Predicting Creep Failure from Cracks in a Heterogeneous Material using Acoustic Emission and Speckle Imaging

Abstract

Finding out when cracks become unstable is at the heart of fracture mechanics. Cracks often grow by avalanches and when a sample fails depends on its past avalanche history. We study the prediction of sample failure in creep fracture under a constant applied stress and induced by initial flaws. Individual samples exhibit fluctuations around a typical rheological response or creep curve. Predictions using the acoustic emission from the intermittent crack growth are not feasible until well beyond the sample-dependent minimum strain rate. Using an optical speckle analysis technique, we show that predictability is possible later because of the growth of the fracture process zone.

Prediction of creep failure time using machine learning

“…Such ensemble tests have been conducted in the published literature and it will be an interesting task for future investigations to apply the present method to actual monitoring data on quasi-brittle disordered materials. In this context quasi-two-dimensional samples such as paper 7,8 or semi-brittle polymer sheets, which approximately match the geometry considered in our simulations, are of particular appeal. Since experimental ensembles are in general much smaller than simulated ones, an important question arises in this context: Can one transfer training results from simulation to experimental data?…”

“…This problem is particularly pronounced when the creep strain rate is itself a stochastic, highly intermittent process; (ii) while empirical observation indicates, on average, a linear relation between and , the scatter is high especially for highly disordered samples; (iii) the prediction for necessarily requires waiting until can be reliably identified. Given that experimentally observed already amount to of and that larger times are needed to reliably identify a minimum, the resulting prediction might be too late to be useful 8 .…”

High-cycle fatigue damage accumulation in paper

“…Consequently, ratchetting is a static damage mechanism, in which fracture occurs as the tensile fracture strain is reached after a few loading cycles. Ratchetting is observed in a wide range of materials including paper [4][5][6][7][8][9] , and is most prominent in materials that show significant timedependent (creep) deformation (reviews by Ohno and Kang 10,11 detail ratchetting and how it is distinguished from fatigue). Ratchetting fracture surfaces in paper are hairy and indistinguishable from tensile fracture and creep because the damage mechanisms are essentially the same.…”

Creep Damage Evolution of Marble From Acoustic Emission and the Damage Threshold

“…AE technique, a non-destructive method, has been used to monitor and forecast the rockburst since the mid-1950s. Researchers have studied the relationship between AE characteristics and rock damage (Viitanen et al, 2019;Zhu et al, 2019). Additionally, AE was used to predict earthquakes and damage characterization (Wang et al, 2017;Yao et al, 2020).…”