An acousto-ultrasonic NDE technique for monitoring material anisotropy

A simpler and better way of monitoring the anisotropy of fiber-reinforced composite materials, based on the acousto-ultrasonic approach, is presented. In this approach, time of flight of the acousto-ultrasonic waves AU, rather than the stress wave factor, is measured. Two fundamental Lamb modes are generated under the first critical frequency: one is the first antisymmetric mode traveling with a slower velocity while the another is the first symmetric mode traveling with a faster speed. The later one is sensitive to the azimuthal angle and nearly nondispersive, and has a phase velocity very close to that of the bulk longitudinal wave of the material. Experimental data measured from two methods, TOF measurement and slope method, are compared with theoretical results; a good agreement is obtained for monitoring the material anisotropy. There is a great potential for this AU approach in material-property evaluation and in quantitative measurements of defects and debonding of fiber-reinforced composites. However, more studies are needed to better understand the effect of the fiber/matrix bonding on the measurements and to extract more information from the AU signals

Measurement of shear impedances of viscoelastic fluids

Shear-wave reflection coefficients from a solid/fluid interface are derived for non-Newtonian fluids that can be described by Maxwell, Voigt, and power-law fluid models. Based on model calculations, we have identified the measurable effects on the reflection coefficients due to fluid non-Newtonian behavior. The models are used to interpret the viscosity data obtained by a technique based on shear impedance measurement

Guided Waves in Piezoelectric Plates

In recent paper [1] Nayfeh and Chimenti presented the analysis of the propagation of free waves in a general anisotropic plate. Closed form secular equations which isolate the mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms were obtained. By paralleling the procedure of Nayfeh and Chimenti [1], Nayfeh and Chien [2] presented exact solutions for the interaction of elastic waves with fluid-loaded piezoelectric plates. The technique used was shown to formally handle the most general anisotropy (i.e. the triclinic) case. The plate was immersed in liquid and incident waves impinged upon it from the liquid at arbitrary polar and azimuthal angles. Simple exact analytical expressions were derived for the reflection and transmission coefficients of different electric boundary conditions, namely open and shorted, from which important propagation characteristics are identified. For general discussions of piezoelectric effects we refer the reader to the standard books of Auld [3], Cady [4], and Tiersten [5]

Under-Sodium Viewing: A Review of Ultrasonic Imaging Technology for Liquid Metal Fast Reactors

This current report is a summary of information obtained in the "Information Capture" task of the U.S. DOE-funded "Under Sodium Viewing (USV) Project." The goal of the multi-year USV project is to design, build, and demonstrate a state-of-the-art prototype ultrasonic viewing system tailored for periodic reactor core in-service monitoring and maintenance inspections. The study seeks to optimize system parameters, improve performance, and re-establish this key technology area which will be required to support any new U.S. liquid-metal cooled fast reactors

An Acousto-Ultrasonic NDE Technique for Monitoring Material Anisotropy

Due to their higher strength-weight ratio, greater stiffness, stronger corrosion and wear resistance, longer fatigue life, and better thermal insulation, fiber-reinforced composite materials have been widely applied, for example, in the aerospace, automobile, marine, spacecraft, and construction industries. Evaluation of material properties, detection of defects, and prediction of life of these material is important but difficult. In the last decade, considerable attention has been focused on the use of acousto-ultrasonic (AU) and Leaky-Lamb wave techniques to evaluate material properties or changes in material properties due to fiber misorientation, flaws an defects, fiber/matrix debonding, or external loading [1–4 AU approach, with bibliography, was presented by Vary setup with a personal computer (PC) used to analyze the AU waveforms was described by Kiernan and Duke [4]. Propagation of Leaky—Lamb waves in fiber-reinforced composites was investigated theoretically and experimentally by Chimenti and Nayfeh [10, 11]. A general discussion of elastic waves in solids can be found in Ref. 9.</p

An acousto-ultrasonic NDE technique for monitoring material anisotropy

A simpler and better way of monitoring the anisotropy of fiber-reinforced composite materials, based on the acousto-ultrasonic approach, is presented. In this approach, time of flight of the acousto-ultrasonic waves AU, rather than the stress wave factor, is measured. Two fundamental Lamb modes are generated under the first critical frequency: one is the first antisymmetric mode traveling with a slower velocity while the another is the first symmetric mode traveling with a faster speed. The later one is sensitive to the azimuthal angle and nearly nondispersive, and has a phase velocity very close to that of the bulk longitudinal wave of the material. Experimental data measured from two methods, TOF measurement and slope method, are compared with theoretical results; a good agreement is obtained for monitoring the material anisotropy. There is a great potential for this AU approach in material-property evaluation and in quantitative measurements of defects and debonding of fiber-reinforced composites. However, more studies are needed to better understand the effect of the fiber/matrix bonding on the measurements and to extract more information from the AU signals

Measurement of shear impedances of viscoelastic fluids

Resume

Guided waves in piezoelectric plates

In recent paper [1] Nayfeh and Chimenti presented the analysis of the propagation of free waves in a general anisotropic plate. Closed form secular equations which isolate the mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms were obtained. By paralleling the procedure of Nayfeh and Chimenti [1], Nayfeh and Chien [2] presented exact solutions for the interaction of elastic waves with fluid-loaded piezoelectric plates. The technique used was shown to formally handle the most general anisotropy (i.e. the triclinic) case. The plate was immersed in liquid and incident waves impinged upon it from the liquid at arbitrary polar and azimuthal angles. Simple exact analytical expressions were derived for the reflection and transmission coefficients of different electric boundary conditions, namely open and shorted, from which important propagation characteristics are identified. For general discussions of piezoelectric effects we refer the reader to the standard books of Auld [3], Cady [4], and Tiersten [5].</p

A method and apparatus for sizing and separating warp yarns

A slashing process for preparing warp yarns for weaving operations includes the steps of sizing and/or desizing the yarns in an acoustic resonance box and separating the yarns with a leasing apparatus comprised of a set of acoustically agitated lease rods. The sizing step includes immersing the yarns in a size solution contained in an acoustic resonance box. Acoustic transducers are positioned against the exterior of the box for generating an acoustic pressure field within the size solution. Ultrasonic waves that result from the acoustic pressure field continuously agitate the size solution to effect greater mixing and more uniform application and penetration of the size onto the yarns. The sized yarns are then separated by passing the warp yarns over and under lease rods. Electroacoustic transducers generate acoustic waves along the longitudinal axis of the lease rods, creating a shearing motion on the surface of the rods for splitting the yarns

Under-Sodium Viewing: A Review of Ultrasonic Imaging Technology for Liquid Metal Fast Reactors

This current report is a summary of information obtained in the "Information Capture" task of the U.S. DOE-funded "Under Sodium Viewing (USV) Project." The goal of the multi-year USV project is to design, build, and demonstrate a state-of-the-art prototype ultrasonic viewing system tailored for periodic reactor core in-service monitoring and maintenance inspections. The study seeks to optimize system parameters, improve performance, and re-establish this key technology area which will be required to support any new U.S. liquid-metal cooled fast reactors