Franck Morel

Effect of Laser Assistance Machining on Residual Stress and Fatigue Strength for a Bearing Steel (100Cr6) and a Titanium Alloy (Ti 6Al 4V)

The use of Laser Assisted Machining (LAM) can improve different aspects of the machinability of high strength materials. A study was undertaken to determine the optimum cutting parameters and to quantify their influence on fatigue strength according to the type of microstructure created. Two different materials were studied: a bearing steel (100Cr6 / AISI 52100) and an aeronautical titanium alloy (Ti6Al4V). In the bearing steel a significant increase of the fatigue resistance was observed due to the transformation of the surface layer into martensite. For the titanium alloy, a slight reduction in the fatigue strength was found as in this case the microstructure and residual stress state of the surface layer was less beneficial. The surface roughness has also been measured and no significant variation has been observed for different laser powers in each material.

On the model order reduction of confined plasticity

Forming processes usually involve irreversible plastic transformations. The calculation in that case becomes cumbersome when large parts and processes are considered. Recently Model Order Reduction techniques opened new perspectives for an accurate and fast simulation of mechanical systems. In some processes, plastic deformations remain very localized, for example in the immediate neighborhood of the surface. In that case, the in-plane characteristic dimension is several orders of magnitude higher than the one related to the deepness in which plasticity localizes. In those situations the use of standard mesh-based 3D discretization is challenging because the extremely different characteristic dimensions that to capture all the information requires the use of millions of nodes.