A comparison of methods used to predict the vibrational energy required for a reliable thermosonic inspection

摘要

Thermosonics is capable of detecting cracks in several types of components. Therncomponent is excited with high-power ultrasonic vibrations, causing cracks to generaternheat, which can be detected by an infrared (IR) camera. However, the excitation in arntypical thermosonic test is non-reproducible and can lead to cracks being undetected ifrnsufficient vibrational energy is not applied at the crack location. The vibrational energyrndissipated as heat at the defect is directly related to the frequency and amplitude of thernvibration, and this energy can be represented by a single parameter (Heating Index)rncomputed from the vibration waveform. The Heating Index parameter is useful as it canrnbe used to predict the vibration level required for a reliable thermosonic inspection. Thernaim of this work is to compare different vibration measuring devices that may be usedrnto capture the vibration waveform required to compute the Heating Index. In this study,rnan aero engine turbine blade is inspected using a practical thermosonic setup, afterrnwhich the vibration waveforms acquired from a laser vibrometer, microphone and strainrngauge are processed. Results from this work will highlight the relative merits andrnlimitations of these different vibration measuring devices for computing the HeatingrnIndex.