scholarly journals EXPERIMENTAL STUDY OF GUIDED WAVES OVER THE OCEAN RIDGE

2018 ◽  
pp. 54
Author(s):  
Gang Wang ◽  
Hong-Quan Yu ◽  
Jin-Hai Zheng
Keyword(s):  
Guided Waves ◽  
Numerical Models ◽  
Tide Gauge ◽  
Guided Wave ◽  
Long Distance ◽  
Ocean Ridges ◽  
Long Wave ◽  
Refraction Effect ◽  
Ocean Ridge ◽  
Over The Top

Long waves can be trapped by oceanic ridges due to refraction effect, and such guided waves travel along the ridge and transfer their energy to rather long distance. The guided wave is constrained over the top of the ridge and propagates slower than the free long wave, which leads to the largest amplitude waves arriving later and duration of tsunami activity longer. The existence of trapping effect of ocean ridges has not only been demonstrated mathematically (Buchwald 1969; Zheng et al. 2016), but also been verified by the interpretation of tide-gauge data and numerical models on global tsunami events (Koshimura et al. 2001; Titov et al. 2005).

Inspection of Concrete-Metal Rod Interface Using Guided Waves

2000 ◽  
Author(s):  
Won-Bae Na ◽  
Tribikram Kundu ◽  
Mohammad R. Ehsani
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Guided Wave ◽  
Ultrasonic Transducers ◽  
Interface Debonding ◽  
Long Distance ◽  
Steel Rebar ◽  
Steel Bars ◽  
Steel Rebars

Abstract The feasibility of detecting interface degradation and separation of steel rebars in concrete beams using Lamb waves is investigated in this paper. It is shown that Lamb waves can easily detect these defects. A special coupler between the steel rebar and ultrasonic transducers has been used to launch non-axisymmetric guided waves in the steel rebar. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of reinforced concrete structures because the Lamb wave can propagate a long distance along the reinforcing steel bars embedded in concrete as the guided wave and is sensitive to the interface debonding between the steel rebar and concrete.

scholarly journals Nondestructive Inspection of Corrosion and Delamination at the Concrete-Steel Reinforcement Interface

2002 ◽  
Author(s):  
Tri Miller ◽  
Christopher J. Hauser ◽  
Tribikram Kundu
Keyword(s):  
Guided Waves ◽  
Guided Wave ◽  
Ultrasonic Guided Waves ◽  
Reinforcing Steel ◽  
Electromagnetic Acoustic Transducer ◽  
Long Distance ◽  
Steel Bar ◽  
Acoustic Transducer ◽  
Steel Bars ◽  
Aging Infrastructure

This paper explores the feasibility of detecting and quantifying corrosion and delamination at the interface between reinforcing steel bar and concrete using ultrasonic guided waves. The problem of corrosion and delamination of the reinforcing steel in the aging infrastructure has increased significantly in the last three decades and is likely to keep on increasing. Ultrasonic cylindrical guided waves that can propagate a long distance along the reinforcing steel bar are found to be sensitive to the interface conditions between steel bar and concrete. Ultrasonic transducers are used to launch and detect cylindrical guided waves along the steel bar. The traditional ultrasonic testing methods, for instance the pulse-echo method, where reflection, transmission, and scattering of longitudinal waves are used for detecting large voids in concrete, are not very efficient for detecting corrosion and delamination at the interface between concrete and steel bar. For this study four sets of specimens were prepared. They are rebars and plain steel bars with corrosion and physical separation. Transducers used during the experiment are the Electromagnetic Acoustic Transducer (EMAT) and the Piezoelectric Transducer (PZT). The experiment suggests that the guided wave inspection technique is feasible for the health monitoring of reinforced concrete structures. It also reveals that the ultrasonic guided waves are sensitive to the type of steel used and to the rib patterns on the reformed steel bars.

‘Acoustic Fiber’ Aluminum-Clad Copper Cable for Communication and Power Transmission

2015 ◽  
Author(s):  
R. B. Litman ◽  
H. A. Scarton ◽  
K. R. Wilt ◽  
G. J. Saulnier
Keyword(s):  
Guided Waves ◽  
Power Transmission ◽  
Wave Mode ◽  
Guided Wave ◽  
Index Of Refraction ◽  
Propagation Loss ◽  
Solid Core ◽  
Long Distance ◽  
Core Diameter ◽  
The Core

