Abstract:
Extrusion is a common technique used in material processing. It can cause changes of the orientation distribution of crystallites (texture) in single phase materials, and preferred alignment of reinforcements in composite materials. These effects are embodied by material anisotropy which are of practical importance in applications. Often the directions of extrusion are given by manufacturers from the processing equipment. This may not be sufficiently accurate for the users, and there is a need for determining the direction of anisotropy from other means.
This paper presents a method to determine the direction of extrusion from ultrasonic velocity measurements. The existing ultrasonic techniques assume that ultrasonic waves propagate in the directions parallel or perpendicular to the direction of extrusion. Wave speeds are calculated accordingly. When the wave propagation directions are not perfectly aligned with the extrusion direction, a deviation of the wave speeds from the calculated values will occur. By solving the equations of wave propagation in arbitrary directions, we establish the relationship between the velocity differences and the misalignment, and hence determine the angle between the wave direction and the extrusion direction. The method is verified by comparing the model prediction with the ultrasonic velocity measurements for silicon-carbid or alumina reinforced aluminum alloys. It is find that the velocity measurements have a sensitivity to a misalignment angle of less than 5°. With further development, this method has the promise to become a useful technique in process control for manufacture of extruded composites.
Source: Proceedings of the 'NDE applied to Process Control of Composite Fabrication' - Conference, 1-2 Oct 1996 St. Louis, Missouri. Publisher and Organizer: Nondestructive Testing Information Analysis Center (NTIAC) Texas Research Institute Austin, Inc. Austin, Texas [http://www.ntiac.com] [Buying the Proceedings]
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