抄録
Sensitive evaluation of the crack, which might be originally present or developed during operation is imperative for assessing the integrity of structural components. In an attempt to overcome the limitations of usual techniques for enhancing the sensitivity of ultrasonic nondestructive evaluation of tightly closed small cracks, a new angle beam approach of shear wave with 50^0 incidence in the solid is proposed. Fatigue cracks vertically situated on the back wall of stainless steel specimens are considered. As a generator and receiver of ultrasound, a single flat pulse-echo transducer in water immersion process is used. The highly sensitive features of the proposed fully automated and computer controlled technique are compared with those of recently developed ones. Based on crack corner echo, cracks ranging 0.1-4.66 mm are tested, and echo amplitudes are analyzed considering the simultaneous effects of crack size and crack closing stress. The proposed technique offers a good possibility of quantitative evaluation of crack size and closing stress by using inverse analysis of crack corner echo response.
