Session: 02-01-02 Structural analysis and optimisation 2

Paper Number: 102747

102747 - A Tensile Test and Its Finite Element Analysis Prediction of Dh36 High-Tensile Steel at Cryogenic Temperature 

The demand for Liquefied Natural Gas (LNG) fueled ships is growing up in response to dealing with Emission Control Area (ECA) that limits sulfur oxide and nitrogen oxide emissions. Consequently, it would increase the demand for LNG bunkering facilities in large quantities in the future such as LNG bunkering ships. Handling the LNG fuel during the loading, unloading, and storing processes requires a different level of safety. Aside from being flammable, LNG can cause damage to the ship's structure due to LNG being stored 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 strengthened steel considering 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 20^oC (room temperature) to -160^oC. The element sizes of 0.5mm, 1.0mm, 2.0mm, 4.0mm, and 5.0mm were used in the FE model of the specimen. This investigation found that the ultimate tensile stress was increased with a slightly increased in the fracture strain along with the decrease in temperature. Meanwhile, the smaller the element size increased the strain fracture. Furthermore, the procedure of the tensile test and FE analysis are discussed in this paper.

Presenting Author: Haris Nubli Pukyong National University

Presenting Author Biography: I am a research assistant (Ph.D. student) at Pukyong National University, Busan. My specialization is computer-aided design, CFD analysis, fire risk analysis, design optimization, and ship structural reliability.

I am recently doing a multi-hazard analysis on LNG bunkering and LNG-fueled ships as my research work. Since the International Maritime Organization has issued a new regulation for reducing exhaust gas emissions, LNG fuel can be an alternative to replace diesel fuel that still contains sulfur oxides. However, storing LNG fuel has a different safety level than diesel fuel since it is flammable and volatile. Thus, research on risk and safety is necessary to prove the reliability of the LNG-fueled ship.

I focus on the accidental LNG release model that leads to consequences such as flammable gas dispersion, fire, vapor cloud explosion, and its cryogenic temperature impact on the ship's structure. By using Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA), or other numerical simulations, it would be possible to build those models of consequences

Authors:

Haris Nubli Pukyong National University
Sang Jin Kim National Sun Yat-sen University
Jung Min Sohn Pukyong National University
Dongho Jung Korea Research Institute of Ships and Ocean Engineering (KRISO)
Joung Hyung Cho Pukyong National University