Development of Composite Grinding Wheels for Hard and Soft Metals

摘要

This research investigates the performance of grinding wheel in terms of its internal granular particles and their effect on the surface finish for both soft and hard metals subjected to both dry and wet conditions of use. The study considers the properties of materials of construction including hardness of the granular particles and their size and distributions that affects the grinding wheel efficiency in abrading of soft and hard metal surfaces. Furthermore, in order to improve grinding performance, the mechanism of clogging the cutting surface of the grinding wheel as a function of for example, the surface properties of granular particles and the chips formed during the grinding operation have been considered.udObjective of this project is to study the overall sharpness of the grinding wheel in terms of its internal granular particles and their effect on the surface finish for both soft and hard metals at different conditions of use. The properties of materials of construction including hardness of the granular particles that affects the grinding wheel efficiency in abrading of soft and hard metal surfaces have been studied.udDuring this project two novel grinding wheels, namely single grooved and crossed grooved wheels, have been developed and their performance has been compared with a selected commercial grinding wheel, the design of grinding wheels incorporated an innovative surface profile which has been shown to be capable of taking potentially large depths of cut at high wheel and workpiece speeds to create a highly efficient material removal process. This aggressive processing generated high temperatures in the contact zone between the wheel and workpiece. The voltage measured by oscilloscope during grinding of different workpiece materials including mild steel, brass and aluminium bars was related to the temperature generated between wheels and workpiece materials.udTemperatures in the ground surface can be predicted with a knowledge of the specific grinding energy and the grinding parameters used. Specific grinding voltage recorded at high specific material removal rates demonstrated a constant value of specific grinding heat dependent on cutting and contact conditions, improving accuracy of the predictive model.ud4udCutting and contact conditions in the different grinding wheels vary dependent on their surface patterns. This thesis shows how temperature, contact stresses, material removal rates vary with the surface profile, size and orientation of the abrasive particles of the grinding wheel, affecting the performance of the grinding wheel during the grinding operations. Redesigning grinding wheels by making grooves on surface of wheel, material removal rate was increased and less voltage has been recorded. Also, time for redressing wheels was reduced. The wheel surface of crossed grooves shape showed a significant improvement in grinding of soft materials e.g. aluminium.udFinally, the different stress distribution, including von_Mises, principal stresses and shear stresses, in the grinding wheels and the three workpiece bars during the grinding process were investigated using Finite Element Analysis (FEA) technique. The maximum von-Mises stress value of the brass bar was found to be 173.2 MPa. Hence the strength of produced grinding wheel calculated as 207 MPa which was extensively higher than the maximum von-Mises stress value obtained from FEA profile, resulting 19.5% higher strength in crossed grooves wheel.