Thermal effects in grinding
Abstract
The nature of grinding burn in steels and its relation to workpiece temperature has been studied in surface grinding using a new experimental approach. First, a test method called taper grinding is developed for efficiently analyzing the effects of grinding process parameters. The method is applied to study forces, residual stress, hardness, temperatures, and the onset and evolution of burn. Second, by using nano-indentation on taper-sectioned ground surfaces, an accurate assessment has been made of the true hardness of ground surfaces. Hardness variations occurring over spatial extents of just a few microns have been resolved. The first occurrence of visible discoloration, i.e. onset of visible burn, on a ground surface is found to correlate with drastic changes in its hardness, residual stress and microstructure. Visible burn is seen to be associated with either a softening or a re-hardening of the surface. The microstructure of a re-hardened layer is found to resemble that of a white etching layer (WL), a characteristic microstructure of steels. Third, measurements of the workpiece temperature field have been made at high spatial and temporal resolution using a charge-coupled device (CCD) based infra-red (IR) imaging system. Various characteristics of the temperature field and their dependence on process parameters have been analyzed. It is shown that the onset of visible burn occurs at a fixed temperature for the steel. Predictions of workpiece temperatures, and efforts to compare them to measured temperature values, have been found to be influenced by uncertainty in the knowledge of the grinding geometry.
Degree
Ph.D.
Advisors
Farris, Purdue University.
Subject Area
Industrial engineering|Mechanical engineering|Materials science
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