Nonlinear laser ultrasonic testing for remote testing of initial material damage and closed cracks

2014 Fiscal Year Final Research Report

• Project/Area Number: 26630339
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Structural/Functional materials
• Research Institution: Tohoku University
• Principal Investigator: YAMANAKA Kazushi 東北大学, 工学(系)研究科(研究院), 教授 (00292227)
• Co-Investigator(Kenkyū-buntansha): OHARA Yoshikazu 東北大学, 大学院工学研究科, 助教 (90520875)
• Project Period (FY): 2014-04-01 – 2015-03-31
• Keywords: 超音波 / レーザ / 表面波 / 非線形

Outline of Final Research Achievements

For the safety of materials and structures, nonlinear ultrasound testing are highly demanded that enables evaluation of closed cracks. Though laser ultrasound (LU) using pulsed laser generation of ultrasound enabling remote testing is useful, nonlinear testing by LU has not been realized.
Therefore, we developed a novel nonlinear LU method in this study where a laser pulse of finite energy is irradiated on the tested object, and image is formed by shift and summation of waveforms detected at different positions. Then we obtain difference of image intensities formed for different laser energy, and evaluate nonlinear response at closed cracks. Then we verified the developed method by performing a damped double node (DDN) model simulation using parameters used in a real LU in-process testing equipment, where a closed crack with 10 MPa closure stress was located near a void. It was shown that the effect of void can be successfully suppressed by the developed method.

Free Research Field

超音波