确定轴向冲击下薄壁圆柱壳第二临界速度的新方法

研究薄壁圆柱壳的动态屈曲模式，有助于构造具有高吸能率的抗冲击结构。根据轴向冲击下的薄壁圆柱壳存在使其屈曲模式由轴对称转换为非轴对称的第二临界速度，且当冲击速度大于第二临界速度时薄壁圆柱壳的屈曲模式先呈现轴对称形式，然后随着冲击响应时间逐渐由轴对称形式转化为非轴对称形式这一理论，基于有限元仿真，比较撞击系统动能的时间历程和屈曲变形的时间历程，提出了用以确定第二临界速度的能量迭代法。应用此方法设计薄壁圆柱壳的动力屈曲结构可有效地减少试验次数，降低实验成本。该方法的可行性和正确性利用落锤实验得到了验证。

New Method for Determining the Second Critical speed of Thin-wall Cylindrical Shells Under Axial Impact

Studying on dynamic buckling modes of thin-wall cylindrical shells is helpful to design anti-impact structures.There exists a secondary critical speed beyond which the axisymmetric buckling mode of a thin-wall cylindrical shell under axial impact would be converted a nonaxisymmetric one,moreover when the axial impact speed is beyond the second critical speed,the axisymmetric buckling mode appears firstly,and then the buckling mode changes to the nonaxisymmetric one gradually with the impact response time.According to the theory described above,by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system,an energy iterative method to determine the second critical speed is presented.Using this new method to design anti-impact structures of the thin-wall cylindrical shell can reduce test times and cost effectively.The feasibility and validity of this method are demonstrated by a dropping hammer experiment.