Analysis of a fibre laser welding case study, utilising a matrix flow chart

For fibre laser welding of an eccentric corner joint, the quality of the resulting weld cross section was studied with respect to the dependence on process parameters like lateral laser beam alignment, beam inclination, focal plane position or welding speed. The complex load situation of the support beamer was simplified to bending of one corner. Due to fatigue load, the weld properties causing the peak stress are essential, in particular the top and root shape of the weld cross section. For the parameters varied, the resulting shapes were categorized into different top and root classes, determined by certain key dimensions, considering also welding defects like undercuts. The shapes are boundary conditions for Finite Element Analysis of the joint under load for quantitative comparative analysis of the maximum stress. As two high strength steel grades were joined, the hardness transition across the weld was of interest, too. High speed imaging of the weld pool surface shape provided additional information on the relation between the parameter input and quality output. The different trends identified were discussed and guidelines were derived. As the systematic documentation of results is unsatisfactory in welding, a new method was developed and applied for the first time, called the Matrix Flow Chart. It enables an illustrative view on the resulting welding trends in a combined manner and is extendable by other researchers. (C) 2010 Elsevier B.V. All rights reserved.