Prediction of cleavage fracture for a low-alloy steel in the ductile-to-brittle transition temperature range

Haušild, Petr; Berdin, Clotilde; Bompard, Philippe

doi:10.1016/j.msea.2004.08.067

Cited by 57 publications

(35 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As the ductile crack grows, it becomes longer at the midwidth of the specimen than at the edges (known as the tunnelling effect). [52] Due to work hardening, the flow stress ahead of the ductile crack increases continuously with the increase in the crack length; as soon as the flow stress reaches the cleavage fracture stress, brittle fracture initiates. Because the local cleavage fracture stress is inversely proportional to the grain size (Eq.…”

Section: Effect Of Bimodality On Toughness In Tmcr Steelmentioning

confidence: 99%

“…Due to the increase in yield stress with the decrease in temperature, at sufficiently low temperatures, the principal stress ahead of the machined notch root becomes so large that almost anything at the notch root (a large grain, an inclusion, or a precipitate [52] ) becomes active, to initiate and propagate cleavage. Hence, the failure occurs entirely by cleavage and the fracture energy values are very low (typically 2 to 10 J).…”

Section: Effect Of Bimodality On Toughness In Tmcr Steelmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

Chakrabarti

Strangwood

Davis

2009

Metall Mater Trans A

View full text Add to dashboard Cite

Blunt-notch tests were performed at À160°C to investigate the effect of a bimodal ferrite grain size distribution in steel on cleavage fracture toughness, by comparing local fracture stress values for heat-treated microstructures with uniformly fine, uniformly coarse, and bimodal grain structures. An analysis of fracture stress values indicates that bimodality can have a significant effect on toughness by generating high scatter in the fracture test results. Local cleavage fracture values were related to grain size distributions and it was shown that the largest grains in the microstructure, with an area percent greater than approximately 4 pct, gave rise to cleavage initiation. In the case of the bimodal grain size distribution, the large grains from both the ''fine grain'' and ''coarse grain'' population initiate cleavage; this spread in grain size values resulted in higher scatter in the fracture stress than in the unimodal distributions. The notchbend test results have been used to explain the difference in scatter in the Charpy energies for the unimodal and bimodal ferrite grain size distributions of thermomechanically controlled rolled (TMCR) steel, in which the bimodal distribution showed higher scatter in the Charpy impact transition (IT) region.

show abstract

Section: Effect Of Bimodality On Toughness In Tmcr Steelmentioning

confidence: 99%

Section: Effect Of Bimodality On Toughness In Tmcr Steelmentioning

confidence: 99%

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

Chakrabarti

Strangwood

Davis

2009

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…Besides dramatically varying upon small temperature change, the toughness in the DBTT region also shows large scattering from one sample to another at the same temperature. [3][4][5][6] As such, predicting the fracture behavior of such materials based on conventional tests is difficult. Moreover, during the manufacturing process, this factor must be considered in the safety design.…”

Section: Introductionmentioning

confidence: 99%

Effect of Bainitic Packet Size Distribution on Impact Toughness and its Scattering in the Ductile-Brittle Transition Temperature Region of Q&T Mn-Ni-Mo Bainitic Steels

Shi

Hou

Jiangbiao

et al. 2015

steel research int.

View full text Add to dashboard Cite

The impact toughness of Q&T Mn-Ni-Mo bainitic steel in the ductile-brittle transition temperature (DBTT) region was measured. The fracture micromechanism associated with the microstructural features was studied, by statistically analyzing the grain sizes of various structures. The results reveal that the cleavage fracture behavior is controlled by bainitic packets. There exists a critical bainitic packet size. When a microcrack formed in the bainitic packet with a size exceeding the critical size propagates into adjacent packets, brittle cleavage fracture occurs. The probability of finding the bainitic packets larger than the critical size dominates the impact toughness and its scattering. It is suggested that refining the bainitic packets and homogenizing their sizes is an effective method of improving the impact toughness and reducing its scattering in the DBTT region.

show abstract

“…Different authors (Brozzo et al, 1978;Curry and Knott, 1978;Beremin, 1983;Zhang and Knott, 1999) observed a scattering of fracture stresses mainly resulting of particle size distribution. More recently, other authors (Yang et al, 2004;Tanguy et al, 2003Tanguy et al, , 2005Lee et al, 2002;Hausild et al, 2005) showed that the initiation of brittle fracture involves multiple microstructural crack initiators, such as lath packets boundaries, carbides or manganese sulfides. All these papers suggested that the metallurgical features involved in the cleavage initiation might change from the lower shelf up to the ductile/brittle transition regime.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependant polycrystal model application to bainitic steel behavior under tri-axial loading in the ductile–brittle transition

Libert

Rey

Vincent

et al. 2011

International Journal of Solids and Structures

View full text Add to dashboard Cite

Keywords:Polycrystal plasticity Steel Mechanical behavior Bainite Cleavage fracture Fracture probability Pressure vessel steel Constraint effect a b s t r a c t A polycrystal finite element (FE) model describing the temperature evolution of low carbon steel is proposed in order to forecast the local mechanical fields as a function of temperature, for bainitic microstructure submitted to tri-axial loading. The model is designed for finite strains, large lattice rotations and temperatures ranging into the brittle-ductile transition domain. The dislocation densities are the internal variables. At low temperature in Body Centred Cubic (BCC) materials, plasticity is governed by double kink nucleation of screw dislocations, whereas at high temperature, plasticity depends on interactions between mobile dislocations and the forest dislocations. In this paper, the constitutive law and the evolution of the dislocation densities are written as a function of temperature and describe low and high temperature mechanisms. The studied aggregates are built from Electron Back Scattering Diffraction (EBSD) images of real bainitic steel. The aggregate is submitted to a tri-axial loading in order to describe the material at a crack tip. Mechanical parameters are deduced from mechanical tests. The local strain and stress fields, computed for different applied loadings, present local variations which depend on temperature and on tri-axial ratio. The distribution curves of the maximal principal stresses show that heterogeneities respectively increase with temperature and decrease with tri-axial ratio. A direct application of this model provides the evaluation of the rupture probability within the aggregate, which is treated as the elementary volume in the weak link theory. A comparison with the Beremin criterion calibrated on experimental data, shows that the computed fracture probability dispersion induced by the stress heterogeneities is of the same order than the measured dispersion. Temperature and stress tri-axiality ratio effects are also investigated. It is shown that these two parameters have a strong effect on fracture owing to their influence on the heterogeneous plastic strain. These inhomogeneities can initiate cleavage fracture.

show abstract

Prediction of cleavage fracture for a low-alloy steel in the ductile-to-brittle transition temperature range

Cited by 57 publications

References 27 publications

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

Effect of Bainitic Packet Size Distribution on Impact Toughness and its Scattering in the Ductile-Brittle Transition Temperature Region of Q&T Mn-Ni-Mo Bainitic Steels

Temperature dependant polycrystal model application to bainitic steel behavior under tri-axial loading in the ductile–brittle transition

Contact Info

Product

Resources

About