Papers by Keyword: Ultrasonic Guided Waves

Abstract: According to the characteristics of ultrasonic guided wave inspection, An exciting power, used for exciting ultrasonic guided waves in pipeline is designed based on DDS and FPGA. The excitation source consists of FPGA, D/A conversion circuit, a low-pass filter circuit and power amplifier circuit. Constructing DDS based on FPGA as the controller and signal generator. Filter circuit and power amplifier circuit are designed in this paper. The experiment results show that the excitation source can have high voltage and high frequency output capability, and can generate desired signal type with a good accuracy to fit the requirements in practice. It can be conveniently used for pipeline ultrasonic guided wave detection.

Abstract: Cone-like pipes are serving in some special area, not common but always pivotal. In order to extend the ultrasonic guided wave detection technique from hollow cylinder to hollow cone, this paper make numeric analysis on both of them. Firstly, some basic theory about the guided waves and related simulation method were introduced. Secondly, a standard hollow cylinder was selected and made simulation for proving the validity and obtaining a group of pre-set parameters for following cone simulation. After that, the simulation about the hollow cone was made and its results were presented. At last, some conclusions were found by comparing the results of two different simulations. The guided waves propagating in hollow cone exhibit a slower velocity, a quicker dispersion ration and a more noisy background.

Abstract: Monitoring the condition of steel corrosion in reinforced concrete (RC) is imperative for ensuring structural serviceability and durability of RC structures. The techniques based on ultrasonic guided wave (UGW) gain more and more popularities as they have many advantages for monitoring corrosion in reinforced concrete. In this paper, UGW based monitoring techniques in the past decade are reviewed, including corrosion monitoring mechanism and feature extraction, monitoring corrosion induced deboning, monitoring pitting corrosion, monitoring corrosion induced interface roughness. Finally, the challenges and future trends in the development of UGW based monitoring techniques for condition assessment of corrosion inreinforced concrete are put forward in this paper.

Abstract: Piezoelectric ceramics sheets are used to excite and receive ultrasonic guided waves in a steel bar. The multi-modes and disperse characteristics of guided waves within that are investigated theoretically and experimentally. The results show that ultrasonic guided waves can be generated and received by piezoelectric ceramics sheets which can be used to measure the length of the steel bar and detect the defection in it.

Abstract: Structural health monitoring refers to the process of making an assessment, based on nondestructive, in-situ, autonomous measurements, about the ability of a structure to perform its intended function. This paper presents work done on a bolted connection in carbon-fiber reinforced polymer composite materials. A composite specimen is bolted in a double lap joint configuration to a test apparatus that applies an increasing tensile load. Ultimately, the load results in bearing failure of the material around the bolt hole. To monitor the progression of damage, macro fiber composite sensors are bonded in a circular array around the bolt hole. These sensors are then used to generate ultrasonic guided waves, a popular technique in nondestructive evaluation because of the favorable combination of propagation distance and sensitivity to damage. As the specimen is subjected to increasing load levels, measurements are taken repeatedly and compared with one another. Because damage will change the local mechanical properties of the material, the ultrasonic waves passing through the damaged region will be scattered differently in each direction, resulting in a different waveform arriving at the other surrounding sensors. By applying appropriate signal processing techniques, these changes may be interpreted as indicating the extent of damage that has occurred in the specimen. Preliminary analysis is presented demonstrating the correlation between changes in received strain signals and increasing damage levels.

Abstract: In this work, Lamb wave generation and propagation have been modelled in composite plates. Actuation and acquisition of signals when the PZT transducers are tied to the structure or bonded with an adhesive layer are investigated. The effect of adhesive thickness and actuation frequency of Lamb wave have been examined.

Abstract: A SMART Platform is developed based on sensor readings for Structural Health Monitoring of a stiffened composite panel. The platforms main function is divided into three categories: Passive sensing, Active sensing and Optimal sensor positioning. The platform has self-diagnostic capabilities, i.e. prior to its application the health of the sensors and their connection will be checked to avoid any false alarm. Passive sensing results in impact location and force magnitude detection. Active sensing is performed for damage detection. It results in detecting the damage location and severity. Finally the optimal sensor location can be provided given the number of sensors and probability of detection value. This platform is the first step in applying the developed SHM methodologies to real size structures in service load conditions.

Abstract: Among structural concerns for the safety of rail transportation are internal flaws and thermal stresses, both of which can cause disruption of service and even derailments. Ultrasonic guided waves lend themselves to addressing both of these problems. This paper reports on two inspection systems for rails being developed at UCSD under the auspices of the US Federal Railroad Administration. Both systems utilize ultrasonic guided waves as the main probing mechanism, for the two different applications of flaw detection and thermal stress detection.

Abstract: The difference between inside circumferential defects and outside circumferential defects was proved using the theory of reflection waves, the course of propagation and reflection from inside circumferential defects and outside circumferential defects in steel pipes was simulated with L(0,2) mode by the numerical simulation program ANSYS, and the curves of the reflection waves were obtained. The investigation indicated that the relationship between reflection coefficient of each kind of circumferential defects and the circumference of the defects was linear; in additional, it was found that the reflection coefficient of outside circumferential defects was a little higher than the reflection coefficient of inside circumferential defects; the difference between inside and outside circumferential defect became more obvious as the thickness of the defect increases. So the results provide a basis for detecting and distinguishing circumferential defects of pipes.

Abstract: In this paper,application of defect detection by ultrasonic guided waves in springs has been studied in three aspects,which are theoretical calculation, simulation modeling and experiments.For the springs structure is helix and it can not be directly described easily,less work has been done on theoretical calculation of elastic wave propagation in the springs.The elastic wave equation of the spiral structure is established and calculated numerically here,considering the theoretical calculation helps to quantitative analyze the law of elastic wave propagation in the springs.Then guided waves dispersion relations corresponding is achieved.The experimental results of spring field testing agree well with the theoretical calculations and simulations,indicating the effectiveness of ultrasonic guided waves inspection in springs.