Dual-frequency acousto-ultrasonic sensing of impact damage in composites for mitigating signal instability

2021 ◽  
pp. 147592172199662
Author(s):  
Chen Gong ◽  
Qi Wu ◽  
Hanqi Zhang ◽  
Rong Wang ◽  
Ke Xiong ◽  
...  
Keyword(s):  
Input Signal ◽  
Lamb Waves ◽  
Amplitude Ratio ◽  
Impact Damage ◽  
Low Frequency ◽  
Temperature Fluctuations ◽  
Signal Amplitude ◽  
Dual Frequency ◽  
Ultrasonic Detection ◽  
Ultrasonic Sensing

Signal instability due to temperature fluctuations, sensor degradation, and debonding introduces additional amplitude loss in the detected signals during acousto-ultrasonic detection, which may be falsely attributed to defects in a structure. First, we determined that the amplitudes of both high-frequency and low-frequency Lamb waves decrease after propagation through a damaged area. Then, we found that the amplitude ratio of such waves not only exhibits a downward trend but is also immune to fluctuations in the input signals. A qualitative numerical expression was proposed to explain this phenomenon, and preliminary experiments were conducted to demonstrate that the amplitude ratio is an effective parameter for mitigating instability in signal detection. Particularly, the number of impacts on a composite laminate was evaluated with respect to changes in the input signal amplitude. Notably, this method can be further simplified by designing a dual-frequency input signal. After conclusively validating the performance of the novel method in a composite subjected to temperature fluctuations, we conclude that the proposed acousto-ultrasonic detection method is robust in mitigating signal instability, and that it yields reliable information for damage evaluation.

Active sensing of impact damage in composite sandwich panels by low frequency Lamb waves

2008 ◽  
Vol 112 (1131) ◽  
pp. 279-283 ◽  
Author(s):  
C. Soutis ◽  
K. Diamanti
Keyword(s):  
Lamb Waves ◽  
Impact Damage ◽  
Low Frequency ◽  
Practical Applications ◽  
Reinforced Plastics ◽  
Composite Sandwich ◽  
Composite Sandwich Structures ◽  
Inspection Strategy ◽  
Extent Of Damage ◽  
Non Destructive

Abstract The development of a robust non-destructive system to detect and monitor the extent of damage in carbon fibre reinforced plastics (CFRP) during service life is a key problem in many practical applications, especially in the aircraft industry. The lack of such technique has severely limited the potentially extensive use of composite materials. In this study a cost and time effective inspection strategy for in-service health monitoring of composites is demonstrated using the fundamental anti-symmetric A 0 Lamb mode at frequencies of 15-20kHz. In principle, this method involves analysis of the transmitted and/or reflected wave after interacting with the test-piece boundaries or discontinuities (defects). In the present work, the applicability of the technique to composite sandwich structures is explored and defects of critical size are successfully detected.

scholarly journals Impact Damage Detection in Laminate and Honeycomb CFRPs using Lamb Wave Ultrasonic Sensing

2021 ◽  
Vol 57 (2) ◽  
pp. 114-124
Author(s):  
M. V. Burkov ◽  
A. V Eremin ◽  
A. V. Byakov ◽  
P. S. Lyubutin ◽  
S. V. Panin
Keyword(s):  
Damage Detection ◽  
Impact Energy ◽  
Cross Correlation ◽  
Lamb Waves ◽  
Impact Damage ◽  
Damage Index ◽  
State Testing ◽  
Accurate Data ◽  
Damage Location ◽  
Ultrasonic Sensing

Abstract The paper presents the results on application of Lamb waves based technique for impact damage detection and severity identification. The PZT network operates in the round-robin mode changing the actuator and sensor roles of the transducers in order to detect the response of the system in the presence of damage. The monitoring is performed via the analysis of three parameters: change of the amplitude (dA), change of the energy (dP) and cross-correlation (NCC) of the signals in baseline and damaged state. Testing of laminate CFRPs shows that the damage location is estimated with an error of 5–15 mm, while the computed Damage index is linearly dependent on the applied impact energy. For honeycomb CFRPs the NCC parameter do not provide accurate results, however, other parameters allow identification within the 5–20 mm error and reflect accurate data on the severity of the damage.

scholarly journals Experimental and numerical evaluation on debonding of fully grouted rockbolt under pull-out loading

