Studies of Some Brittle Fracture Concepts

Wright, R.N.; Hall, W.J.; Terry, S.W.; Nordell, W.J.; Erhard, G.R.

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https://hdl.handle.net/2142/14048 Copy

Description

Title

Studies of Some Brittle Fracture Concepts

Author(s)

• Wright, R.N.
• Hall, W.J.
• Terry, S.W.
• Nordell, W.J.
• Erhard, G.R.

Issue Date

1965-04

Keyword(s)

• brittle fractures
• Steel

Abstract

"Interpretive studies based on available information on the low-stress brittle fracture behavior of mild steel are made to suggest additional guides for the evaluation of the fracture resistance of fabricated steel structures. Linear elastic fracture mechanics is used in evaluation of the fracture toughness disclosed by the arrest of cleavage fractures in notched and welded wide plate specimens. Fracture toughness values also are obtained from strain field measurements in the vicinity of propagating cracks on the verge of arrest in 6-ft-wide plates. The results clearly show the trend towards ""toughening"" at higher temperatures and the major role residual stress fields can play in driving fractures. An experimental investigation was conducted to investigate the influence of welding on the yield behavior of metal from the thermally affected zone in the vicinity of a weld. The rate-temperature dependent component of the yield stress appears to be the same for base metal and metal from the thermally affected zone, but the yield stress of the thermally affected zone metal shows a substantially increased rate-temperature independent component. A critical stress model for the prediction of brittle cleavage fracture is developed. and applied to cleavage initiation, propagation, and arrest. The model approximately accounts for inelastic behavior near a flaw by truncating the elastic stress d1stribution. Effects of rate, temperature, notch' acuity, local strain hardening, residual stress, and propagation velocity are considered; the model demonstrates good qualitative representation of the effects of these parameters on the susceptibility to cleavage. Correlations with experimental results show the model is capable of quantitative representation of the effects of rate and temperature on the applied stress required for the initiation of brittle cleavage fracture and the stress required for continued cleavage propagation. The study suggests that low-stress cleavage initiation at service temperatures can be associated with a marked local reduction of critical fracture stress, that residual stresses can be responsible for the propagation through sound metal of fracture initiated in damaged material and that the critical fracture stress and fracture mechanics approaches are equivalent when applied to cleavage propagation and arrest."

Publisher

University of Illinois Engineering Experiment Station. College of Engineering. University of Illinois at Urbana-Champaign.

Series/Report Name or Number

Civil Engineering Studies SRS-289

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/14048

Sponsor(s)/Grant Number(s)

• Ship Structure Committee. Bureau of Ships, U.S. Navy.
• Contract N0bs 86688
• Project Serial No. S-F 013 0304, Task 2022

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