Crack size monitoring in necked double shear lugs using the electro-mechanical impedance method

2021 ◽  
Author(s):  
Markus Winklberger ◽  
Christoph Kralovec ◽  
Peter Heftberger ◽  
Martin Schagerl
Keyword(s):  
Mechanical Impedance ◽  
Crack Size ◽  
Impedance Method ◽  
Double Shear ◽  
Size Monitoring

scholarly journals Piezoelectric Electro-Mechanical Impedance (EMI) Based Structural Crack Monitoring

2020 ◽  
Vol 10 (13) ◽  
pp. 4648 ◽  
Author(s):  
Tao Wang ◽  
Bohai Tan ◽  
Mingge Lu ◽  
Zheng Zhang ◽  
Guangtao Lu
Keyword(s):  
Resonance Frequency ◽  
Signal To Noise Ratio ◽  
Mechanical Impedance ◽  
Peak Frequency ◽  
Crack Size ◽  
Impedance Method ◽  
Small Scale ◽  
Element Simulation ◽  
Piezoelectric Impedance ◽  
Good Repeatability

To detect small cracks in plate like structures, the high frequency characteristics of local dynamics were studied with the piezoelectric electro-mechanical impedance (EMI) method, and damages were monitored by the changes of the EMI. The finite element simulation model of EMI was established, and numerical analysis was conducted. The simulation results indicated that the peak frequency of the piezoelectric admittance signal is a certain order resonance frequency of the structure, and the piezoelectric impedance method could effectively detect the dynamic characteristics of the structure. The piezoelectric admittance simulation and experimental study of aluminum beams with different crack sizes were performed. Simulation and experimental results revealed that the peak admittance frequency decreases with the increase of crack size, and the higher resonance frequency is more sensitive to the small-scale damage. The proposed method has good repeatability and strong signal-to-noise ratio to monitor the occurrence and development of small-scale crack damage, and it has an important application prospect.

scholarly journals Crack Identification in Necked Double Shear Lugs by Means of the Electro-Mechanical Impedance Method

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 44
Author(s):  
Markus Winklberger ◽  
Christoph Kralovec ◽  
Christoph Humer ◽  
Peter Heftberger ◽  
Martin Schagerl
Keyword(s):  
Crack Detection ◽  
Fatigue Cracks ◽  
Laser Doppler Vibrometer ◽  
Mechanical Impedance ◽  
Impedance Method ◽  
Crack Identification ◽  
Frequency Spectra ◽  
Damage Initiation ◽  
Double Shear ◽  
Critical Locations

This contribution investigates fatigue crack detection, localization and quantification in idealized necked double shear lugs using piezoelectric transducers attached to the lug shaft and analyzed by the electro-mechanical impedance (EMI) method. The considered idealized necked lug sample has a simplified geometry and does not includes the typical bearing. Numerical simulations with coupled-field finite element (FE) models are used to study the frequency response behavior of necked lugs. These numerical analyses include both pristine and cracked lug models. Through-cracks are located at 90∘ and 145∘ to the lug axis, which are critical spots for damage initiation. The results of FE simulations with a crack location at 90∘ are validated with experiments using an impedance analyzer and a scanning laser Doppler vibrometer. For both experiments, the lug specimen is excited and measured using a piezoelectric active wafer sensor in a frequency range of 1 kHz to 100 kHz. The dynamic response of both numerical calculations and experimental measurements show good agreement. To identify (i.e., detect, locate, and quantify) cracks in necked lugs a two-step analysis is performed. In the first step, a crack is detected data-based by calculating damage metrics between pristine and damaged state frequency spectra and comparing the resulting values to a pre-defined threshold. In the second step the location and size of the detected crack is identified by evaluation of specific resonance frequency shifts of the necked lug. Both the search for frequencies sensitive to through-cracks that allow a distinction between the two critical locations and the evaluation of the crack size are model-based. This two-step analysis based on the EMI method is demonstrated experimentally at the considered idealized necked lug, and thus, represents a promising way to reliably detect, locate and quantify fatigue cracks at critical locations of real necked double shear lugs.

scholarly journals Using Hilbert Transform in Diagnostic of Composite Materials by Impedance Method

2020 ◽  
Vol 64 (4) ◽  
pp. 334-342 ◽  
Author(s):  
Volodymyr Eremenko ◽  
Artur Zaporozhets ◽  
Vitalii Babak ◽  
Volodymyr Isaienko ◽  
Kateryna Babikova
Keyword(s):  
Composite Materials ◽  
Nondestructive Testing ◽  
Hilbert Transform ◽  
Instantaneous Frequency ◽  
Information Quality ◽  
Low Frequency ◽  
Mechanical Impedance ◽  
Phase Characteristic ◽  
Impedance Method ◽  
Materials Testing

The article is devoted to the problem of the increasing of information quality for the impedance method of nondestructive testing. The purpose of this article is to get for the pulsed impedance method of nondestructive testing the additional informative parameters. Instantaneous values of the information signal's amplitude is a sensitive parameter to the effects of interference, in particular friction, which necessitates the use of additional informative features. It was experimentally measured signals from defective and defectless areas of the test pattern. Using of the Hilbert transform gave possibility to determine phase characteristics of these signals and realize demodulation to extract a low-frequency envelope for further analysis of its shape. It was received the informative features as a result of researches. Among them are instantaneous frequency of a signal, the integral of a phase characteristic on the selected interval and the integral of a difference signal phase characteristics. In order to compare quality of the defect detection using selected parameters it was carried out evaluation of the testing result reliability for a product fragment made of a composite material. Considering the influence of the change in the mechanical impedance of the researched area on the phase-frequency characteristics of the output signal of the converter, it is proposed to use as the diagnostic signs: the instantaneous frequency and the value of the phase characteristic of the current signal for certain points in time. The proposed informative features enable to increase general reliability of composite materials testing by the pulsed impedance method.

