A Micromechanical Model for Creep Damage and Its Application to Crack Growth in a 12% Cr Steel

2009 ◽  
pp. 37-37-17 ◽  
Author(s):  
M Sester ◽  
R Mohrmann ◽  
H Riedel
Keyword(s):  
Crack Growth ◽  
Micromechanical Model ◽  
Creep Damage

Computational Modelling of High Temperature Steady State Crack Growth Using a Damage-Based Approach

2003 ◽  
Author(s):  
Masataka Yatomi ◽  
Noel P. O’Dowd ◽  
Kamran M. Nikbin
Keyword(s):  
Crack Growth ◽  
Plane Strain ◽  
Plane Stress ◽  
Computational Study ◽  
Creep Crack Growth ◽  
Computational Modelling ◽  
Crack Tip ◽  
Creep Damage ◽  
Creep Model ◽  
Manganese Steel

In this work a computational study of creep crack growth in a carbon manganese steel is presented. The constitutive behaviour of the steel is described by a power law creep model and the accumulation of creep damage is accounted for through the use of a well-established model for void growth in creeping materials. Two dimensional finite element analyses have been performed for a compact tension specimen and it has been found that the predicted crack growth rate under plane strain conditions approaches that under plane stress conditions at high C* levels. Furthermore it has been shown, both experimentally and numerically, that an increase in test temperature causes the convergence of the cracking rate to occur at higher values of C*. This trend may be explained by the influence of crack-tip plasticity, which reduces the relative difference in constraint between plane stress and plane strain conditions. The constraint effect has been quantified through the use of a two-parameter characterisation of the crack tip fields under creep conditions.

A micromechanical model of crack growth along polymer interfaces

1991 ◽  
Vol 11 (3) ◽  
pp. 257-268 ◽  
Author(s):  
D.-B. Xu ◽  
C.-Y. Hui ◽  
E.J. Kramer ◽  
C. Creton
Keyword(s):  
Crack Growth ◽  
Micromechanical Model ◽  
Polymer Interfaces

Finite Element Damage Analyses for Predictions of Creep Crack Growth

2010 ◽  
Author(s):  
Chang-Sik Oh ◽  
Nak-Hyun Kim ◽  
Sung-Hwan Min ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Crack Growth ◽  
Damage Mechanics ◽  
Creep Crack Growth ◽  
Creep Damage ◽  
Simulation Method ◽  
Creep Tests ◽  
Creep Ductility ◽  
Creep Crack

This paper provides the virtual simulation method for creep crack growth test, based on finite element (FE) analyses with damage mechanics. Creep tests of smooth bars are used to quantify the constants of creep constitutive equation. The reduction of area resulting from creep tests of smooth and notched bar is adopted as a measure of creep ductility under multiaxial stress conditions. The creep ductility exhaustion concept is adopted for calculating creep damage, which is defined as the ratio of creep strain to the multiaxial creep ductility. To simulate crack propagation, fully damaged elements are forced to have nearly zero stresses using user-defined subroutine UHARD in the general-purpose FE code, ABAQUS. The results from 2D or 3D FE analyses are compared with experimental data of creep crack growth. It is shown that the predictions obtained from this new method are in good agreement with experimental data.

A Methodology for Evaluating the Integrity of Longitudinally Seam-Welded Steam Pipes in Fossil Plants

1988 ◽  
Vol 110 (3) ◽  
pp. 283-290 ◽  
Author(s):  
R. Viswanathan ◽  
R. Dooley ◽  
A. Saxena
Keyword(s):  
Crack Growth ◽  
Power Plants ◽  
Creep Crack Growth ◽  
Creep Damage ◽  
Electric Power Research Institute ◽  
Fossil Plants ◽  
Damage Initiation ◽  
Catastrophic Failures ◽  
Failure Scenario ◽  
Steam Pipes

Two recent catastrophic failures of steam pipes have generated great concern about the integrity of steam pipes in fossil power plants. In the wake of these failures, extensive pipe inspections have been carried out by utilities. Numerous flaws have been found, but the methodologies for disposition of flawed piping have varied widely. The failure scenario has emerged to be one involving creep crack growth of preexisting flaws located at the weld fusion line. The crack growth susceptibility itself has been found to be a function of the metallurgical condition of the steel. Based on creep damage initiation and crack growth methodologies developed by Electric Power Research Institute under a variety of projects, an overall approach to assessing pipe integrity and for determining inspection intervals has been constructed. This paper will report on the details of this approach.

Micromechanical Analysis of Constraint Effect on Fracture Initiation in Strength Mismatched Welded Joints

2007 ◽  
Vol 555 ◽  
pp. 571-576 ◽  
Author(s):  
M. Dobrojević ◽  
Marko Rakin ◽  
Nenad Gubeljak ◽  
Ivana Cvijović ◽  
Misa Zrilić ◽  
...  
Keyword(s):  
Crack Growth ◽  
Welded Joints ◽  
Volume Fraction ◽  
Hsla Steel ◽  
Micromechanical Model ◽  
Welding Process ◽  
Constraint Effect ◽  
Precracked Specimen ◽  
Flux Cored Arc Welding ◽  
Growth Initiation

In this paper the micromechanical approach to ductile fracture was applied in a study of constraint effect on crack growth initiation in mismatched welded joints. The single-edged notched bend specimens (precrack length a0/W=0.32) were experimentally and numerically analyzed. The coupled micromechanical model proposed by Gurson, Tvergaard and Needleman was used. Constraint effect was tested by varying widths of the welded joints (6, 12 and 18mm). Highstrength low-alloyed (HSLA) steel was used as the base metal in a quenched and tempered condition. The flux-cored arc-welding process in shielding gas was used. Two different fillers were selected to obtain over- and undermatched weld metal. The micromechanical parameters used in prediction of the crack growth initiation on precracked specimen were calibrated on a round smooth specimen. The difference in fracture behavior between over- and undermatched welded joints obtained in experimental results was followed by numerical computations of void volume fraction in front of the crack tip.

An Analysis of Elevated Temperature Fatigue and Creep Crack Growth

1976 ◽  
Vol 98 (4) ◽  
pp. 473-479 ◽  
Author(s):  
M. Do¨ner
Keyword(s):  
Elevated Temperature ◽  
Crack Growth ◽  
Growth Rates ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Creep Damage ◽  
Material Constant ◽  
Temperature Oxidation ◽  
Oxidation Damage ◽  
Crack Growth Rates

Existing crack growth laws which consider time and temperature effects are examined. Based on phenomenological observations, as well as mechanistic considerations, one of these laws is modified in order to provide an improved, universal elevated temperature crack growth law. It is assumed that there are essentially three processes through which crack growth rates are affected: decrease in strength and modulus with temperature, oxidation damage at the crack tip and creep damage at the crack tip. The rate controlling mechanism(s) which may be associated with each of these processes are discussed. The type of experiments which are needed for the determination of material constant(s) that describe the contribution from each process are outlined. The modified crack growth law, when applied to publish data on HS-188 alloy, results in a prediction of the crack growth rates within a factor of 2.5, in the temperature range of 873–1144 K and at cycle frequencies ranging from 0.01 to 10 Hz.

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