Research On Thermal-rheology Effect And Temperature Field Of The Engineering Polymers

Polymers are typical viscoelastic materials, and their mechanical properties depend on temperature, loading time, loading speed and strain etc, among which the loading time and the temperature are the main influence factors. In practice, more and more polymer is used in engineering structures. Studying the deformation and failure theory and structure-property relationship of polymers attracts many researchers' attention.The material deformation process is accompanied by the form of energy conversion and the temperature change. Especially in the quick deformation speed and the big part deformation and distorted degree, the temperature change will be very obvious. This deformation heat effect is more outstanding especially under high strain rate or the alternation loading effect as well as the crack rapid expansion. Its adiabatic temperature rise can make materials reach the degree of serious soften and fail. Therefore, studying material heat dissipation in the deformation process, especially the temperature sensitive material, is of great significance.In this thesis, nonlinearity rheological deformation behavior, the temperature dependence of mechanical properties and deformation-induced heating in polymers are considered theoretically and experimentally. The achievements and conclusions are listed as follows.1. Base on the viscoelastic mechanism of polymer depend on time, we study viscoelastic distortion of high polymer with the dependence on non-linearity and stress specially. We get each material parameter by dealing with the data of experiments, and contrast several theories of one dimension creep.2. We contrast the elastic modulus and yield-limit between ABS samples with and without hole and get the rule that the elastic modulus of ABS changes with the temperature.3. Through the finite element analysis, we obtain the distributed situation of the first principal stress and the Mises stress around the hole and the plastic area boundary expression. Moreover we construct the reasonable heat source density function.4. Considering the thermomechanical coupling in the material deformation and fracture processes, the control equation of the transient temperature field was derived from the basic laws of irreversible thermodynamics. Through carrying on numerical simulation to it, we figure out the temperature field in the flaw evolution process quantificationally and study the influence of the heat source density over the calculate result.