Numerical Simulation And Analysis On The Deformation Process In Cylindrical Compression Experiments

As an important physical simulation method, cylindrical uniaxial compression experiment is an effective way to obtain the deformation resistance of materials under different deformation temperatures and strain rates. However, due to the friction between the hammers and the cylindrical sample and the different height-diameter ratio of the sample,deformation of the cylinder sample is not homogeneous and the drum shape will appear for which after the deformation. As a result, microstructure for different position of the sample and the tested stress-strain curves will be seriously influenced. Obviously, it is of great importance to select an observation point in the sample for metallographic observation and to obtain the true stress-strain curves from the tested ones. Numerical simulation on basis of the finite element method has the important significance to direct the practical experiments and production since it can not only dynamically simulate actual plastic deformation process of the metal materials, but also provide the deformation state of which(such as strain, stress,strain rate) and the force condition of the hammers. So the problems described above will be better analyzed and solved as the numerical simulation method is adopted and the analytical process for inhomogeneity of the deformed samples will be transferred from the qualitative one into the quantitative one.In this paper, the uniaxial compression process of the cylindrical samples is numerical simulated and analyzed by using the rigid-plastic finite element method based on the software DEFORM. The appropriate microstructure observation point, the height-diameter ratio beneficial to reducing inhomogeneous deformation and the experimental method beneficial to reducing the difference between the tested stress-strain curves and the true ones are determined. At the same time, the mathematical models to calculate the convexity of the deformed samples and the true stresses at the different strains and the different deformation temperatures are constructed. The specific contents are as follows:(1) The cylindrical sample with the diameter of 8 mm is selected as the analytical object and the two-dimensional finite element method is adopted in the finite element analysis on thecompression process. As the appropriate microstructure observation point reflecting the deformation characteristics of the true stress-strain curves under inhomogeneous deformation conditions, the typical element is determined. Influence of height-diameter ratio on the inhomogeneity of the compressed samples is analyzed and the height-diameter ratio beneficial to reducing inhomogeneous deformation is determined. And the mathematical model to calculate convexity of the deformed samples is regressed.(2) By using three-dimensional finite element method, the compression of single hammer and the radial directional strain tested methods beneficial to reducing the difference between the tested stress-strain curves and the true ones are determined. Based a large amount of simulation and analysis, the mathematical model to calculate the true stresses at the different strains and the different deformation temperatures based on the tested stress-strain curves is regressed.