scholarly journals Review of Creep Cavitation and Rupture of Low Cr Alloy and its Weldment

2013 ◽  
Vol 744 ◽  
pp. 407-411
Author(s):  
Qi Hua Xu ◽  
Qiang Xu ◽  
Yong Xin Pan ◽  
Michael Short
Keyword(s):  
High Temperature ◽  
Constitutive Equation ◽  
Damage Mechanics ◽  
Experimental Approach ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Safe Operation ◽  
Computational Approaches ◽  
Creep Cavitation

This paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the computational approaches is continuum damage mechanics which has been developed and applied complementary to the experimental approach and assists in the safe operation. However, the existing creep damage constitutive equations are not developed specifically for low stress. Therefore, in order to form the physical bases for the development of creep damage constitutive equation, it is necessary to critically review the creep cavitation and rupture characteristics of low Cr alloy and its weldment.

scholarly journals Analyzing the Characteristics of the Cavity Nucleation, Growth and Coalescence Mechanism of 9Cr-1Mo-VNb Steel (P91) Steel

2013 ◽  
Vol 744 ◽  
pp. 412-416 ◽  
Author(s):  
Li Li An ◽  
Qiang Xu ◽  
Zhong Yu Lu ◽  
Dong Lai Xu
Keyword(s):  
Damage Mechanics ◽  
Experimental Approach ◽  
Axial Stress ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Computational Approach ◽  
Continuum Damage ◽  
Safe Operation ◽  
Cavity Nucleation ◽  
Nucleation Growth

Creep damage is one of the serious problems for the high temperature industries and computational approach (such as continuum damage mechanics) has been developed and used, complementary to the experimental approach, to assist safe operation. However, there are no ready creep damage constitutive equations to be used for predicting the lifetime for this type of alloy, particularly for low stress. This paper presents an analysis of the cavity nucleation, growth and coalescence mechanism of 9Cr-1Mo-VNb steel (P91 type) under high and low stress levels and multi-axial stress state.

Development of continuum damage in the creep rupture of notched bars

1984 ◽  
Vol 311 (1516) ◽  
pp. 103-129 ◽  
Keyword(s):  
New York ◽  
Damage Mechanics ◽  
Axial Stress ◽  
Numerical Procedure ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Constant Load ◽  
Creep Rupture ◽  
Continuum Damage ◽  
Discrete Crack

The creep rupture of circumferentially notched, circular tension bars which are subjected to constant load for long periods at constant temperature is studied both experimentally and by using a time-iterative numerical procedure which describes the formation and growth of creep damage as a field quantity. The procedure models the development of failed or cracked regions of material due to the growth and linkage of grain boundary defects. Close agreement is shown between experimental and theoretical values of the representative rupture stress, of the zones of creep damage and of the development of cracks for circular (Bridgman, Studies in large plastic flow and fracture , New York: McGraw-Hill (1952)) and British Standard notched specimens (B.S. no. 3500 (1969)). The minimum section of the circular notch is shown to be subjected to relatively uniform states of multi-axial stress and damage while the B.S. notch is shown to be subjected to non-uniform stress and damage fields in which single cracks grow through relatively undamaged material. The latter situation is shown to be analogous to the growth of a discrete crack in a lightly damaged continuum. The continuum damage mechanics theory presented here is shown to be capable of accurately predicting these extreme types of behaviour.

Finite Element Simulation of the Creep Behavior of 2.25Cr-1Mo-0.25V Steel Based on Continuum Damage Mechanics

2015 ◽  
Vol 750 ◽  
pp. 266-271 ◽  
Author(s):  
Yu Zhou ◽  
Xue Dong Chen ◽  
Zhi Chao Fan ◽  
Yi Chun Han
Keyword(s):  
Genetic Algorithm ◽  
Finite Element ◽  
Creep Behavior ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Simulation

The creep behavior of 2.25Cr-1Mo-0.25V ferritic steel was investigated using a set of physically-based creep damage constitutive equations. The material constants were determined according to the creep experimental data, using an efficient genetic algorithm. The user-defined subroutine for creep damage evolution was developed based on the commercial finite element software ANSYS and its user programmable features (UPFs), and the numerical simulation of the stress distribution and the damage evolution of the semi V-type notched specimen during creep were studied. The results showed that the genetic algorithm is a very efficient optimization approach for the parameter identification of the creep damage constitutive equations, and finite element simulation based on continuum damage mechanics can be used to analyze and predict the creep damage evolution under multi-axial stress states.

