Creep behavior of titanium alloy used in deep-sea pressure shell considering tensile/compressive asymmetry: Experiments and numerical modeling

Abstract

Titanium alloy pressure shell of deep-sea submersible suffers from room-temperature creep problem, which can affect the safety of the structure. There is currently a lack of research on the tensile/compressive asymmetry of the creep response of titanium alloy structures at room temperature. In this paper, room-temperature creep behavior and mechanism of titanium alloy were investigated by creep test of twisting of titanium alloy square plate. Taking cylindrical pressure shell with geometrical imperfection and multi-sphere pressure shell as examples, the creep mechanical behavior of titanium alloy pressure shells under complex stress states were investigated by numerical simulation. It is found that only under tensile stress can slip bands move across phase boundaries, resulting in tensile/compressive asymmetry in creep behavior. The proposed DTC model can accurately describe the room-temperature creep behavior of titanium alloy structures. For cylindrical pressure shell with geometrical imperfection, creep deformation results in a 121 % increase in the magnitude of geometrical imperfection. The results obtained with the tensile model towards the conservative side. For multi-sphere pressure shell, the evolution of physical quantities cannot be accurately described without considering the tensile/compressive asymmetry in creep properties. The range of relative error when using traditional models is between 5% and 33%.