Abstract

In cold spray; particles undergo large plastic deformation; upon impact; in a rapid dynamic regime (up to 109 s-1); at solid state. The simulation of particle impact is a key for the understanding of the cold spray process. This type of simulation typically involves dynamic material models. However; few data only are available for powders when submitted to cold spray conditions. In this study; an approach based on the use of a laser shock was therefore developed in addition to micro-compression testing to characterize the mechanical behavior of powders and; in particular; to fit parameters of the Johnson-Cook material behavior model. This method was applied to Al-based powders but can be applied to other materials. In situ multi-cyclic microcompression testing of single particles was performed in a SEM equipped with a micro-indentation stage. From subsequent FEM simulations of the test; static coefficients of the Johnson- Cook model could be identified. A highly dynamic test bench was developed using laser shock to accelerate single particles; namely LASHPOL (LAser SHock POwder Launcher). The velocity of LASHPOL’ed particles; measured using high-speed imaging; ranged from 102 m.s-1 to 103 m.s-1; corresponding to the typical range of cold spray particle velocities. In addition; image analysis of particles before and after the impact was developed; together with FEM simulation; to determine coefficients related to strain rate hardening in the Johnson-Cook model. The combination of the two testing methods resulted in an efficient mechanical characterization for powders. This approach is expected to become a powerful industrial tool for developing and/or controlling powders tailored for cold spray. Table 1. Acronym list Acronym Name BSE Back Scattered Electrons CEL Coupled Eulerian Lagrangian FEM Finite Element Method JC Johnson-Cook LASHPOL LAser SHock POwder Launcher SEM Scanning Electron Microscope

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