Research On Dynamic Viscoelastic Properties And Constitutive Relationship Of Polymer Materials

Non-water reacted polymer materials are new kind of environment-friendly materials for seepage prevention and reinforcement of infrastructure engineering.They have advantages of high efficiency,economy and fast construction speed,which are widely applied in emergency treatment of dangerous highway,high-speed railway,reservoirs.Polymer materials have typical viscoelastic property,their mechanical properties are closely related to many factors such as temperature,frequency of dynamic loads,and their performance will change in different application conditions.In practical engineering,polymer materials are constantly under dynamic loads and are often used in the projects with or without water in various regions.It is very important to study its viscoelastic property and its influencial factors;On the other hand,a suitable viscoelastic constitutive model is the basis of dynamic response analysis of polymer composite structures and also the key to the design of structural science.However,the study on viscoelastic properties and constitutive relations of new polymer materials has not been carried out systematically.Aiming at the shadow area of dynamic mechanical properties of polymer materials and the key point of dynamic response analysis—dynamic viscoelastic properties and constitutive relationships,the study was carried out.In this paper,laboratory experiment,theoretical analysis and numerical simulation were used to study the influencial factors of dynamic viscoelastic properties and the constitutive model of polymer materials.The research results provide theoretical and scientific basis for the application and development of polymer materials.The main research works are as follows:(1)Dynamic thermal mechanical analysis was used to study the dynamic viscoelastic properties and its influencial factors of polymer materials.The key problems which affect the accuracy of dynamic viscoelastic parameters were solved.The dynamic modulus and loss factor of polymer materials under different temperature,frequency,density and immersion conditions were measured.The effects of different factors on the dynamic viscoelastic properties of polymer materials were obtained.From the microscopic point of view,the motions of polymer molecules andmolecular chains under the influence of different factors were discussed.According to the test results,the high and low temperature properties and application areas of polymer material were studied,and the relationships between density and dynamic modulus of polymer materials were established which lays a foundation for establishing viscoelastic constitutive model.(2)The dynamic viscoelastic constitutive model of polymer materials is studied.The composition and constitutive equations of various classical viscoelastic constitutive models were discussed,the characteristics and application scope of each model were analyzed and compared,Based on the model parameters are easy to obtain and can be directly used for finite element simulation and other advantages,the dynamic viscoelastic modulus of the polymer materials were fitted and its viscoelastic constitutive model was established by using the fourth-order generalized Maxwell model.The parameters of the model were obtained based on the shared parameter fitting method with multi-objective constraints.The viscoelastic constitutive model of polymer materials with different densities is established by using the relationship between density and dynamic viscoelastic modulus of polymer materials.(3)The correctness of viscoelastic constitutive model of polymer materials was verified.The correctness of viscoelastic constitutive model was initially verified by comparing the dynamic viscoelastic modulus calculation data of the viscoelastic constitutive model with DMA test data.Combining with viscoelastic constitutive model of polymer materials,the numerical model of the earth dam with polymer anti-seepage wall was established by using the ABAQUS finite element software.The dynamic response of earth dam with polymer anti-seepage wall was obtained,comparing the calculation results with early centrifuge test results,the correctness of viscoelastic constitutive model was further verified.Based on the centrifuge test results,the calculation errors of the viscoelastic constitutive model and linear elastic model are compared to verify the accuracy of the viscoelastic constitutive model.The efficient and reasonable viscoelastic constitutive model provides a basis for studying the dynamic response of polymer materials.