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3832 |
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Thursday, May 22, 2014, Hall H3 9:20 AM Modeling & Simulation 1 |
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Modeling of impact and bonding of inhomogeneous particles in cold spraying |
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Hamid Assadi* / Helmut Schmidt University
Dept. of Mechanical Engineering, Germany Thomas Klassen / Helmut Schmidt University, Dept. of Mechanical Engineering, Germany Frank Gärtner/ Helmut Schmidt University, Dept. of Mechanical Engineering, Germany Toshikazu Nanbu/ Nissan Motor Co. Ltd., Nissan Research Center, Japan Yoshio Kawashita/ Nissan Motor Co. Ltd., Nissan Research Center, Japan Yoshitaka Uehara/ Nissan Motor Co. Ltd., Nissan Research Center, Japan |
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In modelling of particle impact in cold spraying, it is often assumed that the impinging particle has uniform properties. For a comprehensive description of the bonding mechanism, however, it is assumed that the bonding between particle and substrate takes place through breakup and removal of a surface oxide layer. This means that the particle should in reality have non-uniform properties, i.e. be covered by a relatively harder and more brittle shell. There are also cases where the opposite is true: the hard and brittle powders are deliberately coated with a soft shell, e.g. in order to facilitate bonding or to produce composites of hard and soft materials. In this study, we explore the role of inhomogeneity of particle properties in impact and bonding behaviour, by means of modelling and numerical simulation. Initially, it is shown that not only shear instability as a necessary condition for bonding but also the entire process of bonding may be represented and investigated numerically through models that consider presence of an oxide layer. Furthermore, the effect of inhomogeneity of particles on the main cold spray characteristic, namely the critical velocity, is investigated for the case of metal-clad hard phases. Simulations show that the condition for bonding of such composite particles may deviate substantially from that of homogeneous particles. The paper also includes a discussion of the optimisation of the composite powder characteristics in view of the modelling results. |