Measurement of pile-up around spherical indentation by image-plane digital holography

Instrumented indentation has been used to measure mechanical properties, residual stresses, hardness, and viscoelastic properties, among others, due to its fast and nondestructive procedure. The accurate determination of the contact area between the indenter and the material is important for material property measurements and usually is masked by the pile-up or sink-in phenomenon. This paper presents the application of dual-wavelength image-plane digital holography in order to achieve a full-field determination of the topography around the indentation mark. The optical configuration was able to identify pile-up with magnitudes close to 25 μm. Measurement results were compared with the references performed by a commercial focus-variation device showing positive agreement between the obtained profiles. Additionally, most of the points presented differences between measurements lower than 3 μm.