The presence of chloride ions in New England bridge decks has caused severe damage and has contributed greatly in reducing service life. The source of the chloride ions is mainly from deicing salts applied for snow and ice removal to enable safer driving during the winter. The chloride ion acts as an accelerator in the corrosion of reinforcing bars causing expansion and therefore deterioration of the bridge deck concrete.

At present the method of determining the percentage of chloride present in bridge decks is a very time consuming, expensive and destructive process. The need for a fast nondestructive procedure to determine the amount of chloride in a concrete bridge deck is apparent. This paper introduces a means of utilizing ground penetrating radar as a viable nondestructive means of detecting areas of high chloride concentration in concrete bridge decks. The technique is based on the attenuation of a radar signal emitted from a radar unit in the presence of chloride.

A numerical solution of the one-dimensional wave equation is used to find the characteristics of wave propagation in a non-homogeneous medium. The solution is used to determine the magnitude and phase of the reflection coefficient at a diffuse interface. The result is found to be strongly dependent on sonic frequency. Comparison is made between theoretical calculations and measurements of the reflection coefficient at a copper-to-nickel diffusion bond.

A series of nondestructive and destructive tests were performed on samples of aluminumto-aluminum bonded plates. The specimens featured a range nominal thickness of the adhesive layer from 0.0 up to 0.5 mm. It was found that a commercial bondtester was inappropriate for assessing the thickness of the adhesive in this range. However, the frequency peak of an ultrasonic echo signal from the adhesive layer was a reliable indicator of bond thickness. It is proposed that nondestructive assessments of the bond thickness could serve as an indicator of the longterm resistance of the adhesive to water ingress and bond degradation.

High frequency ultrasonic energy interacts with metallurgical microstructure to produce scattered energy fields that are useful in characterizing the material. By using a focused transducer whose focal spot size and ultrasonic wavelength are both comparable to the scale of grain structure in high purity copper specimens, the authors have shown a strong correlation between microstructure and the pattern of backscattered ultrasonic signals. A systematic series of experiments logged the ultrasonic returns from cold-rolled copper with the direction of the ultrasonic beam both parallel to and transverse to the rolling direction. Fourteen samples were annealed to various degrees, capturing several stages of recovery and recrystallization. Use of backscattered ultrasonic energy rather than specularly reflected energy allows isolation of grain boundary scattering in an otherwise quiet acoustic environment. Clear differences between returns of backscattered shear waves from parallel and transverse beam orientations relative to the rolling direction gradually disappear as the annealing process re-establishes a field of equiaxial crystals. Backscattered surface waves also show variations that appear to correspond with the relaxation of residual stresses before the onset of recrystallization, and preferred orientation after recrystallization.

Knowledge of structure-properties relationship is a key factor in the development and improvement of new and existing metal alloys through manipulation in their chemical-compositions. In this study, the elastic properties and microstructure of cast Ni-Cr-Be and Ni-Cr dental alloys were studied. The elastic properties, i.e., Young's, shear and bulk moduli and Poisson's ratios, were determined using measurements on the ultrasonic velocities and densities. Both the shear and the longitudinal (dilatational) velocities were measured using an ultrasonic pulse-through-transmission method; density was measured using a buoyant force method. In microstructure, crystallinity, porosity, particle-size and quantitative elemental compositions were studied using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and wavelength dispersive spectrometry (WDS) respectively. These results show that: (1) the addition of Be increased significantly the alloy's elastic moduli and Poisson's ratio; and (2) the presence of Be in Ni-Cr alloy also significantly modified its microstructure by producing a second binary phase, Ni-Be, in eutectic areas.