Constraint Effects on Fracture Initiation Loads in HSST Wide-Plate Tests

Dodds, Robert H., Jr.

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https://hdl.handle.net/2142/14215 Copy

Description

Title

Constraint Effects on Fracture Initiation Loads in HSST Wide-Plate Tests

Author(s)

Dodds, Robert H., Jr.

Issue Date

1994-07

Keyword(s)

• Fracture mechanics
• J-integral
• Micromechancis
• finite elements

Abstract

"During the period 1984-1987, researchers of the Heavy Section Steel Technology program at the Oak Ridge National Laboratory performed a unique series of fracture mechanics tests using exceptionally large, SECT) specimens (a/W = 0.2) fabricated from a reactor pressure vessel material, A533B Class 1 steel. These ""wide-plate"" specimens have test sections of width W = 1000 mm, thickness B = 100 mm and initial crack lengths of 200 mm. While the specimen design, instrumentation and pre, post-test analyses focused on the cleavage run-arrest events, a disturbing outcome of the program centered on the inability of fracture mechanics analyses at that time to predict the loads required to initiate the first cleavage event - required loads exceeded twice those estimated from 3-D finite element analyses. The source of the much larger than expected initiation loads remained unresolved at completion of the wideplate test program. This study re-examines fracture initiation loads in the wide-plate tests using two constraint assessment methodologies developed over the past five years: the J-Q toughness locus approach and the toughness scaling approach based on a local failure criterion for cleavage. Both approaches demonstrate a significant loss of constraint in the elastic-plastic fields ahead of the crack in the wide-plate specimens caused by the inherent negative T -stress of the shallow notch SECT) configuration. Moreover, the 25 mm wide machined notch required for specimen fabrication is shown to further reduce constraint by introducing a traction free surface very near the crack tip. Both of these factors combined to reduce near-tip stresses by 10% below those of the small-scale yielding, SSY CT= 0), fields. This reduction places fracture results for the wide-plate specimens within the J-Q toughness locus defined by fracture toughness tests on the A533B material and within the constraint corrected Jc values defined by the toughness scaling methodology."

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-591

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/14215

Sponsor(s)/Grant Number(s)

Heavy-Section Steel Technology Program. Oak Ridge National Laboratory. Contract 19X-SM986V

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