基体表面粗糙度对冷喷涂粒子沉积过程影响的物质点法数值分析

目的 解决有限元法模拟冷喷涂粒子沉积过程时存在的网格畸变等问题，并探讨粒子和粗糙基板的结合方式。方法 基于物质点法建立冷喷涂粒子沉积的仿真模型。利用FORTRAN语言自编程序对铜粒子冷喷涂铜基板的过程进行仿真分析，并与其他研究中的试验结果进行对照，结果吻合较好，表明物质点法模拟冷喷涂粒子沉积问题是可行且有效的。此外，分析基体表面粗糙度对粒子沉积过程的影响规律，并探讨粒子在不同位置沉积的结合机理。结果 随着表面粗糙度的增大，粒子扁平化趋势增大，回弹动能减小。表面粗糙度足够大时，粒子射流可能和基板形成机械咬合结构；粒子在波谷处沉积时受两侧波峰作用难以扁平化，但是凹坑深度增大，回弹动能减小，粒子基板结合强度增大；粒子在左侧半腰处沉积时，其在切向速度分量作用下与右侧波峰形成二次接触，形成了较长的射流。结论 粒子与基板的结合强度随着表面粗糙度的增大而增大。粒子在波峰处可以形成机械咬合结构；在波谷处凹坑深度增大、回弹动能减小，起填充作用；在半腰处能够与右侧波峰产生二次接触，增大结合强度。研究结果可为冷喷涂工艺生产提供一定指导。

Numerical Analysis of the Effect of Substrate Surface Roughness on the Process of Cold Spray Particle Deposition Based on the Material Point Method

The work aims to solve the problem of grid distortion in simulation of the cold spray particle deposition by the finite element method and discuss the bonding method of particles and rough substrate. The simulation model of cold spray particle deposition was established based on the material point method. The effect of surface roughness on particle deposition and the deformation behavior of particle deposition at different locations were discussed. The process of cold spray copper substrates with copper particles was simulated and analyzed by the program written in FORTRAN language. At the same time, the simulation results of the residual height and surface morphology of the particles were compared with the experimental results in the literature. The material point method was feasible and effective for simulating the cold spray particle deposition process. With the deposition of particles at the wave crest as an example, the effect of surface roughness on particle deposition was analyzed, and the bonding mechanism of particles deposited at different locations on the substrate surface was discussed. Under the action of the convex structure on the wave crest, with the increase of surface roughness, the jet became longer and had a development trend from top to bottom, the flattening trend of particles increased, the degree of deformation increased, and the kinetic energy of rebound decreased. When the surface roughness was large enough, the particle jet contacted the wave crests on both sides, which might form a mechanical occlusal structure. When the particles were deposited at the trough, they were difficult to be flattened by the wave crests on both sides, and the degree of deformation was reduced. When the wave crest height was large enough, the deformation degree of the particle and the substrate decreased, but the depth of the pit had a tendency to increase after deposition, the kinetic energy of rebound had a tendency to decrease, and the degree of bonding of the particle and substrate was improved. When the particle was deposited at the half waist, there was a certain angle between the particle velocity direction and the contact of the normal line. Under the action of the tangential velocity component, the particles tended to slip to the right and form secondary contact with the right wave crest, resulting in a longer jet. When the height of the crest increased, the jet became longer, the secondary contact strength of the particle and the right wave peak increased, and the bonding strength at this point increased. The bonding strength between the particles and the substrate increases as the surface roughness increases, and the particles can form a mechanical occlusal structure at the crest of the wave. The depth of the pit increases and the kinetic energy of rebound decreases at the trough, which plays a filling role. At the half waist, secondary contact is generated, which increases the bonding strength between the particles and substrate. The study results provide some guidance for the production of cold spray process.