An experimental assessment of methods for mitigating plasticity error during nanoindentation with continuous stiffness measurement

Abstract

A comprehensive model for simulating a constant indentation strain rate test with continuous stiffness measurement (CSM) has been developed in a previous work [20]. A procedure for correcting errors associated with plasticity during CSM based testing is also developed. Furthermore, a new method that uses a fixed ratio of the amplitude of the sinusoidally varying portion of the instantaneous load to the load's mean value (AC to DC) during CSM testing is proposed that can reduce the plasticity error and improve the signal-to-noise ratio (SNR) in stiffness. In this work, experimental results are presented to assess the accuracy of the simulation results in terms of the displacement waveforms in response to the imposed load oscillations, the functional dependence of the plasticity error and the SNR. A comparison of the experimental results between the new and the traditional CSM methods is also presented and the advantages of the new method are demonstrated. Furthermore, recommendations for performing indentation testing using CSM with improved precision and accuracy are provided.