Creep failure of amorphous solids under tensile stress

Applying constant tensile stress to a piece of amorphous solid results in a slow extension, followed by an eventual rapid mechanical collapse. This creep process is of paramount engineering concern, and as such was the subject of study in a variety of materials, for more than a century. Predictive theories for tau(w), the expected time of collapse, are incomplete, mainly due to its dependence on a bewildering variety of parameters, including temperature, system size, tensile force, but also the detailed microscopic interactions between constituents. The complex dependence of the collapse time on all the parameters is discussed below, using simulations of strip of amorphous material. Different scenarios are observed for ductile and brittle materials, resulting in serious difficulties in creating an all-encompassing theory that could offer safety measures for given conditions. A central aim of this paper is to employ scaling concepts, to achieve data collapse for the probability distribution function (pdf) of ln tau(w). The scaling ideas result in a universal function which provides a prediction of the pdf of ln tau(w) for out-of-sample systems, from measurements at other values of these parameters. The predictive power of the scaling theory is demonstrated for both ductile and brittle systems. Finally, we present a derivation of universal scaling function for brittle materials. The ductile case appears to be due to a plastic necking instability and is left for future research.

Automated summary

Applying tensile stress to an amorphous solid results in slow extension and eventual mechanical collapse. Predictive theories for the time of collapse are incomplete due to its dependence on various parameters. This paper employs scaling concepts to achieve data collapse and provides a universal function to predict the collapse time for both ductile and brittle materials.