Modeling Snow Failure Behavior and Concurrent Acoustic Emissions Signatures With a Fiber Bundle Model

Abstract

Snow failure is the result of gradual damage accumulation culminating in macroscopic cracks. The failure type strongly depends on the rate of the applied load or strain. Our aim was to study the microstructural mechanisms leading to the macroscopic loading rate dependence. We modeled snow failure and the concurrent acoustic emissions for different loading rates with a fiber bundle model and compared the model results to laboratory experiments. The fiber bundle model included two time‐dependent healing mechanisms opposing the loading‐induced damage process: (a) sintering of broken fibers and (b) relaxation of load inhomogeneities due to viscous deformation. The experimental acoustic emissions features could only be reproduced correctly if both healing mechanisms were included in the model. We conclude that both sintering and viscous deformation at a microscopic level essentially contribute to the macroscopic loading‐ and strain‐rate dependent behavior of snow.

Studying Snow Failure With Fiber Bundle Models

“…Capelli et al [55] applied the FBM including healing of broken fibers and viscous fibers for modeling load-controlled snow failure experiments at different loading rates (32,128, and 400 Pa s −1 ) and the concurrent acoustic emissions [68]. Using parameters in agreement with the snow values reported in the literature, they reproduced the main features of the experimental results.…”

“…Capelli et al [5] introduced a load-controlled FBM including both healing of broken fibers and viscous deformation and described the effects of these two mechanisms on the failure behavior. With the same model it was possible to reproduce the mechanical characteristics and the concurrent acoustic emissions (AE) characteristics of load-controlled snow failure experiments with different loading rates spanning over the ductile-to-brittle transition [55]. Acoustic emissions are acoustic waves generated by the occurrence of damage in solid materials.…”

“…The intrinsic disorder of heterogeneous materials (such as snow) is represented in the FBM by a large number of fibers with varying strengths (Figure 1). The Weibull distribution, which is commonly used for strength distributions in statistical models [8], was also employed in snow models for fiber strength [4,5,55]. The density function for the fiber strength σ th is given by:…”

“…Reiweger et al [4] looked at the sensitivity to k in the range of 0.5 to 3 on the FBM and used k = 0.7 for fitting their mechanical experiments. Further studies used the value k = 1.1 [5,55].…”

“…In case of load-controlled FBMs [5,55], the load on the fibers is increased step wise to the strength of the weakest fiber that consequently fails. As a fiber fails, its load is distributed to the other surviving fibers according to a redistribution rule ( Figure 1B).…”