Finite element modelling and simulation of welding of aerospace components

Sammanfattning: Fusion welding is one of the most used methods for joining metals. This method has largely been developed by experiments, i.e. trial and error. The problem of distortion and residual stresses of a structure in and around a welded joint is important to control. This is especially important in the aerospace industry where the components are expensive and safety and quality are important issues. The safety requirements and the high costs of performing experiments to find different manufacturing routes is the motivation to increase the use of simulations in design of component as well as its manufacturing. Thus, in the case of welding, one can evaluate the effect of different fixtures, welding parameters etc on the deformation of the component. Then it is possible to optimise a chain of manufacturing processes as, for example, the welding residual stresses will affect the deformations during a subsequent heat treatment. The aim of the work presented in this thesis is to develop an efficient and reliable method and tool for simulation of the welding process using the Finite Element Method. The simulation tool will then be used when designing and planning the manufacturing of a component, so that introduction of new components can be made with as little disturbance as possible. In the same time the developed tool will be suitable for the task to perform an optimal design for manufacturing. Whilst this development will also be valuable in predicting the component's subsequent in-service behaviour, the key target is to ensure that designs are created which are readily manufactured. If this understanding is captured and made available to designers, true design for manufacture will result. This will lead to right first time product introduction and minimal ongoing manufacturing costs as process capability will be understood and designed into the component. When creating a numerical model, the aim is to implement the physical behaviour of the process into the computer model. However, it may be necessary to compromise between accuracy of the model and the required computational time. Different types of simplifications of the problem and more efficient computation methods are discussed. Methods for alleviating the modelling, and in particular the creation of the weld path, of complex geometries is presented. Simulations and experiments have been carried out on simple geometries in order to validate the models.