The universality of b-value and size effect in acoustic emission: Experimental investigations in quasi-brittle fracture

Abstract

Convergence of the b-value, the exponent of Gutenberg-Richter law, to unity near failure is considered as a universal phenomenon observed in many natural and artificial complex systems. The existence of universality implies that the underlying mechanism in various systems at the critical stage is universal too, irrespective of size, shape, and ingredient (heterogeneity) of the medium. The present work intends to discuss the size effect phenomenon on the b-value and apparent universality through experimental evidences. To study the size effect on the acoustic emission in concrete, geometrically similar, single edge notch beams of three different sizes are tested under three-point bending. The trend exhibited by critical b-value with respect to specimen size confirms its size-dependence which indeed originates from the size dependence of the fracture process zone.

Damage detection using wavelet entropy of acoustic emission waveforms in concrete under flexure

“…Investigation methods based on time-domain parameters of AE signals are competently developed for damage analysis in concrete fracture. [3][4][5] For crack mode classification, a parametric method uses the rise angle (RA-rise time/amplitude) and the average frequency (AF-counts/duration). Such crack mode classification is often conducted in studies on reinforced (steel and fiber) concrete using the RA-AF method.…”