Post-yield characterisation of metals with significant pile-up through spherical indentations

Finite element simulations of spherical indentations accounting for frictional contact provide validated load–indentation output for assessing and improving existing methods used to determine the stress–strain curve of materials with significant pile-up. The importance of friction to the proper assessment of the pile-up effect is established. Weaknesses in current characterisation relations and procedures are also identified. Existing correction formulae accounting for pile-up are modified so that the contact area radius is more accurately determined. This modification is implemented in the context of a characterisation process that relies on analysing unloading portions of load–indentation curves. Post-yield material behaviour predictions from such analysis are found to be in very good agreement with the initial finite element material input.