Ultra-delayed material failure via shear banding after straining an amorphous material

TL;DR

This paper predicts a sudden, catastrophic failure in amorphous materials after a long delay following deformation, driven by shear banding instability, with implications for material design and safety.

Contribution

It introduces a universal physics-based model for ultra-delayed shear banding failure in amorphous materials, validated across multiple modeling approaches.

Findings

Delay time increases with decreasing strain amplitude

Failure time increases with lower temperature and more annealing

The physics is consistent across different constitutive models

Abstract

We predict a phenomenon of catastrophic material failure arising suddenly within an amorphous material, with an extremely long delay time since the material was last deformed. By simulating a mesoscopic soft glassy rheology model in one dimension (1D), a mesoscopic elastoplastic model in 1D and 2D, and a continuum fluidity model in 1D, we demonstrate the basic physics to involve a dramatic ultra-delayed shear banding instability, in which strain suddenly strongly localises within the material and the stress drops precipitously. The delay time after the long historical shear strain was applied before failure occurs increases steeply with decreasing strain amplitude, decreasing working temperature, and increasing sample annealing prior to shear. In demonstrating the same physics -- which is directly testable experimentally and in particle simulations -- to obtain within three different constitutive models, we suggest it may be generic across amorphous materials. The counter-intuitive prediction of catastrophic material failure long after any deformation was last applied could have important consequences for material processing and performance.