An ‘acoustic fiber’, analogous to optical fiber, is presented as a means of long-distance data and energy transfer. Low-loss axial guided waves are produced along a cable-like waveguide, which is composed of a solid core and a cladding layer, where the cladding’s acoustic speeds of sound, both longitudinal and transverse, exceed those of the core. A similar condition exists in glass fiber optic cables consisting of a core surrounded by a cladding of lower index of refraction. This results in total internal reflection of light at the core-cladding interface and effective confinement of light to the core. A specific acoustic waveguide construction is analyzed, composed of an aluminum cladding with longitudinal wave speed of 6.198 km/s and shear wave of 3.122 km/s and copper core with longitudinal speed of 4.505 km/s, and shear speed of 2.164 km/s. Finite element simulations show that a guided wave mode that is confined largely to the core exists and is capable of propagating long distances with very little loss to the surroundings. A 6 mm diameter aluminum-cladded copper core (2 mm diameter) fiber was found to have a propagation loss of 0.023 dB/m when operating at 2 MHz predict (neglecting material attenuation). When including material attenuation, the same waveguide produced a propagation loss of 0.24 dB/m. Similarly, a 12 mm cladding with 4.8 mm core at 1 MHz had losses of 0.10 dB/m, and a 22 mm diameter cladding with 9 mm core at 500 kHz had losses of 0.062 dB/m. Relationships were found between frequency, total diameter and core diameter yielding the highest efficiencies. The minimum total dimension of an aluminum-clad-copper acoustic fiber was found to have an inverse relationship with frequency. The optimum ratio of core to total diameter was about 0.45 but between values of 0.35 and 0.5, attenuation was relatively constant (insensitive to frequency). Outside of that range, attenuation climbed rapidly. Due to this property, attenuation in properly designed fibers should always be dominated by, and roughly equivalent to, the material attenuation rather than attenuation due to leakage.

Health Monitoring of Piping Weld With Guided Waves

2004 ◽  
Author(s):  
Younho Cho ◽  
Chong Myoung Lee ◽  
Joseph L. Rose ◽  
Ikkeun Park
Keyword(s):  
Guided Waves ◽  
Frequency Tuning ◽  
New Technology ◽  
Mode Selection ◽  
Wave Structure ◽  
Conventional Technique ◽  
Guided Wave ◽  
Long Distance ◽  
Promising Alternative ◽  
Scanning Procedure

In this study, a new technology based on the ultrasonic guided wave to inspect the weld part is presented. The characteristic of a guided wave to travel a long distance over a welded part provides an efficient inspection. This guided wave technique overcomes a tedious scanning procedure using a conventional bulk shear wave angle beam technique. A proper mode and frequency tuning process with knowledge of dispersion curves and wave structure profiles allows us to propose a promising alternative which makes it possible to alleviate such limitations encountered with the conventional technique. Some sample experimental data are also provided with a detailed guideline showing the utility of guided waves when using a proper mode selection for the weldment.

Nonlinear Guided Waves for Structural Health Monitoring: Numerical Algorithm and Application to Railroad Track

2012 ◽  
Author(s):  
Claudio Nucera ◽  
Francesco Lanza di Scalea
Keyword(s):  
Thermal Stress ◽  
Temperature Measurement ◽  
Large Scale ◽  
Guided Waves ◽  
Thermal Stresses ◽  
Numerical Models ◽  
Guided Wave ◽  
Cold Weather ◽  
Test Bed ◽  
Neutral Temperature

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments. UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.

EMAT-Based Inspection of Concrete-Filled Steel Pipes for Internal Voids and Inclusions

2002 ◽  
Vol 124 (3) ◽  
pp. 265-272 ◽  
Author(s):  
Won-Bae Na ◽  
Tribikram Kundu
Keyword(s):  
Guided Waves ◽  
Acoustic Method ◽  
Guided Wave ◽  
Long Distance ◽  
Steel Pipes ◽  
Acoustic Transducers ◽  
Bending Resistance ◽  
Good Potential ◽  
Internal Volume ◽  
Electro Magnetic

Concrete-filled steel pipes have been used as piles for supporting civil and marine structures. These piles provide good bending resistance, and can be easily spliced for long depth installation. However, these piles are usually exposed in hostile environments such as seawater and deicing materials. Thus, the outside corrosion of the steel pipe can reduce the wall thickness and the corrosion-induced delamination of internal concrete can increase internal volume or pressure. In addition, the void that can possibly exist in the pipe reduces the bending resistance. To avoid structural failure due to this type of deterioration, appropriate inspection and repair techniques are to be developed. The acoustic method is attractive for this inspection since it is relatively simple and versatile. Especially, guided wave techniques have strong potentials for this inspection because of long-distance inspection capability. There are different transducer-coupling mechanisms available for the guided wave inspection techniques. Electro-magnetic acoustic transducers (EMATs) give relatively consistent results in comparison to piezoelectric transducers since they do not need any couplant. EMATs are used for transmitting and receiving cylindrical guided waves through concrete-filled steel pipes. It is shown that EMAT-generated cylindrical guided wave techniques have good potential for the interface inspection of concrete-filled steel pipes.

