Numerical Simulation And Systematic Research Of Robotic Cold Spray

Cold spray is a coating technology,which has been widely used in aerospace,automotive,new energy and other fields.In recent years,cold spray technology has been advanced from coating technology to additive manufacturing technology.Compared to traditional additive manufacturing processes,cold spray additive manufacturing(CSAM)has much lower processing temperature,shorter production time,unlimited product size and high flexibility,which can be used to repair damaged parts,especially for high reflectivity metals such as copper and aluminum.However,the cold spray coating usually has rough,undulating and porous surface,whose dimensional accuracy is also low.This makes it important to improve the uniformity of the cold spray deposited body surface by studying the influence mechanism of the process parameters to obtain the basis for the regulation of the system parameters.Therefore,this paper investigates key issues such as gas-solid two-phase flow,particle deposition,coating profile influence mechanism in cold spray additive manufacturing and robotic cold spray system.Firstly,the gas-solid two-phase flow behavior of cold spray was numerically simulated by ANSYS FLUENT software,and the two-dimensional physical model of Laval nozzle was established.Based on the consideration of powder flow,the influence of spray temperature,spray pressure and standoff distance on gas flow characteristics and particle acceleration performance inside and outside the nozzle were analyzed.At the same time,the influence of particle factors on the acceleration performance of particles was analyzed.It is found that the velocity of gas and particles increases with the increase of spray temperature and spray pressure,and the effect of increasing temperature is more significant than increasing pressure.In addition,the particle velocity also increases with the decrease of molecular weight.The variation of the standoff distance leads to the change of the distribution of the excitation wave outside the nozzle,which affects the action time and effect on the acceleration and deceleration of the particles.The study in this chapter can provide a reference for the selection of temperature,pressure,distance and particles in the experiments.Secondly,the particle deposition process of cold spray was simulated by ANSYS LS-DYNA software,and a three-dimensional axisymmetric physical model of single particle impacting substrate was established to analyze the effects of particle and substrate material properties,particle impact velocity and particle impact angle on deposition effect and plastic deformation,etc.The deformation behavior of particle and substrate during the deposition of particles was analyzed.The results show that material properties of particle and substrate can significantly influence their combination effect,the particle velocity is the key parameter for the successful deposition of particles,and the decrease of spray angle will reduce the deposition efficiency of the coating.The research in this chapter provides important guidance for the determination of the particle and substrate materials and further research on the spray angle in subsequent experiments.Then,the mathematical model of cold spray coating thickness was established by using Gaussian model,and the coating thickness was simulated by MATLAB software to analyze the effect of nozzle traverse speed and nozzle scanning step on the coating profile.It is found that both nozzle traverse speed and nozzle scanning step have an impact on coating thickness and surface roughness.The reasonable selection of traverse speed and scanning step will significantly improve the uniformity of the coating,which can provide a reference for the subsequent relevant experimental studies and reduce the blindness of the cold spray experiments.Finally,a robotic cold spraying system was built on the basis of the above simulation analysis,its composition,working principle and control scheme were analyzed,and then a series of cold spraying experiments were conducted according to the requirements to further investigate the effects of spraying kinematic parameters on coating deposition efficiency,surface uniformity and mechanical properties.The study in this chapter verifies the correctness of the above-mentioned conclusions about cold spray,which helps the cold spray be better applied in the field of additive manufacturing.