Simulation Of Acceleration And Impact Of Particles During Abrasive Water Jet

Abrasive water jet(AWJ)is a new surface strengthening technology,in which the particles first accelerate in the water jet and then impact the target,thus introducing compressive residual stress on the surface of the target and improving the fatigue strength of the target.However,most studies on particles acceleration in AWJ focus on single particle and there are few studies on the acceleration of large numbers of particles.At the same time,the research on particles impact on target is mostly the result of direct research on particles impact on target,but the research on transient process and energy transfer of particles impact on target is less.In addition,in the study of particles acceleration and impact target,the selected parameters are not comprehensive enough.Therefore,this paper studied particles acceleration and impact target with different parameters through simulation.The main research contents are as follows:(1)Firstly,the acceleration mechanism of a single particle is studied,the force analysis is carried out and the motion equation is established.Then,the simulation model of AWJ particles acceleration is established by using the CFD-DEM coupling method and the reliability of the simulation model is verified.The effects of water flow velocity,particle diameter and mass flow rate on particles acceleration are studied.The simulation results show that the particles near the wall of the sand tube moves not only along the axial direction of the sand tube,but also gradually towards the axis of the sand tube.The particle velocity is maximum at the center of sand tube.The particle outlet velocity increases with the increase of water flow velocity,and decreases with the increase of particle diameter or mass flow rate.The acceleration time of particles increases with the increase of particle diameter or mass flow rate.In this simulation range,when the water flow velocity is 80m/s,the particle diameter is 0.1mm and the mass flow rate is 1kg/min,the particles accelerate the fastest.(2)The generation and coupling mechanism of residual stress during particles impact on target is studied,and the mathematical model of residual stress is established.Then,the simulation model of particles impact on target is established through DEMFEM coupling method and the reliability of simulation model is verified.The effects of particles diameter,particles velocity,particles impact angle and particles mass flow rate on energy transfer,residual stress and surface roughness are studied.The simulation results show that for a planar target,the energy transferred from the particles to the target,the surface roughness,the maximum compressive residual stress and the depth of compressive residual stress layer increase first and then decrease with the increase of the particle incident angle,and all reach the maximum value when the incident angle is 75°.With the increase of particle initial velocity or particle diameter,the energy transferred from particles to target,surface roughness,maximum compressive residual stress and depth of compressive residual stress layer increase.With the mass flow rate increasing,the energy transferred from the particles to the target,the surface roughness,the maximum compressive residual stress and the depth of the compressive residual stress layer increase first and then decrease,and all reach the maximum value when the mass flow rate is 2kg/min.For v-shaped grooves,the maximum compressive residual stress and the depth of compressive residual stress layer increase with the increase of particle diameter or the decrease of mass flow.