This article presents the results of an experimental program to investigate the sensitivity of the hybrid laser-MAG welding process to gaps between the work pieces being welded. It was concluded that the minimum throat depth of the welds remained surprisingly stable for fillet welds as long as the metal active gas (MAG) parameters were set high enough to fill the gaps involved (up to a gap size of approximately 3 mm). If the MAG parameters were insufficient then the welding process collapsed with increasing gap widths.

This article presents the results of an experimental and theoretical analysis of the effect of joint gap on the strength of hybrid laser-metal inert gas welds. The welds were of the partial penetration butt type with various joint gaps but identical weld penetration. Impact testing established that a zero gap gave a weak weld because the weld geometry contained the equivalent of a sharp crack where the unwelded parts met each other. A small gap between the workpieces improved the weld impact strength as the sharp crack effect became dissipated. Further increases in gap width resulted in a weakening of the joint and this is the subject of a discussion on joint gap optimization

This paper presents the results of an experimental program to investigate the sensitivity of the hybrid laser-MIG welding process to gaps between the work pieces being welded. It was concluded that the minimum throat depth of the welds remained surprisingly stable for fillet welds as long as the MIG parameters were set high enough to fill the gaps involved (up to a gap size of approximately 3 mm). If the MIG parameters were insufficient then the welding process collapsed with increasing gap widths.

This paper presents the results of an experimental and theoretical analysis of the effect of joint gap on the strength of hybrid laser-MIG welds. The welds were of the partial penetration butt type with various joint gaps but identical weld penetration. Impact testing established that a zero gap gave a weak weld because the weld geometry contained the equivalent of a sharp crack where the unwelded parts met each other. A small gap between the workpieces improved the weld impact strength as the sharp crack effect became dissipated. Further increases in gap width resulted in a weakening of the joint and this is the subject of a discussion on joint gap optimization

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.