Non-Destructive Acoustic Determination of Residual Stresses in Hydrostatically Extruded Aluminum Rods

Date
1981-09-01
Authors
Scott, M.
Barnett, D.
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Abstract

Third order elasticity theory may be used to show that a longitudinal acoustic wave normally incident on a sample in a state of plane deformation experiences a relative velocity shift given by [equation] where B is the acoustoelastic constant, σ1 and σ2 are the principal stresses normal to the direction of wave propagation, and V0 is the wave velocity in undistorted material. Hence, wave transit time measurements may be used to ascertain the sum σ1 + σ2 in the deformed state. We use a double pulse-echo technique to provide an accurate measure of transit time through the thickness of aluminum discs produced by hydrostatic extrusion (25% area reduction). The residual stress state produced during extrusion is axi-symmetric and we are able to separately determine residual radial and hoop stresses by a single longitudinal wave measurement at points on the disc face. The technique is extremely rapid and accurate, and the acoustic results are cross-checked by both x-ray measurements and finite element simulation of the extrusion process.

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Nondestructive Evaluation
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