Can stress–strain relationships be obtained from indentation curves using conical and pyramidal indenters?

Applying the scaling relationships developed recently for conical indentation in elastic–plastic solids with work-hardening, we examine the question of whether stress–strain relationships of such solids can be uniquely determined by matching the calculated loading and unloading curves with that measured experimentally. We show that there can be multiple stress–strain curves for a given set of loading and unloading curves. Consequently, stress–strain relationships may not be uniquely determined from loading and unloading curves alone using a conical or pyramidal indenter.