Mateusz Rosiek

Application of electromechanical impedance-based SHM for damage detection in bolted pipeline connection

The work discusses the effectiveness of the electromechanical impedance-based Structural Health Monitoring system for damage detection in a laboratory test stand – a bolted pipeline section. The impedance-based system developed by the authors and equipped with 12 piezoelectric transducers was used to acquire the data. Different damage scenarios related to loosened bolts and measurement configurations are analysed. Both point and transfer frequency response functions are applied to deterministic and stochastic damage metrics, which are used to assess the condition of the monitored structure. The thresholds levels are proposed for different measurement configurations. Moreover, the authors discuss the perspective to determine the size and localisation of a damage. As confirmed in the work, the stochastic damage metric, preferably applied with a transfer frequency response, is found as of the most practical significance for the tested structure. The carried out analyses consider an outlier removal technique, which becomes necessary to prevent from errors due to temporary variation of the acquired characteristics after initialisation of the measurements.

Electromechanical Impedance Based SHM System for Aviation Applications

This paper concerns an approach based on the electromechanical impedance for damage detection and monitoring of aircraft components. In the introductory part of the paper the theory of proposed method and the characteristics of elaborated structural health monitoring system are briefly described. Afterwards, applications of described system applied to damage detection in different aircraft components are presented. First, the process of monitoring of bolted joints localized in the fuselage is described and effectiveness of this process is discussed. In the application four PZT patches were used to track a torque decrease in three joints. The latter application deals with monitoring of riveted engine housing made of aluminium. Introduced notch was monitored with two MFC transducers. In both mentioned cases the frequency characteristics of measured impedance were compared using different deterministic and statistical damage indexes.

Damage Detection in Riveted Aircraft Elements Based on the Electromechanical Impedance Measurements

This work is devoted to the use of the electromechanical impedance method for the damage detection in a riveted aircraft element. In the first part of the paper a theoretical background of the impedance-based damage detection technique is made. Next, the description of the utilised experimental set-up is described. Then, an application of the method used to detect damage in a wing sheathing of a turboprop training aircraft is presented. A damage scheme incorporating multiple notches through the selected rivets is considered. Finally, the suitability of the described method to distinguish close and far field damages is discussed.

Numerical Modelling and Experimental Verification of Interdigital Transducers for Lamb Wave Generation

Recently, intensive research activity in the application of guided waves (GWs) for structural health monitoring (SHM) has been observed. Interdigital Transducer (IDT) is one of the types of transducers used for generating GWs. The main advantages of such transducers include their ability in generating directional and mode-selective waves. The parameters of IDTs have to be adjusted for the excited wavelength. Some geometric parameters as well as the properties of materials used for manufacturing transducers may be defined using widely known analytical relationships [1]. However, in order to accurately determine the parameters of the IDT, numerous simulations and their experimental verification are required [2]. The paper presents a novel, time efficient approach to the virtual prototyping of complex shaped transducers. The proposed procedure consists of the following four steps: (1) designing a transducer based on analytical relations, (2) approximate numerical simulations of designed transducers with a custom-made, computationally efficient code for screening tests, (3) detailed numerical tests employing the multiphysics Finite Element Method (FEM) for the developed IDT design and (4) experimental tests.

Improving the Design of Capacitive Micromachined Ultrasonic Transducers Aided with Sensitivity Analysis

The paper presents the results of analysis performed to search for feasible design improvements for capacitive micromachined ultrasonic transducer. Carried out search has been aided with the sensitivity analysis and the application of Response Surface Method. The multiphysics approach has been taken into account in elaborated finite element model of one cell of described transducer in order to include significant physical phenomena present in modelled microdevice. The set of twelve input uncertain and design parameters consists of geometric, material and control properties. The amplitude of dynamic membrane deformation of the transducer has been chosen as studied parameter. The objective of performed study has been defined as the task of finding robust design configurations of the transducer, i.e. characterizing maximal value of deformation amplitude with its minimal variation.

Elastic Interdigital Transducers for Lamb Wave Generations

During recent years structural health monitoring (SHM) systems have gained growing attention. Widely applied methods in SHM are methods based on the ultrasonic Lamb waves (LWs) which are also known as plate waves. LWs may be generated and sensed using different types of transducers and their selection is essential for the SHM systems performance. Among transducers used for generation and sensing of such waves, Interdigital Transducers (IDTs) are ones of the most promising types. Their main advantages are: mode selectivity, high excitation strength, wave directivity, small sizes and relatively low cost. In most cases IDTs are made of piezoceramics or piezoelectric polymers what makes them stiff and fragile. Contrary to the piezoceramic transducers, the ones based on piezocomposites (i.e.: macro-fiber composite) are flexible with the comparable efficiency of piezoelectric effects. The MFC transducers are usually optimized as actuators and they are not designed to any specific frequency. It appears, however, that sparse comb-like electrodes used in interdigital transducers create very interesting properties of mode selectivity. In the paper, after the introduction and short discussion about advantages and disadvantages of the IDTs, a novel type of the interdigital transducer, based on elastic macro-fiber composite, is presented. Next, the results of the numerical and experimental tests of the MFC based IDT designed for the A0 mode excitation in a 4mm-thick aluminium plate is presented. In the final part of the paper advantages and disadvantages of the investigated transducer are discussed.

Design Process of IDT Aided by Multiphysics FE Analyses

Presented work is devoted to a design process performed for the interdigital transducer, which is a perspective application for the area of structural health monitoring. In order to obtain the desirable characteristic of the transducer fully coupled numerical analyses were performed in ANSYS Multiphysics software. Utilised finite element models considered both structural dynamics and properties of used piezoelectric material. The process of design improvement was preceded by the sensitivity analysis. In order to search for the best electrode pattern selected geometrical features of the transducer were assumed to vary within allowed ranges. The design parameters, which were taken into account, related to the efficiency of proposed transducer design for the emission of acoustic waves in the monitored structure. The search objectives considered the criteria related to the shape of the beampattern and amplitudes of generated Lamb waves. As a result of the optimization procedure, the simultaneous increase of anti-symmetric mode amplitude and the reduction of undesirable symmetric mode amplitude of generated Lamb waves in the direction perpendicular to the transducer fingers was expected. Another aim of the optimization was to minimize the main lobe width and undesirable contribution of both symmetric and anti-symmetric waves in the parallel direction to the transducer fingers. The response surface method and genetic algorithms were used for fast and effective search through the input design domain.