Acoustical Imaging/NDE of Complex Geometries Using Refraction and Reflection Transmission Techniques in Acoustic Microscopy

Abstract

The application of scanning laser acoustic microscopy (SLAM) for flaw detection, metallurgical characterization and evaluation of processing variable influence has been limited to components (ceramic turbine blades, plastic IC packages, metal cylinders, etc.) which allow access to two surfaces. Such specimens were tested based only on amplitude variations of transmitted 10 to 500 MHz sonic energy. This paper presents practical SLAM applications where parts are tested based on amplitude variations of refracted and/or reflected 10 to 100 MHz sonic energy. This distinction allows testing of components that restrict access to only one surface and of components where the area of interest is masked by intervening material. For example, miniature welded or brazed corner and T joints, thin wall tubing and the bonding of small electronic parts on thick heat sinks can be nondestructively tested using refraction and reflection SLAM imaging.