R. B. Thompson, F. J. Margetan, Iowa State University, Ames, IA
The interaction of ultrasound with microstructure is important in many material problems. Attenuation and backscattering reduce the detectability of flaws, particularly in materials with coarse grains or complex microstructures such as titanium alloys. In addition, the value of these wave propagation properties provide information about the microstructure that can be used in materials characterization studies, e.g. the nondestructive determination of grain size. This paper will summarize the current status of models for ultrasonic velocity, attenuation and backscattering that take into account two major sets of factors, those of the measurement system (frequency, transducer diameter and focusing, etc.) and those of the material (a property known as the backscattering coefficient). Also included will be a discussion of the relationship of the backscattering coefficient to the microstructure (grain size and shape in the simplest case). Applications of these models to predict signal-to-noise ratios in flaw detection experiments, to predict flaw response distributions in assessment of probability of detection, to use that information to design optimal inspections, and to characterize microstructures will be reviewed.
Summary: This paper describes models that predict how microstructure influences the propagation of ultrasonic waves, most importantly their attenuation and backscattering, as influenced by the properties of the measurement system and microstructure. Applications to the prediction of signal-to-noise in flaw detection, to optimize inspection strategies, and to characterize microstructure are discussed.