Extracting Quantitative Information on Pipe Wall Damage in Absence of Clear Signals From Defect

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Amit Shelke ◽  
Umar Amjad ◽  
Milos Vasiljevic ◽  
Tribikram Kundu ◽  
Wolfgang Grill
Keyword(s):  
Guided Waves ◽  
Pipe Wall ◽  
Low Frequency ◽  
Time History ◽  
Quantitative Information ◽  
Guided Wave ◽  
Long Distance ◽  
Acoustic Transducers ◽  
Small Defect ◽  
Electro Magnetic

It has been well established that guided waves are sensitive to structural damages encountered on their path of propagation and for this reason this technique is very efficient for distinguishing defective structural components from defect-free ones. Although the guided wave technique can identify a specimen having a distribution of defects, detecting and quantifying a small defect on its path from a long distance, as required for structural health monitoring (SHM) applications, is not an easy task for the guided wave inspection technique even today, especially when the transducers cannot come in direct contact with the pipe wall. The current technological challenges for pipe inspection by generating guided waves using noncontact transducers are to detect a small defect on the pipe wall and estimate its location and size from a long distance when the reflected signal from the defect cannot be clearly identified as is the case for low frequency guided waves that can propagate long distances. Electro-magnetic acoustic transducers (EMATs) are used here to generate guided waves in the pipe by the noncontact technique. This paper shows how small a defect in a pipe wall can be detected and its location and dimension can be estimated using relatively low frequency guided waves generated and received by EMATs even when the defect signal is not clearly visible in the time history plot because various wave modes reflected from the defect and pipe ends overlap.

Stress evaluation in seven-wire strands based on singular value feature of ultrasonic guided waves

2021 ◽  
pp. 147592172110053
Author(s):  
Qian Ji ◽  
Li Jian-Bin ◽  
Liu Fan-Rui ◽  
Zhou Jian-Ting ◽  
Wang Xu
Keyword(s):  
Dispersion Curve ◽  
Support Vector Regression ◽  
Stress Level ◽  
Guided Waves ◽  
Guided Wave ◽  
Singular Value ◽  
Support Vector ◽  
Support Vector Regression Model ◽  
Various Boundary Conditions ◽  
Wave Methods

The seven-wire strands are the crucial components of prestressed structures, though their performance inevitably degrades with the passage of time. The ultrasonic guided wave methods have been intensely studied, owing to its tremendous potential for full-scale applications, among the existing nondestructive testing methods, for evaluating the stress status of strands. We have employed the theoretical and finite element methods to solve the dispersion curve of single wire and steel strands under various boundary conditions. Thereafter, the singular value decomposition was adopted to work with the simulated and experimental signals for extracting a feature vector that carries valuable stress status information. The effectiveness of the vector was verified by analyzing the relationship between the vector and the stress level. The vector was also used as an input to establish a support vector regression model. The accuracy of the model has been discussed for different sample sizes. The results show that the fundamental mode dispersion curve offset on the high-frequency part and cut-off frequency increases as the boundary constraints enhance. Simulated and experimental results have demonstrated the effectiveness and potential of the proposed support vector regression method for evaluating the stress level in the strands. This method performs well even at low stress levels and the reliability can be enhanced by adding more samples.

Ultrasonic unilateral double-position excitation lamb wave defect detection and quantification method for ground electrode of transmission tower

2021 ◽  
pp. 1-15
Author(s):  
Kuan Ye ◽  
Kai Zhou ◽  
Ren Zhigang ◽  
Ruizhe Zhang ◽  
Chunsheng Li ◽  
...  
Keyword(s):  
Guided Waves ◽  
Power Transmission ◽  
Geometric Model ◽  
Guided Wave ◽  
Quantization Error ◽  
Dispersion Function ◽  
Stable Operation ◽  
Transmission Tower ◽  
Ultrasonic Guided Wave ◽  
Transmission Towers

The power transmission tower’s ground electrode defect will affect its normal current dispersion function and threaten the power system’s safe and stable operation and even personal safety. Aiming at the problem that the buried grounding grid is difficult to be detected, this paper proposes a method for identifying the ground electrode defects of transmission towers based on single-side multi-point excited ultrasonic guided waves. The geometric model, ultrasonic excitation model, and physical model are established, and the feasibility of ultrasonic guided wave detection is verified through the simulation and experiment. In actual inspection, it is equally important to determine the specific location of the defect. Therefore, a multi-point excitation method is proposed to determine the defect’s actual position by combining the ultrasonic guided wave signals at different excitation positions. Besides, the precise quantification of flat steel grounding electrode defects is achieved through the feature extraction-neural network method. Field test results show that, compared with the commercial double-sided excitation transducer, the single-sided excitation transducer proposed in this paper has a lower defect quantization error in defect quantification. The average quantization error is reduced by approximately 76%.

scholarly journals Longitudinal Guided Wave Inspection of Small-Diameter Elbowed Steel Tubes with a Novel Squirrel-Cage Magnetostrictive Sensor

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Yao Liu ◽  
Xiucheng Liu ◽  
Chehua Yang ◽  
Wenxin Guo ◽  
Bin Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Guided Waves ◽  
Mode Conversion ◽  
Small Diameter ◽  
Longitudinal Mode ◽  
Guided Wave ◽  
Wall Defect ◽  
Squirrel Cage ◽  
Simulation Results ◽  
Magnetostrictive Sensor

In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.

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