model of the polymer material considering ageing, temperature, stress level and damage and establish the validity of the constitutive model method.
The verified nonlinear creep deformation type viscoelastic constitutive model of the polymer material, which considers ageing, temperature, stress level and damage, is applied to the application fields related to materials such as plastics, solid propellant, explosive and the like, realizes accurate description and prediction of creep deformation mechanical response of the material, is particularly suitable for accurate description and prediction of creep deformation mechanical response when the material is subjected to loading of loading loads under different environment temperatures after undergoing different storage periods, and solves the engineering problem of application fields related to creep deformation of the polymer material.
The application fields related to the creep deformation of the polymer material comprise the formula optimization field of polymer materials such as plastics, solid propellants, explosives and the like which show viscoelastic characteristics, the finite element user subroutine development field of the constitutive model, the finite element numerical calculation field of the constitutive model, the structural integrity evaluation field of structural members made of the materials, and the use reliability evaluation field of typical equipment such as solid rocket engines and the like under specific conditions such as storage and the like.
Compared with the prior art, the invention has the beneficial effects that:
1. the method for constructing the nonlinear creep deformation type viscoelastic constitutive model of the polymer material, which takes ageing, temperature, stress level and damage into consideration, can macroscopically characterize the damage effect in the creep deformation process in a cumulative damage mode, further accurately describe and predict the whole creep deformation process of materials such as plastics, solid propellants, explosives and the like, and breaks through the defects and limitations in the conventional method for constructing the creep deformation type constitutive model of the polymer material.
2. The method for constructing the nonlinear creep deformation type viscoelastic constitutive model of the polymer material, which takes the ageing, the temperature, the stress level and the damage into consideration, can effectively reflect the influences of the ageing, the ambient temperature and the stress level on the creep deformation process and the damage behavior, further can describe and predict the creep deformation mechanical response of the polymer material such as plastics, solid propellant, explosive and the like which are subjected to different storage periods, wide temperature use environments and bearing different fixed load ranges, and has a wider application range.
3. The method for constructing the nonlinear creep-type viscoelastic constitutive model of the polymer material, which takes ageing, temperature, stress level and damage into consideration, has the advantages of clear physical meaning, simple form, fewer model parameters and easy determination. Thus, the model can be conveniently numerically implemented and finite element calculations can be performed based thereon to accurately assess the structural integrity of a structure made of polymeric material or the reliability of use of typical equipment.
Drawings
FIG. 1 is a graph of typical creep strain versus time for a three-component HTPB composite solid propellant at various aging times, temperatures, and stress levels.
FIG. 2 is a graph of a curve and fit of stress shift factor as a function of stress level.
FIG. 3 is a graph of the curve and fitting results of the aging time shift factor and aging coefficient as a function of aging time.
Fig. 4 is a graph of a curve and a fitting result of a temperature shift factor with temperature.
FIG. 5 is a graph of the cumulative damage index versus aging time and the fit.
FIG. 6 is a graph of the curve and fitting results of parameters in a cumulative damage index fitting model as a function of temperature.
FIG. 7 is a graph comparing typical creep mechanical response test data and constitutive model prediction results for three-component HTPB composite solid propellants at different aging times, temperatures, and stress levels.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description and examples, but the invention is not limited to the embodiments disclosed, but is intended to cover all modifications and adaptations of the invention without departing from the scope of the invention. Furthermore, the drawings are merely exemplary of the manner in which the invention may be practiced, and are not intended to limit the invention to the particular embodiments disclosed.
Example 1
To verify the feasibility and effectiveness of the method of the invention, the polymeric material chosen is a three-component butylol-Hydroxy (HTPB) composite solid propellant, formulated as follows: 88% of solid filler particles (ammonium perchlorate (AP) solid particles and aluminum powder (Al) particles), 12% of HTPB binder and other additives or auxiliaries.
