Investigating the effect of nonlinear strain path on the mechanical properties of sheet metal to predict burst pressure of composite Rupture disc

In this paper, to investigate the effect of strain caused by biaxial stress on the mechanical properties of the sheet in a uniaxial tensile state, several metallic blank discs were bulge formed in the hydroforming process under different biaxial stress due to different fluid pressures. Then, the slotting process was done on bulge formed sheet to change the loading from biaxial stress to uniaxial tension. Again, these specimens were subjected to fluid pressure to determine their resistance to fluid pressure at uniaxial stresses. By using the results of this paper, the burst pressure of composite Rupture discs can be predicted in any size by numerical simulation with an error of about 8%. A Rupture disc is a safety device that burst as the fluid pressure increase and prevents damages due to excessive pressure on the equipment. In a composite Rupture disc, a nonlinear strain path occurs. If the type of load changes during sheet metal forming, e.g., the sheet forms under biaxial stress and then under uniaxial tension, the maximum failure strain and force will change. The burst pressure comparison of vacuum annealed specimens with similar non-annealed discs after work-hardening shows the possibility of increasing burst pressure more than 64% in proportion to created strain due to biaxial stress. Also, in this paper, by using analytical and numerical simulations, the equality of strain due to biaxial stress in the equal ratio of forming height to diameter (h/d) proved to be the same.