Revisiting the Fundamentals and Capabilities of the Stack Compression Test

Knowledge of the flow curve in metal forming is crucial to analyse formability, to describe strain-hardening and to set-up the non-linear constitutive equations of metal plasticity. Commonly available mechanical testing of materials supplied in the form of sheets and plates, under low loading rates, is limited to small values of strain. As a result of this, there is a generalized practice, and important source of modelling errors, of extrapolating the remaining part of the flow curves that are usually determined by means of tensile and bulge tests. The aim of this paper is to provide a new level of understanding for the stack compression test and to evaluate its capability for constructing the flow curves of metal sheets under high strains across the useful range of material testing conditions. The presentation draws from the fundamentals of the stack compression test to the assessment of its overall performance by comparing the flow curves obtained from its utilisation with those determined by means of compressive testing carried out on solid cylinder specimens of the same material. Results show that mechanical testing of materials by means of the stack compression test is capable of meeting the increasing demand of accurate and reliable flow curves for sheet metals.