Bolt-joint structural health monitoring by the method of electromechanical impedance

Abstract

Purpose – The purpose of this paper is to present the problems of the electromechanical impedance (EMI), especially its applications for structural health monitoring of aircraft bolt-joints and innovative approach of EMI prediction at loosening of bolt-joints. Design/methodology/approach – This experimental study includes the results of a full-scale test of the Mi-8 helicopter tail beam, particularly, its bolt-joints of a beam with other parts of the structure. One of the connecting frames of the tail beam was equipped with piezoelectric transducers (PZT) glued on the surface of the frame near the bolts. The bolts' loosening was investigated by using the EMI technology. Findings – It was demonstrated that loosening of the bolt-joint produces a significant and statistically stable change of the EMI metric. Presumably, both the small shift of resonance frequencies and the EMI magnitude and resistance change are caused mainly by damping variation at the bolt-joint loosening. In this analytical study, the 2D model of a constrained PZT is proposed. In contrast with the existing model, the modal decomposition analysis is used as a universal mean to express the dynamic properties and dynamic responses of both the transducer and the host structure. This approach, together with the finite element modal analysis, allows simulation of any complex system “PZT-host structure”. The model can be easily transformed also to the 3D one. The bolt-joint of the Mi-8 helicopter with the EMI measurement system was simulated by using the developed 2D model. The simulation results satisfactorily correspond to the test. Practical implications – The results of this research can be used for implementation in the structural health monitoring of bolt-joints and other aerospace structural components. Originality/value – The new experimental results on aircraft real bolt-joints were obtained. Especially significant is the original 2D model of the electromechanical impedance, based on the modal decomposition method, which can significantly improve the accuracy and the realistic description of the dynamic interaction between PZT and structure, as well as the dynamic response to the appearance of structural damage.

A Review Paper on Looseness Detection Methods in Bolted Structures

“…The theoretical basis of this method were first proposed by Liang et al (1994) and were then expanded by Zhou et al, Bhalla, Sou, and Anamandas, who proposed 2D and 3D models for dynamic interactions between a structure and its piezoelectric adapters (Krishnamurthy, et al, 1996;Pavelko, et al, 2014;Krishnamurthy, et al, 1996;Annamdas & S., 2007). In addition to the studies on modeling of this method, there have been other researchers who conducted studies on adequacy of this method in detection and evaluation of looseness of bolted structures.…”

“…Providing an index for evaluation of the looseness of bolts, Park et al surveyed the efficiency of the method in detecting looseness in bolted joints of pipelines (Overly, et al, 2007;Park, et al, 2001). Pavelko et al also conducted experiments on thin plates, and by investigating the effects of structure firmness, they described the mechanism of this method (Pavelko, et al, 2011). In addition to the conducted case studies, innovations have also been proposed in performing the experiments.…”

“…Although the method is theoretically simple, to use the method, all paints and covers must be removed from the structure and sensors must be placed around every bolt, and this leads to unfavorability of this method You, et al, 2010). (Park, et al, 2003;Park, et al, 2001), thin plates (Pavelko, et al, 2011) and experimental setups (Ritdumrongkul, et al, 2004;Wait, et al, 2005;An & Sohn, 2012;Mascarenas, et al, 2009 (Trendafilova & Brussel, 2001;Tjahjowidodo, et al, 2007), metal (Guarino & Hamilton, 2009) and composite (Caccese, et al, 2004) structures, pipelines (Esmaeel, et al, 2012) and experimental setups (Adams & Farrar, 2002;Wit, et al, 1995;Nichols, 2007;Razi, et al, 2013 Case studies: Experimental setup Chang & Yang, 2006;Doyle, et al, 2010 Case studies: bolted joints in steel structures (Liew, et al, 2006) and experimental setups (Hirao, et al, 1994;Kawashima & Yasui, 2000). …”

Electromechanical impedance for SHM of aircraft bolted joints

“…It is also seen that selection of the frequency range is not significant to relative change of RMSD at different bolts loosening. The real part of EMI Z relative increment (1) was also selected as a other parameter for estimation of loosening effect 18,19 . …”

Reduced Order Model of Circular Flange-Bolted Connection and Its Application to Dynamic Substructuring of Telecommunication Towers

“…According to the recent trends in structural health monitoring (SHM) it is necessary, among others, to monitor and detect structural damages. Two main methods in SHM can be recognized: local methods [2,3,4] and global ones [5][6]. In local methods connections are monitored directly at the vicinity of the damage.…”