2021 ◽  
Author(s):  
Shuisheng Yu ◽  
Wancheng Zhu ◽  
Leilei Niu
Keyword(s):  
Wave Propagation ◽  
Amplitude Ratio ◽  
Country Rock ◽  
Low Frequency ◽  
Axial Loading ◽  
Signal Amplitude ◽  
Guided Wave ◽  
Pull Out ◽  
Ultrasonic Guided Wave ◽  
Guided Wave Propagation

Abstract The axial loading in rockbolts changes due to stress redistribution and rheology in the country rock mass. Such a change may lead to debonding at rockbolt to grout interface or rupture of the rockbolt. In this study, based on laboratory experiments, ultrasonic guided wave propagation in fully grouted rockbolt under different pull-out loads was investigated in order to examine the resultant debonding of rockbolt. The signals obtained from the ultrasonic monitoring during the pull-out test were processed using wavelet multi-scale analysis and frequency spectrum analysis, the signal amplitude and the amplitude ratio (Q) of low frequency to high frequency were defined to quantify the debonding of rockbolt. In addition to the laboratory test, numerical simulation on the effect of the embedment lengths on ultrasonic guided wave propagation in rockbolt was conducted by using a damage-based model, and the debonding between rockbolt and cement mortar was numerically examined. It was confirmed that the ultrasonic guided wave propagation in rockbolt was very sensitive to the debonding because of pull-out load, therefore, the critical bond length could be calculated based on the propagation of guided wave in the grouted rockbolt. In time domain, the signal amplitude in rockbolt increased with pull-out load from 0 kN to 100 kN until the completely debonding, thus quantifying the debonding under the different pull-out loads. In the frequency domain, as the Q value increased, the debonding length of rockbolt decreased exponentially. The numerical results confirmed that the guided wave propagation in the fully grouted rockbolt was effective in detecting and quantifying the debonding of rockbolt under pull-out load.

Study of the effect of strain amplitude ratio at two-frequency cyclic loading

2018 ◽  
Vol 84 (12) ◽  
pp. 50-60 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Amplitude Ratio ◽  
Low Frequency ◽  
Frequency Component ◽  
Single Frequency ◽  
High Frequency Component ◽  
Dual Frequency ◽  
Operating Modes ◽  
Cyclic Durability ◽  
Cycle Loading

The operating modes of loading elements of machines and structures exhibit, as a rule, more complicated character of their loading cycles compared to sinusoidal used in the practice of calculations and experiments. It is noted that in a number of cases the actual conditions of load changing can be schematized by dual-frequency loading modes with superposition of the high-frequency component of the main workload attributed to the effects of vibrations, aero- and hydrodynamic impacts, regulation of the working process, etc. Testing of three steel samples which differ in their cyclic properties has shown that such two-frequency regimes lead to a decrease in the durability in comparison with single-frequency loading, equal in the amplitude of maximum stresses. This reduction depends on the parameters of the basic low-frequency and imposed high-frequency loads. Evaluation of this reduction can be performed both i) using the laws of summation of the damage expressed in the strain terms, and ii) using an analytical expression considered below, which includes calculated or experimentally determined durability for single-frequency loading with the maximum (total) amplitude of the effective stress and durability coefficient, characteristic of each type of material and determined by the ratio of amplitudes and hours of low- and high stresses. A computational-experimental analysis of the effect of the amplitude of low-frequency and superimposed high-frequency loading under two-frequency modes of stress change on the cyclic durability showed that the imposition of the high-frequency component of cyclic deformation on the main low-cycle loading process leads to a significant decrease in the cyclic durability, the level of the decrease correlates with the level of amplitudes and frequencies ratios of the summarized harmonic processes of load application.

scholarly journals Data analysis of low frequency transmitter signals received at a midlatitude site with regard to planetary wave activity

2012 ◽  
Vol 10 ◽  
pp. 279-284 ◽  
Author(s):  
E. D. Schmitter
Keyword(s):  
Continuous Monitoring ◽  
Planetary Wave ◽  
Amplitude Ratio ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Wave Activity ◽  
Time Range ◽  
Seasonal Temperature ◽  
Amplitude Data ◽  
Winter Time

