a1 Naval Research Laboratory, Code 6176, Washington, DC 20375
The quality of hardness H and indentation modulus E* measurements from instrumented indentation is investigated. Load-displacement data from glass and sapphire are obtained by Vickers indentation and converted to H and E* through a series of equations, including those for tip-shape correction. The quality of H and E* is determined by calculating the statistical uncertainty at each step and propagating the uncertainty to the next step. Conventional tip-shape corrections, assuming either constant hardness or constant modulus, introduce significant errors in H and E* when single, continuous correction functions are used. Piecewise correction functions are shown to improve the quality of H and E*. This investigation demonstrates the importance of calculating and propagating uncertainty at each step when converting instrumented indentation load-displacement data to mechanical properties.
(Received August 11 1997)
(Accepted March 17 1998)
p1 Current address: Caterpillar Inc., Technical Center E 854, P.O. Box 1875, Peoria, Illinois 61656.