Introducing Heterogeneity into Brittle Fracture Modeling of a 22NiMoCr37 Ferritic Steel Ring Forging

This article describes an investigation into the ability of a number of different fracture mechanics approaches to predict failure by brittle fracture under general elastic/plastic loading. Data obtained from C(T) specimens of A508 ferritic steel subjected to warm pre-stressing and side punching were chosen as such prior loadings produce considerably non-proportionality in the resulting stress states. In addition, failure data from a number of round notched bar specimens of A508 steel were considered for failure with and without prior loading. Failure prediction, based on calibration to specimens in the as received state, was undertaken using two methods based on the J integral and two based on local approach methodologies.

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Prediction of the Absence of Brittle Failure Risk for Ferritic Steel Piping Components in the Brittle-Ductile Region

ASME 2011 Pressure Vessels and Piping Conference: Volume 3 ◽

10.1115/pvp2011-57365 ◽

2011 ◽

Author(s):

S. Marie ◽

J. Schwab ◽

S. Vidard

Keyword(s):

Brittle Fracture ◽

Fracture Risk ◽

Brittle Failure ◽

Risk Evaluation ◽

Critical Stress ◽

Ferritic Steel ◽

Loading Condition ◽

Maximum Principal Stress ◽

Fracture Transition ◽

Secondary Loop

This paper deals with the brittle fracture risk evaluation for a C-Mn piping component in the upper shelf of the brittle to ductile fracture transition temperature range, with the main objective to validate a predictive criteria, able to demonstrate the complete absence of brittle fracture risk. The criteria is based one a critical stress and the volume around the crack were the maximum principal stress exceed this critical stress. The model is calibrated on notched tensile specimens and CT specimens. A four-points bending pipe test has then been designed using this criterion to insure that no brittle fracture will occurs at a temperature that all CT specimens failed by cleavage. The material is a French secondary loop Tu42C ferritic steel and the pipe dimensions for the test are the same than the size of the principal secondary loop pipes. The results of the pipe test confirm the prediction with the model and the interpretation lead to define an equivalence between the loading conditions (based on the J parameter) of the pipe and the loading condition of a CT specimen.

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Protecting against failure by brittle fracture in ferritic-steel shipping containers greater than four-in. thick

10.2172/6770062 ◽

1982 ◽

Author(s):

M.W. Schwartz

Keyword(s):

Brittle Fracture ◽

Ferritic Steel ◽

Shipping Containers

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Assessing the Effect of Intrinsic Microscale Heterogeneity on Brittle Fracture of a Ferritic Steel

Volume 6: Materials and Fabrication ◽

10.1115/pvp2007-26752 ◽

2007 ◽

Author(s):

Xinglong Zhao ◽

David Lidbury ◽

Joa˜o Quinta da Fonseca ◽

Andrew Sherry

Keyword(s):

Fracture Mechanics ◽

Brittle Fracture ◽

Cleavage Fracture ◽

Ferritic Steel ◽

Plastic Anisotropy ◽

Fracture Probability ◽

Local Approach ◽

Transition Range ◽

Micro Scale ◽

Scale Heterogeneity

Brittle fracture can have potentially catastrophic consequences on the safety and integrity of engineering components. For this reason, the accurate prediction of cleavage failure probability is of importance in assessing the defect tolerance of high-integrity ferritic steel components, given the possibility of operation in the presence of significant loads at temperatures in the ductile-brittle transition range. In current safety assessments, fracture mechanics treats polycrystalline steels as homogeneous continua. In reality, deformation is heterogeneous, due to the elastic and plastic anisotropy of their constituent (often randomly orientated) grains. Heterogeneity at the micro (grain) scale is currently not considered by conventional fracture mechanics. This paper describes the initial results of a programme of work on a 22NiMoCr37 steel forging to assess the effect of micro-scale heterogeneity on cleavage fracture probability using an adaptation of the Beremin local approach model. The results of cleavage fracture modelling allowing for the effects of micro-scale heterogeneity are compared with the results of modelling based on the assumption of homogeneous materials behaviour. Application of the micro-scale heterogeneity model is providing some new insights into the prediction of cleavage fracture probability.

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