The present work is concerned with the analysis of elastic unloading data in conventional methods of analysis of nanoindentation test data.Experimental and finite element results are used to show that the reloading of a residual impression with and without the presence of residual stress is an elastic event,and further show that the estimation of modulus and hardness computed using established techniques is in error due to the assumption the sides of the residual impression are straight.This work calls into question the validity of commonly used methods of test and analysis of instrumented indentation test data that use the elastic unloading data as the basis for the calculation of modulus and hardness of the specimen material.
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