Accession Number:

ADA248440

Title:

A Combined Experimental and Analytical Investigation of the Theory of Plasticity Involving Strain Induced Anisotropy

Descriptive Note:

Final rept. 1 Oct 1988-30 Sep 1991

Corporate Author:

RENSSELAER POLYTECHNIC INST TROY NY DEPT OF MECHANICAL ENGINEERING AERONAUTICAL ENGINEERING AND MECHANICS

Personal Author(s):

Report Date:

1992-03-03

Pagination or Media Count:

43.0

Abstract:

Experiments were carried out which subjected tubes of ductile metals to histories of straining in combined tensioncompressiontorsion space. The computer controlled servo-hydraulic testing machine recorded the resulting stress histories together with the imposed strain histories. Intermittently along the path, the straining was halted to probe for the current yield locus. The nose of the yield locus in the direction of straining exhibited quite accurately a circular geometry, which implied isotropic-kinematic hardening. The centers of the fitted yield circles in generalized tension-shear space, define the back stress which expresses the anisotropic component of the hardening, and expresses the strength and orientation of the impediment to dislocation flow through the crystal, i.e. the yield stress required to maintain plastic flow. Application of a polygonal closed straining path caused the back sum tensor to rotate about 330 degrees while the material rotation due to shear was only about 1 degree. Thus plastic spin, which in the literature has been considered to cause spin of the plastic anisotropy, turns out to be very much smaller. Measurements of stress response to linear and nonlinear strain paths have been used to generate the evolution law for the back stress and hence the constitutive relation.

Subject Categories:

  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE