Analysis and correction of the effect of sample tilt on results of nanoindentation

Finite-element simulations were carried out to study the effect of sample tilt on the results of conical and Berkovich nanoindentation. For conical indentation into tilted samples, of materials exhibiting either sink-in or pile-up, it is found that the projected contact area would be underestimated by the Oliver and Pharr (O&P) method; consequently, the hardness and elastic modulus would be overestimated. It is shown that a simple geometric correction can be used to account for the effect of sample tilt on the contact area. The validity of a similar geometric correction is also verified for Berkovich indentation into fused quartz. Finite-element analysis shows that a 5° tilt causes a 12% error in hardness by the O&P method, which would be reduced to 2% by the geometric correction. However, experiments show only a 5% error by the O&P method, likely due to the lateral force and the horizontal compliance of the indenter stem.