A TENSILE TEST AND FINITE ELEMENT ANALYSIS OF DH36 HIGH-TENSILE STEEL AT CRYOGENIC TEMPERATURE

Excessive exposure to LNG weakens and causes a brittle fracture to steels. Therefore, all risks that can lead to LNG spillage must be minimized or mitigated by applying a cryogenic temperature resistance material to the ship's structure. Higher strength steel that considers low temperature such as DH grade is recommended to be used for ships carrying LNG cargo. In this study, material fracture idealization of DH36 steel under a tensile load and low temperature is presented. The fracture strain of the steel could be affected by temperature reductions due to the hardening effect, as well as the element size in the Finite Element (FE) model would influence the fracture strain behavior. Thus, the stress-strain curve of DH36 has to be calibrated for the use in FE model. A sensitivity analysis with temperatures and element sizes was presented. The strain rate effect was neglected since the quasi-static mode was performed in the tensile test. The temperature is applied from 25 degrees C (room temperature) to -160 degrees C. The element sizes of 0.5mm to 5.0mm were used in the FE model of the specimen. This investigation found that the ultimate tensile and yield stresses were increased with a slightly increased upon the fracture strain along with the decrease in temperature. Furthermore, the procedure of the tensile test and FE analysis are discussed in this paper.