Typical creep strain-time test curves for the three-component HTPB composite solid propellant at wide temperatures and different stress levels after different heat accelerated aging times are shown in fig. 1. FIG. 1 (a) is a graph showing the creep strain-time test of the propellant at a stress level of 20℃and 0.2MPa at room temperature after 0d of aging, FIG. 1 (b) is a graph showing the creep strain-time test of the propellant at a stress level of 20℃and 0.4MPa at room temperature after 0d of aging, FIG. 1 (c) is a graph showing the creep strain-time test of the propellant at a stress level of 20℃and 0.4MPa at room temperature after 32d of heat accelerated aging, and FIG. 1 (d) is a graph showing the creep strain-time test of the propellant at a stress level of 0.2MPa at a low temperature of-20℃after 0d of aging. From fig. 1, it can be seen that the creep strain-time test curve of the three-component HTPB composite solid propellant is significantly affected by aging time, temperature and stress level, and the influence of these factors must be considered when constructing the constitutive model.
The disclosed embodiments provide for the creation of a non-linear creep-type viscoelastic constitutive model of a polymeric material taking into account aging, temperature, stress level and damage, the method comprising the steps of:
(1) The building of a viscous-elastic constitutive model of the polymer material creep type taking into account aging, temperature and stress levels.
The creep-type viscoelastic constitutive model taking aging, temperature and stress level into consideration is shown in formulas (2), (3) and (4).
The construction of a non-linear creep-type viscoelastic constitutive model of a polymeric material taking into account aging, temperature, stress level and damage.
The non-linear creep-type viscoelastic constitutive model of the polymer material taking into account aging, temperature, stress level and damage is shown in formulas (5) and (7).
The embodiment of the invention also discloses a parameter solving and model verification method of the nonlinear creep type viscoelasticity constitutive model of the polymer material, which takes ageing, temperature, stress level and damage into consideration, and the method comprises the following steps:
(1) And solving parameters of a nonlinear creep-type viscoelastic constitutive model of the polymer material in consideration of aging, temperature, stress level and damage.
And when the uniaxial tensile creep is fixed, the creep type viscoelasticity constitutive model of the polymer material, which is expressed by adopting Prony series and equivalent relation and takes ageing, temperature and stress level into consideration, is shown as a formula (8).
Before 10% creep strain, the three-component HTPB composite solid propellant has negligible damage during creep deformation. Therefore, first, 0d aging time is selected as the reference aging time, α ta =1; selecting 0.2MPa stress level as reference stress level, and then alpha σ =1; selecting 20deg.C as reference temperature, and then alpha T =1. Next, based on creep strain-time curve data before 10% creep strain at 0d, 0.2MPa and 20 ℃, the creep strain-time curve is performed by global genetic algorithm using formula (8)Fitting calculation, the better result can be obtained when 7-order Prony fitting is found, and the corresponding model parameter J in the formula (8) 0 、J n And τ n The values of (2) are shown in the following table.
The model parameter values shown in the table are brought into the formula (8), and based on creep strain-time curve data before the reference aging time 0d, the reference temperature 20 ℃ and the stress level are respectively 0.4MPa and 10% creep strain under the condition of 0.6MPa, data fitting is carried out through a global genetic algorithm, and model parameters alpha under different stress levels in the formula (8) are obtained through comprehensive calculation σ As shown in FIG. 2, corresponding alpha σ The fitted mathematical expression of (σ) is as follows:
log(α σ )＝2.2275σ-0.4251 (9)
based on the model parameter determination, based on creep strain-time curve data before 10% creep strain under the conditions of a reference stress level of 0.2MPa, a reference temperature of 20 ℃ and aging time of 32d, 74d and 98d respectively, performing data fitting through a global genetic algorithm, and comprehensively calculating to obtain model parameters alpha under different aging times in a formula (8) ta And g (t) a ) As shown in fig. 3, the corresponding fitting mathematical expression is as follows:
