L. I. Salminen

Acoustic emission from paper fracture

We report tensile failure experiments on paper sheets. The acoustic emission energy and the waiting times between acoustic events follow power-law distributions. This remains true while the strain rate is varied by more than 2 orders of magnitude. The energy statistics has the exponent beta approximately 1.25+/-0.10 and the waiting times the exponent tau approximately 1.0+/-0.1, in particular, for the energy roughly independent of the strain rate. These results do not compare well with fracture models, for (brittle) disordered media, which as such exhibit criticality. One reason may be residual stresses, neglected in most theories.

Strength Distribution in Paper

Abstract Tensile strength distributions are studied in four paper samples that exhibit a variety of brittle-to-ductile properties. 1005 tensile specimens were measured in each case. The standard Gumbel and Weibull distributions, and a recently proposed double exponential modification of the former are compared with the observations visually and using chi-squared and Kolmogorov–Smirnov tests. The Gumbel distribution fails to fit the data while the Weibull distribution gives satisfactory agreement. However, the double exponential distribution fits the data best, regardless of the ductility of the material.

Crackling noise in paper peeling

Acoustic emission or crackling noise is measured from an experiment on splitting or peeling of paper. The energy of the events follows a power law, with an exponent β ~ 1.8 ± 0.2. The event intervals have a wide range, but superposed on scale-free statistics there is a time scale, related to the typical spatial scale of the microstructure (a bond between two fibers). Since the peeling takes place via steady-state crack propagation, correlations can be studied with ease and shown to exist in the series of acoustic events.

Acoustic Emission or Crackling Noise in Paper Fracture

Acoustic emission experiments in paper, a disordered material, give evidence for power‐law probability distributions of statistical quantities as event energies or intervals. Two setups, usual mode I tensile tests and a nip‐in‐peel one have been studied in our work. In both cases, even using the same material, we observe “criticality”. This has wide implications for theories of statistical fracture.