Modeling the Propagation of Bounded Beams Through Curved Interfaces

In modeling ultrasonic immersion inspections involving complex geometries, one of the more difficult tasks is to predict the effect that a curved surface has on a beam of sound as it propagates from the fluid into the solid. In this paper, we will consider a hierarchy of models for this problem (see Fig. 1)

Predictions of Pulse-Echo Ultrasonic Signals from Cracks Observed Through an Interface with a Step Discontinuity: Comparison with Experiments

In ultrasonic nondestructive evaluation, one of the factors that can greatly affect the inspectibility of a part is the condition of its surface. In nuclear reactor components, factors such as weld overlay, claddings, grinding and diametrical shrink can generate interfaces with wavy, corrugated or abruptly stepped topographies. These large scale surface roughnesses could, in turn, cause excessive beam distortion and produce unreliable results. Therefore, there has been a need to quantify the adverse effects of surface conditions during ultrasonic inspections

Application of Gauss-Hermite Beam Model to the Design of Ultrasonic Probes

Work is currently underway to develop and test prototypic ultrasonic instrumentation that will produce unipolar stress pulses in a pulse-echo mode. The instrument will be used to detect and characterize flaws in materials and for the measurement of material properties important in material processing applications. In conjunction with this work, a Gauss-Hermite Beam Model [1,2,3,4] is used to predict the response of various transducer element geometries to maintain the unipolar response over a longer propagation distance

Modeling of Ultrasonic Signals from Weak Inclusions

Recent research efforts aimed at improving the detection of hard-alpha inclusions have emphasized the need for accurately modeling the responses from such weakly-reflecting inclusions. The need arises because of the rare natural occurrence of hard-alpha inclusions, and consequently, the lacks of suitable experimental samples. These difficulties lend impetus to the application of signal modeling to augment and extend the experimental data in assessing detectability. Currently, a new approach is being developed for the purpose of predicting time-domain echoes from inclusions of specified morphology. This work is the continuation of our previous study of flat-bottomed holes [1–2] in constructing a methodology for estimating the probability of detection of flaws in titanium alloys based on a combination of physical and statistical models

Development and Comparison of Beam Models for Two-Media Ultrasonic Inspection

This paper reports on an effort to model the radiation pattern of a submerged ultrasonic transducer exciting a beam which is incident on a liquid-solid interface. The important aspects of this process are the diffraction of the beam as it propagates in the liquid and solid media, focussing of the beam due to a lens at the transducer face and/or the curvature of the interface, and aberrations induced by refraction at the interface.</p

Application of magnetic attachments in implant-supported prostheses - A preliminary report

One factor which influences the performance of ultrasonic examinations is the condition of the surface of a component through which the ultrasound must pass to enter the material. Often in nuclear reactor components, factors such as weld overlays, claddings, and diametrical shrink can give part surfaces a wavy, corrugated, or abruptly stepped topography. Having to pass an ultrasonic probe over such a surface during an inspection can result in a redirection of beam energy, beam partitioning, or possibly a partial truncation of the beam. These factors could leave regions of the part uninspected or give rise to mislocation of defects or geometrical reflectors

The Social space in guangzhou city, China

Principal components analysis and cluster analysis we used to analyze the urban social spatial structure of socialist China, using the city proper of Guangzhou in 1984 as the study area. Unlike the urban social spatial structure in Western cities, which are commonly differentiated by socioeconomic status, family status, and ethnicity, it was found that the main components of social space in Guangzhou are population density, educational level, employment, housing quality, and household composition. Five types of social areas are identified: (i) high density, mixed function areas, (2) cadre (government worker) areas, (3) worker areas, (4) intellectual areas, and (5) scattered agricultural areas. The spatial pattern of the social areas of Guanghou has a concentric elliptical shape. The city is composed of a high-density, mixed-function center surrounded by consecutive rings of workers' residences and agricultural land, with a cadre sector abutting the northeastern edge of the city center and two intelectual clusters within the worker areas. The urban social spatial structure of Guangzhou reflects the history of urban development, the housing allocation system, and socialist urban land use planning. Occupation and the location of employment were the major determinants of residential location and the social spatial structure of Chinese cities

Method of HDR image acquirement based on space light modulator

A new acquirement method is offered, in which a space light modulator is used to acquire images with different exposure, and then a HDR image is made with these images. The principle of this method is discussed, and experiment system including LCOS and CMOS is built up to acquire a series of images with different exposure. HDR image is composed with synthesize arithmetic. The system is cheap and easy to extend.link_to_subscribed_fulltex

Ultrasonic Transducer Radiation through a Curved Fluid-Solid Interface

A number of typical ultrasonic immersion inspections require the transducer radiation to propagate through components with non-planar surfaces. As the complexity of the component’s surface increases in terms of shape and curvature, the effects of the part’s curvature on the transmitted wavefield become difficult, if not impossible, to predict by simple heuristic approaches. The development of accurate transducer beam models that can handle these types of fluid-solid interfaces, therefore, becomes essential