Parameter Identification Method And Verification Of Bammann-Chiesa-Johnson Constitutive Model Of Pure Aluminum

High plastic metal,such as pure aluminum 1060,is one kind of difficult-to-machine materials in the precision or ultra-precision machining.To reveal the machining mechanism and improve the surface quality and manufacturing efficiency for the high plastic materials,it is of significant importance to understand the static/dynamic mechanical behavior.Meanwhile,the mechanical behavior is one of the fundamental conditions for machining process simulations.The machining process simulation technology has been developed rapidly in recent years.The material constitutive model determines,to a large extent,the accuracy and the reliability of simulation results.Therefore,the research concerning the mechanical behavior and constitutive models of the high plastic materials,such as the high pure aluminum,has become one important area for precision machining.The Bammann-Chiesa-Johnson(BCJ)viscoplastic constitutive model is one of the physics-based models which has been used for metals and geological materials.Compared with the traditional empirical and semi-empirical constitutive models,the BCJ model is more powerful,more accurate,and can be used to describe more complicated phenomena.However,the BCJ model includes too many model parameters to accurately identify them.In this paper,a new parameter identification method for the BCJ model was proposed.And the mechanical response of pure aluminum 1060 was simulated for the dynamic loading.The main achievements obtained were summarized as follows.A new method for parameter identification was proposed for the BCJ viscoplastic model at elevated strain rates and temperatures with three types of experimental tests,i.e.qusi-static,dynamic and creeping tests.The model parameters were decoupled and the eighteen model parameters were identified by separating the fitting process into six independent steps,and adopting the nonlinear fitting approach and the Particle Swarm Optimization(PSO)algorithm.It was demonstrated that the developed BCJ model was able to predict mechanical behaviors with a strain rate range of 1000?10000 s-1,and a temperature range of 25?500?.The strain-rate sequence experiments were designed to validate the capability of the BCJ model.The preparation method of samples for the SHPB-Gleeble sequence test was explored.The test conditions of the Gleeble-Gleeble sequence tests were also improved successfully.Furthermore,the BCJ model was able to describe the history effect presented in the sequence tests with the strain-translation method.Finally,validation for capturing the strain-rate history was conducted by using SHPB-Gleeble sequence test data,which shows good agreement.