INVESTIGATION OF BRINELL INDENTATION DIAMETER FROM CONFOCAL MICROSCOPE MEASUREMENT AND FEA MODELING

Abstract Significant measurement differences have been continually observed worldwide in Brinell hardness tests, even in the secondary calibration laboratories that calibrate test block reference standards. The main cause of this problem is the edge of the indentation is not a distinct boundary, but is instead a curved surface from either material piling up (pile-up) or sinking in (sink-in) caused by plastic flow of the material surrounding the ball indenter. This makes it difficult to clearly resolve the edge of the indentation and thus determine the indentation diameter. In this research, Brinell hardness indentations were made using various indentation forces and ball indenter sizes. Using a confocal microscope, the indentations were measured in three dimensions from which the indentation profiles were determined. Additionally, finite element analysis (FEA) models were developed for studying the location of contact points at indentation pile-up edges. From both microscope measurements and FEA simulations, the difference between the measured indentation diameter and the actual contact diameter was determined for each indentation