For the long range inspection of ultrasonic guided wave using array transducer, phase tuning methods are quite often adopted to generate ultrasonic guided waves with particular modes. The phase tuning method is able to control wave modes but not to focus waves on the defects under interrogation. Thus, a robust tool that can control not only generated wave modes but also focus the guided waves on the flaw is strongly desired. To address such a need, in this study, we adopted the time reversal technique for focusing ultrasonic guided waves generated by array transducers on the defects since the time reversal technique can provide proper time delays for focusing on the defect and tuning wave modes. For investigation and verification of the time reversal method, we performed focusing of ultrasonic guided waves on the three types of flaws generated from an array transducer with time delays calculated by the D.O.R.T method using numerical simulation software. Then, we compared results obtained by adopting the time reversal technique to those by a conventional method. In this paper, numerical simulation results and comparison results were presented.
A 3D model based on the finite element method (FEM) was built to simulate the infrared thermography (IRT) inspection process. Thermal contrast is an important parameter in IRT and was proven to be a function of defect parameters. Parametric studies were conducted on internal defects with different depths, thicknesses, and orientations. Thermal contrast evolution profiles with respect to the time of the defect and host material were obtained through numerical simulation. The thermal contrast decreased with defect depth and slightly increased with defect thickness. Different orientations of thin defects were detected with IRT, but doing so for thick defects was difficult. These thermal contrast variations with the defect depth, thickness, and orientation can help in optimizing the experimental process and interpretation of data from IRT.
Ultrasonic guided waves have been widely utilized for long range inspection of structures. Especially, development of array guided waves techniques and its application for long range gas pipe lines(length of from hundreds meters to few km) were getting increased. In this study, focusing algorithm for array guided waves was developed in order to improve long range inspectability and accuracy of the array guided waves techniques for long range inspection of gas pipes, and performance of the developed techniques was verified by experiments using the developed array guided wave system. As a result, S/N ratio of array guided wave signals obtained with the focusing algorithm was increased higher than that of signals without focusing algorithm.
In this study, the expanded multi-Gaussian beam model is adopted to develop a model to calculate the ultrasonic beam fields radiated from an ultrasonic phased array transducer. Combining this beam model with three other components including time delays, a far-field scattering model and a system efficiency factor, we develop a complete ultrasonic measurement model for predicting the phased array ultrasonic signals that can be captured from a flat-bottom hole in a steel specimen in a pulse-echo set-up using an array transducer mounted in a solid wedge. This paper describes the complete model developed with its key ingredients.
In this paper an ultrasonic measurement model is developed using three main elements: 1) a multi‐Gaussian beam model for simulating the ultrasonic wave fields incident on a flaw 2) a hierarchical triangular meshing (HTM) method for representing the flaw geometry and 3) the Kirchhoff approximation for modeling the waves scattered from the flaw Using this measurement model, we have simulated the angular scattering responses for pores, cracks, and stringer‐like flaws. The possibility of using such results for flaw classification studies is discussed.
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