References of "Schiry, Marc 50021846"
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See detailInfluence of laser parameter on weld bead shape and process stability of laser welded steel sheets
Schiry, Marc UL; Plapper, Peter UL

in Proceedings of 10th Conference on Photonic Technologies LANE 2018 (2018)

Laser butt-welding of dissimilar heat sensitive materials is one of the most challenging tasks. Significant differences in melting and transition temperatures are typical and occur frequently. Therefore ... [more ▼]

Laser butt-welding of dissimilar heat sensitive materials is one of the most challenging tasks. Significant differences in melting and transition temperatures are typical and occur frequently. Therefore, accurate control of the temperature profile at the interface of the weld is essential. In this paper, the influence of the laser parameter power and velocity, as well as laser spot diameter on the laser process were investigated. It is shown that the beam diameter has a significant impact on the weld bead formation. Further variation of the type of shielding gas showed an effect on the bead geometry depending on the used laser spot diameter. Spectroscopic process observations showed a significant impact of the spot diameter and shielding gas on the energy input and the efficiency of the laser process. A homogeneous damping effect of the laser radiation was obtained by using the larger fiber diameter accompanied with a higher overall intensity of process radiation. [less ▲]

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See detailAcoustic-Emission-Analysis of Dissimilar Laser-welds of Aluminium and Polyamide 6.6
Schiry, Marc UL; Lamberti, Christian UL; Böhm, Peter et al

in Universal Journal of Materials Science (2016), 4(6), 119-124

A novel laser joining process for hybrid polymer-metal structures has proven a strong bond between polyamide and aluminium. This welding technique is strongly requested by the automobile producing ... [more ▼]

A novel laser joining process for hybrid polymer-metal structures has proven a strong bond between polyamide and aluminium. This welding technique is strongly requested by the automobile producing industry for numerous applications within structure components. However, the joining quality exhibits a strong dependency on process-related variables, which highlights the need for an online inspection technique. The requirements for a chosen inspection technique are [1], [2]: 1. Showing the results on-line during the joining process; 2. Working non-destructive; 3. Working as an integral method; Being able to determine weld defects. In that case only the Acoustic Emission Analysis (AEA) as a Non-Destructive-Technique (NDT) can be used to guarantee reasonable results. During the first tests at the welding laboratory at the Laser Technology Competence Centre (LTCC) at the University of Luxembourg, AEA sensors are applied onto the surface of the test specimen which has to be welded. In this principle acoustic events, caused by welding defects, are recorded during the laser joining. The most important laser process parameters, like velocity, power and horizontal focal position of the laser spot, have been verified and evaluated by the AEA. It was observed that insufficient laser power can lead to the break of the melting bath, which is often not recognizable by non-destructive optical methods [2]. The AEA however was able to detect this lack of fusion. Using high laser power, the appearance of gas bubbles arising from the Polyamide 6.6 could be detected afterwards in a microscopic micrograph. The AEA signals related to this effect can be correlated clearly. Due to the high pressure of the gas bubbles, the aluminium weld is often interrupted, which can be traced back to the solidification of the aluminium molten mass. Due to the actual situation, the AEA is a well-working NDT online monitoring method and can be used for the correlation of acoustic events and welding defects within the mentioned joining method. Future tasks will develop some algorithms to separate the different defects by pattern recognition of the AEA signals and parameter [less ▲]

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