University of Illinois Urbana-Champaign

Mechanisms of environment induced subcritical flaw growth in AISI 4340

Van Der Sluys, William Alan

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https://hdl.handle.net/2142/112014

Description

Title
Mechanisms of environment induced subcritical flaw growth in AISI 4340
Author(s)
Van Der Sluys, William Alan
Issue Date
1966-08
Keyword(s)
  • Subcritical Flaw Growth
  • Steel
Abstract
The results of an experiment designed to study the effect of several variables on the subcritical crack growth rate of a high-strength steel in a water environment are presented in this paper. Double cantilever beam specimens of an AISI 4340 steel, heat treated to a yield strength level of 217,000 psi. with a fracture toughness of KIc = 51.5 ksi.√(in.) , were employed to study crack extension rates. The environmental variables included temperature, pH of the liquid environment, electric charging, and the combined effect of pH and electric charging. Tapered double cantilever beam specimens were designed so that the G level was maintained constant at a constant load and independent of crack length. Thus steady-state crack growth measurements were possible in constant load and constant environment experiments. With this specimen design, it was possible to make a series of measurements that covered the entire range of effects of a particular variable using only one specimen. From the effect of temperature on crack growth rate, it was found that an activation energy was required for this process which was approximately 8500 cal/g mole. It appeared that this activation energy was slightly dependent on the G level applied to the specimen. When the pH and the applied electrical environment were controlled, it was found that at all pH levels the crack growth rate increased as the applied cathodic potential was increased. It was further found that at low pH levels, the crack growth rate decreased as the applied anodic potential was increased, and at high pH levels the growth rate increased as the anodic potential was increased. It was concluded from these results that both hydrogen embrittlement and chemical corrosion assisted crack growth. The relative contributions of the two mechanisms were dependent on the pH and the applied potential.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 292
  • 1967-0690
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112014
Sponsor(s)/Grant Number(s)
U.S. Army Research Office-Durham, DA Project No. 20014501B320, Intrinsic Studies of Materials, DA-31-124-ARO-D-378
Copyright and License Information
Copyright 1966 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.