Bond Quality Evaluation of Bimetallic Strips: Acousto-Ultrasonic Approach
Plain journal bearings used in engines such as aircraft, automobile and stationary are fabricated from bimetallic strips. In view of the performance requirements, one hundred percent nondestructive inspection of these strips is of paramount importance. But, manufacturers in general still seem to rely on destructive examination through peel-off tests for want of a suitable nondestructive evaluation (NDE) tool. To obtain a solution to this problem, in the recent past, we attempted to develop an NDE method using acoustic emission (AE) technique.1 These attempts indicated that while the method is useful as a ‘go/no go’ test in the final stage of production, its applicability for one hundred percent inspection on production line does not appear to be practicable. Therefore, a program has been initiated at the Aerospace Engineering Department of the Indian Institute of Science to explore the feasibility of utilizing acousto-ultrasonic (AU) technique. To start with, two different sets of experiments were carried out. In the first set the ultrasonic and AE probes were fixed on the same side of the strip at either end. This test, though, yielded positive results; repeatability was poor. So, in the second set of tests, evaluation was carried out with the ultrasonic and AE probes mounted as in a through transmission ultrasonic test. The results of this set show that a bad bond area gives rise to higher stress wave factor (SWF) with good repeatability.
KeywordsAcoustic Emission Bond Quality Good Bond Bond Zone Acoustic Emission Parameter
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