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DAMAGE DETECTION FOR COMPOSITE STRUCTURE UNDER TEMPERATURE CHANGES USING LAMB WAVES
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作者 严刚 周丽 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2011年第3期231-239,共9页
A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distingui... A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distinguish whether the changes of Lamb wave signals are induced by damage within a monitoring area or are only affected by temperature changes.Damage indices are defined after the Lamb wave signals are processed by Fourier transform,and a Monte Carlo procedure is used to obtain the damage threshold value for the damage indices at the undamaged state.If the damage indices in the operation state exceed the threshold value,the presence of damage is determined.Then,a probabilistic damage imaging algorithm displaying probabilities of the presence of damage within the monitoring area is adopted to fuse information collected from multiple actuator-sensor paths to identify the location of damage.Damage indices under damaged state are used to generate the diagnostic image.Experimental study on a stiffened composite panel with random temperature changes is performed to demonstrate the effectiveness of the proposed method. 展开更多
关键词 structural health monitoring composite structure Lamb wave statistical outlier analysis probabilistic damage imaging temperature changes
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A time reversal damage imaging method for structure health monitoring using Lamb waves 被引量:1
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作者 张海燕 曹亚萍 +2 位作者 孙修立 陈先华 于建波 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第11期448-455,共8页
This paper investigates the Lamb wave imaging method combining time reversal for health monitoring of a metallic plate structure. The temporal focusing effect of the time reversal Lamb waves is investigated theoretica... This paper investigates the Lamb wave imaging method combining time reversal for health monitoring of a metallic plate structure. The temporal focusing effect of the time reversal Lamb waves is investigated theoretically. It demonstrates that the focusing effect is related to the frequency dependency of the time reversal operation. Numerical simulations are conducted to study the time reversal behaviour of Lamb wave modes under broadband and narrowband excitations. The results show that the reconstructed time reversed wave exhibits close similarity to the reversed narrowband tone burst signal validating the theoretical model. To enhance the similarity, the cycle number of the excited signal should be increased. Experiments combining finite element model are then conducted to study the imaging method in the presence of damage like hole in the plate structure. In this work, the time reversal technique is used for the recompression of Lamb wave signals. Damage imaging results with time reversal using broadband and narrowband excitations are compared to those without time reversal. It suggests that the narrowband excitation combined time reversal can locate and determine the size of structural damage more precisely, but the cycle number of the excited signal should be chosen reasonably. 展开更多
关键词 Lamb wave time reversal damage imaging structure health monitoring
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QoE Assessment and Prediction Method for HighDefinition Video Stream Using Image Damage Accumulation 被引量:2
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作者 Yang Geng Luoming Meng +2 位作者 Yao Wang Yu Yang Zhiguo Qu 《China Communications》 SCIE CSCD 2016年第7期48-59,共12页
The accuracy of the traditional assessment method of the quality of experience(Qo E) has been facing challenges with the growth of high-definition(HD) video streaming services.Image display-quality damage is the main ... The accuracy of the traditional assessment method of the quality of experience(Qo E) has been facing challenges with the growth of high-definition(HD) video streaming services.Image display-quality damage is the main factor that affects the Qo E in HD video services through UDP network transmission.In this paper,we introduce a novel objective factor known as image damage accumulation(IDA) to assess user's Qo E in HD video services.First,this paper quantitatively analyzed the effect on user quality of experience by IDA and established a mapping relationship between mean opinion scores and IDA.Furthermore,the probability of image damage caused by compression and transmission were analyzed.Based on this analysis,an objective Qo E assessment and prediction method for HD video stream service that evaluated the user experience according to IDA are proposed.The proposed method can achieve assessment and prediction accuracy on three distinct subjective tests. 展开更多
关键词 high-definition video stream quality of experience(QoE) image damage accumulation
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In-service Structural Health Monitoring of a Full-scale Composite Horizontal Tail
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作者 武湛君 GAO Dongyue +1 位作者 WANG Yishou Gorgin RAHIM 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第6期1215-1224,共10页
