Hybrid laser-MIG welding an investigation of geometrical considerations

Abstract: This thesis presents a collection of theoretical and experimental investigations into various geometrical aspects of hybrid laser-MIG welding. The work is divided up into four parts; A review of the hybrid laser-MIG welding technique with brief summaries of the three papers which make up the remainder of the thesis. A paper entitled "Fundamental analysis of hybrid laser-MIG welding". This paper provides a theoretical insight into the hybrid laser-MIG welding process. This fundamental analysis includes a description of the effect of process parameters on the cross-sectional geometry of the weld. A paper entitled "The influence of joint geometry and fit-up gaps on hybrid laser-MIG welding" This paper analyses the effect of the geometry of the pre-welded joint on the final weld cross-section. This paper specifically investigates the influence of gaps between the workpieces and their effect on the welding process. From this work, guidelines on the achievement of successful welds have been developed. A paper entitled "The influence of joint gap on the strength of hybrid Nd:YAG laser-MIG welds". This paper looks into a specific feature of weld geometry; the effect of different size gaps at the root of partial penetration butt welds. It was postulated (and confirmed) that an optimum range of fit-up gaps gives maximum weld strength. If the gap is smaller than this optimum then the fit-up gap acts as a sharp "crack" at the base of the weld. If the gap is larger than the optimum range then the root of the weld takes on a more complex geometry which, once again, includes stress raising features.