【摘要】 本文研究裂纹快速扩展的动力特性,特别是裂纹扩展速度的规律.主要考虑在裂纹扩展量不很大的情况(如冲击载荷下裂纹快速扩展的情况)下,将裂纹快速扩展-止裂过程作为一种瞬态振动问题求解,而通过能量相当(等效)的原则与断裂力学基本概念(断裂准则等)相联系.计算模型的主要假设是:在裂纹快速扩展过程中,断裂能的消耗用等效的阻尼能来表达.经过近似处理,最后归结为求解有阻尼的单自由度非线性系统在初位移下的瞬态响应计算问题.以DCB试件为例说明计算程序,并给出实例计算结果与实验结果和其他工作的比较.用涡流检测法记录裂纹快速扩展的全过程,以提供实验数据。计算结果与各种实验结果符合较好,初步证明所用的计算模型的有效性,可以作进一步的推广研究以及用于更复杂的问题.更多还原

【Abstract】 The dynamic properties of the unstable (fast) propagation of cracks, especially the rule of the variation of propagating velocity, are discussed. The case to be considered is that the extension of cracks is not very long (as the cases of rapid crack propagation under impulsive load) , the main idea of this paper is that the rapid propagation of cracks may be treated as a vibration problem and is connected to the basic conceptions of fracture mechanics (such as criterior of fracture, etc.) by the principle of energy equivalence. The rapid propagation of cracks is essentially a specific type of the transient vibration of elastic bodies, with the boundary conditions varying with the time. Under the assumption of equivalence, the above problem may be treated as the initial-value problem of a damped system with multiple degrees of freedom, considering the nonlinear effect of stiffness due to the extension of crack. After further simplification, it is deduced to a transient response problem of a damped nonlinear system of single degree of freedom under the initial condition of displacement, so that the solution can be obtained numerically. The fundamental conceptions for which the model is constituted, is the principle of the whole amount of energies being equivalent between the model and practical element, and the primary (main) hypothesis is that the fracture energy dissipated during the propagation oi crack is equivalent to the damping energy of the model system. The DCB specimens are taken as an example for explaining the theory and computing procedure. Numerical examples are calculated and compared with experimental results.In order to record the complete procedure of the rapid propagation and arrest of the crack by experiments, a new method of eddy-current type is developed.Computational results of several specimens of different materials are all coincided well with the experiments. So it can be concluded that the computational model can be used at least for such cases. Further research would be studied for more compli cate cases.更多还原