The International Maritime Organization (IMO) is currently rolling out more restrictive regulations in order to achieve net-zero GHG emissions by 2050. In response, the shipping industry is planning to pivot to green energy sources such as hydrogen fuel. However, since hydrogen has an extremely low boiling point (−253 °C), materials for storing liquid hydrogen must be highly resistant to low-temperature brittleness and hydrogen embrittlement. A 316L stainless steel is a typical material that meets these requirements, and various welds have been studied. In this study, 3 pass butt welding was performed by applying the FCAW (flux cored arc welding) process to 10 mm thick ASTM-A240M-316L stainless steel, with the size of the fusion zone and HAZ investigated by mechanical testing and heat transfer FE analysis according to process variables, such as heat input, welding speed, and the number of passes. In all cases, the yield and tensile strengths were about 10% and 3% higher than the base metal, respectively. Furthermore, heat transfer FE analysis showed an average error rate of 1.3% for penetration and 10.5% for width and confirmed the size of the HAZ, which experienced temperatures between 500 °C and 800 °C.

Liquified hydrogen is considered a new energy resource to replace conventional fossil fuels due to environmental regulations by the IMO. When building tank for the storage and transportation of liquified hydrogen, materials need to withstand temperatures of -253°C, which is even lower than that of LNG (-163°C). These materials mainly include austenitic stainless steel and high-manganese steel, especially STS 304 steel mainly used to build liquified hydrogen tank. When building the tanks, both the base material and welding zone need to have excellent strength in cryogenic condition, however, manual arc welding has several issues due to prolonged exposure of the base material to high temperatures. Laser welding, which has some benefits like short period of exposure time and decrease of thermal affected zone, is used many industries. In this study, to determine the laser butt welding condition for STS 304 steel, laser bead on plate welding was conducted. After the BOP test, cross-section observation was conducted to analyze the penetration characteristics. After observation, four bead parameters were measured, and these tendency result of laser welding for STS 304 steel can be used as conditions laser butt welding of STS 304 steel.

The structural safety of lithium-ion battery systems in electric vehicles (EVs) has become increasingly important with growing concerns over battery-related accidents. In particular, external impacts on the battery pack case (BPC) can cause cell deformation or short-circuiting, potentially leading to thermal runaway. In this study, the mechanical integrity of a commercial BPC was evaluated using both drop-weight impact tests and finite element method (FEM) simulations. A 10 kg hemispherical or cylindrical weight was dropped from a height of 7 m to generate high-energy vertical impacts. The deformation and potential failure of the BPC were examined experimentally, and equivalent FEM simulations were conducted to analyze stress and deformation responses. In both cases, the BPC maintained structural integrity without cracking or intrusion into the battery cell region. The hemispherical impact resulted in relatively shallow, distributed deformation, whereas the cylindrical impact produced more localized indentations due to stress concentrations. The close agreement between experiment and simulation confirms the suitability of FEM for pre-assessment of BPC impact on safety. These findings provide a useful basis for establishing mechanical design criteria and improving battery protection strategies for EV applications.

As the demand for eco-friendly energy increases, offshore wind power structures are gradually becoming larger to increase power generation capacity, which in turn requires the use of thick TMCP steels and the securing of structural integrity. In this study, multi-pass FCAW was applied to 40 mm thick S355ML and S420ML steels in 2G and 3G welding positions, and the welding conditions for each experiment were designed to simulate actual industrial site construction conditions. After the experiments, tensile, low-temperature impact, and hardness tests were performed on the welded joints, and a comparative analysis was conducted on whether the relevant standards were satisfied and their major characteristics. As a result of the tensile test, tensile strengths exceeding the standard requirements were measured under all conditions, and base metal fracture occurred. In addition, the low-temperature impact test conducted at −50 °C exceeded the standard requirement of 27 J, ensuring sufficient low-temperature toughness, and the Vickers hardness test results were measured to be less than the reference value of 380 HV10. Through this study, the structural integrity and mechanical reliability of multi-pass FCAW welded joints for thick TMCP steel plates were secured.

The fire resistance and thermal propagation delay of a flame-retardant battery pack case (BPC) were investigated in this study for electric vehicles. Following the Lithium-ion traction battery pack and system for electric vehicles, Part 3: Safety requirements and test methods 31467.3-2015 standards, the BPC specimen was exposed to 500–600 °C for 15 min. Six thermocouples monitored the non-exposed surface, which reached a maximum of 149.7 °C, below the 150 °C limit. No flame occurred during or after heating, and the structure maintained integrity without cracks. The results confirm the flame-retardant BPC’s excellent thermal shielding and demonstrate its potential to enhance EV battery safety by delaying heat transfer and preventing secondary ignition.