Study On Design And Fabrication Of Novel Flexible Composite Abrasive Tools And High-shear And Low-pressure Grinding Experiments

Nickel-based superalloys have excellent high-temperature performance,thermal fatigue resistance,and thermal stability.Therefore,they are widely used in the manufacturing of key components of large high-end equipment such as the aviation,aerospace,marine,and chemical industries.Especially in the manufacture of hot-end parts(turbine blades,turbines,turbine drive shafts,etc.)of aviation aircraft,it is most widely used.Nickel-based superalloys are typical difficult-to-machine metal materials with high strength and toughness.The excellent material properties lead to poor machining performance.Grinding,as a commonly used surface finishing technology,is usually used for the efficient and precise machining of nickel-based superalloy parts.However,there are a series of problems such as easy adhesion of the grinding wheel,excessive grinding force,grinding burns,and poor surface quality during the grinding process.From the analysis of grinding mechanism,an excessively high ratio of normal grinding force to tangential grinding force is an important cause for frequent grinding problems of nickel-based superalloys.This thesis focuses on the problems of excessive grinding force and grinding burns in the grinding process of nickel-based superalloys.The research mainly draws on the bulletproof principle of liquid bulletproof clothing,that is,during the processing process,the removal of workpiece material is controlled by the “particle cluster effect” of abrasive particles under the control of high-performance fiber fabric.The novel flexible composite abrasive tools based on the shear thickening abrasive system and Kevlar plain weave was designed and fabricated.A serial of experiments of the nickel-based superalloy were carried out to evaluate the grinding performance.The main research carried out is as follows:(1)According to the processing principle of the novel flexible composite abrasive tools,the novel abrasive tool structure scheme was determined.The finite element analysis was used to achieve the optimal design of the novel abrasive tool.The simulation model of the principle of high-shear and low-pressure grinding was studied.The validity of the high-shear and low-pressure grinding mechanism was verified.(2)The composition of abrasive layer for the novel flexible composite abrasive tools was determined.The preparation process of the shear thickening fluid,shear thickening abrasive fluid and the novel abrasive layer were formulated.The rheological properties of the shear thickening fluid and the shear thickening abrasive fluid as the core component of the abrasive layer were tested and analyzed.Meanwhile,the shear thickening characteristics of the two solutions were verified.Microscopic observation was performed on the surface of the novel abrasive layer.The uniform distribution status of shear thickening abrasive system on the surface of high-performance fabric was determined.(3)A novel abrasive tool grinding test platform was set up.High-shear and low-pressure grinding tests were carried out on selective laser melting Inconel718 superalloy.The surface roughness change,surface morphology change,wear state of the novel abrasive layer,element change of workpiece and abrasive layer before and after Inconel718 superalloy grinding were studied.The grinding characteristics of the novel flexible composite abrasive tools were investigated.The effectiveness of the novel abrasive tool for Inconel718 superalloy grinding was verified.(4)The experimental investigation on the optimization of the grinding process of the Inconel718 superalloy was carried out.The influence of the grinding velocity,workpiece feed rate and grinding depth of cut on the surface roughness of the workpiece was studied.The experimental results showed that the grinding performance was best when the grinding speed was 1 m/s,the feed speed was 2000 mm/min,and the grinding depth was 180 ?m.The surface roughness of the workpiece is reduced from 473.7 nm to 153.0 nm after grinding.The ratio of the tangential grinding force to the normal grinding force during the grinding of the novel abrasive tools was studied.The results showed that the ratio was larger than that of the conventional grinding for nickel-based superalloys,which validated the effectiveness of high-shear and low-pressure grinding.