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This paper describes a thermal numerical model accessible to all users for predicting temperature in friction stir welding from the power, material thermal properties, process parameters, tool, and plate dimensions. Starting with the information obtained from the machine, power or torque, the heat flux is modeled as a circular moving source with a diameter equal to that of the shoulder. The model calibrated in a specific setup (CNC machine) successfully predicted without recalibration the weld temperature field in another one (robot). The simple thermal model was applied without recalibration to data available in the literature to test its effectiveness. The results obtained with this model are promising, although more tests are needed to cover all possible varieties of tool geometries and material thickness. If extended over a broader range of configurations (i.e., process parameters and tool-workpiece geometries), it could be a handy tool for all FSW users. The tool may help study the thermal cycles in the heat affected zone that influence final mechanical properties and make it easier to identify optimal parameters if the desired optimal peak temperatures are determined.

Relationships between subsurface damage (SSD) depth and peak to valley surface roughness (Rt ) have been widely studied and present a major interest for an easy assessment of the SSD depth. We seek the relation between SSD depth and other surface roughness parameters using the Abbott-Firestone curve on a large campaign of grinding tests (with different abrasive grain size, grinding speed and grinding mode). The results reveal that the Abbott-Firestone parameter Mr2 , which can be linked to the volume fraction of valley in the roughness profile, is more accurate than Rt for an assessment of the SSD depth and that the relationship between Mr2 and the SSD depth varies when changing the grinding mode. Keywords: subsurface damage, surface roughness, Abbott Firestone, fused silica glass 1. INTRODUCTION Many studies tried to define an empi rical relationship between subsurface damages and surface roughness because these damages under surface, mainly due to the manufacturing steps, limit greatly the lifetime of optical components in high energy laser applications such as Laser Megajoule (LMJ) or National Ignition Facility (NIF)