Research On Shear Fracture Mechanism Of Cylindrical Shells Subjected To Explosive Loading

Cylindrical shells deformation, crushing process and mechanism study under blast loading is of great significance in the design of modern weapons, protective structure. The adiabatic shear failure mode is the main mode of cylindrical shell damage. Although there are many theoretical and experimental studies for damage of cylindrical shell which deepen people’s understanding on the column shell damage and failure mechanism, due to the fact that adiabatic shear mechanism is not entirely clear, especially the multiple adiabatic shear instability mechanism needs further research, the numerical analysis to predict the results are far not accuracy, and the shear failure mechanism of cylindrical shell under blast loading need further research.The experimental results were summarized and analyzed and numerical simulation were carried out to study on the shear fracture mechanism of cylindrical shells under explosive loading. The results are showed that:(1) 45 # steel and titanium metal tube damage mainly in two categories, namely double and single direction shear failure mode, which adiabatic shear is generated from the cylindrical shell inner wall, along the 45 ° or 135 ° direction toward outer wall.(2) Load characteristics influence the deformation, localized process and failure modes. Under the ideal load, The failure mode is that first produced shear deformation localized zone(adiabatic shear band) in the middle of shell, then cracks develop along the shear band, format 45 ° or 135 ° fracture. The lower the peak load, the greater the shear band spacing. The wider load width, the more serious cases the middle column shell along the ring damage, The smaller shear band spacing is.(3) Non-uniform cylindrical wave, which will cause disturbance in the inner surface. Tube deformation response by the non-uniformity load. the stronger of the non-uniformity, the sooner the adiabatic shears instability occur in the tube wall. The frequency of nonuniformity of the disturbance has two critical value. when lower than a certain frequency, the effect of the response caused by the disturbance load impact on the cylindrical shell can be ignored; When above a certain frequency, adiabatic shear instability point is drastically reduced, modal control the response of the tube, in the middle of the two frequencies, adiabatic shear instability points are controlled by the frequency of the disturbance.(4) When the cylindrical wave generating oblique incidence, instability occurs first at the point, which is the maximum angle between the normal of the cylindrical inner wall and the tube wave. The stress state around the point force the crack growth appearing directional, Thereby affecting the directions of the peripheral cracks. At the two endpoints that occurred the normal incidence, the direction of the crack growth appearing random.(5) The geometric imperfections make tube damage in advance, crack initiation controlled by the geometry of the defect, the more the defect, the more number of cracks.