HighlightsAn In situ quality monitoring for AM is presented Our approach combines acoustic emission with machine learning Fiber Bragg grating is used as acoustic sensors spectral convolutional neural networks is used for classification in terms of quality level The classification accuracy of the events ranged between 83 -89%.

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. A B S T R A C TThis paper describes a hybrid additive manufacturing process -3D Laser Shock Peening (3D LSP), based on the integration of Laser Shock Peening (LSP) with selective laser melting (SLM). The well-known tensile residual stresses (TRS) in the as -built (AB) state of SLM parts in the subsurface region have a detrimental effect on their fatigue life. LSP is a relatively expensive surface post treatment method, known to generate deep CRS into the subsurface of the part, and used for high end applications (e.g. aerospace, nuclear) where fatigue life is crucial. The novel proposed 3D LSP process takes advantage of the possibility to repeatedly interrupt the part manufacturing, with cycles of a few SLM layers. This approach leads to higher and deeper CRS in the subsurface of the produced part, with expected improved fatigue properties. In this paper, 316L stainless steel samples were 3D LSP processed using a decoupled approach, i.e. by moving back and forth the baseplate from an SLM machine to an LSP station. A clear and significant increase in the magnitude and depth of CRS was observed, for all investigated process parameters, when compared to the AB SLM parts, or those traditionally LSP (surface) treated.

Using a combination of first-principles and magnetization-dynamics calculations, we study the effect of the intense optical excitation of phonons on the magnetic behavior in insulating magnetic materials. Taking the prototypical magnetoelectric Cr2O3 as our model system, we show that excitation of a polar mode at 17 THz causes a pronounced modification of the magnetic exchange interactions through a change in the average Cr-Cr distance. In particular, the quasi-static deformation induced by nonlinear phononic coupling yields a structure with a modified magnetic state, which persists for the duration of the phonon excitation. In addition, our time-dependent magnetization dynamics computations show that systematic modulation of the magnetic exchange interaction by the phonon excitation modifies the magnetization dynamics. This temporal modulation of the magnetic exchange interaction strengths using phonons provides a new route to creating non-equilibrium magnetic states and suggests new avenues for fast manipulation of spin arrangements and dynamics. arXiv:1707.03216v3 [cond-mat.str-el]