Modelling and simulation of welding and metal deposition

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 due to welding is important to control. This is especially important in the aerospace industry where the components are expensive and safety and quality are very 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 components 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. The effects of previous processes are also important to consider, as well as it is important to bring forward the current state to subsequent processes.When creating a numerical model, the aim is to implement the physical behaviour of the process into the model. However, it may be necessary to compromise between accuracy of the model and the required computational time. The aim of the work presented in this thesis was to develop a method and model for simulation of welding and metal deposition of large and complex components using the finite element method. The model must be reliable and efficient to be usable in the designing and planning of the manufacturing of the component. In this thesis, the meaning of efficiency of a model is wider than just the computational efficiency. The time for creation and definition of the model should also be included. The developed methods enable the user to create a model for welding or metal deposition with a minimum of manual work. The method for defining weld paths and heat input together with activation of elements is now implemented in the commercial finite element software MSC.Marc. The implementation is based on the experience in this work and communication with the author. The approach has been validated against test cases. Naturally, this validation is dependent on sufficient accuracy of the heat input model and material model that are used. It is the first time a dislocation density model has been used to describe the flow stress in a welding simulation. The work has also demonstrated the possibility to calibrate heat input models with a physical based heat input model, thus relieving the need to calibrate the heat source versus measurements.Efficiency in terms of computing time has also been investigated in the course of this work. Three different methods has been explored and used, adaptive meshing, substructuring and parallel computation. The method that is found to be the most versatile and reduce the overall simulation time the most is parallel computation. It is straightforward for the user to employ and it introduces no reduction in the accuracy.Godkänd; 2010; 20091124 (andlun); DISPUTATION Ämnesområde: Datorstödd maskinkonstruktion/Computer Aided Design Opponent: Professor Jesper Hattel, Danmarks tekniska universitet Ordförande: Professor Lennart Karlsson, Luleå tekniska universitet Tid: Fredag den 5 februari 2010, kl 09.00 Plats: E 243, Luleå tekniska universitet</p

Modelling of weld path for use in simulations

The most frequent used method for joining metal structures together is fusion welding. This method has largely been developed by experiments, i.e. trial and error. The problem of distortion, residual stresses and reduced strength of a structure in and around a welded joint are a major concern of the welding industry, especially in the aerospace industry where safety and economy are important issues. The objective of this thesis is to develop and evaluate a method for introducing a moving heat source into a FE-model. The heat source should be able to move along any general 3D curve. The aim is to facilitate the simulation of welding for complex weld paths and geometries. The basic idea is that the user defines the weld path in a CAD-program with the geometry as basis, then information about the weld path is to be exported to a separate file. This file is processed later in the FE-program by user-defined routines in order to create nodal heat input corresponding to the weld for the finite element model. The aim of this work has in general been fulfilled. The method for welding simulation that can follow any general 3-D curve as welding path fulfils the expectations perfectly. In the whole process of welding simulation there are a couple of things that must be added or corrected. One of these things is that this model gives no feed-back or verification if the correct amount of energy is given into the model. This may wary due to mesh and geometry changes. To be able to do simulations with adequate results this must of course be attended to. This simplification of the process of modelling welding will contribute to make simulations more commonly used by the industry.Validerat; 20101217 (root

Finite element modelling and simulation of welding of aerospace components

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.Godkänd; 2003; 20070216 (ysko

Idrottsläraren plus Idrottsledaren? : en studie i idrottslärarens attityd till samverkan med föreningsidrotten

Validerat; 20101217 (root

Dislocation density based constitutive model for Ti-6Al-4V used in simulation of metal deposition

Godkänd; 2007; 20070905 (ysko

Repair welding and local heat treatment

One application for repair welding is to restore the integrity of a component where a crack has been found. Cracks can appear during in-service or already in the manufacturing process. The latter is usually the case for large castings where cracks may have formed. The repair welding in this entry is the process of filling a premachined slot. This slot has been milled in order to remove the crack that has been found. The welding process can be any kind of arc, beam, or gas welding process. However, manual arc welding is the most common method for repair welding. Thereafter, the component may need to be heat treated in order to reduce residual stresses and/or restore material microstructure. Local heat treatment means that only a part of the structure is heat treated. This is in contrast to global heat treatment where the entire structure is heat treated by placing it in a furnace. We focus on the use of induction heating for local heat treatment in the current entry

Beräkning och loggning av bränsleförbrukning samt implementering av MOST

Validerat; 20101217 (root

Modeling the Evolution of Grain Texture during Solidification of Laser-Based Powder Bed Fusion Manufactured Alloy 625 Using a Cellular Automata Finite Element Model

The grain texture of the as-printed material evolves during the laser-based powder bed fusion (PBF-LB) process. The resulting mechanical properties are dependent on the obtained grain texture and the properties vary depending on the chosen process parameters such as scan velocity and laser power. A coupled 2D Cellular Automata and Finite Element model (2D CA-FE) is developed to predict the evolution of the grain texture during solidification of the nickel-based superalloy 625 produced by PBF-LB. The FE model predicts the temperature history of the build, and the CA model makes predictions of nucleation and grain growth based on the temperature history. The 2D CA-FE model captures the solidification behavior observed in PBF-LB such as competitive grain growth plus equiaxed and columnar grain growth. Three different nucleation densities for heterogeneous nucleation were studied, 1 × 1011, 3 × 1011, and 5 × 1011. It was found that the nucleation density 3 × 1011 gave the best result compared to existing EBSD data in the literature. With the selected nucleation density, the aspect ratio and grain size distribution of the simulated grain texture also agrees well with the observed textures from EBSD in the literature.Validerad;2023;Nivå 2;2023-11-06 (joosat);Part of Special Issue: Multi-Scale Simulation of Metallic Materials (2nd Edition)CC BY 4.0 LicenseFunder: EU Just Transition Fund and the Swedish Agency for Economic and Regional Growth (FINAST project, grant number 20358499)</p