On the relationship between critical tensile stress and fracture toughness in mild steel

Ritchie, Robert O.; Knott, J. F.; Rice, James R.

doi:10.1016/0022-5096(73)90008-2

Cited by 1,409 publications

(406 citation statements)

References 15 publications

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“…The fracture toughness is critically influenced by volume fractions and distributions of voids or particles which affect the fracture initiation inside the material. [38] Thus, the reduced spacing of crack or void initiation sites due to the reduced spacing between oxides can cause the reduction in fracture toughness. However, this explanation cannot be applied to the present case of the steel HAZ.…”

Section: Discussionmentioning

confidence: 99%

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

Sung

Sohn

Shin

et al. 2014

Metall Mater Trans A

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This study is concerned with effects of complex oxides on acicular ferrite (AF) formation, tensile and Charpy impact properties, and fracture toughness in heat affected zones (HAZs) of oxidecontaining API X80 linepipe steels. Three steels were fabricated by adding Mg and O 2 to form oxides, and various HAZ microstructures were obtained by conducting HAZ simulation tests under different heat inputs. The no. of oxides increased with increasing amount of Mg and O 2 , while the volume fraction of AF present in the steel HAZs increased with increasing the no. of oxides. The strengths of the HAZ specimens were generally higher than those of the base metals because of the formation of hard microstructures of bainitic ferrite and granular bainite. When the total Charpy absorbed energy was divided into the fracture initiation and propagation energies, the fracture initiation energy was maintained constant at about 75 J at room temperature, irrespective of volume fraction of AF. The fracture propagation energy rapidly increased from 75 to 150 J and saturated when the volume fraction of AF exceeded 30 pct. At 253 K (À20°C), the total absorbed energy increased with increasing volume fraction of AF, as the cleavage fracture was changed to the ductile fracture when the volume fraction of AF exceeded 45 pct. Thus, 45 vol pct of AF at least was needed to improve the Charpy impact energy, which could be achieved by forming a no. of oxides. The fracture toughness increased with increasing the no. of oxides because of the increased volume fraction of AF formed around oxides. The fracture toughness did not show a visible correlation with the Charpy absorbed energy at room temperature, because toughness properties obtained from these two toughness testing methods had different significations in view of fracture mechanics.

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Section: Discussionmentioning

confidence: 99%

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

Sung

Sohn

Shin

et al. 2014

Metall Mater Trans A

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“…Stresses are caicuiated and stored at each ioad step as the body is deformed toward a limit state. Sufficient mesh refinement is needed to fully define the stresses over distances of [2][3][4][5][6][7][8][9][10] times the crOD at all load levels. Such analyses require a considerably more detailed mesh than does a routine analysis to determine 1.…”

Section: Crack-tip Stresses In Finite Bodiesmentioning

confidence: 99%

The influence of weld strength mismatch on crack-tip constraint in single edge notch bend specimens

Kirk

Dodds

1993

Int J Fract

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Interim: 1-1-91 to 1-1-92 14. Dodds and Anderson provide a framework to quantify finite size and crack depth effects on fracture toughness when failure occurs at deformation levels where 1 no longer uniquely describes the state of stresses and strains in the vicinity of the crack-tip. Size effects on cleavage fracture are quantified by defining a value termed lssy: the J to which an infinite body must be loaded to achieve the same stressed volume, and thereby the same likelihood of cleavage fracture, as in a finite body. In weld metal fracture toughness testing, mismatch between weld metal and baseplate strength can alter deformation patterns, which complicates size and crack depth effects on cleavage fracture toughness. However, the virtually limitless number of weld joint geometry / crack depth combinations preclude calculation of lssy for each individual case. This study addresses the accuracy with which lssy for a welded single edge notch bend, SE(B), specimen can be approximated by previously published results for homogeneous specimens. The case of a crack located on the weld joint centerline is treated. The combined effects of weld groove type, degree of mismatch, and crack depth to specimen width (all¥) ratio are considered by performing plane-strain elastic-plastic finite clement analyses ofSE(B) specimens containing a variety of common weld groove details. These results demonstrate virtually no effect of ± 20% mismatch on lssy if the distance from the crack-tip to the weld/plate interface (Lmin) exceeds 0.2-inches. If Lmin falls below 0.2-inches, there exists a deformation (applied-J) dependent value of Lmin below which reasonably accuratelssy estimation is possible. At higher levels of overmatch (500/0 to 100%), it is no longer possible to parameterize departure of1ssy for a weldment from that for a homogeneous SE(B) based on Lmin alone. Weld geon1etry significantly influences the accuracywith whichlssy for a welded SE(B) can be approximated by lssy for a homogeneous specimen at these extreme overmatch levels. ABSTRACTDodds and Anderson provide a framework to quantify finite size and crack depth effects on fracture toughness when failure occurs at deformation levels wherel no longer uniquely describes the state of stresses and strains in the vicinity of the crack-tip. Size effects on cleavage fracture are quantified by derming a value termed lssy: the 1 to which an infinite body must be loaded to achieve the same stressed volume, and thereby the same likelihood of cleavage fracture, as in a finite body. In weld metal fracture toughness testing, mismatch between weld metal and baseplate strength can alter deformation patterns, which complicates size and crack depth effects on cleavage fracture toughness. However, the virtually limitless number of weld joint geometry I crack depth combinations preclude calculation of lssy for each individual case. This study addresses the accuracy with which lssy for a welded single edge notch bend, SE(B), specimen can be approximated by prcviously published results ...

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“…The basis for the void growth modeling is a plastic flow rule for progressively cavitating solids due to Gurson [2] and the cleavage model draws on the critical stress over a critical distance criterion of Ritchie, Knott and Rice [3].…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of the Ductile-Brittle Transition

Needleman

1996

J. Phys. IV France

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Abstract. Numerical studies of the ductile-brittle transition are described that are based on incorporating physically based models of the competing fracture mechanisms into the material's constitutive relation. An elastic-viscoplastic constitutive relation for a porous plastic solid is used to model ductile fracture by the nucleation and subsequent growth of voids to coalescence. Cleavage is modeled in terms of attaining a temperature and strain rate independent critical value of the maximum principal stress over a specified material region. Various analyses of ductilebrittle transitions carried out within this framework are discussed. The fracture mode transition emerges as a natural outcome of the initial/boundary value problem solution.

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On the relationship between critical tensile stress and fracture toughness in mild steel

Cited by 1,409 publications

References 15 publications

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

The influence of weld strength mismatch on crack-tip constraint in single edge notch bend specimens

Numerical Modeling of the Ductile-Brittle Transition

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