Relations between Acoustic Emission and Stress Intensity Factor for Notched Mortar

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The three point bending tests using the square beam specimen with a notch at the center were carried out to find the relations between stress intensity factor and acoustic emission in hardened mortar. The Virtical displacement where load was applied at the center of the beam was measured and then acoustic emission (AE)was detected from the adjacent point of the notch. The J-integral was estimated from the area of load-displacement curve and the critical value of stress intensity factor was calculated from the J-integral using fracture mechanics formula.FEM and approximate analysis were done to compare the experimental results , and it was recongnized that the experimental method was very useful in estimating the K value of mortar. Because an AE process is considered to be corresponding to events in fracture process of mortar, a method was studied to determine the critical stress intensity factor K_c based on the characteristic information of AE. It was obtained that the total AE pulse <SIGMA> (AE) could be written approximately as following form in many cases.where, A and B are constant.