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Internal Elliptic Surface Creep Crack Growth Analysis In Pressure Vessels For 2.25Cr Steel
Subject area: Science,Engineering and Technology · Area of research: Mechanical Engineering
Abstract
Nonlinear fracture mechanics based methodologies is common practice to model an elliptic axial surface crack located at the internal or external surface of a cylindrical pressure vessel as an infinitely long axial crack. This simplification considerably reduces the amount of computation needed for evaluating high temperature fracture parameters such as C*and Ct and for determining crack growth life. This simplification on the estimated component life have never been systematically assessed in detail except stating that the assumption leads to a conservative estimate of life. In this study, an analysis method is developed that does not require any assumption. Using this developed method, a procedure for life assessment was demonstrated for an elliptic axial surface crack located on the internal surface of a pressurized vessel at high temperature. Equations are proposed for estimating Ct at both the deepest point along the crack front and also at the crack tip on the surface. Using these equations, the aspect ratios of the surface crack were updated for every time step of crack growth calculations and were reflected in determining Ct value of the next step. Changes of crack depth, crack size and Ct values at the deepest point and surface point of the crack tip are estimated and used to predict the evolution of crack shape during creep crack growth.
Keywords
Life Assessments; Pressurized Vessel; Surface Cracks; C*; Ct
How to cite this paper
@article{1701633,
author = {Nwe Ni Tun, Zar Chi Thaung},
title = {Internal Elliptic Surface Creep Crack Growth Analysis In Pressure Vessels For 2.25Cr Steel},
journal = {Iconic Research And Engineering Journals},
year = {2019},
volume = {3},
number = {3},
pages = {89-95},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1701633.pdf},
abstract = {Nonlinear fracture mechanics based methodologies is common practice to model an elliptic axial surface crack located at the internal or external surface of a cylindrical pressure vessel as an infinitely long axial crack. This simplification considerably reduces the amount of computation needed for evaluating high temperature fracture parameters such as C*and Ct and for determining crack growth life. This simplification on the estimated component life have never been systematically assessed in detail except stating that the assumption leads to a conservative estimate of life. In this study, an analysis method is developed that does not require any assumption. Using this developed method, a procedure for life assessment was demonstrated for an elliptic axial surface crack located on the internal surface of a pressurized vessel at high temperature. Equations are proposed for estimating Ct at both the deepest point along the crack front and also at the crack tip on the surface. Using these equations, the aspect ratios of the surface crack were updated for every time step of crack growth calculations and were reflected in determining Ct value of the next step. Changes of crack depth, crack size and Ct values at the deepest point and surface point of the crack tip are estimated and used to predict the evolution of crack shape during creep crack growth.},
keywords = {Life Assessments; Pressurized Vessel; Surface Cracks; C*; Ct},
month = {September},
}