Based on the code LS-DYNA, the simulation strategy on the quasi-static crushing process of composite tubes is studied by conducting two series of comparison simulations: one is at different virtual loading speeds with the real material density and the other is with different virtual material densities at the given loading speed. The simulation results are summarized as three types, namely mode-varying type (MVT), unstable type (UT) and stable type (ST), depending on the change of the structural failure mode and the occurrence of the load-fluctuating stage in the load-displacement curve. Analysis has shown that the steady load possesses the stability, the peak load has the convergence zone, and the thresholds of energy ratio can be adopted to evaluate the simulation results. In the end, the simulation strategy is proposed to makes it possible to acquire the simulation results with a higher query precision at a lower computing cost.

In order to get high quality forgings, it is significant to predict the microstructure evolution during hot forging process accurately. In this study, a simulation model is built by combining FEM with the dynamic recrystallization model of 42CrMo, and the finite element model is proved to be reliable by a serial of upsetting deformation experiment. Then the distributions of microstructure evolution are obtained on upsetting process. Upsetting is beneficial to refine the grain size and drawing can make the distribution of grain size homogeneous. By comparing the simulation results with experiments, the distributions of microstructure are a close match in the middle part of steering arm. The forgings formed by this process have a good microstructure and have high comprehensive mechanical properties.