Interpretation of damage mechanics behaviour of two-bar structures for the life extension of high-temperature components

2003 ◽  
Vol 38 (2) ◽  
pp. 125-132 ◽  
Author(s):  
S-T Tu ◽  
X Ling
Keyword(s):  
High Temperature ◽  
Damage Mechanics ◽  
Creep Damage ◽  
Life Extension ◽  
Continuum Damage ◽  
Basic Model ◽  
Different Dimensions ◽  
Damage Theory ◽  
High Temperature Components

The creep damage behaviour of two-bar structures of different dimensions and materials is studied in terms of continuum damage theory. The basic model is used to interpret the effectiveness of life extension measures for complicated structures. It is found that replacement of the more damaged component prior to rupture will result in an optimized life extension efficiency, depending on the geometric or material difference between the damaged and less damaged components. This has potential to provide guidance on the effectiveness of life extension repairs in high-temperature plants.

Life Prediction of High Temperature Welded Component by Skeletal Point Rupture Stress

2010 ◽  
Vol 118-120 ◽  
pp. 156-160 ◽  
Author(s):  
Guo Dong Zhang ◽  
Yan Fen Zhao ◽  
Fei Xue ◽  
Zhao Xi Wang ◽  
Chang Yu Zhou
Keyword(s):  
High Temperature ◽  
Life Prediction ◽  
Power Plants ◽  
Damage Mechanics ◽  
Welded Joint ◽  
Stress Rupture ◽  
Continuum Damage Mechanics ◽  
Chemical Plants ◽  
Continuum Damage ◽  
Rupture Stress

At the present time, as the steam conditions and capability of the supercritical power unit increasing, the unit reliability is an important factor for the unit efficiency. High temperature, thick walled pipes are widely used in power plants and chemical plants. In this paper, life of the welded joint was predicted by the methods of skeletal point (SP) rupture stress rupture stress, which was calculated by finite element method (FEM). For the life prediction of welded component, the continuum damage mechanics was employed too. The life prediction of the welded joint by SP rupture stress was compared with the life prediction by the method of continuum damage mechanics (CDM). The research results showed that the two predicted methods were consistent. So, it can be concluded that the SP rupture stress can be used for predicting life of the high temperature welded component. The SP rupture stress method was used conveniently for the structure of power plant or other high temperature components.

A Unified Continuum Damage Mechanics Model for Predicting the Stress Relaxation Behavior of High-Temperature Bolting

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
J. Q. Guo ◽  
X. T. Zheng ◽  
Y. Zhang ◽  
H. C. Shi ◽  
W. Z. Meng
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Stress Relaxation ◽  
Constitutive Equations ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Relaxation Behavior ◽  
Continuum Damage ◽  
Creep Equation ◽  
Stress Relaxation Behavior

Two stress relaxation constitutive models have been developed to predict the stress relaxation behavior for high-temperature bolting according to continuum damage mechanics, Kachanov–Robatnov (K–R), and Othman–Hayhurst (O–H) creep constitutive equations as well as stress relaxation strain equations. To validate the effectiveness of constitutive equations, the predicted results were compared with the experimental data of uniaxial isothermal stress relaxation tests using 1Cr10NiMoW2VNbN steel. The results show that the results obtained by the stress relaxation constitutive model based on the K–R creep equation overestimates the stress relaxation behavior, while the model deduced by the O–H creep equation is more in agreement with the experimental data. Moreover, the stress relaxation damage predicted increases with the increment of initial stress significantly. These indicate that the new models can predict the stress relaxation behavior of high-temperature bolting well.

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