The determination of material properties for very small specimens such as biological cells or semiconductor microchips is extremely difficult and has been a challenging issue for several decades. One important constraint during these measurements is not to harm the specimens during the test process because the specimens, biological cells in particular, are vulnerable to the test itself even during a short period of testing time.Nondestructive evaluation (NDE) is the only suitable precess for such applications. It is fast, causes no disturbance and can give a real time response while being cost effective. Many NDE methods are available today, such as, laser based techniques, Radiography, Magnetic techniques, High resolution photography and other optical techniques, MRI, acoustic and ultrasonic techniques to name a few. Ultrasound is the most popular tool for NDE. As specimens become smaller, the need for shorter wave length ultrasound increases dramatically.The use of acoustic waves in microscopy technology provides many more benefits than its conventional optical microscope counterpart. One such benefit is its ability to inspect a specimen in dark. Another is the capability to see inside an optically opaque specimen. Today, very high frequency, higher than 1 Giga Hertz (109 Hz), ultrasound is being used. This technology has improved at the same pace as the development of electronics and computer science. In acoustic microscopy experiments wave speed and wave attenuation in the specimen are measured by the V(f) technique. A specimen's density, Poisson's ratio and Young's modulus are directly related to the wave speed. V(f) method, as discussed in this dissertation, has some advantages over the more commonly used V(z) method. In order to correctly estimate the wave speed and attenuation in the specimen, the transducer modeling should be completed first. The Distributed Point Source Method (DPSM) is used in this dissertation to model a 1 GHz acoustic microscope lens. Then the model-predicted pressure field is used in a FORTRAN program to calculate the thickness profile and properties of biological cell specimens from experimental data.Transducer modeling at 1 GHz has rarely been attempted earlier because it requires an immense amount of computer time and memory. In this dissertation 1 GHz transducer modeling is conducted by taking advantage of the axisymmetric geometry of the acoustic microscope lens. This exploitation of symmetry in the modeling process has not been attempted prior to this dissertation.

A wideband digital signal acquisition instrument intended primarily for ultrasonic experimentation has been designed and built. It comprises an integrated array of modules which combine to provide: a pulser for transducer excitation, wideband amplification (>80 MHz bandwidth), high speed sampling (>160 MHz), on-board memory (4K x 16 bits capacity), control hardware and real-time coherent averaging. The integration of the modules offers significant benefits over systems consisting of a number of separate items of equipment. The major benefit is a reduction in acquisition time which is accomplished as follows. The time relationship between the sampling clock and the input signal is controlled to minimise the signal repetitions required for interleaving. This is achieved by triggering the input signal using a pulser board locked to the sample clock. In addition, signal averaging is implemented in hardware using two memory modules and an adder module. Since the time relationship between the sampling clock and the input signal is controlled it cannot be tested using a sinewave because it is not possible to produce a sinewave which is correlated with the sampling clock. Instead, a rectangular pulse, triggered by the instrument, is applied to a single-pole low pass filter to provide the test signal. The time constant and start time is ascertained and used to reproduce the single-pole response. The reproduced response is then compared to the sampled signal to produce an error plot from which the system's linearity and effective bits can be deduced. As the system was designed for fast acquisition, and hence has a short aperture time, it is highly applicable to dynamic processes. The dynamic process application chosen was the measurement of absorption and velocity on rapidly flocculating and sedimenting colloids.

Thesis (M.S.) in Mechanical Engineering--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 76-83).

Thesis (M.S. in civil engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Dec. 28, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 51).

No description available.

Thesis (Ph.D.)--Tufts University, 2000. / Adviser: Masoud Sanayei. Submitted to the Dept. of Civil Engineering. Includes bibliographical references (leaves 152-159). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [149]-153).

Thesis (M.S.)--Rowan University, 2006. / Typescript. Includes bibliographical references.

Ultrasonic velocity and attenuation measurements have been used to characterise a range of phosphate bonded, alumina filled, magnesia ceramics and other ceramic materials... Measurements were made over a range of frequency from 50kHz - 1 OM Hz, using a variety of commercial probes and equipment, and a variety of techniques. An ultrasonic double-probe method was used to monitor the setting process of the cementitious ceramics using commercial 2.25MHz and 2MHz transducers, for compressional and shear wave modes, respectively, in samples with alumina content in the range of 0 - 60 wt 0/0. The elastic properties of the material were determined from ultrasonic velocity measurements and were found to be dependent upon the filler volume fraction. The measured elastic moduli were found to Increase as porosity decreased, and this effect might possibly be used to estimate porosity. The composition dependence of the elastic moduli is compared with the Hashin and Shtrikman theoretical bounds for the elastic moduli of two-phase materials. All data lie between these bounds, suggesting that the alumina particles were well dispersed and well bonded to the matrix. However, the fact that the data are slightly above the lower bound suggested that the particles are not spherical, and this, together with other evidence obtained from an analysis of reaction rates, indicates the predominence of plate-like gram structures.

Gas Metal Arc welding (GMAW) is one of the primary techniques used to join structural components together. The major obstacle precluding full closed-loop control of GMAW has been the lack of robust techniques using non-destructive and non-contact sensors capable of operating in high temperature and harsh environments typical of GMAW processes. This research uses laser generated ultrasound and electromagnetic acoustic transducer (EMAT) to receive ultrasound. Previous research has focused on ultrasonic shear wave time of flight (TOF) techniques to determine weld penetration depth, a key measure of weld quality. The objective of this research was to use a new technique, frequency modulation of a laser phased array (FMLPA), to determine weld penetration depth. Theoretical background of the FMLPA was developed. An analytical model of the FMLPA was derived and validated through experimentation. The FMLPA was experimentally validated. However, both the FMLPA and shear wave TOF techniques have proven to be impractical for real-time control. These techniques are impractical because the required ultrasonic waves are difficult to acquire due to attenuation and interference from other waves. A new type of wave called the RGLS wave was discovered during the course of this research. The RGLS wave was used to create a new RGLS TOF method for measuring weld penetration depth. The RGLS TOF method for measuring weld penetration depth has proven to be highly accurate, precise, and repeatable. The RGLS TOF method for measuring weld penetration depth has been demonstrated to work both off-line after welding and real-time during welding. Although the FMLPA and shear wave TOF technique was proven to be impractical, the RGLS TOF method has met the ultimate goal of this research area. Other new methods such as the RGSL, RGLL, and RGSS TOF methods related to the RGLS TOF method was also developed. The RGLS TOF method is suited for non-destructive and non-contact sensing. It will help future researchers achieve closed-loop control and automation of the GMAW process, which will help to improve quality and efficiency of welding, and also reduce waste and cost of welding parts together.