An Investigation into Thermal Damage during the Grinding Process
Introduction
One of the main limitations to increasing the removal rates during the grinding process is thermal damage to the workpiece. In severe cases thermal damage is evidenced by the appearance of temper colours on the surface. This condition is known as ‘burn’. With the occurrence of burn, cracks may appear under or at the workpiece surface. Other problems may be softening and re-hardening of the surface material, accompanied by residual stresses. Thermal models have been developed to determine when thermal damage to the workpiece will occur.
Coursework Specification
You are required to use the previously recorded grinding data to determine the accuracy of the thermal model presented below in equation (1).
a) For each data point calculate the experimental specific energy. 20%
b) For each data point, using equation (1) below, calculate the theoretical critical specific energy 25%
N.B. one sample calculation only should be included. The remaining results should be included in a tabular form.
c) Plot a graph to compare the experimental and theoretical values of specific energy at which burn occurs. The values of experimental and theoretical specific energy should be plotted against an axis of workpiece speed. 20%
d) By reference to the graph, discuss the validity of the thermal model.
Your discussion should include:
Suitability of the thermal model (equation 1) for process control purposes
possible sources of error within the thermal model
consideration of suitable alternative machining processes
outlining of optimum and ‘safe’ machining parameters
Selection of the most appropriate type of grinding wheel 25%
e) The inclusion of a suitable bibliography with appropriate referencing together with
the overall structure, presentation and English. 10%
