Experimental Study On The Effect Of Loading Rate On The Fracture Characteristics Of Cylindrical Shell

The research on the deformation,damage and failure modes of cylindrical shell structures under explosive loading mainly comes from the military field.Expansion of shell under explosive load is a complex process involving material failure under strong impact load and structural failure under high strain rate loading.This problem is of great significance in structural protection and weapon design.Therefore,the problem of expansion and fracture of cylindrical shell under explosive load has always been the focus of research.The failure process and fracture mode of the metal cylindrical shell under the detonation load are related to various factors.The physical mechanism of the expansion and fracture behavior of the cylindrical shell under explosive loading can be deeply understood,which can provide a basis for military and industrial design and manufacture.Based on the plastic theory,the evolution characteristics of stress state in the expansion process of cylindrical shells under different explosive pressures are discussed,and the effects of explosive pressures on tensile and shear fracture are analyzed.Experiments were carried out to investigate the effects of load pulse width and explosive pressures on the fracture characteristics of the shell.Through the macroscopic and microscopic analysis of the recovered fragments,the effects of different load characteristics on the expansion deformation,failure process and fracture mode of the shell structure were discussed.The results show:(1)The results of plastic theory analysis show that when the detonation pressure is small,the zero hydrostatic pressure interface determined by the stress condition is closer to the inner wall,and the tensile fracture zone is larger.As the explosion pressure increases,the hydrostatic stress region increases,indicating that the material thermoplastic instability occurs at the near inner surface,forming a shear weak zone,and it is easy to form adiabatic shear failure initiated by the near inner wall.(2)When the TA2 titanium alloy cylinder shell is loaded with different density explosives,the shells all exhibit a shear fracture mode initiated by the inner wall.When the explosion pressure is low,there is only adiabatic shear band at the front of the crack and the size of the debris is large;as the explosion pressure increases,there are a large amount of adiabatic shear bands distributed on the inner surface of the casing,and the crack starts from the inner wall and expanded along the adiabatic shear band;when the explosion pressure is high,the cylindrical shell exhibits a form of single-spin shear failure,and the adiabatic shear bands initiated by the inner wall all develop in a direction parallel to the fracture surface.(3)Under different charges(solid explosive and layered explosive),the fragments of TA2 shell exhibit shear fracture mode,but the formation process is different: The adiabatic shear bands along 45° or 135° occur in the inner wall of the cylindrical shell when Solid explosive is used,the crack emerges from the inner wall and expands along the adiabatic shear bands to cause fragmentation;When the layered explosive is exploded,a micro-damage zone is first formed in the middle of the solid part of the cylindrical shell,and the crack extends from the micro-damage zone to the inner and outer surfaces along 45° or 135°.