α ta ＝0.9553exp(-t a /366.4240)+0.04454 (10)
g(t a )＝0.7848exp(-t a /3243.2356)+0.2183 (11)
based on the model parameter determination, based on creep strain-time curve data before 10% creep strain under the conditions of the reference aging time 0d, the reference stress level 0.2MPa and the test temperature of-20 ℃, 20 ℃ and 40 ℃ respectively, carrying out data fitting through a global genetic algorithm, and comprehensively calculating to obtain the model parameter alpha in the formula (8) under different temperature conditions T As shown in FIG. 4, corresponding alpha T The fitted mathematical expression of (T) is as follows:
α T ＝-298.7815exp(-T/46.7396)+1.5678 (12)
based on the creep rupture time of the three-component HTPB composite solid propellant after 0d, 32d, 74d and 98d aging time under the conditions of-20 ℃, 20 ℃ and 40 ℃ and under the conditions of 0.2MPa, 0.4MPa, 0.6MPa and 0.8MPa, the corresponding relation between stress levels and creep rupture time under different aging time and temperature conditions is fitted by adopting a global optimization algorithm, so that a model parameter beta (t a T) as shown in fig. 5 and 6. The corresponding mathematical expression of the fit over time and temperature is shown below, the first plot in FIG. 6 being the model parameter β (t a T) fitting the curve of A and C with temperature and the fitting result in the fitted expression, the second graph in FIG. 6 being the model parameter β (T) a T) fitting the curve of B in the expression along with the temperature and fitting the result. Together, these two maps reflect the temperature versus model parameter β (t a The effect of T), i.e. the effect of temperature on the time at which the three-component HTPB propellant undergoes creep rupture, is reflected.
Based on the above steps, it is achieved that all parameter values of a non-linear creep type viscoelastic constitutive model of a polymer material taking into account aging, temperature, stress level and damage are determined by fitting calculations.
(2) Verification of a non-linear creep-type viscoelastic constitutive model of a polymeric material taking into account aging, temperature, stress level and damage.
The creep deformation mechanical response and damage behavior of the three-component HTPB composite solid propellant under the residual loading condition which does not participate in model parameter solving can be predicted by bringing the parameter values in the table and the expressions (9) - (13) into the expression (5), the expression (7) and the expression (8), and the comparison of typical prediction results and test data is shown in figure 7. FIG. 7 (a) is a graph of predicted creep-time obtained based on the constitutive model at room temperature of 20℃and stress level of 0.4MPa after 32d of heat accelerated aging, and a graph comparing the predicted result with the test curve. FIG. 7 (b) is a graph of predicted creep-time obtained based on the constitutive model at room temperature of 20℃and stress level of 0.6MPa after heat accelerated aging for 74d, and a graph comparing the predicted result with the test curve. FIG. 7 (c) is a graph of predicted creep-time obtained based on the constitutive model at a stress level of 0.2MPa at-20℃at a low temperature after 32d of heat accelerated aging, and a graph of the predicted result compared with a test curve. FIG. 7 (d) is a graph of predicted creep-time obtained based on the constitutive model at a stress level of 0.6MPa at a high temperature of 40℃after 32d of heat accelerated aging, and a graph of the predicted result compared with the test curve.
As can be seen from fig. 7, the prediction result obtained based on the constructed model is better in fit with the test data, and has smaller error, that is, the constructed model can better describe the creep deformation mechanical response of the three-component HTPB composite solid propellant under different environmental temperatures and stress levels after different aging times, and the constructed nonlinear creep deformation type viscoelastic constructed model considering aging, temperature, stress level and damage is effective, and the method for constructing the constructed model is also effective.
