Surface Topology Evolution Of Monolayer Brazed Superabrasive Wheels And Undeformed Chip Thickness Distribution

As an advanced manufacturing technology,grinding is a procedure of many micro-cutting processes with bonded grains,which usually acts as material removal in macro-aspect.It is very important to reliably control the process and accurately predict the results during high efficiency and precision grinding difficult-to-cut materials.However,at present,the development of grinding process controlling and grinding results prediction is limited by the assumption of uniform undeformed chip thickness.Monolayer brazed superabrasive wheels have the advantages of large grain protrusion height and chip space,and they can hold and pattern the grains firmly.Therefore,an investigations on surface topology evolution of monolayer brazed superabrasive wheels and undeformed chip thickness distribution have been carried out in this work.The effects of grain shape,undeformed chip thickness and grain morphology evolution on grinding process have been confirmed.The evolutions of surface topology and undeformed chip thickness distribution have been revealed.And the models for grinding process controlling and surface roughness prediction have been built.The findings can help to develop more accurate and reliable models to control the grinding process and predict the surface roughness.The main contents are as follows:(1)A new single grain grinding system has been developed to accurately control the cutting edge and undeformed chip thickness.Single grain grinding experiments of nickel-based superalloy GH4169 have conducted in case of the controllable undeformed chip thickness.Then,the effects of cutting edge,undeformed chip thickness and wheel speed on grinding forces,specific grinding energy,workpiece scratch and pile-up ratio have been investigated.A critical undeformed chip thickness(i.e.0.3 μm)has been revealed for chip formation in grinding.(2)The single grain wear experiments have been conducted under the conditions of the different undeformed chip thickness and wheel speed.The grain wear behavior mainly includes four types: crescent depression on the rake face,abrasion on the flank face,grain micro-fracture,and grain macro-fracture.Then,the evolution of grain morphology has been revealed and it has been found the radial wear and the abrasion area increase during the grain wear process.From the analysis of grinding force(ratio)theoretically and experimentally,it has been confirmed that the essence of grain blunt is the increase of negative rake angle.Meanwhile,the material removal efficiency is decreased,the pile-up on the two sides of a single grain scratch is enlarged and the surface is rougher.(3)Based on the local surface topology measured by replica samples,the entire wheel surface topology has been reconstructed through Johnson transformation and its inverse Johnson transformation.The wheel wear experiments have been conducted to study the wheel surface topology evolution.Besides,a new accurate model has been developed with consideration of wheel topology non-uniformity.Then,the evolution of undeformed chip thickness distribution in the wear process has been quantitatively described as the synchronous decrease of mean value and standard deviation.(4)The experiments on the grinding of nickel-based superalloy with a monolayer brazed wheel have been carried out.The influences of undeformed chip thickness on some grinding process parameters(i.e.grinding force,energy and temperature)have been analyzed.Then,the predicting models of the above parameters have been built with active grain percentage,mean value and standard deviation.Based on the function of a single grain moving path,the ground surface topography has been simulated.A predicting model of ground surface roughness has also been developed and compared with the experimental results.Finally,the accuracy of developed models to control the grinding process and predict the ground surface has been proved in real cases.