Study Of Dynamic Impact Property Of Monocrystal Copper Made By Onho Continuous Casting

Based on the concept of dislocation kinematics and kinetics, Mechanical threshold stress (MTS) model including an internal state variable (ISV) related to material strength in current microstructure, can well describe dynamic mechanical properties and is widely used at high strain rate. By using MTS model and the experimental technique of the split Hopkinson bar with the synchronization assemblage, the dynamic constitutive models of the monocrystal copper made by Ohno continuous casting and the polycrystal copper made by up-continuous casting were investigated.By using a narrow heated furnace, designed and manufactured by NPU, dynamic impact experiments at temperature 1200K were accomplished. The optimized parameters of the pressure, which push output bar, and the distance between incident bar and transmission bar were obtained.Through the theory analysis and experimental research, the optimized parameters of the dynamic constitutive models of monocrystal and polycrystal copper were obtained and the theoretical stress-strain curves have a good agreement with experimental curves. Based onexperiment analysis, the concept of threshold energy of dislocation restoration was proposed and the parameters of MTS model were discussed in detail. It turns out that in parameters of MTS model only seven parameters are independent and MTS model is not very good to describe dislocation restoration, recrystallization and associated strain softening.