An impedance-based structural health monitoring approach for looseness identification in bolted joint structure

The task of structural safety has been always vital throughout the life span of a structure. The situation deteriorates, when it is subject to repeated loading as seen in cases of railway joints. Generally, the bolted joints are frequently used connections for mainteinance of structural integrity. The most common type of fault observed in bolted joints is looseness of the nuts and bolts which leads to a damaging change by contact pressure that may cause an untoward incident. To avoid such incidents, it is required to monitor the bolted joints very meticulously and regularly. This study presents an investigational work for the looseness assessment of bolted butt joint structure using glued piezoelectric transducer and the implementation of an analytical approach based on the electro-mechanical impedance (EMI) method. For the purpose of investigation, the experiments are being conducted in pristine condition of the structure, wherein the plate bars and girder beam are bolted with four similar bolts without being pressed adequately and no part of the joint is glued. The test measurement of undamaged state and loosed state has been conducted using impedance-based monitoring approach. To study the effectiveness of the proposed method, an experimental investigation is conducted using the impedance chip AD5933 on a bolted joint structure. The results provide cogent indication about the use of piezoelectric lead zirconate titanate sensor based on EMI method for monitoring the status of the bolted joint structures.