Estimation of Temperature Rise in Magnetorheological Fluid-Based Finishing of Thin Substrate: A Theoretical and Experimental Study

Abstract

Magnetorheological finishing (MRF) is used to precisely finish various materials such as hard crystals, optical, and brittle materials. In this paper, the thermal behavior of the MRF process is studied theoretically and experimentally on thin copper substrate surface by varying rotational speed and working gap. The wall shear stress (WSS) represents the frictional force per unit area exerted by the flowing magnetorheological (MR) fluid on the workpiece surface and it is determined using three-dimensional computational fluid dynamics numerical simulations that use a dynamic viscosity model based on the variable magnetic flux density. A thermal model is proposed to predict heat generation and temperature rise on the workpiece surface with the help of energy partitioning, heat conduction equations, and WSS. It is observed that the temperature rises with increasing the rotational speed and reducing the working gap. Considering MR fluid with only abrasive particles, the theoretical temperature rise of 21.32 °C was predicted. When MR fluid is with carbonyl iron particles and abrasive particles, the theoretical temperature rise was 19.37 °C. In experiments, the maximum temperature rise of 14.8 °C was obtained. Finite element analysis is performed to estimate magnetic flux density variation on the workpiece surface and viscosity variation over the workpiece surface. Surface roughness (Sa) reduced from an initial value of 0.236 µm to 0.079 µm at 600 rpm tool rotational speed and 3 mm working gap.