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Title: Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel

Abstract

In the present study, the crack opening displacement (COD) tests of specimens of C-Mn base and weld steel were carried out in the ductile-brittle transition temperature region. The majority of the specimens were fractured and others were unloaded prior to fracture after ductile fracture initiated and extended. The cavities and cleavage microcracks located in the vicinities of tips of fibrous cracks of the unloaded specimens were observed in detail. The finite element method (FEM) calculations of the stress and strain distribution ahead of the tip of an extending fibrous crack were completed. The mechanism of the ductile-to-brittle fracture transition was further investigated. It was revealed that in the ductile-brittle transition temperature region, the ductile fracture process was independent of temperature. The ductile-to-brittle fracture transition was triggered by initiating a catastrophic extension of a cleavage crack ahead of the fibrous crack tip, which occurred in a condition satisfying a combined criterion composed of three items, i.e., {var_epsilon}{sub p} {ge} {var_epsilon}{sub pc} for initiating a crack nucleus; {sigma}{sub m}/{bar {sigma}} {ge} {Tc} for preventing the crack nucleus from blunting; and {sigma}{sub yy} {ge} {sigma}{sub f} for propagating the crack nucleus. For a specimen in which a fibrous crack occurred and propagated, themore » critical event for initiating a brittle cleavage fracture was the propagation of a ferrite grain-sized crack into neighboring grains. With extension of a fibrous crack, the behavior of the ductile-to-brittle fracture transition could be analyzed by the effect of the size of an active zone on the initiation of the brittle cleavage fracture.« less

Authors:
;  [1];  [2]
  1. Gansu Univ. of Technology, Lanzhou, Gansu (China). Welding Research Inst.
  2. Xian Jiaotong Univ. (China). Mechanics Dept.
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
540995
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 28; Journal Issue: 8; Other Information: PBD: Aug 1997
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; FRACTURE PROPERTIES; STEELS; CARBON ADDITIONS; MANGANESE ADDITIONS; WELDED JOINTS; DUCTILE-BRITTLE TRANSITIONS; TEMPERATURE DEPENDENCE; CRACKS; FINITE ELEMENT METHOD; STRESSES; STRAINS; CRACK PROPAGATION

Citation Formats

Wang, G Z, Chen, J H, and Li, Z H. Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel. United States: N. p., 1997. Web. doi:10.1007/s11661-997-0260-x.
Wang, G Z, Chen, J H, & Li, Z H. Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel. United States. doi:10.1007/s11661-997-0260-x.
Wang, G Z, Chen, J H, and Li, Z H. Fri . "Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel". United States. doi:10.1007/s11661-997-0260-x.
@article{osti_540995,
title = {Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel},
author = {Wang, G Z and Chen, J H and Li, Z H},
abstractNote = {In the present study, the crack opening displacement (COD) tests of specimens of C-Mn base and weld steel were carried out in the ductile-brittle transition temperature region. The majority of the specimens were fractured and others were unloaded prior to fracture after ductile fracture initiated and extended. The cavities and cleavage microcracks located in the vicinities of tips of fibrous cracks of the unloaded specimens were observed in detail. The finite element method (FEM) calculations of the stress and strain distribution ahead of the tip of an extending fibrous crack were completed. The mechanism of the ductile-to-brittle fracture transition was further investigated. It was revealed that in the ductile-brittle transition temperature region, the ductile fracture process was independent of temperature. The ductile-to-brittle fracture transition was triggered by initiating a catastrophic extension of a cleavage crack ahead of the fibrous crack tip, which occurred in a condition satisfying a combined criterion composed of three items, i.e., {var_epsilon}{sub p} {ge} {var_epsilon}{sub pc} for initiating a crack nucleus; {sigma}{sub m}/{bar {sigma}} {ge} {Tc} for preventing the crack nucleus from blunting; and {sigma}{sub yy} {ge} {sigma}{sub f} for propagating the crack nucleus. For a specimen in which a fibrous crack occurred and propagated, the critical event for initiating a brittle cleavage fracture was the propagation of a ferrite grain-sized crack into neighboring grains. With extension of a fibrous crack, the behavior of the ductile-to-brittle fracture transition could be analyzed by the effect of the size of an active zone on the initiation of the brittle cleavage fracture.},
doi = {10.1007/s11661-997-0260-x},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
number = 8,
volume = 28,
place = {United States},
year = {1997},
month = {8}
}