University of Illinois Urbana-Champaign

Analysis of cyclic stress behavior for conditions of controlled strain

Morrow, JoDean; Sinclair, G.M.

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https://hdl.handle.net/2142/112276

Description

Title
Analysis of cyclic stress behavior for conditions of controlled strain
Author(s)
  • Morrow, JoDean
  • Sinclair, G.M.
Issue Date
1957-08
Keyword(s)
  • Cyclic Stress
  • Controlled Strain
Abstract
The problem of the significance of residual stress in fatigue is attacked by making analogy of residual stress to mean stress in axial fatigue tests. An assumed stress-strain relationship was successfully employed to predict the decay, or change of mean stress, which occurred in less than a million cycles in SAE 4340 steel tested under conditions of controlled strain. The fundamental cause of changes in mean stress was determined to be the accumulation of microstrain due to repeated loading. The analysis predicts, and the tests substantiated, that this form of microstrain occurs more readily if soft steel than in hard steel for the same conditions of testing. It was found experimentally that the fatigue limit of the soft condition (30 Rc) was relatively insensitive to mean stress while the hard condition (50 Rc) showed a large effect of mean stress on the fatigue limit. Only a small part of the difference in the fatigue behavior of the two materials could be attributed to observed differences in the cyclic stress behavior for the following reason: although there was sizeable loss of mean stress for large amplitudes of alternating stress in the soft condition compared to the hard, there was little loss of mean stress in either the soft or hard condition for alternating stresses near the fatigue limit. By analogy, it appears that: A. Residual stress is particularly important in hard steel. B. The change which occurs in the residual stress during fatigue loading does not affect the fatigue limit appreciably, but may have an effect on the fatigue life.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 543
  • 1971-8575
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112276
Sponsor(s)/Grant Number(s)
General Electric Company Evendale Plant Lab 57/08
Copyright and License Information
Copyright 1957 Board of Trustees of the University of Illinois

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Technical Reports - Theoretical and Applied Mechanics (TAM) PRIMARY
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.