Method for measuring the mechanical properties of materials using depth sensing indentation

Abstract

Apparatus for use in determining a property of a sample material tested by a depth- sensing indentation system comprises a memory storing data representative of points on a load-displacement curve for a test of the sample generated by the depth-sensing indentation system. The data includes an unloading curve of the measured displacement, h, of the probe of the depth-sensing indentation system as the previously applied indentation load, P, thereon is released. The apparatus further comprises a full elastic point, FEP, determination module configured to determine, based on the unloading curve data, a point on the unloading curve having the highest load at which the measured acceleration of the indenter displacement (optionally using (I) instead of (II), as (III) is constant), becomes a constant indicating that the indenter and sample thereafter move together at the same speed, said point taken to be the full elastic point, FEP, at which any delayed elasticity in the sample in response to the indentation ceases. The apparatus further comprises a material property determination module configured to determine, based on the unloading curve data at the full elastic point, FEP, one or more material properties of the sample.