scholarly journals Crack Growth Signal Processing Approach Combining Wavelet Threshold Denoising and Variable Amplitude DCPD Technique

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Chenqiang Ni ◽  
He Xue ◽  
Shuai Wang ◽  
Xiurong Fang ◽  
Hongliang Yang
Keyword(s):  
Signal Processing ◽  
Crack Growth ◽  
Potential Drop ◽  
Compact Tension ◽  
Growth Monitoring ◽  
Interference Signal ◽  
Adaptive Wavelet ◽  
Processing Approach ◽  
Reference Potential ◽  
Unbiased Risk

The direct current potential drop (DCPD) method is widely used in laboratory environments to monitor the crack initiation and propagation of specimens. In this study, an anti-interference signal processing approach, combining wavelet threshold denoising and a variable current amplitude DCPD signal synthesis technique, was proposed. Adaptive wavelet threshold denoising using Stein’s unbiased risk estimate was applied to the main potential drop signal and the reference potential signal under two different current amplitudes to reduce the interference caused by noise. Thereafter, noise-reduced signals were synthesized to eliminate the time-varying thermal electromotive force. The multiplicative interference signal was eliminated by normalizing the main potential drop signal and the reference potential drop signal. This signal processing approach was applied to the crack growth monitoring data of 316 L stainless steel compact tension specimens in a laboratory environment, and the signal processing results of static cracks and propagation cracks under different load conditions were analyzed. The results showed that the proposed approach can significantly improve the signal-to-noise ratio as well as the accuracy and resolution of the crack growth measurement.

Health Monitoring of the Aircraft Structure during a Full Scale Fatigue Test with Use of an Active Piezoelectric Sensor Network

2015 ◽  
Vol 220-221 ◽  
pp. 328-332
Author(s):  
Michal Dziendzikowski ◽  
Krzysztof Dragan ◽  
Artur Kurnyta ◽  
Sylwester Klysz ◽  
Andrzej Leski
Keyword(s):  
Signal Processing ◽  
Damage Detection ◽  
Crack Growth ◽  
Fatigue Test ◽  
Piezoelectric Sensor ◽  
Full Scale ◽  
Growth Monitoring ◽  
Aircraft Structure ◽  
System Functioning ◽  
Signal Processing Methods

The paper presents an approach to develop a system for fatigue crack growth monitoring and early damage detection in the PZL – 130 ORLIK TC II turbo-prop military trainer aircraft structure. The system functioning is based on elastic waves propagation excited in the structure by piezoelectric PZT transducers. In the paper, a built block approach for the system design, signal processing as well as damage detection is presented. Description of damage detection capabilities are delivered in the paper and some issues concerning the proposed signal processing methods and their application to crack growth estimation models are discussed. Selected preliminary results obtained during the Full Scale Fatigue Test thus far are also presented.

Crack Growth Rates of Alloy 600 From the Davis-Besse Reactor CRDM Nozzle #3 in PWR Environment

2005 ◽  
Author(s):  
Omesh K. Chopra ◽  
Bogdan Alexandreanu ◽  
William J. Shack
Keyword(s):  
Crack Growth ◽  
Potential Drop ◽  
Compact Tension ◽  
Constant Load ◽  
Alloy 600 ◽  
Pressurized Water ◽  
Control Rod ◽  
Environmentally Assisted Cracking ◽  
Water Reactors ◽  
Nickel Base

Reactor–vessel internal components made of nickel–base alloys are susceptible to environmentally assisted cracking. A better understanding of the causes and mechanisms of this cracking may permit less conservative estimates of damage accumulation and requirements on inspection intervals of pressurized water reactors (PWRs). This paper presents crack growth rate (CGR) results for Alloy 600 removed from nozzle#3 of the Davis–Besse (D-B) control rod drive mechanism (CRDM). The tests were conducted on 1/4-T or 1/2-T compact tension specimens in simulated PWR environment, and crack extensions were determined by DC potential drop measurements. The experimental CGRs under cyclic and constant load are compared with the existing CGR data for Alloy 600 to determine the relative susceptibility of the D-B CRDM nozzle alloy to environmentally enhanced cracking. The CGRs under constant load for the nozzle material are higher than those predicted by the best-fit curve for Alloy 600 at 316 °C. The results also indicate significant enhancement of CGRs under cyclic loading in the PWR environment. Characterization of the material microstructure and tensile properties is described.

scholarly journals Online fatigue crack growth monitoring with clip gauge and direct current potential drop

2016 ◽  
Vol 7 (1) ◽  
pp. 6 ◽  
Author(s):  
Steven De Tender ◽  
Nahuel Micone ◽  
Wim De Waele
Keyword(s):  
Crack Growth ◽  
Direct Current ◽  
Potential Drop ◽  
Offshore Wind ◽  
Stress Intensity Factor Range ◽  
Offshore Wind Turbine ◽  
Growth Monitoring ◽  
Paris Law ◽  
Direct Current Potential Drop ◽  
Current Potential

Fatigue is a well-known failure phenomenon which has been and still is extensively studied. Often structures are designed according to the safe-life principle so no crack initiation occurs. Nowadays there is a high emphasis on cost-efficiency, and one might rather opt for a fail-safe design. Therefore a certain amount of crack growth can be allowed in structures, but then a good knowledge of stresses and related crack growth rates is needed. To this end, extensive studies are done to obtain a material’s Paris law curve. Within the framework of research for offshore wind turbine constructions, tests were done to determine the crack growth rate of a high strength low alloy (HSLA) steel. A dedicated LabVIEW program was developed to be able to determine an entire Paris law curve with a single specimen, by controlling the stress intensity factor range (ΔK). The program is controlled by the readings of a clip gauge, which make it possible to plan the amount of crack growth per ΔK block and thus plan an entire test in advance. The potential drop technique was also applied in order to obtain the Paris law curve. Clip gauge results were compared with direct current potential drop monitoring. This comparison was done by means of an a/W-N diagram and the resulting Paris law curves. The results show a very good correlation between both methods and with the visual confirmation.

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