The Research On The Precision Grinding Mechanisms And Simulation Prediction Techniques For Nanostructured Ceramic Coatings

This dissertation deals with the precision grinding mechanisms, grinding process simulation and prediction techniques for nanostructured and conventional ceramic coatings (n/c-WC/Co and n/c-Al2O3/TiO2) which have emerged in recent years. Through experimential investigation and theoretical modeling and analysis, precision grinding mechanisms for nanoatructured ceramic coatings are discussed, a guideline of grinding of nanoatructured ceramic coatings has been established preliminarily. Combined with the development of grinding process simulation and prediction software, the grinding processes are optiumed to realize low damage, high precision and cost-effective machinning of nanostructured ceramic coatings. The theoretical and experimental results add a great value to the nanoatructured ceramic coatings in terms of industrial application.Firstly, based on the literature reviews, the dissertation puts forward the preliminary analysis for the guideline of grinding of nanoatructured ceramic coatings, as well as the train of thought for studying it. The dissertation comprehensively introduces the scheme for the experimental study in grinding of nanoatructured ceramic coatings.The dissertation discusses the influences of the grinding process parameters, grinding wheel characteristics, material responses to grinding and coating mirostructure on grindablity, including grinding forces, grinding force ratio, specific grinding energy, surface roughness, surface integrity and materail removal mechanisms. Grindability is analyzed based on the experimental results and the theoretical modeling. The theoretical model of grinding force involves grinding depth of grinding wheel, feedrate of worktable, speed of grinding wheel, and the break-in force of material as well as material response to grinding. Different grinding force models have been established for single abrasive grits at different stages of the grinding process. It turns out that grinding forces and specific grinding energy for the nanostructured ceramic coatings are greater than that for conventional ceramic coatings. The abrasive grits of the grinding wheel, the tribological interactions of bond/chip/workpiece surface in the grinding zone, and defects from the spraying process all have an effect on the grindability. The bearing ratio of ground surfaces can be improved by precision grinding. There is a proper grinding depth for getting lower ground surface roughness.The dissertation reviews material removal mechanisms in grinding of ceramic ofthree kinds. Material removal mechanism including inelastic deformation and brittle damage of nanostructured ceramic coatings are explored in the dissertation, based on the experimental result of grindability combined the SEM analysis of ground surface of nanostructured ceramic coatings.Theoretical analysis is conducted on material deformation and crack formation during grinding process of nanostructured ceramics coatings. The dissertation proposes critical grinding condition models for predicting grinding induced lateral crack and median carak in the nanostuctured ceramic coatings, and verifies the models with experiments. The models reflecting the quantitative relation between the grinding parameters and the average depth of grinding induced subsurface damage (cracks) in the nanostrucured ceramic coatings is also proposed in the paper. It turns out that the critical force for lateral crack is higher than that of median carak. The formation and propagation of grinding induced subsurface damage (cracks) depend directly on the normal grinding force of single abrasive grit. They are also related to the grinding energy consumed during the grinding process and the defects from the spraying process. The effect of material grain size on the grindability of grinding for the nanostructured ceramic coatings is also discussed in the dissertation.Finally, this dissertation describes the simulation and prediction software developed for grinding nanostructured ceramic coatings. Described are also the key techniques and system str...