Showing papers by "Giuseppe Casalino published in 2005"

FEM simulation of metal sheets laser welding with wire filler material

Abstract: Worldwide manufacturers have already recognized the advantages of using laser welding for a number of applications. Although laser welding is usually performed autogenously, the use of wire filler allows a broader range of welding applications. In this paper a finite element model for key-hole laser welding sources based on experimental observations is presented. The shape for the heat source can be easily changed so to simulate both autogeneous and wire filler laser welding. In the thermal and mechanical calculations the material properties were considered with full temperature dependence. Austenitic stainless and aluminum alloy welds were chosen to validate the model. Simulations of out-of-plane welds were computed using a local coordinates system. A personal computer was used for the calculations. For different plate thicknesses and weld geometries, the calculated fused zones were found in very good agreement with the experimental ones, which proved that the thermal history was computed correctly. When materials with thermal induced microstructure changes are welded, the microstructure in every point of the heat affected zones can be determined as a function of the local temperature cycle.

Characterisation of Al-Mg alloys mig-laser CO2 combined welding

Abstract: This paper contains the metallurgical and technological characterizations of CO2 Laser-MIG combined welding of Al-Mg alloy sheets. The bead-on-plate welds were either 3 mm and 10 mm thick.Metallurgical structures either of the fused zone and the welding boundaries were identified.Porosity and solidification cracks were localised and explained.Then, full penetration 3 mm thick samples with a low defectiveness underwent 3-points bending tests. The strain hardening in those welds, which was due to the bending deformation, was evaluated by the hardness test.A finite element numerical model for the bending was built in order to evaluate the residual stress and the internal strain of the welds.This paper contains the metallurgical and technological characterizations of CO2 Laser-MIG combined welding of Al-Mg alloy sheets. The bead-on-plate welds were either 3 mm and 10 mm thick.Metallurgical structures either of the fused zone and the welding boundaries were identified.Porosity and solidification cracks were localised and explained.Then, full penetration 3 mm thick samples with a low defectiveness underwent 3-points bending tests. The strain hardening in those welds, which was due to the bending deformation, was evaluated by the hardness test.A finite element numerical model for the bending was built in order to evaluate the residual stress and the internal strain of the welds.

Laser welding of the synchronizer stop ring and the rear gear in a manual transaxle

Abstract: The focused laser beam is one of the highest power density sources available to industry today. When the “keyhole mode” is used for welding the result is characterized by a parallel-sided fusion zone, narrow width, and deep penetration. Therefore, a higher value of the joining efficiency (i.e., the reciprocal of the specific welding energy) is obtained and less energy is necessary for heating which generates a large heat affected zone and low mechanical distortion. This article focuses on the application of the CO2 seam laser welding of the stop ring of the synchronizer hub and the rear idle gear in a five-speed manual transaxle. This weld requires precision, repeatability, and welding efficiency. Unfortunately, stresses generated by the thermal cycle can produce cold cracks in the fused zone, which was highly stressed during the cooling phase. The different thermal expansion coefficients of the metals can also produce misalignment during the welding cycle. Here, the welding process was investigated with ...