나노압흔의 3차원 형상분석을 통한 압입경도의 정밀측정

Abstract

The material pile-up around indenter/surface contact region can make the conventional Oliver and Pharr`s analysis of the nanoindentation curve inaccurate. We suggests a novel methodology for characterizing pile-up incorporated contact properties by adopting the Matlab(R)visualization tool in this study. Based on our approximation of contact boundary as peak of the pile-up region, radial indentation surface profiles observed with an atomic force microscope are differentiated with the distance from the indent center and a closed contact boundary is formed by connecting special differentiated points having their values as zero. The calculated load-off hardness was nearly consistent with the result of nanoindentation curve analysis for pileup free material such as fused quartz. This experimental result supports validity of the newly proposed method, However, the load-off hardness of metallic solids such as (100) tungsten monocrystal and pure copper showed that the nanoindentation curve analysis could overestimate the hardness more than 50% in the cases of severe pile-up.