The use of synthetic focusing of torsional guided waves for detecting and sizing defects in pipes using an array of piezoelectric shear transducers clamped around the pipe circumference has been investigated. The performance of the focused system is tested and compared to an unfocused system using data from finite element simulations on pipes of different diameters with circumferential cracks; ...

It is shown that the dispersive Rayleigh wave propagating around a concave cylindrical surface is substantially less attenuated by fluid loading than the corresponding wave on a flat surface. First, the analytical solution for vertically polarized shear wave scattering from a fluid-filled cylindrical cavity is formulated in the time domain, then the signal of interest is gated out and spectrum ...

This paper describes a wave and finite element (WFE) method for the numerical prediction of wave propagation in axisymmetric structures. A small segment of the structure is modelled using conventional finite element methods, commonly using a commercial package, and the mass and stiffness matrices found. This typically involves a single shell element or, especially for laminate structures, a sta...

In this paper, the reflection of ultrasonic guided waves from simple dent in pipes has been investigated using finite element method and the relationship between reflection coefficient of these waves and deformation rate has been determined. Also, the effect of the parameters of wave generation source on the generated wave field has been investigated using normal modes expansion method. At firs...

BACKGROUND Arterial stiffness directly influences cardiac function and is independently associated with cardiovascular risk. However, the influence of the aortic reflected pulse pressure wave on left ventricular function has not been well characterized. The aim of this study was to obtain detailed information on regional ventricular wall motion patterns corresponding to the propagation of the r...

In cylindrical shells, the lowest natural frequency is not necessarily associated with the lowest wave index. In fact, the natural frequencies do not fall in ascending order of the wave index either. Solution of the vibration problem of cylindrical shells also indicates repeated natural frequencies. These modes are referred to as double peak frequencies. Mode shapes associated with each one of ...

Electromagnetic acoustic transducers (EMATs) can generate non-dispersive T(0,1) mode guided waves in a metallic pipe for nondestructive testing (NDT) by using a periodic permanent magnet (PPM) EMAT circular array. In order to enhance the excitation efficiency of the sensor, the effects of varying the number of elements of the array on the excitation efficiency is studied in this paper. The tran...

AIMS the ratio of early diastolic transmitral flow velocity (E) to early diastolic mitral annular velocity (E(a)) is frequently used to predict an increase in left ventricular filling pressure (LVFP). However, this approach has several limitations. The aim of this study was to test whether additional information is gained by new echocardiographic indexes utilizing strain and strain rate (SR) de...

To simulate pulse wave propagation, we set up a wave propagation model using blood-wall interaction in previous work. In this paper, our purpose is to investigate wall stress and deformation of the wave propagation model. The finite element method is employed for solving the governing equations of blood and wall. Our results suggest that there are two peaks in the circumferential stress and str...