Work hardening of soft glassy materials, or a metallurgist’s view of peanut butter

Abstract

The non-linear rheology of colloidal gels, glasses, and pastes is rather complex. For instance, colloidal glasses and pastes yield at a certain strain, followed by shear thinning. A detailed understanding of the yielding point, and what causes it, is lacking. Here, we perform constant shear rate rheology on a pre-sheared material, smooth peanut butter, which is a glassy colloidal paste. Controlling the ageing appears to control the yield stress value, whose associated stress scales with the applied pre-shear with a power law of 1/2. This corresponds to the governing formula for the work hardening mechanism in metals, from which an analogy is drawn.