On the measurement of energy dissipation using nanoindentation and the continuous stiffness measurement technique

New experimental methods have been developed to optimize the accuracy and precision of the measured phase angle in nanoindentation experiments on viscoelastic materials performed with a Berkovich indenter. Measurements conducted in fused silica and sapphire form the basis of a new instrument calibration. Experimental verification of the new calibration and an enhanced test method is demonstrated in polycarbonate (PC) and polymethyl methacrylate (PMMA). In comparison to the standard continuous stiffness measurement (CSM) technique, the new calibration and test method reduces the measurement error in the phase angle of PC from 1900% to 10% and from 135% to 10% in PMMA. Scatter in phase angle measured by the new test method is nearly 10 times less than the level observed using the standard CSM technique. The effect of time dependent deformation on the measured phase angle is also documented. The experimental observations and results are applicable to a variety of dynamic nanoindentation test methods.