Modelling of copper particle – copper wall collision at high velocities
The particle – wall impact is a physical phenomenon encountered in various technological processes and in study of the mechanical properties of materials. Impact behavior of particles has been extensively studied at relatively low speeds (Thornton and Ning, 1998), (Etsion et. al., 2005). Recently, the importance of this phenomenon at higher velocities has increased with the advancement of laser metal deposition technology, where more accurate particle - wall interaction evaluation may lead to higher resolution of complex 3D printed metal structures.
In this report, normal impact of metal (copper) micro particle with smooth copper wall is simulated numerically at high velocities from 5 to 600 m / s, resulting in high temperature from deformations (Uzi and Levi 2018). Impact is characterized by purely plastic behavior because contribution of elastic deformation is negligible.
Plasticity behavior is governed by Johnson-Cook yield criterion dependent on plastic strain, strain rate and temperature occurring during deformation (Schmidt et. al., 2009). As the impact velocity increases the yield is spread throughout large part of volume of the particle, while the temperature reaches melting point (Wang et. al., 2015), two opposing effects are observed: with increase of temperature and particle deceleration at the end of the loading phase yield point decreases while increasing with the accumulation of plastic deformations. Therefore, different stages of impact, strain rates and temperature are examined independently.
The problem specific numerical integration tool using variable time step was developed. Several combinations of plasticity criteria with different impact velocities are investigated. Plastic deformation of particle – wall contact is corrected with results of refined axisymmetric finite element analysis.