Chapters authored
Residual Stress Evaluation with Contour Method for Thick Butt Welded Joint
Thick plate with high tensile strength steel is increasingly employed for offshore structure fabrication, and welding residual stress is essential for assessment of mechanical performance and fatigue toughness. Therefore, it has been becoming the research issue to evaluate the distribution and magnitude of welding residual stress during butt welding of thick plate. With its advantages, contour method (CM) can be used for longitudinal residual stress evaluation by means of measuring sectional shrinkage after cutting the butt welded joint perpendicular to the welding line. Meanwhile, inverse finite element method (IFEM) code is programmed with C++ language to analyze the measured data to reestablish the welding residual stress. And based on the parallel computation of high-performance server, considering the effect of weld remelting and back-gouging during multi-pass welding process, the welding residual stress is predicted by using efficient thermal elastic plastic finite element method (TEP FEM). Results show that longitudinal residual stress turned from tensile stress in welded vicinity into compressive stress in base metal and the maximum tensile stress is 269 MPa. The computed longitudinal residual stress and welding displacement through TEP FEM are identified with the experimental results. In addition, the back-gouging has an insignificant effect on the residual stress but increases the welding displacement of butt welded joint. The proposed TEP FEM can accurately predict the welding residual stress in welded joint and is also an effective method to control welding displacement.
Part of the book: New Challenges in Residual Stress Measurements and Evaluation
Ongoing of Energy Saving and Emission Reduction during Fabrication Processing in China’s Shipyards
Due to the serious situation and deterioration tendency of the atmosphere environment, energy saving and emission reduction are concentrated and desired for each government and international organization. In this research, energy consumption and pollution emission during fabrication processing in shipyards and ocean engineering factories were holistically surveyed for the first time, while the ship industry is the key pillar of manufacturing for national economic development and dominant monitoring objects with severe environment pollution in China. With the visiting and investigation of six representative factories with construction and repair of ship and offshore structure, consumptions of electrical energy as well as chemical energy were summarized for each fabrication processing according with elementary manufacturing flow, which are mainly determined by working load, requirement of quality, and utilization efficiency of energy. Then, various pollutants generated during fabrication procedures were classified and surveyed, while their emission amounts were also summarized by considering their harm level to human health, atmosphere, and ecological environments. In addition, advanced and practical solutions for emission reduction of dust particles and VOCs (volatile organic compounds) were introduced and carried out while the application results were compared with requirements of corresponding laws and regulations.
Part of the book: Welding - Materials, Fabrication Processes, and Industry 5.0