Diagnosis of fire damage depth in mortar using nonlinear harmonic method and scanning airborne ultrasound technique

Abstract

Abstract This paper reports the effectiveness of a new fire depth diagnosis of mortars using airborne ultrasonic source scanning method and non-linear harmonic method(NHM). We propose a model of fire damage mortar in which Young's modulus gradually decreases from the surface layer at high temperature during fire. In addition, based on the model, we also propose to diagnose the depth of fire damage from changes in the propagation velocity of surface acoustic waves. In addition, in order to verify the theory of the proposed method, the propagation speed of surface acoustic waves propagating in the fire damage mortar is simulated by FEM analysis, and the possibility of diagnosing the depth of fire damage is obtained. Finally, we measure the propagation velocity of surface acoustic waves using an experimental sample simulating the fire damage mortar model described above, and obtain results with almost the same tendency as that of FEM analysis.