Detection of Internal Cracks in Square Billets Using Time of Flight of Longitudinal Waves

Abstract

We propose a method for the reconstruction of internal cracks using time of flight (TOF) of longitudinal waves. Since the longitudinal wave is the fastest elastic wave, it is possible to reconstruct cracks using a matrix method with apparent sound velocities calculated from the TOF. This method can neglect mode transformation and other waves because the first wave received is always the longitudinal wave. In addition, this method has the potential to be free from a blind sector and to detect the cracks precisely, because it is a transmission method and uses time domain analysis. We simulate crack detection using the transmission-line matrix (TLM) method. This proposed method detects cracks regardless of their location, direction, and number. It was also possible to detect the cracks when their length was smaller than the wavelength or when the billet had some error in its shape. This technique is expected to be useful for ultrasonic testing.

Detection of fish passing through a narrow path using reflected and transmitted ultrasonic waves

“…In the field of nondestructive inspection using ultrasound, increases in the TOFs of transmitted waves caused by diffraction at voids in steel have been observed, even in transmitted waves with shorter wavelengths than the size of the voids. [35][36][37][38][39] Therefore, there is a possibility that the deviations in the ΔTOFs in the transmitted waves around the swim bladder were caused by diffraction, although the swim bladder is a few centimeters 11) and the wavelength of the transmitted ultrasound in the fish body is a few millimeters. These profiles of transmitted waves through a fish body show different characteristics from the profiles of the echoes from fish.…”

“…In addition, waves transmitted through the fish body have not been explored, although transmitted waves have been used for nondestructive inspection. [35][36][37][38][39] For the measurement of fish behavior using a small number of transducers rather than acoustic cameras, it is necessary to extract many features from the ultrasonic signals from each part of the fish body. Here, we investigated the properties of echoes and transmitted waves from a fish body, from the tail to the head, to construct a fish detection method with a simple measurement structure in a narrow path.…”

Transmission detection of internal defects in billets using shear ultrasonic waves

“…For these reasons, research on transmitted waves, available for billets, especially using the time-of-flight (TOF), has been conducted in recent years. [18][19][20] In this method, An ultrasonic wave is injected from a certain surface, and the transmitted wave is measured by a transducer from the other surface, and the deviation in TOF of the transmitted wave is used to detect the defect. Compared to the TOFD method, the method used in this study has the advantage that the transmitting and receiving transducers are placed face to face and the transmitted waves can be used to receive a constant amplitude, so it can be applied to thick billet.…”

Direction of Arrival Estimation Based on Delayed-Sum Method in Reverberation Environment

“…The proposed method of estimating DOA has high tolerance to the effect of reverberation and can be applied to the measurement of the difference in the time of flights. [20][21][22][23][24][25][26][27][28][29][30] This paper consists of five sections. In x2, we describe the algorithmic procedure of the proposed signal processing.…”