A STUDY OF SOME SURFACE CHARACTERISTICS WHEN BURNISHING WITH A NEW TOOL

Abstract

Burnishing is used increasingly as a finishing operation which gives additional advantages such as increased hardness, fatigue strength, wear resistance. It is well known that burnished surface characteristic can significantly affect the resistance of components to failure when subjected to high cycle fatigue loads. The fatigue crack, in general, nucleates at the surface of the part, and then propagates into the bulk. Consequently, it is the state of the surface characteristic, where the crack nucleates, that is of paramount importance. Experimental work based on Response Surface Methodology was carried out on a lathe to establish the effect of four roller burnishing tool parameters; namely, burnishing speed, depth of penetration, burnishing time and the initial hardness of five different materials on the surface hardness, the out-of-roundness and the change in workpiece diameter. The latter plays an important role to determine the required tolerance and consequently the type of fit. It was found that all input parameters have a controlling effect, with different percentage, on the three output responses. The results showed that depth of penetration and burnishing time are the most important two parameters controlling the values of both out-of-roundness and change in workpiece diameter. Also, an increase in burnishing speed leads to a considerable reduction in the microhardness index. Out-of-roundness increases with a decreasing in the initial hardness of workpiece material