Research On The Rupture Behaviour And Mechanism Of Cylindrical Shell Structure With Defects Subjected To Internal Explosive Loading

Cylindrical shell is a kind of extremely symmetrical structure, widely used in industrial containers, warhead structure, aerospace, etc., and its rupture characteristics under blast loading are the important issues of structural safety and destruction. The stress process of prefabricated defects cylindrical shell under the condition of explosive loading is extremely complex, involving the material mechanics, fracture mechanics and mechanics of explosion, and other disciplines, the current related research results are less. Regarding prefabricated defects cylindrical shell as the research object, the expansion cracking behavior and fracture mechanism under internal explosive loading are studied by the combination of experiment, numerical simulation and theoretical way, and then guide the prefabricated defects of cylindrical shell structure design. The main results as follows:(1) Cylindrical shell structure with pre-notches is designed. The fracture behavior of the cylindrical shell under internal explosive loading is studied by experiments to investigate the influence factors on the rupture characteristic, such as the types of explosive and the notch depth. The crack point and crack propagation path under blasting loading are analyzed by the velocity and mass distribution of fragments recovered by the soft recovery unit. The results show that the fracture trace of the inner and outer notches are along radial direction or with a 45 degree of radial direction. The fracture ratio of inner and outer notches is influenced by explosive load and depth of outer notches.(2) The cylindrical shell rupture properties are analyzed by the expanding process of cylindrical shell structure numerical simulation, with the ALE algorithm of finite element software LS-DYNA. A universal fitting for expression of stress concentration factor is obtained by numerical simulation of series of working conditions of the notches. The results show that the numerical results agree well with the experimental results can be further used for the experimental program guidance and optimization.(3) On the basis of damage evolution equation proposed by Feng, cylindrical shell with pre-notches damage evolution equation is obtained, considering the accelerating effect of stress concentration of holes or cracks. The cylindrical shell rupture process can be divided into stages of accelerated expansion and uniform expansion. The rupture criterion of pre-notch cylindrical shell is deduced with the high strain rate constitutive considering the stress and strain rate. The results show that critical fracture strain of cylindrical shell is affected by stress concentration, material constitutive relations and internal load. The stress concentration is related with the size of the notches.(4) The cylindrical shell with pre-notches under the condition of explosive loading is guided by the rupture regularity, dynamic crack growth and the rupture criterion. The results show that cylindrical shell with pre-notches design needs to consider the dynamic mechanical properties of materials, shape and size of notches, grid density and the charge.