ACOUSTIC EMISSION ANALYSIS WHEN CEMENT MORTAR SPECIMENS ARE SUBJECTED TO THREE POINT BENDING REPETITIVE CYCLES

Abstract

THIS WORK DISCUSSES THE EXPERIMENTAL RESULTS OF ACOUSTIC EMISSION (AE) RECORDINGS DURING REPETITIVE LOADING/UNLOADING LOOPS PRO-CESSES OF CEMENT MORTAR BEAMS SUBJECTED TO THREE-POINT BENDING. SIX REPETITIVE LOADING CYCLES WERE CONDUCTED AT A GRADUALLY HIGHER LOAD LEVEL UNTIL THE FAILURE OF THE SPECIMENS. THE EXPERIMENTAL RESULTS CLEARLY SHOW THE EXISTENCE AND DOMINANCE OF THE KAISER EFFECT DURING EACH LOADING LOOP. REGARDING THE AE DATA, ALTERNA-TIVE ANALYSIS WAS CONDUCTED USING THE IMPROVED B-VALUE, AND THE CUMULATIVE ENERGY BEHAVIOUR. BOTH QUANTITIES CONSIDERED, SHOW QUALITATIVE AND QUANTITATIVE CHARACTERISTICS THAT COULD BE USED AS PRE-FAILURE INDICATORS. IN ADDITION, A NOVEL STATISTICAL PHYSICS ANAL-YSIS INVOLVING THE AE INTEREVENT TIMES WAS CONDUCTED BY CALCULAT-ING THE CUMULATIVE PROBABILITY FUNCTION P(>δÏ) THAT FOLLOWS A Q-EXPONENTIAL EQUATION. THE ENTROPIC INDEX Q AND THE RELAXATION PARAMETER βQ OF THIS EQUATION SHOW SYSTEMATIC CHANGES DURING THE DIFFERENT STAGES OF THE FAILURE PROCESS. THE LAST CYCLE LED TO A Q VALUE EQUAL TO 1.42, IMPLYING THE UPCOMING FRACTURE WHICH IS IN GOOD AGREEMENT WITH PREVIOUS RESULTS OBTAINED FROM A WIDE RANGE OF FRACTURED MATERIALS.