Study Of The Mechanical Properties Of Hight Strength Steel Laser Welding T-joints

As the proposal of resource-saving society concept, higher requirements to lightweight and reliability of industrial equipment are put forward. Metal sandwich plate is a new type sandwich structure composed of upper and lower panels that connected by core board. It has advantages of high specific stiffness, low-density, heat insulation, fire resistance, impact resistance, etc. The Welding process and structure design affect the performance of the whole sandwich plate. With the Lightweight of ship structure as the research background, and laser welding of marine steel960and780sandwich plate T-joint as the main research object. The bending stiffness and yield strength along with the failure stress state of T-joint were studied in this paper..Firstly in this paper, the composition and weldability of the two kinds of welding base metal were analyzed, and the mechanical properties of base metal and welds of different welding parameters were test, the test result show that the base metal960has higher yield strength and tensile strength, its yield is relatively large, while the elongation was16%, so its plastic is poor. The base metal780also has higher yield strength and tensile strength, but its extensibility is better.secondly, the bending and shear test by fixture were made for the T-joint, and the effects of welding power, gap and offset on the bending stiffness and bending strength of T-joints were analyzed, the sample results indicated that the connection width is the main factor affecting the stiffness of joint, the bending stiffness could be larger with a wider joint, and the welding power affects the joint organization and grain size, the bending strength of the joint could be larger with higher welding power, and when the welding power was low, the bending fracture was brittle fracture, the welding gap and offset have small effect on bending stiffness, but they can reduce the bending strength of joint. Through the study of statistical analysis and related empirical formula of the test results, a definition was given in this paper about the bending stiffness and the tensile strength.In the end, the commercial finite element software Abaqus was used to simulate the bending process of T-joint and three point bending test of sandwich plate. Through the simulation of T-joint bending process, the stress change of failure process in joint bending process was studied, and the effects of welding gap, offset and width on bending performance of T-joints were also studied. The finite element method was used to simulate the three point bending test of sandwich plate, the stress change in the sandwich plate joint and panel from yield to failure was analyzed, the weak links of960sandwich plate is in the weld of T-joint, and the960sandwich plate is in the panel, the load-displacement curve obtained from simulation was consistent with the test results, so conditions for further optimization of sandwich plate were provided.