Fatigue Monitoring of Double Surface Defects Using PZT Based Electromechanical Impedance and Digital Image Correlation Methods

Abstract:

Most of the engineering failures especially in mechanical and aerospace industry are due to the fatigue. Fatigue cracks and their propagation can be monitored by observing changes in the structural stiffness resulting from strength reduction as a function of the number of loading cycles. This monitoring can be observed using piezoceramic (PZT) transducer based electromechanical impedance (EMI) technique, and digital image correlation (DIC) system which uses variations on structural surface. The fatigue load usually aggravates the fracture if any defects pre-exist in the structure. The present work monitors multiple-crack emanating from electrode sparked multiple plane defects which are induced in to the specimens prior to the fatigue test, using EMI technique and DIC system. The fracture occurs much below the ultimate stress for the structures which already have defects as in the present case. EMI technique uses signature comparison of healthy and cracked state of the structure to depict crack growth. Initial detection of surface hair-line cracks from the corners of induced defects and their propagation till merging and subsequent failure were explained by signature variations and DIC techniques. Thus, a signal processing technique EMI, and image processing technology DIC were found to complement each other in prediction of early crack and their appearance on surface of the specimens.

• Periodical: Advanced Materials Research (Volumes 891-892)
• Pages: 551-556
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.891-892.551
• Online since: March 2014
• Authors: Venu Gopal Madhav Annamdas, John Hock Lye Pang*, You Xiang Chew, Hsin Jen Hoh, Kun Zhou, Bin Song
• Keywords: Crack, Digital Image Correlation (DIC), Electromechanical Impedance (EMI), Fatigue, Propagation, PZT, Structural Health Monitoring (SHM)

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