scholarly journals The Auto-Correlation of Ultrasonic Lamb Wave Phased Array Data for Damage Detection

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 666 ◽  
Author(s):  
Haiyan Zhang ◽  
Jiayan Zhang ◽  
Guopeng Fan ◽  
Hui Zhang ◽  
Wenfa Zhu ◽  
...  
Keyword(s):  
Damage Detection ◽  
Phased Array ◽  
Time Synchronization ◽  
Signal To Noise Ratio ◽  
Correlation Method ◽  
High Sensitivity ◽  
Measured Signal ◽  
Correlation Technique ◽  
Destructive Testing ◽  
Auto Correlation

Ultrasonic phased array is widely used for damage detection recently because of its high sensitivity and rapid scanning without sensor movements. However, the measured signal is always influenced by the remnants of the initial excitation and the nonlinear signals from the instrumentation, which limits its application in thin-plate structures. To address this issue, an approach called auto-correlation subtraction is proposed to extract the scattering information of defects in this paper. In order to testify the feasibility of this method for damage detection, the experiments were carried out on three thin aluminum plates combined with the total focusing method (TFM) for imaging. By auto-correlating the full matrix data received by sensors and then subtracting the average auto-correlation of noise recorded by all receivers, the coherent scattered signal containing defect information is recovered. The experimental results indicate that the coherent travel time is in agreement with the theoretical value and the signal-to-noise ratio are improved. Additionally, compared with the cross-correlation technique, the time synchronization between different receivers is not necessary with the auto-correlation method. Results indicate that the presented method can improve the imaging resolution and has a great potential in the field of non-destructive testing.

Nondestructive Damage Detection of Bridges: A Status Review

2001 ◽  
Vol 4 (2) ◽  
pp. 75-91 ◽  
Author(s):  
Xiaotong Wang ◽  
Chih-Chen Chang ◽  
Lichu Fan
Keyword(s):  
Damage Detection ◽  
Rapid Development ◽  
Low Frequency ◽  
Basic Research ◽  
Digital Signal ◽  
Point Of View ◽  
Detection Methods ◽  
Measured Signal ◽  
Destructive Testing ◽  
Bridge Damage

The recent advances in detecting and locating damage in bridges by different kinds of non-destructive testing and evaluation (NDT&E) methods are reviewed. From the application point of view, classifications for general bridge components and their damage types are presented. The relationships between damage, bridge components, and NDT&E techniques are summarized. Many useful WEB sources of NDT&E techniques in bridge damage detection are given. It is concluded that: (1) vibration-based damage detection methods are successful to a certain extent, especially when the overall damage is significant and, low frequency vibration can identify those areas where more detailed local inspection should be concentrated; (2) robust identification techniques that are able to locate damage based on realistic measured data sets still seem a long way from reality, and, basic research is still necessary in the mean time; (3) the rapid development of computer technology and digital signal processing (DSP) techniques greatly impacts upon the conventional NDT techniques, especially in control data processing and data displaying, as well as in simulation and modeling; (4) most of the NDT&E techniques introduced in this paper have their own practical commercial systems, but the effort required for combining the theoretical, experimental and engineering achievements, is still a challenging task when establishing the relationship between the unknown quantities and the measured signal parameters and specialised instruments have shown great advantages for doing some things more effectively than general ones; (5) in bridge damage detection, a problem usually requires the application of different NDT&E techniques; two or more independent techniques are needed to enable confidence in the results.

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

scholarly journals Sparse-TFM Imaging of Lamb Waves for the Near-Distance Defects in Plate-Like Structures

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 503 ◽  
Author(s):  
Haiyan Zhang ◽  
Yaqun Liu ◽  
Guopeng Fan ◽  
Hui Zhang ◽  
Wenfa Zhu ◽  
...  
Keyword(s):  
Phased Array ◽  
Lamb Waves ◽  
High Sensitivity ◽  
Thin Plates ◽  
Rapid Imaging ◽  
Destructive Testing ◽  
Full Matrix ◽  
Sparse Array ◽  
Ultrasonic Phased Array ◽  
Imaging Resolution

The ultrasonic phased array total focusing method (TFM) has the advantages of high imaging resolution and high sensitivity to small defects. However, it has a long imaging time and cannot realize near-distance defect imaging, which limits its application for industrial detection. A sparse-TFM algorithm is adopted in this work to solve the problem regarding rapid imaging of near- distance defects in thin plates. Green’s function is reconstructed through the cross-correlation of the diffuse full matrix captured by the ultrasonic phased array. The reconstructed full matrix recovers near-distance scattering information submerged by noise. A sparse array is applied to TFM for rapid imaging. In order to improve the imaging resolution, the location of active array elements in the sparse array can be optimized using the genetic algorithm (GA). Experiments are conducted on three aluminium plates with near-distance defects. The experimental results confirm that the sparse-TFM algorithm of Lamb waves can be used for near-distance defects imaging, which increases the computational efficiency by keeping the imaging accuracy. This paper provides a theoretical guidance for Lamb wave non-destructive testing of the near-distance defects in plate-like structures.

