L. W. Schmerr

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Transmitting and receiving properties of ultrasonic piezoelectric crystal transducers that directly affect the measured output voltage in an ultrasonic measurement system are described. These transducer properties are the transducer's electrical impedance and sensitivity, the transducer's radiation impedance, and the transducer's effective parameters(More)
The role that an ultrasonic piezoelectric transducer plays in an ultrasonic measurement system can be described in terms of the transducer's input electrical impedance and its sensitivity. Here, a new model-based approach is proposed to determine both the transducer impedance and sensitivity in a pulse-echo setup. This new method is much simpler to apply(More)
By using a small number of Gaussian basis functions, one can synthesize the wave fields radiated from planar and focused piston transducers in the form of a superposition of Gaussian beams. Since Gaussian beams can be transmitted through complex geometries and media, such multi-Gaussian beam models have become powerful simulation tools. In previous studies(More)
This work characterizes the electrical and electromechanical aspects of an ultrasonic linear phased array inspection system, using a matrix of system functions that are obtained from the measured response of individual array elements in a simple reference experiment. It is shown that for the arrays tested all these system functions are essentially(More)
A new transducer beam model is developed for the generation of Rayleigh surface wave and Lamb plate waves by an angle beam transducer, which is one of the configurations commonly used for the generation of these wave types. The beam model is a fully 3-D model that takes into account the fields generated by the transducer acting on the surface of a wedge.(More)
Ultrasonic phased array transducers can be used to extend traditional time-of-flight diffraction (TOFD) crack sizing, resulting in more quantitative information about the crack being obtained. Traditional TOFD yields a single length parameter, while the equivalent flaw time-of-flight diffraction crack sizing method (EFTOFD) described here uses data from(More)
To date, ultrasonic measurement models have primarily treated systems where circular transducers are used. Recently, however, a highly efficient ultrasonic beam model for a rectangular transducer has also become available where the transducer is represented as a superposition of a relatively few Gaussian beams. Thus, using the multi-Gaussian beams, we(More)
A new transducer beam model, called a multi-Gaussian array beam model, is developed to simulate the wave fields radiated by ultrasonic phased-array transducers. This new model overcomes the restrictions on using ordinary multi-Gaussian beam models developed for large single-element transducers in phased-array applications. It is demonstrated that this new(More)
Characterizing the wave field produced by an ultrasonic transducer is one important part of developing a complete measurement model of an ultrasonic NDE system. Within the paraxial approximation [1], this wave field can be expressed as a quasi plane wave field modified by a diffraction correction tenn to account for the 3-D effects of having a finite beam(More)
A complete ultrasonic measurement model for surface and plate wave inspections is obtained, where all the electrical, electromechanical, and acoustic/elastic elements are explicitly described. Reciprocity principles are used to describe the acoustic/elastic elements specifically in terms of an integral of the incident and scattered wave fields over the(More)