Predictive modelling of long term creep performance of critical plant components

A summary is given of the constitutive equations that have been developed for use in design assessments of elevated temperature components of liquid metal fast breeder reactors. The discussion addresses representations of short-term (plastic) and long-term (creep) inelastic material responses. Attention is given to improved representations of the interactions between plastic and creep deformations. Most of the discussion is in terms of constitutive equations that make use of the concept of separating the total strain into elastic, plastic, and creep portions. Additionally, some discussion is given of progress being made toward establishing design equations based on unified measures of inelastic strain that do not distinguish different strain portions.

Download Full-text

Prediction of Long Term Stress Rupture Data for 2124

Materials Science Forum ◽

10.4028/www.scientific.net/msf.519-521.1041 ◽

2006 ◽

Vol 519-521 ◽

pp. 1041-1046 ◽

Cited By ~ 6

Author(s):

Brian Wilshire ◽

H. Burt ◽

N.P. Lavery

Keyword(s):

Q Methodology ◽

Fracture Behavior ◽

Stress Rupture ◽

Creep Data ◽

Short Term ◽

Rupture Data ◽

Term Creep ◽

Term Data ◽

Short Term Creep

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.

Download Full-text

Influence of Stress on Degradation and Life Prediction of High Strength Ferritic Steels

Experience With Creep-Strength Enhanced Ferritic Steels and New and Emerging Computational Methods ◽

10.1115/pvp2004-2566 ◽

2004 ◽

Cited By ~ 10

Author(s):

Kazuhiro Kimura ◽

Kota Sawada ◽

Kiyoshi Kubo ◽

Hideaki Kushima

Keyword(s):

Yield Stress ◽

Elastic Limit ◽

High Strength ◽

Time To Rupture ◽

Limit Stress ◽

Creep Resistant Steels ◽

Grade 91 ◽

Term Creep ◽

Grade 91 Steel

Influence of stress on creep deformation and degradation behavior has been investigated. Corresponding to inflection of stress vs. time to rupture curve, difference in recovery phenomena, that was homogeneous in short-term and inhomogeneous in long-term, was observed. Inflection of stress vs. time to rupture curve took place at the stress condition corresponding to half of 0.2% offset yield stress at the temperature. Elastic limit stress of Grade 91 steel was evaluated to be 150MPa at 600°C and 100MPa at 650°C, by means of stress abrupt change test. These stresses were found to be almost the same as half of 0.2% offset yield stress at the temperatures. Inflection of stress vs. time to rupture curve is caused by transient of applied stress from higher level than elastic limit to within elastic range. It has been concluded that long-term creep strength of ferritic creep resistant steels should be predicted from the selected creep rupture data under the stresses lower than elastic limit by considering half of 0.2% offset yield stress at the temperature, by means of Larson-Miller parameter with a constant of 20.

Download Full-text