TWI Industrial Member Report Summary 971/2010
By Daowu Zhou
Welding is the primary method of joining used for part assembly in the automobile and ship industry, and, increasingly for aerospace applications. One major industrial concern is that welding distortion often results in problems such as dimensional inaccuracies during the assembly and increased fabrication costs. Optimisation of the welding sequence and process is one way to reduce the costs and effort associated with rework.
Welding distortion is the result of the non-uniform thermal expansion and contraction of the weld and surrounding base material caused by the heating and cooling cycle of the welding or cutting process. Tensile stresses were generated around the weld combined with compressive stresses in the rest of the plate due to the expansion and subsequent contraction of the yielded material which is restrained by the surrounding colder material. Distortion occurs when the stresses exceed a certain level.
With increasing competition in the manufacturing sector in the global market, the quantification of the level of distortion from welding processes is crucial to meet the increasingly stringent accuracy requirements. Clearly, there is a strong need for a fabricator to develop the capability to design and manufacture innovative, large and complex welded products at competitive rates with manageable levels of technological and financial risk. This is being achieved by replacing physical experimentation and construction of prototypes with cost-effective real-time virtual welding technology where the efficient distortion modelling is the key.
The present work was initiated as a result of issues arising from the OPTWELD (Real-Time Virtual Prototyping Tools for OPTimising WELDed Products) project which is a collaborative project, funded by the Technology Strategy Board and includes industry and university partners. The OPTWELD project aims to develop a virtual welding system using an efficient distortion modelling approach which enables non-expert users to predict distortion and achieve better fatigue performance in welded structures.
The present report is intended to carry out a state-of-the-art literature review of welding distortion simulation approaches with a focus on the simulation of large welded structures. The outcomes are to be used to select the most appropriate approaches in welding distortion modelling for practical use for the OPTWELD virtual welding system.
Provide an overview of recent advances in computer-based weld distortion for large welded structures.