Experimental Study On Abrasive Shearing And Processing Of SCA Wheels Under Non-uniform Curvature Surfaces

At present,the mold industry is developing in the direction of high precision and automated production.As a flexible finishing method,the soft-consolidated abrasive pneumatic pressure grinding wheel and the industrial robot's flexible grinding wheel finishing system realize the automatic polishing of complex mold surfaces.In the past,the research on the polishing of flexible grinding wheels basically adjusted the parameters of the grinding wheels to realize the movement control of the grinding wheels,thereby improving the machining efficiency and machining quality.These methods have achieved certain results,but when machining surfaces with complex curvatures,if the internal changes of the grinding wheel caused by the curvature changes are ignored,it will cause a bottleneck to improve the polishing quality of the flexible grinding wheel.In order to solve the above problems,in order to achieve the repeatable and definitive polishing of complex curved surfaces,it is necessary to study the processing characteristics of pneumatic grinding wheels with non-uniform curvature surfaces.This paper presents a militancy constitutive model for soft-consolidated abrasive particles.The relationship between the micro-grind contact mechanics and the macro-wheel mechanics system under non-uniform curvature conditions was studied,and a material removal model for soft-consolidated abrasive grain air pressure wheels under non-uniform curvature conditions was established.It was verified through corresponding simulation,force measurement test and machining test.The main research contents are as follows:(1)The meso-analysis of the militancy effect of the abrasive grain group in the soft-consolidated abrasive grain pressure wheel is first analyzed from the militancy mechanism of the soft-consolidated abrasive grain group,and the state parameters defined by the porosity ratio are introduced to reflect the softness Based on the change of the internal state of the consolidated abrasive grain group,a soft-consolidated abrasive grain militancy constitutive model based on the phase transition state was established.Secondly,the internal deformation of the grinding wheel under a non-uniform curvature condition was analyzed to follow a Gaussian distribution.A two-layer elastic mechanics system establishes a model of wheel contact mechanics with non-uniform curvature.(2)Analyze the contact model of abrasive particles in soft-consolidated abrasive particles from a mesoscopic perspective,and establish a contact model of soft-consolidated abrasive particles based on JKR theory.The discrete element analysis software EDEM is used to numerically simulate the transmission process of the contact force of the abrasive grains inside the abrasive particle-bonding layer and the contact force to the work piece when the soft-consolidated abrasive grain pneumatic wheel is processing a non-uniform curvature surface.The following rules are obtained:(1)The polishing contact area formed by the grinding wheel and the work piece is different in size under different work piece curvature surfaces.The higher the degree of fit between the curvature radius of the work piece contact area and the curvature radius of the grinding wheel,the larger the contact area formed,and the higher the polishing efficiency.,And due to the different deformation of the grinding wheel caused by the curvature,the contact force network between the particles is therefore greatly different;(2)the radius of curvature is(the concave radius of curvature is defined as negative)-35 mm and + 35 mm contact force between the wheel and the work piece surface The difference in size is 50.8%;(3)When the grinding wheel processes a work piece surface with a convex curvature,the shape of the contact area appears non-circular,and there is a missing area where the grinding wheel leaves the work piece surface.When the grinding wheel's depression is 1.5mm,the problem of regional loss of abrasive particles is significantly improved.(3)Analyze the model of abrasive particle velocity in the contact area of the grinding wheel under the surface with non-uniform curvature,and combine the grinding wheel mechanical model established in Chapter 2.The traditional Preston equation is modified,the curvature correction factor and militancy effect correction factor of the work piece are proposed,and a material removal model of the wheel under a non-uniform curvature surface is established.First,the contact force model of the grinding wheel was verified.The results showed that the error between the actual contact force and the theoretical value was less than 6%.By performing material removal experiments on three groups of workpieces with different curvatures,and comparing the traditional Preston equation with the modified material removal model of the grinding wheel,the results show that the modified model fits the actual material removal law better and can be used in the polishing test of air pressure wheels Quantitative analysis of material removal.