Ultrasonic Immersion Technique Research Articles

Ultrasonic properties of PVC (S‐27/R63) in the glassy region

AbstractThe ultrasonic properties of PVC (S‐27/R63) in the glassy region have been investigated as a function of temperature. The propagation velocities and absorption of the longitudinal and transverse ultrasonic waves have been measured at constant frequency of 2 MHz and at temperatures varying between −5°C and 75°C, using the ultrasonic immersion technique. The variation of the elastic moduli with temperature has been derived from these measurements. The results thus obtained have been compared to those previously published in the literature for different PVC and other polymer samples. ©1995 John Wiley & Sons, Inc.

Anisotropic elasticity of oriented polyethylene materials

In this paper we compare the elastic anisotropy of three classes of oriented polyethylene-based materials. The material types were a range of polyethylene/epoxy composites, made in both unidirectional and 0/90 cross-ply forms; polyethylene/polyethylene composites manufactured by the new process of hot compaction, again in both unidirectional and cross-ply form; and large-section solid-phase oriented polyethylene produced by the die drawing process. The elastic properties of these different materials were determined and compared by means of an ultrasonic immersion technique. By using the properties of the compacted polyethylene/polyethylene composites, it was possible to obtain a complete description of the elastic properties of the original polyethylene fibre. The measured elastic constants of the polyethylene/epoxy composites were then compared with those predicted on the basis of theoretical models developed in this laboratory. It was of particular interest that the modified Brody/Ward model was found to be very satisfactory.

Nondestructive characterization of metal matrix composite by ultrasonic measurement

Nondestructive characterization of a composite using ultrasonic technique has been conducted systematically on A1 2O 3 short fiber reinforced AC8A aluminium metal-matrix composites. For this purpose, A1 2O 3/AC8A with volume fraction of A1 2O 3 short fiber varying up to 30% were fabricated by the squeeze casting technique. Ultrasonic properties of composites were measured by the ultrasonic immersion technique based on pulse-echo method. It was found that ultrasonic velocities were primarily correlated with the volume fraction of A1 2O 3 short fiber. The elastic constants of composites including Young's modulus, shear modulus, and bulk modulus were determined on the basis of the longitudinal and shear wave velocities measured by an ultrasonic technique. The Young's modulus of the composites obtained by ultrasonic technique demonstrated a slightly more conservative value than those measured by the three-point bend test and showed relatively good agreement with the results predicted from the equal stress condition. It was also found that the attenuation and the backscattering behaviors of the composites were primarily related to the volume fraction of fiber and these relations could be used to predict the condition of fiber distribution in matrix nondestructively.

Modelling the elastic properties of fibre-reinforced composites: II theoretical predictions

This paper evaluates different models for predicting the elastic properties of fibre reinforced composites. The modelling is broken into two discrete components. First, the properties of the individual composite unit, envisaged as a fibre embedded in a circular sheath of matrix, are determined. Four models for determining the elastic properties of the unit are evaluated. The second stage in the modelling is to predict the effects of a range of orientations of the simple composite unit. This is achieved by applying the aggregate model proposed by Ward. The orientation averages needed for the second stage were obtained by image analysis, and their measurement was detailed in a previous paper. Finally the predicted elastic constants were compared with experimental values determined using an ultrasonic immersion technique.

The elastic constants of moulded polymeric composites

AbstractThe paper makes an approach to the determination of the five independent elastic constants of uniaxial symmetric material with the ultrasonic immersion technique. Only five ultrasonic wave velocities are required during measurement. The elastic constants of the moulded composites comprised of poly(phenylene sulfide), poly(aryl ether sulfone) with cardo side groups, short carbon fiber and carbon black are measured by using the suggested treatment. The results exhibit a close relationship between the elastic properties and the structure of the materials.

Elastic anisotropy in unidirectional fibre reinforced composites

A theory is presented to calculate bounds on the elastic constants for unidirectional fibre reinforced composites, where the fibres and matrix both show transverse isotropy. This, and a more intuitive theory due to Brody and Ward (1971) tested using new comprehensive measurements for the elastic constants of a range of unidirectional composites using the ultrasonic immersion technique. These composites are based on epoxy resin reinforced either by glass fibres or with ultrahigh modulus polyethylene fibres and polyetheretherketone reinforced with carbon fibres (APC2). Agreement between experimental data and the theoretical bounds is very satisfactory considering the present uncertainties in some of the fibre elastic constants.

