Bobbin Coil Probe With Sensor Arrays for Imaging and Evaluation of Longitudinal Cracks Inside Aluminum Tubes

Imaging and evaluation of inner-wall cracks are significant for the integrity management of aluminum tubes. In this paper, a novel bobbin coil probe with sensor arrays is presented for the imaging and evaluation of longitudinal cracks inside aluminum tubes. The finite element method model is developed to analyze the characteristic signals of the crack. The bobbin coil probe with inside tunnel magneto resistance (TMR) sensor arrays is developed for imaging of inner-wall longitudinal cracks. The depth and length of longitudinal cracks are evaluated by the characteristic signals. The results show that the detection sensitivity of the longitudinal crack can be improved greatly when the lift-off of the bobbin coil decreases with inside TMR sensors. The inner-wall cracks inside the aluminum tube can be imaged visually using the bobbin coil with inside TMR sensor arrays. The crack depth and length can be evaluated accurately by the detection sensitivity of the Bxin and the distance between the peaks of the Bzin respectively.