Research on expansion failure of titanium Gr2 coil

The expansion fracture behavior of titanium coil shell wall is not only affected by bursting load characteristics, but also related to material characteristics, column shell structure characteristics and other factors. This paper mainly analyzes titanium Gr2 alloy tube with specific structural size under different bursting pressures.

The researchers combined finite element and experimental analysis to study the explosive expansion and destruction machine of titanium tube and its influencing factors. By analyzing the laws of shock wave propagation, strain and stress state evolution and development in ideal titanium tube under different explosive loads, the fragmentation phenomenon of titanium tube is discussed. The results show:

1. The failure of titanium Grade 2 coils under different burst pressures is shear fracture with radial direction of 45 or 135, but the crack initiation and failure process are different. Under high explosive pressure, the microfacies of the fragment section can be seen in the middle of the wall thickness, and the cracks form from the middle of the specimen section to the inner and outer surface. At lower explosion pressure, cracks start from the inner wall of the specimen and expand outwards, resulting in fracture. The finite element results are in good agreement with the experimental trend.

2. The finite element analysis shows that under high burst pressure, the equivalent plastic strain in the middle region of the specimen wall thickness is larger than that on the inner and outer surfaces because the shock wave reflects back and forth between the inner and outer walls of the specimen to form a secondary plastic zone, and the fracture occurs at the loading stage of the shock wave, and the damage crack first starts from the middle part of the specimen wall thickness and expands to the inner and outer walls, resulting in the fracture. The failure occurs in the free expansion stage, when the whole specimen enters the tensile stress state, and the equivalent plastic product at the inner wall increases, and the fracture starts from the inner surface to the outer wall.

3. Some tensile fracture phenomena of the outer wall in relevant experiments may be related to sample geometry, material defects and other factors, and the influence of defects on the burst failure characteristics of titanium coils deserves further attention.