DESIGN, CONSTRUCTION AND TRIALS OF A PRECISION DOUBLE-PROBE ULTRASONIC CONIOMETER FOR HIGH FREQUENCY MEASUREMENTS.

Abstract A precision double-probe ultrasonic goniometer and two air-backed ultrasonic transducers were designed and constructed for use in the investigation of the surface and sub-surface structures of engineering materials, using the ultrasonic water immersion technique. The instrument has specifications which are a considerable improvement over those described elsewhere. Measurements with high frequency Lamb waves in thin films are described.

Portable Flaw Detector With Built‐in LCD Thickness Meter

A new high performance portable flaw detector has been introduced by Wells‐Krautkramer. The latest of the USL range, the USL 48 is a high resolution instrument with selectable 5 band amplifier, range from only 4mm to over 6 metres, built in 4 digit LCD thickness meter and electronic DAC. Capable of being matched to almost any probe/material combination for examination and measurement, its exceptional near surface resolution makes it well suited for example, to aerospace applications and for thin materials. Immersion ultrasonic techniques can also be used with this instrument.

High Resolution, Portable Flaw Detector

A NEW high performance portable flaw detector has been introduced by Wells‐Krautkramer. The latest of the USL range, the USL 48 is a high resolution instrument with selectable 5 band amplifier, range from only 4mm to over 6 metres, built in 4 digit LCD thickness meter and electronic DAC. Capable of being matched to almost any probe/material combination for examination and measurement, its exceptional near surface resolution make it well suited, for example, to aerospace applications and for thin materials. Immersion ultrasonic techniques can also be used with this instrument it is stated.

Ultrasonic investigations of a second bulk compressional wave in a porous solid

A second bulk compressional wave has been observed in water‐saturated porous solids using a transmission ultrasonic immersion technique. In this technique, the bulk modes are generated in a solid layer based on the concept of mode conversion and refraction at liquid‐solid interfaces. With this technique, the sound speeds of the normal compressional wave, shear wave, and second compressional wave were determined. The pulsed ultrasonic system incorporated commercially available pulser/receiver electronics and nondestructive testing type broadband transducers with a center frequency of about 1 MHz. The porous solids studied included samples composed of sintered glass spheres and samples from two types of commercially available filtration materials. The porosity of the samples ranged from 10%–40% and the fluid permeability ranged from 1–10 μm2 (i.e., 1–10 Darcy). Velocity data will be presented as a function of porosity and fluid permeability. The second compressional wave speed is approximately 25% of the normal compressional wave speed. The data will be interpreted in terms of the Biot theory of wave propagation in a fluid‐saturated porous solid [J. Appl. Phys. 28, 168–178 (1956)].

Ultrasonics in the determination of susceptibility of rolled products to lamellar tearing

When lamellar tearing increasingly appeared in certain welded constructions the French Welding Institute investigated the effect of rolling on materials. The institute sought a non-destructive method of assessing the susceptibility of plate to lamellar tears and investigated non-destructive tests of the properties of materials across their shortest dimension. This paper describes work on the development of an immersion ultrasonic technique to inspect steels containing non-metallic inclusions which are precursors of lamellar tearing. The researchers used small focused probes to detect these small inclusions

Ultrasonic Elastic Constants of Carbon Fibers and Their Composites

The elastic constants of carbon-fiber-reinforced composites have been measured with an ultrasonic immersion technique. Both carbon and graphite fibers were studied. These fibers were derived from both rayon and polyacrylonitrile (PAN), and had Young's moduli ranging from 6 to 80×106 psi. The composite elastic constants varied with fiber modulus and fiber type (carbon or graphite) but not with the fiber-matrix bond. The fiber elastic constants c11 and c66, corrected for porosity, varied with fiber modulus but not with fiber type. The fiber constants c44 and c13 were independent of fiber modulus but varied with fiber type.