"Under repeated stressing microscopic deformations occur at random locations in the polycrystalline structure. The accumulation of damage that occurs prior to the appearance of a visible crack is discussed in terms of the factors influencing the deformation mechanism. The highly localized and progressive nature of the inelastic deformation bands and the heterogeneity of the structure explain the apparent ""weakness"" under dynamic stressing as constrasted to static strength. When one considers the randomness of crystal sizes, grain orientations, and distribution of hardening constituents present in real metals, it becomes more apparent why the fatigue life or the fatigue strength of a part is statistical in nature and is altered by chance effects. Experimental evidence indicates that fatigue damage of a permanent nature develops at an early stage in the repeated stress history. The amount of damage is not linearly related to the number of stress cycles. Phenomenological studies of effect of grain size, metallurgical structure, and temperature are discussed in relation to the micro-structural changes that constitute basic fatigue damage. Due to the statistical scatter inherent in fatigue life, it is impossible to predict accurately the cycles to rupture any individual part subjected to high stresses. A given life can be predicted only in terms of a probability of failure. Elimination of severe stress raisers, a decrease in nominal stress range, and prevention of corrosive conditions are suggested as the most effective means of improving fatigue strength of a member."
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
TAM R 36
1967-0333
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112073
Sponsor(s)/Grant Number(s)
Office of Naval Research 53/10 Contract N6 ORI 71 TO 4 53/10 TR 36
Copyright and License Information
Copyright 1953 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.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
