Visco-elastic-plastic Unified Constitutive Model Parameters For Assessment

The history and quality of the Unified Constitutive Model theory are stated in the thesis. Based on the modern unified plasticity, the Unified Constitutive Model can simulate all the material deformations with a set of equations.By studying the experiment information, the visco-elastic deformations were pointed out. That means there is time dependent deformation during the elastic deformation stage. This kind of deformation is not included into the constitutive models before. By introducing the visco-elastic deformation into the unified constitutive model a Visco-elastic-plastic Unified Constitutive Model is created. The new model is used to simulate deformations of monotonic> cyclichardening and temperature effect tests. It shows many superioritiesBecause traditional parameters evaluation has drawbacks and there are many parameters in the visco-elastic-plastic unified constitutive model equations, It is very difficult to apply the theory into engineering. The traditional approach to parameter estimation is sequential and requires a large number of tests. Many scholars devote themselves to resolving this problem. They are good at experiment data analysis and have the mathematic background. Many results about the parameter evaluation are produced.In the thesis it is traced to the method of estimating unified constitutive model parameters and the development of it. A framework of the Visco-elastic-plastic Unified Constitutive Model's parameters estimation is set up. The sensitivity analysis method is studied in details, and it is put into the framework. The optimized parameters of the visco-elastic-plastic unified constitutive model are obtained by a nonlinear optimization algorithm and relative sensitivities analysis. The method is used to estimate the Visco-elastic-plastic Unified Constitutive Model's parameters of braze alloys experiments of different constant strain rate. It shows the method is rational and effective.