Cheng-Kuei Jen

Leaky torsional acoustic modes in infinite clad rods

Dispersion curves, leakage loss, and displacement profiles obtained from the exact analysis of leaky torsional acoustic modes in infinitely thick cladded rods are presented. Two different structures, in which both the longitudinal and the shear velocities of the core are either larger or smaller than those of the cladding, are considered. Similarities are observed between results obtained and dispersion curves which have been reported previously by other workers. Analytic loss relations are also reported for specific modes at either the low‐ or the high‐frequency limit. Applications for this analysis are discussed.

Fabrication and characterization of continuously cast clad metallic buffer rods

The fabrication, characterization, and ultrasonic measurements of clad metallic ultrasonic buffer rods are presented. The core and the cladding consist of tin/lead alloy and pure tin, respectively, produced by a vertical continuous casting technique. The acoustic velocity profiles across the rod diameter are measured using a 225‐MHz line focus beam scanning acoustic microscope. A schlieren visualization system confirms the concentration of acoustic energy in the core. Spherical acoustic lenses have been fabricated at the ends of the rods. Focused and unfocused ultrasonic measurements at frequencies between 2 to 10 MHz and signals with excellent signal to noise ratios have been obtained.

Characterization of lead zirconate titanate ceramics using surface acoustic wave

Abstract Lead zirconate titanate (PZT) is widely used as a piezoelectric transducer material for bulk and surface acoustic wave (SAW) devices. In this Paper a novel laser-ultrasound technique for measuring the SAW properties of PZT for quality control purposes is presented.

AISI/DOE Advanced Process Control Program Vol. 4 of 6: ON-LINE, NON-DESTRUCTIVE MECHANICAL PROPERTY MEASUREMENT USING LASER-ULTRASOUND

The goal of this project was to demonstrate the feasibility to measure the mechanical properties, such as yield strength, tensile strength, elongation, strain hardening exponent and plastic strain ratio parameters, of low carbon steel sheets on the production line using laser ultrasound. The ultrasound generated by the developed apparatus travels mostly back and forth in the thickness of the steel sheet. By measuring the time delay between two echoes, and the relative amplitude of these two echoes, one can measure ultrasound velocity and attenuation. These are governed by the microstructure: grain size, crystallographic texture, dislocations, etc. Thus, by recording the time behavior of the ultrasonic signal, one can extract microstructural information. These microstructural information together with the modified Hall-Petch equation allow measurement of the mechanical properties. Through laboratory investigations with a laboratory laser ultrasound system, followed by the installation of a prototype system at LTV Steel Companys No.1 Inspection Line in Cleveland, all target mechanical properties of ultra low carbon (ULC), low carbon (LC) and high strength low alloy (HSLA) steel sample lots were measured meeting or nearly meeting all the target accuracies. Thus, the project realized its goal to demonstrate that the mechanical properties of low carbon steel sheets can be measured on-line using laser ultrasound

Ultrasonic Attenuation Measurements at 300 MHz

In the CANDU™ (CANada Deuterium Uranium) nuclear reactor, the primary heat transport containment is a matrix of cold-worked Zr-2.5Nb pressure tubes containing pressurized heavy water, which extracts heat from the fuel bundles in the tube. In the last few years, periodical tests on removed tubes have established a significant tube-to-tube variability in fracture toughness due to variability in the as-installed tubes [1].

Acoustic characterization of optical fiber glasses

Acoustic characterization of doped silica glasses with a Ge02, P205, F, Ti02, A1203 or B203 dopant having different concentrations is presented. The quantitative measurements are performed by a 225 MHz line-focus-beam scanning acoustic microscope. The acoustic velocity variation due to different dopant concentrations for each dopant is given. It has been found that the A1203 dopant increases but the other dopants decrease the acoustic velocity as compared to that of the pure fused silica. The fiber preforms having step and graded refractive index profiles also show step and graded acoustic velocity profiles respectively. We have also found that the acoustic velocity is more sensitive to the dopant concentration as compared with that of optical refractive index.

Quasi-distributed optical fiber sensors using multiple frequency shifters

Quasi-distributed optical fiber sensors using multiple frequency shifters (FSs) in two-mode elliptical core fiber (TMECF) are presented. Sensing measurand is the phase shift between the two propagating modes in the fiber. In the present experimental configuration, four FSs provide three independent sensing regions along a single TMECF. We construct one sensor in each region to measure localized strain and/or bending simultaneously. Cross talk among the sensors is theoretical and experimentally evaluated. Measurements were carried out using a computer system that allows a real time data acquisition and display.