Scaling Theory for W\"ohler plots in amorphous solids under cyclic forcing

TL;DR

This paper develops a scaling theory for W"ohler plots in amorphous solids under cyclic loading, linking damage accumulation to failure statistics, and extends previous models to tensile loads with atomistic simulation validation.

Contribution

It extends the scaling theory of W"ohler plots to cyclic tensile loads in amorphous materials, emphasizing damage accumulation and enabling failure probability predictions.

Findings

Scaling theory applies to both bending and tensile cyclic loads.

Damage accumulation and average damage per cycle are key to failure statistics.

The theory predicts failure distributions from measurements at different load amplitudes.

Abstract

In mechanical engineering W\"ohler plots serve to measure the average number of load cycles before materials break, as a function of the maximal stress in each cycle. Although such plots are prevalent in engineering for more than 150 years, their theoretical understanding is lacking. Recently a scaling theory of W\"ohler plots in the context of cyclic bending was offered [1]. Here we elaborate further on cyclic bending and extend the considerations to cyclic tensile loads on an amorphous strip of material; the scaling theory applies to both types of cyclic loading equally well. On the basis of atomistic simulations we conclude that the crucial quantities to focus on are the accumulated damage and the average damage per cycle. The dependence of these quantities on the loading determines the statistics of the number of cycles to failure. Finally we consider the probability distribution functions of the number of cycles to failure and demonstrate that the scaling theory allows prediction of these distributions at one value of the forcing amplitude from measurements and another value.