Optimization of crashworthiness of the thin shell structure composed from polycrystal metals by crystal shear banding

对于韧性金属，局域剪切带是断裂的先兆。剪切带的形成和发展对多晶材料的晶相结构和加载路径有重要影响。本研究的目的是通过控制剪切带的形成和发展，发展减震元件耐撞性的优化方法，取得了如下成果。对于面心立方晶体，建立了剪切带形成判据的数学模型。将该准则所定义的假设的第13滑移系引入到有限元多晶模型中，建立了适用于剪切带发展引起的晶体弱化问题的数值模拟器。2.面心立方多晶平面应变压缩的数值模拟和实验结果表明，剪切带是否穿透取决于相邻晶粒之间晶体取向的相对构型。研究结果表明，可以通过控制多晶金属的晶态织构来优化多晶金属减震元件的耐撞性。开发了梁和圆柱壳碰撞问题的数值模拟器。结果表明，材料的应变率敏感性略微提高了梁和薄壳结构的耐撞性。

For a ductile metal, localized shear banding appears as the preceding phenonemenon to the fracture. Initiation and developing of the shear band significantly influenced on the crystarograhic structure of the polycrystal materials and on loading paths. The puropose of the research project is to develop the method of optimization of crashworthiness of shock absorbing components by controlling the initiation and the developing of shear banding the obtained results are as follows.1. For FCC crystals, the mathematical model of the criterion to the initiation of shear band is established. Introducing the hypothetical 13th slip system defined by the proposed criterion into the finite element polycrystal model, numerical simulator which can be applied to the problem of weakning of crystals caused by developing of shear banding is established.2.Results of the numerical simulation and the experiment for plane strain compression of the FCC polycrystal shows that the shear banding penetrates or not according to the relative configuration of crystarographic orientation between ajacent crystal grain. The result suggests the possibily of the optimization of crashworthiness of the shock absorbing component made of polycrystal metals by controlling crystarographic texture of them.3. Numerical simulater for impact problems of a beam and of a cylindrical shell is developed. It is clarified that strain rate sensitivety of a material slightly improve the crashworthiness of a beam and a thin shell structure.