Material Characterization of Layered Structures with Ultrasound

AbstractThis contribution presents a method for the simultaneous determination of sound velocity and thickness of a system consisting of two layers. To obtain additional information, beside the time of flight (TOF), the amplitude is evaluated. The amplitude of a reflected sound wave depends on the position of the interface in the sound field of the probe and is maximal, if the focus lies on the interface. The focus position is varied by the use of an annular array and the amplitude as a function of the adjusted focus position is evaluated. Since the sound field of the ring elements of the annular array has distinctly side lobes, transverse waves are excited in the specimen and the sound velocity of the transversal wave can also be determined.The method is demonstrated for the determination of layer thicknesses and sound velocities (longitudinal and transversal) on a two layered system

A review of environmental noise protection in Hong Kong

Integral transform methods are applied to calculate the sound field in a solid half-space generated by a transducer [1]. To overcome the restriction of plane interfaces and to calculate an extended three-dimensional transient field in a layered body with non-parallel and curved interfaces a separation approach was developed [2]. The separation method was applied successfully to obtain calculation programs for the design of ultrasonic transducers with time-harmonic excitation. Figure 1 shows the different approaches to calculate the sound field generated by a transducer. While the approaches A and B are suitable to simulate the time-harmonic sound field in a two-layered problem (angle beam probe coupled on a half-space) [3], the approach C yields the time-harmonic sound field in a layered test object with curved interfaces [4,5]. In continuation of way C, a superposition of time-harmonic wave fields (harmonic synthesis) yields the transient sound field in a layered body with curved interfaces [6]. This is an optimized approximation method. The direct method D is based on transient Green’s functions. This approach is an exact calculation of the transient sound field in a half-space or in a layered medium with plane interfaces [6,7]. Therefore, it is used to evaluate the optimized approximation method [6]

Annular arrays for novel ultrasonic measurement techniques

The paper shows how the precise knowledge of the sound field of an ultrasonic annular array can contribute to the development of novel measurement techniques. Emphasis is placed on (a) a non-invasive method for sound velocity measurements in fluids using the echo signals from scattering p]articles, (b) a non-invasive method for the combined determination of thickness and sound velocity in layered structures by using a novel focusing technique, and (c) a non-scanning curvature measurement method exploiting the wave front curvature of a reflected wave. To demonstrate the methods, the principles as well as results of simulations and measurements are discussed

Non-scanning measurement of local curvature with an ultrasound annular array

The paper studies a novel approach for measuring local object curvature radii without scanning. Instead of scanning, an ultrasound annular array is used, and the phase and amplitude differences on the different receiver rings, which contain the curvature information, are used to determine the object curvature radius. Two evaluation methods are compared: One method is based on changing the focus of the transducer, whereas the other one is based on measuring phase differences between several receiving channels

Inclusive two-particle correlations in 40 GeV/c pi /sup -/p collisions and particle production mechanisms

Inclusive two-particle correlations in rapidity variables between pi /sup +/ pi /sup -/, pi /sup +/ pi /sup +/ and pi /sup -/ pi /sup -/ obtained in 40 GeV pi /sup -/p collisions are discussed in the framework of the Mueller Regge model and the multiperipheral cluster model. The data show features similar to the data reported at much higher energies from the CERN ISR. This behaviour is more easily understood from the multiperipheral cluster model. Data on transverse momentum correlations in the same reactions can be qualitatively understood from the same model. (23 refs)