Abstract. More than 2 yr of continuously recorded signal amplitude data from the MSK transmitters NRK/TFK (37.5 kHz, Iceland) and NSY (45.9 kHz, Sicily) received at (52° N 8° E) in the time range from August 2009 to September 2011 are analyzed with regard to planetary wave activity. Wavelet analysis of the day/night amplitude ratio reveals clear evidence of quasi 16 day periods mainly during winter time as well as traces of 5 and 10 day periods on both paths. The amplitude ratio is well correlated to the typical stratospheric (10 hPa) seasonal temperature profile – more clearly to be seen on the northern path. The results are in line and an extension of manifold research with regard of ionospheric absorption phenomena caused by atmospheric wave activity. Continuous monitoring of transmitters in the 40 kHz frequency range proved as an inexpensive tool for investigating mesospheric response to forcing from below.

Design and Application of a Low Frequency VCO

2014 ◽  
Vol 668-669 ◽  
pp. 808-811
Author(s):  
Hui Min Zhang ◽  
Qing Ping Wu ◽  
Zheng Yuan Zhou ◽  
Xun Wang
Keyword(s):  
Experimental Test ◽  
Input Signal ◽  
Operational Amplifier ◽  
Output Signal ◽  
Analog Circuit ◽  
Low Frequency ◽  
Voltage Controlled Oscillator ◽  
Frequency Range ◽  
Innovative Design ◽  
Design Cost

The low frequency voltage controlled oscillator (VCO) is designed using integrated operational amplifier. The frequency of the output signal of VCO changes with the magnitude of the input signal voltage, and show a linear relationship within a certain range through the experimental test. Experiments show that, under the input of certain amplitude and frequency range of the square wave, triangle wave, saw-tooth wave, the output waveform of VCO respectively is ambulance, fire siren and other kinds of ambulance siren Signal. This innovative design’ cost is low, realized by analog circuit. It can be used in the practice of teaching case, electronic production or development of sound panels.

Low-frequency critical current noise in Josephson junctions induced by temperature fluctuations

2012 ◽  
Vol 101 (9) ◽  
pp. 092601 ◽  
Author(s):  
S. M. Anton ◽  
C. D. Nugroho ◽  
J. S. Birenbaum ◽  
S. R. O’Kelley ◽  
V. Orlyanchik ◽  
...  
Keyword(s):  
Critical Current ◽  
Josephson Junctions ◽  
Low Frequency ◽  
Temperature Fluctuations ◽  
Current Noise

scholarly journals Large Temperature Fluctuations due to Cold-Air Pool Displacement along the Lee Slope of a Desert Mountain

2017 ◽  
Vol 56 (4) ◽  
pp. 1083-1098 ◽  
Author(s):  
Matthew E. Jeglum ◽  
Sebastian W. Hoch ◽  
Derek D. Jensen ◽  
Reneta Dimitrova ◽  
Zachariah Silver
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Atmospheric Modeling ◽  
Large Temperature ◽  
Complex Flow ◽  
Near Surface ◽  
Cold Air ◽  
Flow Interactions ◽  
Initial Drop ◽  
Program Temperature

AbstractLarge temperature fluctuations (LTFs), defined as a drop of the near-surface temperature of at least 3°C in less than 30 min followed by a recovery of at least half of the initial drop, were frequently observed during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. Temperature time series at over 100 surface stations were examined in an automated fashion to identify and characterize LTFs. LTFs occur almost exclusively at night and at locations elevated 50–100 m above the basin floors, such as the east slope of the isolated Granite Mountain (GM). Temperature drops associated with LTFs were as large as 13°C and were typically greatest at heights of 4–10 m AGL. Observations and numerical simulations suggest that LTFs are the result of complex flow interactions of stably stratified flow with a mountain barrier and a leeside cold-air pool (CAP). An orographic wake forms over GM when stably stratified southwesterly nocturnal flow impinges on GM and is blocked at low levels. Warm crest-level air descends in the lee of the barrier, and the generation of baroclinic vorticity leads to periodic development of a vertically oriented vortex. Changes in the strength or location of the wake and vortex cause a displacement of the horizontal temperature gradient along the slope associated with the CAP edge, resulting in LTFs. This mechanism explains the low frequency of LTFs on the west slope of GM as well as the preference for LTFs to occur at higher elevations later at night, as the CAP depth increases.

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