ON SECOND ORDER STRAIN ACCUMULATION IN TORSION FATIGUE,

Abstract

Superpurity aluminum specimens subject to reversed cyclic torsion are extending in axial direction because of the accumulation of second order plastic strain increments in quasi-isotropic strain-hardening metals arising from the quadratic term in their stress-strain relation required by the condition of tensorial invariance. Accordingly, a quadratic relation was found between the accumulated second order axial strain to the start of macroscopic crack propagation and the reversed torsion angle producing it. Second order strain accumulation was also found in Armco iron both below and above the yield range, in the regions where stress-strain relations exist; within the yield range which is governed by a yield condition, axial strain accumulation is erratic. For aluminum and Armco iron a linear relation exists between the accumulated axial strain at any torsion angle and the applied axial stress. Fatigue life was related to the second order strain accumulation. (Author)

Document Details

Document Type
Technical Report
Publication Date
Feb 01, 1965
Accession Number
AD0612712

Entities

People

  • Maria Ronay

Organizations

  • Columbia University

Tags

DTIC Thesaurus Topics

  • Aluminum
  • Crack Propagation
  • Cracks
  • Fatigue Life
  • Hardening
  • Invariance
  • Mechanical Properties
  • Metals
  • Strain Hardening
  • Stress Strain Relations
  • Stresses

Readers

  • Calculus or Mathematical Analysis
  • Materials Science and Engineering.
  • Structural Health Monitoring of Composite Structures.