Analysis of Adaptive Detection Threshold for High Sensitivity Compass Navigation Receiver

2012 ◽  
Vol 239-240 ◽  
pp. 489-493
Author(s):  
Wei Xiang ◽  
Shao Jie Ni ◽  
Wei Wu ◽  
Fei Xue Wang
Keyword(s):  
Probability Distribution ◽  
Cross Correlation ◽  
Detection Threshold ◽  
High Sensitivity ◽  
Correlation Technique ◽  
Optimal Detection ◽  
Adaptive Detection ◽  
Differential Correlation ◽  
Auto Correlation ◽  
Sensitivity Gain

Compared with fixed detection threshold, adaptive detection threshold substantially improves the reception sensitivities in high sensitivity receivers. The optimal detection threshold depends on probability distribution of the received signals. The out-of-phase auto correlation values and cross correlation values of Chinese Compass B1-I signal were analyzed, and the probability distribution of the signal with the differential correlation technique was provided. Then the optimal detection threshold and the sensitivity gain that can be obtained by the adaptive detection threshold were provided.

Triple Correlation Technique for Damage Detection in Composite Materials

2013 ◽  
Vol 588 ◽  
pp. 310-317
Author(s):  
Marcin Strączkiewicz ◽  
Andrzej Klepka ◽  
Wieslaw Jerzy Staszewski ◽  
Francesco Aymerich
Keyword(s):  
Damage Detection ◽  
Composite Structures ◽  
Impact Damage ◽  
Correlation Technique ◽  
Highly Qualified ◽  
Destructive Testing ◽  
New Developments ◽  
Triple Correlation ◽  
Large Structures ◽  
Non Destructive

Over the last few decades a number of different techniques have been developed for impact damage detection in composite structures. The most frequently used methods in Non-Destructive Testing (NDT) are: ultrasonic testing, acoustics emission, X-ray and visual inspection. These methods are quite effective but often require expensive equipment, a large number of transducers or highly qualified staff. Additionally, these techniques are used locally. Therefore monitoring of large structures in many cases is very difficult or even impossible. Recent years have seen many new developments mostly free from these limitations. This paper investigates the triple correlation technique for impact damage detection in composite structures. The method correlates fundamental and higher harmonics of signal vibration response

scholarly journals Quaternion Processing Techniques for Color Synthesized NDT Thermography

2021 ◽  
Vol 11 (2) ◽  
pp. 790
Author(s):  
Pablo Venegas ◽  
Rubén Usamentiaga ◽  
Juan Perán ◽  
Idurre Sáez de Ocáriz
Keyword(s):  
Signal To Noise Ratio ◽  
High Capacity ◽  
Synthetic Data ◽  
Relevant Information ◽  
Color Images ◽  
Destructive Testing ◽  
Application Procedure ◽  
Definition Of ◽  
Characterization Procedure ◽  
Processing Techniques

Infrared thermography is a widely used technology that has been successfully applied to many and varied applications. These applications include the use as a non-destructive testing tool to assess the integrity state of materials. The current level of development of this application is high and its effectiveness is widely verified. There are application protocols and methodologies that have demonstrated a high capacity to extract relevant information from the captured thermal signals and guarantee the detection of anomalies in the inspected materials. However, there is still room for improvement in certain aspects, such as the increase of the detection capacity and the definition of a detailed characterization procedure of indications, that must be investigated further to reduce uncertainties and optimize this technology. In this work, an innovative thermographic data analysis methodology is proposed that extracts a greater amount of information from the recorded sequences by applying advanced processing techniques to the results. The extracted information is synthesized into three channels that may be represented through real color images and processed by quaternion algebra techniques to improve the detection level and facilitate the classification of defects. To validate the proposed methodology, synthetic data and actual experimental sequences have been analyzed. Seven different definitions of signal-to-noise ratio (SNR) have been used to assess the increment in the detection capacity, and a generalized application procedure has been proposed to extend their use to color images. The results verify the capacity of this methodology, showing significant increments in the SNR compared to conventional processing techniques in thermographic NDT.

Sign in / Sign up

Export Citation Format

Share Document