To guide the new process making of the nose shell and improve the utilization ratio of the material on the premise of meeting ejecting performance of the nose shell

the relation model between fracture expansion direction and material's microstructure factors was tried to be established on the basis of the fracture mechanics principle.After macro and micro analysis of the current product and its fragments

it is concluded that the smashing is a dynamic crack expansion course and the main expansion direction is consistent with flow lines.The theory criterion of the fracture expansion of the nose shell is established that the fracture can penetrate stably along some flow line while the vertical shift of the crack tip is less than the distance between the flow lines by considering the plastic area of crack tip and equivalent processing the fracture expansion model.The fact that the calculation results coincide well with the static explosion experimental results indicates the fracture expansion model is basically reasonable

which can be used to guide the new forming process.