Measurement And Numerical Simulation Analysis Of 3d Welding Residual Stress

With the development of the modern industry, welding technology has been penetrating into the fields of bridges, cars, ships, electric power, petroleum, petrochemical, and aerospace. The quality criteria of welded products have been becoming more and more complex, especially regarding welding residual stress. Accordingly, the detection of residual stress have been also subjecting to more advanced criteria and required to be accurate, rapid, and non-destructive. The use of numerical simulation in studying the field of welding plays an important role in the application of computer to the welding process. By modeling the soldering and the input of welding process parameters, the distribution of stress field of welded components can be obtained by conducting a large number of computer calculations. Furthermore, the optimal design, optimal technical methods and optimal welding process parameters for welding various structures and materials can also be determined by computer.Using the method of layers stripping by electrolytic corrosion and X-ray diffraction, the welding residual stress of Q345, which is a kind of steel used on ship and has two kinds of welded parts--butt joint welding and angle joint welding, was measured in the current study. With the method of numerical simulation, a 3D finite element model was developed using the finite element software ANSYS, which can model and analyze of the welding temperature field and stress-strain field. The measurements and simulation results were compared to validate the accuracy of the results of the numerical simulation. The factors that affected the accuracy and precision of the X-ray diffraction measurement of welding residual stress and the finite element model of were summarized. The results show that:â‘ In this study, the method of electrolytic corrosion was used to strip the butt joint welding specimens of steel Q345 into layers. During the corrosion process, a variety of factors, such as the impact of corrosion, the corrosion surface quality and the corrosion rate were considered. According to the variation of corrosion current and the variation of corrosion effect versus time, corrosion process could be divided into stages of electrolytic corrosion and electrolytic polishing. With constant corrosion and other appropriate control of several key factors, better corrosion effects were obtained by corrosion of long time, large area and large depth on the Q345 welding specimen. The results showed that the method of electrolytic corrosion to strip the layers had a better application to the measurement of surface welding residual stress.â‘¡The finite element model was divided into different areas. Small mesh was used to ensure accuracy in the weld area and heat- affected zone, while large mesh to reduce computation and improve processing efficiency in the away from the weld area. Direct methods and coupling unit SOLID5 were used in every area to improve the convergence of nonlinear calculation. The method of"elements with live or dead"were used to realize the pass weld simulation of different welding to make the model closer to the actual process of multi-pass welding.â‘¢The comparison between the measurements and simulation results indicated that, for both butt joint welding and angle joint welding, the distribution of welding residual stress along the deep layer agreed well with the simulation results, in the direction of both parallel and perpendicular to the deep layer. The fitting curves had similar trend, but the individual test points and simulation points were different. This result suggests that the numerical simulation matched well with the real welding situation.The study provided a valid reference point for further study on the determination of reasonable welding method and parameters, the deformation of welding, and the variation of welding residual stress.