A method for measuring the spatial variation of the macroscopic poling state of a piezoelectric material using an ultrasonic transducer is described. The relatively simple method clearly indicates the distribution of poling within the material, demonstrated by the testing of a collection of partially poled lead zirconate titanate samples.

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SummaryConventional peak amplitude ultrasonic techniques have proven to be unreliable when used to evaluate solid state bonds. Of particular concern are bonds of intermediate strength that would pass a typical ultrasonic examination. These are commonly called "kissing bonds." Several advanced ultrasonic techniques were compared to determine the best technique for predicting the bond strength of diffusion bonded beryllium-copper. After an extensive literature search, several advanced ultrasonic techniques were chosen for inclusion in this study. Integrated backscatter calculations, frequency domain reflection coefficients, and time-of-flight variance techniques, which showed varying degrees of success on other material interface systems, were compared in their ability to characterize the bond strength of twenty-two beryllium-copper diffusion bond samples with varying bond qualities. Modifications to previously reported time-of flight histogram and reflection coefficient techniques were also suggested and implemented as a part of this study.Correlation of integrated backscatter calculations and time-of-flight variance with bond strength was good for low, intermediate, and high strength bonds. Correlation of the slope of the frequency based reflection coefficient was poor when considering all bond strengths; however, some correlation was found for medium and high strength bonds. The Y-intercept of the frequency based reflection coefficient curve showed moderate correlation for all bond strengths. 2 Discussion Scope and PurposeDiffusion bonding is a joining process that is becoming increasingly popular as a metallurgical joining method, and offers many advantages over other processes such as fusion welding and brazing. It allows similar and dissimilar metals to be joined at temperatures that are not only far below their melting temperature, but in many cases below their heat treating and annealing ranges. It can also avoid the drastic changes in microstructure typically seen in and adjacent to fusion welds, and the numerous undesirable conditions that can occur during the solidification process. The diffusion bonding process involves applying pressure at an elevated temperature to two samples which have their mating surfaces prepared as flat and smooth as possible. Initially, diffusion begins where contact is made between the two surfaces at the highest points. As the pressure and heat are increased, plastic deformation causes the interface to transform into one of isolated voids, thus increasing the contact area and the rate of diffusion. The voids are then reduced in size until they are completely closed, at which time the rate of atomic diffusion is a maximum. This process is accomplished principally by interstitial or vacancy diffusion, depending upon the materials at the interface (1,2).The quality of a diffusion bond, as in other bonds, is of critical importance in ensuring the proper performance of the bond for its intended application. Nondestructive test methods, particularly ultrasonic techniques,...

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