A static stiffness reference object for instrumented indentation with integrated fiber Fabry–Perot displacement measuring interferometer

Abstract

Instrumented indentation is a technique used for measuring the mechanical response of materials to deformation. The accuracy of these measurements relies on force and displacement values recorded during the indentation process. This paper presents a miniature fused silica parallelogram flexure to serve as a reference object for calibrating the applied indentation force based on Hooke’s law, F = kz, where k is the stiffness of the reference object and z is the displacement of the flexure under force F. This study discusses two independent experimental approaches to determine the stiffness of the flexure. In both cases, the stiffness was calculated from the measured flexure displacement while known forces are applied. In the first method, the displacement is measured using a built-in fiber-based interferometer while reference masses of 100 mg and 200 mg are placed on the flexure. A stiffness of is determined with this method. The second method uses a commercial indenter to apply a cyclic force of 100 mN magnitude on the flexure while recording the displacement of the indenter probe. Experiments using a 5 μm and a 50 μm conospherical tip estimate the stiffness to be , and respectively.Disclaimer: Certain commercial equipment, instruments are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.