Evaluation of bolt looseness in bolted structures using nonlinearities of lamb waves

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Evaluation of bolt looseness in bolted structures using nonlinearities of lamb waves

 

Author: Wei, Junhao
Title: Evaluation of bolt looseness in bolted structures using nonlinearities of lamb waves
Degree: M.Sc.
Year: 2014
Subject: Steel, Structural -- Testing.
Lamb waves.
Bolts and nuts -- Testing.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Engineering
Pages: xi, 86 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2748965
URI: http://theses.lib.polyu.edu.hk/handle/200/7501
Abstract: Steel bolt connections are widely used in engineering and industry manufacturing. Different loading conditions such as shock, vibration or transverse cyclic loading applied to structures result in stress concentration at screw bolts which may lead to looseness. Linear ultrasonic methods are general methods for Non-Destructive ultrasonic detection in varies of damages and defects which may however lose their effectiveness to the detection of looseness of bolts in the joint structures. For another, nonlinear guided waves are sensitive to microcracks, degradation, fatigue deformation and voids which can be applied on evaluating the looseness of bolts. Principle of detection with nonlinear Lamb wave is introduced first, to detect the presence of the fatigue damage and the location of the loosen bolt. Two rows of PZT transducers were placed to build up as a sensor network to actuate and receive the fundamental and second harmonic Lamb waves in the pitch-catch method. The approach successfully detected the presence of bolts’ looseness. Furthermore, a probability-based imaging algorithm was applied to reconstruct looseness area of the bolt.

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