Co-Integration-Based Compensation Technique for Dynamic Load Effects on the Electro-mechanical Impedance Method

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xiaoluo Jie ◽  
Wenzhong Qu ◽  
Li Xiao ◽  
Ye Lu
Keyword(s):  
Dynamic Load ◽  
Mechanical Impedance ◽  
Piezoelectric Transducers ◽  
Impedance Method ◽  
Operational Conditions ◽  
Load Effects ◽  
Compensation Technique ◽  
Aluminum Beam ◽  
Stress Variations ◽  
Stationary Behavior

Abstract The electro-mechanical (EM) admittance signals acquired from piezoelectric transducers (PZT) surface bonded to the host structure are often used for structural health monitoring (SHM). However, it is well known that the method is susceptible to contamination from environmental and operational conditions. This paper introduces a co-integration method to remove dynamic load effects from electro-mechanical admittance data. The proposed method is based on the concept of co-integration that is partially built on the analysis of the non-stationary behavior of time series. Instead of directly using admittance signatures of PZT for damage detection, the analysis of the co-integrated residual obtained from the co-integration procedure of EM admittance responses and the resonant peaks frequency of the real part of admittance (conductance) are chosen as co-integrated variables. The experiments of aluminum beam bolt loosening identification, which is under dynamic stress, were carried out to verify the effectiveness of the proposed method. The results showed that the method can isolate damage-sensitive features from stress variations, so as to successfully detect the existence of damage.

scholarly journals Detection of Pin Failure in Carbon Fiber Composites Using the Electro-Mechanical Impedance Method

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3732
Author(s):  
Jochen Moll ◽  
Matthias Schmidt ◽  
Johannes Käsgen ◽  
Jörg Mehldau ◽  
Marcel Bücker ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Damage Detection ◽  
Fiber Composite ◽  
Mechanical Impedance ◽  
Impedance Method ◽  
Carbon Fiber Composites ◽  
Carbon Fiber Composite ◽  
Bending Loads ◽  
Metallic Parts ◽  
Hybrid Carbon

This paper presents a proof of concept for simultaneous load and structural health monitoring of a hybrid carbon fiber rudder stock sample consisting of carbon fiber composite and metallic parts in order to demonstrate smart sensors in the context of maritime systems. Therefore, a strain gauge is used to assess bending loads during quasi-static laboratory testing. In addition, six piezoelectric transducers are placed around the circumference of the tubular structure for damage detection based on the electro-mechanical impedance (EMI) method. A damage indicator has been defined that exploits the real and imaginary parts of the admittance for the detection of pin failure in the rudder stock. In particular, higher frequencies in the EMI spectrum contain valuable information about damage. Finally, the information about damage and load are merged in a cluster analysis enabling damage detection under load.

scholarly journals Rotordynamic Force Coefficients of Pocket Damper Seals

2006 ◽  
Vol 128 (4) ◽  
pp. 725-737 ◽  
Author(s):  
B. Ertas ◽  
A. Gamal ◽  
J. Vance
Keyword(s):  
Dynamic Pressure ◽  
Mechanical Impedance ◽  
Experimental Tests ◽  
Impedance Method ◽  
Force Density ◽  
Frequency Dependent ◽  
Force Coefficients ◽  
Cross Axis ◽  
Positive Direct ◽  
Stiffness And Damping

This paper presents measured frequency dependent stiffness and damping coefficients for 12-bladed and 8-bladed pocket damper seals (PDS) subdivided into four different seal configurations. Rotating experimental tests are presented for inlet pressures at 69 bar (1000 psi), a frequency excitation range of 20–300 Hz, and rotor speeds up to 20,200 rpm. The testing method used to determine direct and cross-coupled force coefficients was the mechanical impedance method, which required the measurement of external shaker forces, system accelerations, and motion in two orthogonal directions. In addition to the impedance measurements, dynamic pressure responses were measured for individual seal cavities of the eight-bladed PDS. Results of the frequency dependent force coefficients for the four PDS designs are compared. The conclusions of the tests show that the eight-bladed PDS possessed significantly more positive direct damping and negative direct stiffness than the 12-bladed seal. The results from the dynamic pressure response tests show that the diverging clearance design strongly influences the dynamic pressure phase and force density of the seal cavities. The tests also revealed the measurement of same-sign cross-coupled (cross-axis) stiffness coefficients for all seals, which indicate that the seals do not produce a destabilizing influence on rotor-bearing systems.

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