In-service structural health monitoring(SHM) technologies are critical for the utilization of composite aircraft structures. We developed a Lamb wave-based in-service SHM technology using built-in piezoelectric actu... In-service structural health monitoring(SHM) technologies are critical for the utilization of composite aircraft structures. We developed a Lamb wave-based in-service SHM technology using built-in piezoelectric actuator/sensor networks to monitor delamination extension in a full-scale composite horizontal tail. The in-service SHM technology combine of damage rapid monitoring(DRM) stage and damage imaging diagnosis(DID) stage allows for real-time monitoring and long term tracking of the structural integrity of composite aircraft structures. DRM stage using spearman rank correlation coeffi cient was introduced to generate a damage index which can be used to monitor the trend of damage extension. The DID stage based on canonical correlation analysis aimed at intuitively highlighting structural damage regions in two-dimensional images. The DRM and DID stages were trialed by an in-service SHM experiment of CFRP T-joint. Finally, the detection capability of the in-service SHM technology was verified in the SHM experiment of a full-scale composite horizontal tail. Experimental results show that the rapid monitoring method effectively monitors the damage occurrence and extension tendency in real time; damage imaging diagnosis results are consistent with those from the failure model of the composite horizontal tail structure. 展开更多
关键词 in-service structural health monitoring full-scale composite horizontal tail lamb wave damage rapid monitoring damage imaging diagnosis
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Damage Imaging in Mesoscale Concrete Modeling Based on the Ultrasonic Time-Reversal Technique 被引量:1
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作者 Kan Feng Qian Zhao Yaping Qiu 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2020年第1期61-70,共10页
A novel method combining the time-reversal method(TRM)with wavelet analysis was proposed for damage imaging in mesoscale concrete modeling.The damage was imaged by the convergence of time-reversed wave signals after w... A novel method combining the time-reversal method(TRM)with wavelet analysis was proposed for damage imaging in mesoscale concrete modeling.The damage was imaged by the convergence of time-reversed wave signals after wavelet analysis.Through numerical study,three concrete models of different damage sizes were built with randomly distributed aggregate particles.The time-reversal process was simulated using the reverse damage-scattered ultrasonic wave signals as excitations recorded by the sensors.Then,the wavelet analysis was employed to extract certain frequency component,which can enhance detection precision and the signalto-noise ratio.The damage imaging showed clearly the location of the defect.The results from experimental testing also demonstrated that this detection technique is an efficient and effective method for damage imaging in mesoscale concrete. 展开更多
关键词 Damage imaging Mesoscale concrete Time-reversal method Wavelet analysis
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Sparse Reconstruction and Damage Imaging Method Based on Uniform Sparse Sampling
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作者 Pengfei Li Ying Luo +2 位作者 Kan Feng Yang Zhou Chenguang Xu 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2020年第6期744-755,共12页
The full wavefield detection method based on guided waves can efficiently detect and locate damages relying on the collection of large amounts of wavefield data.The acquisition process by scanning laser Doppler vibrom... The full wavefield detection method based on guided waves can efficiently detect and locate damages relying on the collection of large amounts of wavefield data.The acquisition process by scanning laser Doppler vibrometer(SLDV)is generally time-consuming,which is limited by Nyquist sampling theorem.To reduce the acquisition time,full wavefield data can be reconstructed from a small number of random sampling point signals combining with compressed sensing.However,the random sampling point signals need to be obtained by adding additional components to the SLDV system or offline processing.Because the random sparse sampling is difficult to achieve via the SLDV system,a new uniform sparse sampling strategy is proposed in this paper.By using the uniform sparse sampling coordinates instead of the random spatial sampling point coordinates,sparse sampling can be applied to SLDV without adding additional components or offline processing.The simulation and experimental results show that the proposed strategy can reduce the measurement locations required for accurate signal recovery to less than 90%of the Nyquist sampling grid,and the damage location error is within the minimum half wavelength.Compared with the conventional jittered sampling strategy,the proposed sampling strategy can directly reduce the sampling time of the SLDV system by more than 90%without adding additional components and achieve the same accuracy of guided wavefield reconstruction and damage location as the jittered sampling strategy.The research results can greatly improve the efficiency of damage detection technology based on wavefield analysis. 展开更多
关键词 Scanning laser Doppler vibrometer Lamb waves Compressed sensing Wavefield sparse reconstruction Damage imaging
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You’re Damaging Our Image
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作者 FRANCISCO LITTLE 《Beijing Review》 2010年第24期48-48,共1页
"Hey man, how are you doing?"I looked around to see three fashionably dressed African guys approaching me, wearing broad grins and looking for all intents and purposes to be finalists in a Mr. Friendly 2010 ... "Hey man, how are you doing?"I looked around to see three fashionably dressed African guys approaching me, wearing broad grins and looking for all intents and purposes to be finalists in a Mr. Friendly 2010 contest. 展开更多
关键词 You’re Damaging Our Image
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