Mixed-Mode Creep Crack Growth Simulations Using Continuum Damage Mechanics and Virtual Node XFEM

2019 ◽  
pp. 275-284 ◽  
Author(s):  
V. B. Pandey ◽  
M. Kumar ◽  
I. V. Singh ◽  
B. K. Mishra ◽  
S. Ahmad ◽  
...  
Keyword(s):  
Crack Growth ◽  
Mixed Mode ◽  
Damage Mechanics ◽  
Creep Crack Growth ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Virtual Node ◽  
Creep Crack

The role of continuum damage in creep crack growth

1984 ◽  
Vol 311 (1516) ◽  
pp. 131-158 ◽  
Keyword(s):  
Crack Growth ◽  
Damage Mechanics ◽  
Experimental Studies ◽  
Creep Crack Growth ◽  
Stress Rupture ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Creep Crack ◽  
Theoretical Predictions ◽  
Rupture Criterion

Theories that have been used to predict the rate of growth of cracks due to creep are reviewed and assessed. The need is expressed for a sounder understanding of the mechanisms by which creep crack growth takes place. The aim of this paper is to answer the question: can continuum damage mechanics provide the mechanism by which cracks grow by creep? The paper reports the results of theoretical and experimental studies on internally and externally cracked, plane strain, tension members, in an aluminium alloy, in copper and in 316 stainless steel, all of which undergo high temperature creep rupture under steady loads. Theoretical predictions of lifetimes, expressed as a representative rupture stress, of damage fields and of crack growth are made by using a previously developed finite element system (Hayhurst, Dimmer & Morrison, Phil. Trans. R. Soc. Lond . 311, 103 (1984)) based on the theory of continuum damage mechanics. The theoretical predictions are shown to be in close agreement with experimental observations. The effect of the growth of continuum damage is to produce considerable stress redistribution and to cause the nullification of stress singularities. The multi-axial stress rupture criterion of the material plays an important role in the determination of lifetimes and of the planes upon which crack propagation takes place. The numerical solution procedure is automatic but requires that the constitutive equations model the elastic response, the creep strain rates, including tertiary behaviour, and the multiaxial stress rupture criterion of the material at the appropriate stress levels. Continuum damage mechanics theory is shown to be capable of modelling the propagation of cracks through material which has suffered relatively low damage.

scholarly journals Creep crack simulations using continuum damage mechanics and extended finite element method

2017 ◽  
Vol 28 (1) ◽  
pp. 3-34 ◽  
Author(s):  
VB Pandey ◽  
I V Singh ◽  
BK Mishra ◽  
S Ahmad ◽  
AV Rao ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Growth ◽  
Damage Mechanics ◽  
Extended Finite Element Method ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Extended Finite Element ◽  
Creep Crack ◽  
Element Method

In the present work, elasto-plastic creep crack growth simulations are performed using continuum damage mechanics and extended finite element method. Liu–Murakami creep damage model and explicit time integration scheme are used to evaluate the creep strain and damage variable for various materials at different temperatures. Compact tension and C-shaped tension specimens are selected for the simulation of crack growth analysis. For damage evaluation, both local and nonlocal approaches are employed. The accuracy of the extended finite element method solutions is checked by comparing with experimental results and finite element solutions. These results show that the extended finite element method requires a much coarser mesh to effectively model crack propagation. It is also shown that mesh independent results can be achieved by using nonlocal implementation.

Crack Propagation in Mixed-Mode Ductile Fracture with Continuum Damage Mechanics

1989 ◽  
Vol 203 (3) ◽  
pp. 189-199 ◽  
Author(s):  
C L Chow ◽  
J Wang
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Ductile Fracture ◽  
Crack Growth ◽  
Mixed Mode ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Propagation Model ◽  
Element Formulation ◽  
Continuum Damage

This paper presents a crack propagation model based on an anisotropic theory of continuum damage mechanics proposed earlier by the authors capable of characterizing sub-critical crack growth in mixed-mode ductile fracture. The embedded β angles of mixed-mode specimens include 75, 60, 45 and 30 degrees. The crack growth criteria chosen are essentially those developed for crack initiation and are postulated as: 1. A crack propagates in the direction of maximum effective damage equivalent stress αd. 2. The threshold condition of crack initiation is satisfied when the overall damage w in an element ahead of the crack tip at the prospective crack growth direction reaches its critical value, wc. The crack growth behaviours of the mixed-mode specimens are analysed using a finite element formulation of the non-proportional loading based on the anisotropic model, and the predicted and measured results are found to be satisfactory. The proposed model is also adapted to predict the critical loads of unstable crack propagation and the results are compared favourably with those determined experimentally. Hence the application of the above two fracture criteria can be made to address the entire history of crack development from initiation to rapid growth.

Analysis of Creep Crack Growth Behavior of the Brazed Joint Using Continuum Damage Mechanics Approach

2018 ◽  
Author(s):  
Yu-Cai Zhang ◽  
Wenchun Jiang ◽  
Shan-Tung Tu ◽  
Xian-Cheng Zhang ◽  
Guo-Yan Zhou
Keyword(s):  
Crack Initiation ◽  
Diffusion Zone ◽  
Damage Mechanics ◽  
Creep Crack Growth ◽  
Continuum Damage Mechanics ◽  
Crack Growth Behavior ◽  
Continuum Damage ◽  
Initiation Time ◽  
Creep Crack ◽  
Brazed Joint

Creep crack growth behavior of the Inconel625/BNi-2 brazed joint considering the diffusion zone at 650 °C was investigated by a continuum damage mechanics approach based on the finite element method. The results show that creep crack nucleate and develop at the region of the brazing filler metal. The crack initiates at about 0.2 mm ahead of the crack tip. When the load is 1000 N, the crack initiation time of the CT specimen is 1664 hour. While when the load is 1135 N, the crack initiation time is only about 891 hour. The simulated results correspond well with the experimental data, presenting that the used finite element method can accurately simulate the creep damage behavior of the brazed joint. When the mechanical properties of the diffusion zone are not considered, the crack initiation time and fracture time decrease significantly compared to the result with properties of the diffusion zone included, indicating that the result from the conventional simulating method without considering the diffusion zone is quite conservative compared to the experimental life of the component.

Defect Assessments at Elevated Temperature

1983 ◽  
Vol 105 (3) ◽  
pp. 263-268 ◽  
Author(s):  
R. A. Ainsworth ◽  
I. W. Goodall
Keyword(s):  
Damage Mechanics ◽  
Creep Crack Growth ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Initiation Time ◽  
Creep Crack ◽  
Reference Stress ◽  
Statistical Approaches ◽  
Assessment Requirements ