The Reliable Implementation of Thermosonics NDT
Thermosonics (also known as Sonic-IR) has potential for detecting small fatigue cracks in metals and delaminations in composites. A high power acoustic horn excites a strain pulse in the testpiece which causes relative motion of the defect surfaces, so generating heat by friction; the resulting local increase in temperature can be detected by an IR camera. Unfortunately the vibration generated by the horn is inherently non-reproducible as it is a function of the precise contact conditions between the horn and the testpiece. This means that it is difficult to determine whether the test has been carried out successfully. This paper introduces the Heating Index which is a measure of the excitation and is a function of the induced vibration amplitude and frequency. The Heating Index can be calculated from measurement of the vibration of the testpiece made with any convenient transducer, for example a laser vibrometer or a simple, high frequency microphone. The correlationbetween the Heating Index and the measured temperature rise at the defect is shown on a variety of laboratory cracked beam specimens. It is shown that measurement of the Heating Index provides a means of ensuring that the test has been carried out satisfactorily. The use of the Heating Index for the practical thermosonic inspection of safety critical components in industry has been proposed and is currently being validated.
Marco MORBIDINI Peter CAWLEY
UK Research Centre in NDE, Department of Mechanical Engineering, Imperial College, London, SW7 2AZ, United Kingdom.
国际会议
第十七届世界无损检测会议(17th World Conference on Nondestructive Testing)
上海
英文
1801-1808
2008-10-25（万方平台首次上网日期，不代表论文的发表时间）