A comparative investigation of the efficacy of CO2 and high power diode lasers for the forming of EN3 mild steel sheets

A comparative investigation of the effectiveness of a high power diode laser (HPDL) and a CO2 laser for the forming of thin section EN3 mild steel sheet has been conducted. The buckling mechanism was identified as the laser forming mechanism responsible for the induced bending. For both lasers it was found that the induced bending angles increased with an increasing number of irradiations and high laser powers, whilst decreasing as the traverse speed was increased. Also, it was apparent from the experimental results that the laser bending angle was only linearly proportional to the number of irradiations when the latter was small due to local material thickening along the bend edge with a high number of irradiations. Owing to the mild steel’s greater beam absorption at the HPDL wavelength, larger bending angles were induced when using the HPDL. However, under certain conditions the performance of the CO2 laser in terms of induced bending angle was seen to approach that of the HPDL. Nevertheless, similar results between the two lasers were only achieved with increasing irradiations, thus it was concluded that the efficacy of the HPDL was higher than that of the CO2 laser insofar as it was more efficient. From graphical results and the employment of an analytical procedure, the laser line energy range in which accurate control of the HPDL bending of the mild steel sheets could be exercised efficiently was found to be 53 J mm-1 < P/v < 78 J mm-1, whilst for the CO2 laser the range was 61 J mm-1 < P/v < 85 J mm-1

High speed joining process by laser shock forming for the micro range

The importance to implement more functionality on the same space pushes miniaturization and makes hybrid joints under various conditions, also in the micro range, necessary. Conventional joining processes, which are used in macro range, cannot be easily transferred to micro range dimensions. In this work a new high speed joining method for the micro range is presented, which is realized by a plastic forming process based on TEA-CO2-Laser induced shockwaves. In a first step it is shown how sheet-sheet joints can be realized with this method. The experimental results illustrate the possibilities as well as the limits of the joining process by laser shock forming. Also the possible defects which can occur during the joining process are presented. Especially fracture of material at the edge. This is explained by the sharp edges in the joining area, which are caused by the production process of the specimen