The Dynamic Expansion And Shear Failure Behavior Of Cylindrical Shell Of Aluminum Alloy

The study of localization deformation and fragmentation for expanding metal cylinder is of great significance in military, plastic molding and other fields. The electromagnetical loading technique and the finite element numerical analysis were adopted for studying the behavior of dynamic expansion of 6063 aluminum alloy tube.Firstly, ANSYS /Multiphysics coupled field was used to analyze the force and deformation of cylindrical shell in the process of the electromagnetic coil driven metal cylindrical shell expanding loading, and established the experimental device and observation system of the electromagnetic driven thin-walled metal cylindrical shell localized damage process. Based on the experimental device and the observation system, 6063 thin-walled cylindrical shell of aluminum alloy(Outer diameter, D = 60 mm, Wall thickness, t = 0.8 mm, The ratio of diameter to wall thickness, D/t = 75) was studied under different loading rates of expansion fracture behavior. In the experiment process, principle of Rogowski coil was used to measure transient discharge current; FASTCAM highspeed camera was used to record electromagnetic expansion pipe outside surface failure process; laser displacement sensor was used to measure circular tube in the process of expansion radial displacement variation, and the cylindrical shell’s localized starting fracture moment, fracture moment, and localized strain, macro fracture critical strain, etc could be judged accurately.The results show that the expanding velocity reaches 140-200m/s, whose corresponding strain rate is 4500s-1- 6500s-1, and that the approximate high-speed uniform expansion can be realized. The dynamic fracture of the cylindrical shell of aluminum alloy experiences the process of uniform expansion, shear localization and fracture occurring along the localization band, and the angle between shear localization band and the axial direction of shell is 45° or 135° approximately. As a result of analysis, the characteristics of fragment size decreases with increasing strain rate, and correspondingly, the fracture strain increases with increasing strain rate. Furthermore, the process of shear localization, the strain rate effect and the temperature rise during loading are discussed.