Simultaneous recovery of an infinite rough surface and the impedance from near-field data

In this paper, we consider an inverse rough surface scattering problem in near-field optical imaging. This problem is actually to reconstruct the scattering surface as well as its impedance coefficient from multifrequency near-field data, and can be reduced into an integral scheme by employing an integral representation. We solve this integral scheme by a non-linear integral equation method, and further develop a fast inversion algorithm for reconstructing both the rough surface and the impedance coefficient. Numerical experiments are presented to illustrate the effectiveness of the algorithm.     

Thermometric investigations for the characterization of fatigue crack initiation and propagation in Wire and Arc Additively Manufactured parts with as-built surfaces

Metal Additive Manufacturing (AM) allows for the fabrication of complex shapes with high added value at low costs. Indeed, as-built structures are near net shape: they require few to no finishing operations. However, as-built AM parts present significant roughness caused by the layer discretization. In the case of the Wire and Arc Additive Manufacturing (WAAM) process, used for large-scale structures, the as-built roughness is estimated to several hundreds of micrometers. For complex geometries, a complete machining of the surfaces is not necessarily possible. In this study, an experimental method is proposed, relying on thermoelastic stress analysis, to characterize the effect of as-built WAAM surface roughness on high-cycle fatigue properties. Using an infrared camera, multiple cracks can be detected and monitored over a large surface on rough WAAM samples under cyclic bending. The collected data constitutes valuable information for the identification of a fatigue model dedicated to as-built WAAM structures.