Experimental and numerical investigation on detection fatigue crack in metallic plate by vibro-thermography

Abstract

Vibro-thermography is a promising nondestructive testing technique owning to its full-field and defect-selective imaging which excites ultrasonic waves to locally stimulate defects in large-scale and complex shape key components. In this paper, a low-power piezoelectric transducer was used as an actuator of vibro-thermography, and the detection and quantitative evaluation of the fatigue crack in metal structure were investigated. Experiments were conducted on an aluminum plate with a prefabricated fatigue crack. Both temperature data and thermal images were analyzed to validate the proposed method. The crack length was measured from the amplitude and phase image by the fast Fourier transform. The experimental error of crack length was less than 4.3% from the phase image. Furthermore, the finite element method (FEM) was implemented to simulate the detection of fatigue crack by vibro-thermography. The mechanism of heat generation was investigated by clapping motion and frictional contact of the crack surface. The effects of excitation time, frictional coefficient, and crack width were also discussed. The experimental and numerical results demonstrate the ability of quick detection and quantitative measurement of fatigue crack in metallic structures by vibro-thermography.