Application of the Fatigue Crack Opening/Closing Effect for SHM Using Electromechanical Impedance Technology

2015 ◽  
Vol 811 ◽  
pp. 228-235
Author(s):  
Vitalijs Pavelko
Keyword(s):  
Fatigue Crack ◽  
Fatigue Testing ◽  
Mechanical Load ◽  
Crack Opening ◽  
Central Fatigue ◽  
Guided Wave ◽  
Central Hole ◽  
Electromechanical Impedance ◽  
Guided Wave Propagation ◽  
Host Structure

Earlier the effect of fatigue crack opening/closing (FCOC) to ultrasound guided wave propagation was investigated. The purpose of this article is to evaluate this effect to the electromechanical impedance (EMI) of the system "piezoelectric transducer / host structure. Experimental study performed using the flat samples of aluminum alloy. One of them had the 4 mm central hole. Other sample after fatigue testing had central fatigue crack of 40 mm length (including a 4 mm central hole for the initiation of a fatigue crack. Each sample was loaded by tensile axial static load from zero to 12 kN and the EMI measurement after eacn 2 kN incrementat of load. The EMI was measured in the frequency range of 20-40 kHz. It is established that the FCOC effect to magnitude and reactance of EMI mainly associated with variation of the capacitance of PZT under mechanical load. But the effect to the PZT resistance is more complex and more significant. The result of the study is the base of some procedure of fatigue crack detecting by the EMI method without baseline use. The developed model of EMI of ’host structure – PZT’ that is based on the modal decomposition of dynamic response of this system allows to solve main problems of the SHM system designing and optimizing of its parameters.

Temperature and damage influence on electromechanical impedance method used for carbon fibre–reinforced polymer panels

2016 ◽  
Vol 28 (6) ◽  
pp. 782-798 ◽  
Author(s):  
Tomasz Wandowski ◽  
Pawel H Malinowski ◽  
Wieslaw M Ostachowicz
Keyword(s):  
Carbon Fibre ◽  
Damage Detection ◽  
Low Frequency ◽  
Guided Wave ◽  
Impedance Method ◽  
Electromechanical Impedance ◽  
Reinforced Polymer ◽  
Guided Wave Propagation ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This article deals with damage detection process under varying temperature. Carbon fibre–reinforced polymer samples are investigated using electromechanical impedance method. In the article, influence of changing temperature on resistance in electromechanical impedance is investigated. Authors propose new approach for compensation of temperature influence on damage detection. Damage detection is based on root mean square deviation index. Due to strong damping of utilized composite material, low-frequency range is utilized in this research. Real part of electromechanical impedance is measured for frequency band 1–20 kHz. Damage is in the form of artificially made delamination with different sizes. Authors also discuss the problem of influence of structure’s boundary condition on low-frequency measurements. In the research, scanning laser vibrometry for guided wave propagation method is utilized for visualization of the introduced delamination.

Manipulation of the guided wave propagation in multilayered phononic plates by introducing interface delaminations

2021 ◽  
pp. 104266
Author(s):  
Yanzheng Wang ◽  
Elias Perras ◽  
Mikhail V. Golub ◽  
Sergey I. Fomenko ◽  
Chuanzeng Zhang ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Guided Wave ◽  
Guided Wave Propagation

Guided Wave Acoustic Emission from Fatigue Crack Growth in Aluminium Plate

2006 ◽  
Vol 13-14 ◽  
pp. 23-28 ◽  
Author(s):  
C.K. Lee ◽  
Jonathan J. Scholey ◽  
Paul D. Wilcox ◽  
M.R. Wisnom ◽  
Michael I. Friswell ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Elastic Waves ◽  
Fatigue Cracks ◽  
Guided Wave ◽  
Experimental Results ◽  
Multiple Reflections ◽  
Alloy Plate

Acoustic emission (AE) testing is an increasingly popular technique used for nondestructive evaluation (NDE). It has been used to detect and locate defects such as fatigue cracks in real structures. The monitoring of fatigue cracks in plate-like structures is critical for aerospace industries. Much research has been conducted to characterize and provide quantitative understanding of the source of emission on small specimens. It is difficult to extend these results to real structures as most of the experiments are restricted by the geometric effects from the specimens. The aim of this work is to provide a characterization of elastic waves emanating from fatigue cracks in plate-like structures. Fatigue crack growth is initiated in large 6082 T6 aluminium alloy plate specimens subjected to fatigue loading in the laboratory. A large specimen is utilized to eliminate multiple reflections from edges. The signals were recorded using both resonant and nonresonant transducers attached to the surface of the alloy specimens. The distances between the damage feature and sensors are located far enough apart in order to obtain good separation of guided-wave modes. Large numbers of AE signals are detected with active fatigue crack propagation during the experiment. Analysis of experimental results from multiple crack growth events are used to characterize the elastic waves. Experimental results are compared with finite element predictions to examine the mechanism of AE generation at the crack tip.

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