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A Computerized Ultrasonic Gauging System (CUGS) has been developed to generate very precise topographical maps of the outer and inner surfaces of tubes during various stages of manufacture and life-cycle of the parts. Measurements of the tube dimensions are obtained with a resolution of 2.5 μm (10−4 inches) and accuracies of the order of 10 μm (4×10−4 inches) or better. A typical output of CUGS is an ultrasonic image, in which the horizontal and vertical axes represent the axial and angular position of the part, respectively[1]. The system is currently utilized to gauge tubes as long as 7.5 m (25 feet) resulting in the acquisition of more than 15,000,000 data points, which require up to 60 Mbytes of disk memory on a computer. A Wavelet Transform Image decomposition technique was developed for compression and processing of the ultrasonic images, resulting in a great decrease in time and resources needed to perform such operations. Waveletbased image analysis has two distinct characteristics: multiresolution and high spatial localization[2]. Multiresolution refers to the possibility of obtaining representations of the same image with different resolutions. The high spatial localization properties of the filters used for the wavelet decomposition can also be utilized for the enhancement of features such as erosion pattern without the loss of localization, a problem commonly encountered in Fourier analysis. In the application here discussed, CUGS is utilized to map the wear of the internal surface of steel tubes, before and after exposure to extreme environments involving temperature, pressure, corrosive gases and mechanical forces.

A Computerized Ultrasonic Gauging System (CUGS) has been developed to generate a visually useful as well as a quantitative mapping of the outer and inner surfaces of tubes during the various stages of manufacture. Measurements of the outside radius and of the thickness of the tube are performed with a resolution of 0.0025 mm (0.0001 in) as the part is rotating on a lathe with speeds of up to 1000 surface feet per minute. Typically, 500 measurements are made and displayed for each revolution of the part. The transducer is scanned along the axial dimension by the lathe carriage to which it is attached. The axial scan rate is typically 0.25 mm (0.01 inches) per revolution, resulting in very precise topographical maps of all the cylindrical surfaces of the part. The system was developed so that the run-out and the straightness of the part are calculated from the dimensional data obtained. The surface finish of the outside and inside of the part is also available in a post process, color mapped, display, and CUGS is also capable of simultaneously detecting internal flaws in the part. A fluid stream couples the ultrasound to the part, and high speed electronics is employed to perform the measurements. A description of the system is presented with experimental results.

The measurement of porosity content in composites has been an area of interest to the NDE community. Theoretical and experimental work have related ultrasonic scattering to the amount of porosity in composites and metals [1]. By monitoring the frequency dependence of the ultrasonic scattering, information concerning the amount of porosity in the material can be determined. The scattering of ultrasonic waves can be measured by monitoring the attenuation of the waves as they travel through a material. To accurately measure the attenuation associated with material properties such as porosity scattering, corrections must be made to the ultrasonic amplitude data. These corrections concern other ultrasonic loss mechanisms that are attributed to the measurement process such as surface or boundary effects and transducer focus effects.

An ultrasonic system has been assembled to provide real time thickness gauging on a lathe during a cutting operation. The same ultrasonic system provides flaw detection so that NDE of the part being machined is simultaneously accomplished. A key feature for good gauging performance is that the ultrasonic apparatus is configured to minimize sensitivity of the time interval measurements, used for the gauging operations, to variations in echo amplitude over a 30 dB dynamic range. Thickness data or flaw echo data can be displayed in a pseudo colored image format in near real time. The goal for this research is to make thickness measurements with an accuracy of better than 0.0005 in. over a minimum range of 0.1 to 1.0 in.

Quantitative multiparameter ultrasonic methods are under development for the evaluation of composite materials. Dual frequency, throughtransmission, tone burst signals are used to provide calibrated attenuation data and the frequency dependence thereof. Pulse-echo, spike pulse signals are used to obtain depth information for internal reflectors. Monostatic and bistatic backscatter and bistatic forwardscatter techniques are also used to increase sensitivity to small flaws. Example results are presented for silicon carbide (SiC) fiber reinforced lithium alumino silicate (LAS) glass-ceramic matrix composites. Results include those for manufactured and naturally occurring flaws.

Ultrasonic attenuation in superconductors is used to study the temperature-dependent superconducting energy gap parameter Δ(T) in metal single crystals for different orientations of q with respect to the crystal axes. The electronic attenuation coefficients α s and α n for the superconducting and normal states at T are related to Δ(T) by the BCS equation $${{\alpha }_{s}}/{{\alpha }_{n}}=2{{\left[ \exp \left( \Delta \left( T \right)/kT \right)+1 \right]}^{-1}}$$ (1) The gap parameter at 0°K, Δ0, is obtained by extrapolation. Table I summarizes the most recent determinations of Δ0 for In. The ultrasonic values are significantly lower than the values determined by other methods. Anisotropy in Δ0 for the different orientations is probably not larger than the imprecision of the ultrasonic method (see also Table II). Since the In lattice, fct, departs so little from fcc, the superconducting energy gap would be expected to be nearly isotropic.

The nondestructive evaluation of metal matrix composite precursor wires is being pursued by measurements of the attenuation and velocity of both torsional and longitudinal ultrasonic pulses propagating along the wire axis. The sound waves are generated by non-contacting electromagnetic transducers. Continuous scans of the attenuation and velocity are made along wires of any length by use of a four-transducer arrangement. The attenuation and velocity have been related to physical wire properties which are important for nondestructive evaluation and characterization.

The objective of the work was to nondestructively examine the effects of thermal cycling on properties (e.g., torsional velocity and electrical resistance) of graphite/aluminum (Gr/A1) precursor wire. Precursor wires were periodically heated at selected temperatures for various periods of time; the exact heating period being dependent on the test temperature. Wires were tested in the as-received condition and after each thermal excursion. Changes occurred in both the torsional velocity and the resistance; although at different rates and to different extents. Subsequent longitudinal velocity tests run on the heat treated sections of the wires showed little if any changes in the longitudinal velocities.