항공기 다중구조물의 부식 검출 및 평가

Abstract

From the large equipment-structure including the aircraft, thermal power, nuclear power generation, oil refining, induction space station, and etc to the micro type member including the IC package, VLSI, and etc, the direct cause for the damage is caused by the generation of the defect and growth. In particular, aircraft experiences high load and vibration, differences in temperature and pressure between inside and outside of it while in operation, transformation at the speed of hundreds km/h, and residuals of salt and moisture while in operation. Therefore, aircraft can be vulnerabled by fatigues and corrosions. These damages would bring serious problems for passengers and economic loss if they well not detected on time. The aircraft is assembled by rivet and multi-layered structures in aluminum alloy, which aims at making the aircraft stronger and lighter. The rivet connection part of such multi-layered structure is easy to develop multi-site crack and corrosion due to concentration of stress or owing to remaining salt or moister. These cracks and corrosions on skin of aircraft could be inspected by using the visual testing, ultrasonic testing, penetration testing and magnetic particle testing. However, far-side cracks and corrosions in multi-layered structure are difficult to inspect by using these methods. In this paper, an NDT method that can inspect far-side corrosion in the multilayered structure with riveting is proposed. The magnetic source for inducing the electrical field in a specimen, Hall sensors array for measuring the distorted magnetic field, and scanning equipment are used in this method. Far-side corrosion on an elliptical pipeline, which modified intake of aircraft are examined to verify the effectiveness of the proposed method. In addition, the position and size of corrosion are evaluated quantitatively by comparing the 3-dimensional numerical analysis with the measured data.