Claims (1)
1. A method for constructing a nonlinear creep-type viscoelastic constitutive model of a polymer material is characterized by comprising the following steps of: the process of establishing the nonlinear creep-type viscoelastic constitutive model of the polymer material takes ageing, temperature, stress level and damage factors into consideration; the parameter solving and model verifying process of the nonlinear creep type viscoelastic constitutive model of the polymer material considers ageing, temperature, stress level and damage factors;
the establishment process of the nonlinear creep type viscoelastic constitutive model of the polymer material comprises the following steps:
the establishment of a creep-type viscoelastic constitutive model of a polymer material taking into account aging, temperature and stress levels;
based on the Boltzmann superposition principle, the integral creep deformation viscoelastic constitutive model without considering the influence of other factors is as follows:
wherein:creep strain under uniaxial tensile loading that is independent of other factors; j (J) 0 And Δj is the initial instantaneous compliance and the time dependent instantaneous creep compliance, respectively; />Is a step load with a value of creep stress level; t is the actual physical time;
the creep-type viscoelastic constitutive model of the polymer material taking into account aging, temperature and stress levels is:
wherein: t is t a Is the aging time; g (t) a ) Is the ageing coefficient; ζ is the reduced loading time associated with stress level, aging time, and ambient temperature; alpha σ 、α ta And alpha T Stress shift factor, aging time shift factor, and ambient temperature shift factor, respectively, and stress level sigma, aging time t, respectively a And an ambient temperature T; the method comprises the steps of (1) establishing a nonlinear creep-type viscoelastic constitutive model of a polymer material taking ageing, temperature, stress level and damage into consideration;
based on the strain equivalent assumption, the effective stress can be expressed as
Secondly, when the mechanical state of the material is analyzed by adopting the damage mechanical theory, the damage state or damage evolution D of the material can be quantified by using macro-micro characterization parameters; the damage evolution D is characterized by adopting a macroscopic method based on an accumulated damage concept, and a polymer material nonlinear creep type viscoelasticity constitutive model considering ageing, temperature, stress level and damage is established as follows:
wherein: d is accumulated damage in the creep deformation process of the polymer material; sigma (sigma) 0 Stress level at creep deformation; beta and N are model parameters affected by aging time and temperature;
the load when creep deformation is assumed to occur satisfies the constant stress condition, and t=t f When d=1 in formula (6), formula (6) can be further simplified to:
wherein: t is t f The breaking time of creep deformation of the polymer material under the loading of a fixed stress;
bringing the formula (7) into the formula (5) to obtain the nonlinear creep type viscoelastic constitutive model of the polymer material under different constant stress loads, wherein the aging, the temperature, the stress level and the damage are considered;
the parameter solving of the nonlinear creep type viscoelastic constitutive model of the polymer material comprises the following steps: for constant load creep deformation, due to τ>Load at 0 timeNo longer changes; thus, the integral term in equation (2) is integrated only at τ=0; the formula (2) can further be adopted in the constant-load uniaxial stretching creepThe steps are as follows:
wherein: j (J) n Is equal to the nth delay time tau n Coefficients of corresponding Prony series; n is the number of Prony series expansion;
first based on a reference aging time alpha ta =1, reference stress level α σ =1 and reference ambient temperature α T Creep strain-time curve data before critical damage strain threshold under the condition of (1), calculating to obtain model parameter J in the formula (8) through a global optimization algorithm 0 、J n And τ n Is a numerical value of (2);
then the obtained model parameter value is carried into the formula (8), and the model parameter alpha in the formula (8) is calculated by a global optimization algorithm based on the aging time, the stress level and the typical creep strain-time curve data before critical damage strain at loading temperature σ 、α ta And alpha T And establish a corresponding mathematical expression alpha σ (σ)、α ta (t a ) And alpha T (T)；
Based on creep mechanical property tests of polymer materials at different environmental temperatures and constant stress levels after different ageing times, the creep time t of material fracture under corresponding conditions is obtained f ；
Based on the corresponding relation between the determined stress level and creep rupture time, adopting a global optimization algorithm to determine beta (t) under different ageing times and ambient temperature in the formula (6) and the formula (7) a T) and N (T) a T) numerical value, and then establishing a corresponding mathematical expression;
finally, determining all parameter values of the nonlinear creep-type viscoelastic constitutive model of the polymer material taking into account aging, temperature, stress level and damage through fitting calculation;
the verification process of the nonlinear creep type viscoelastic constitutive model of the polymer material comprises the following steps: and (3) respectively carrying the obtained model parameter values into the formula (5) and the formula (7), and predicting the creep deformation mechanical response and damage behavior of the polymer material under the residual loading condition which does not participate in the model parameter solving, and comparing the prediction result with creep mechanical property test data under the corresponding condition to verify the validity of the built nonlinear creep type viscoelasticity constitutive model of the polymer material considering ageing, temperature, stress level and damage and establish the validity of the constitutive model method.
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