Forty five papers on the subject of cyclic deformation and fracture behavior of metals are reviewed in an Appendix. Cyclic changes in the deformation resistance of metals make the monotonic stress-strain curve inadequate for characterizing the mechanical resistance of a metal during fatigue. Instead, a cyclic stress-strain curve is needed which relates the cyclic stress and strain after the metal has adjusted to the cyclically stable steady-state condition.
Cyclic stress-strain results are reported for annealed, cold worked and partially annealed OF HC copper. Specimens are strained between completely reversed limits and the stress range required to enforce the controlled strain range is measured. The cyclic stress is found to increase as much as a factor of five for the annealed copper and to decrease as much as a factor of two for the initially cold worked condition. After the initial transient adjustments in the deformation resistance, a nearly stable hysteresis loop develops.
The locus of the tips of a set of stable hysteresis loops is defined as the cyclic stress-strain curve. Cold worked metals cyclically soften so that the cyclic stress-strain curve is below the monotonic stress strain curve. Annealed metals harden and the cyclic strain-strain curve is above the monotonic.
Several experimental techniques for quickly obtaining the cyclic stress-strain curve from only a few specimens are explored. These include two step, multiple step, and incremental step straining, and monotonic tension after cycling. An analytical expression is presented for the cyclic stress-strain curve.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
TAM R 239
1967-0535
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/111957
Copyright and License Information
Copyright 1963 Board of Trustees of the University of Illinois
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.
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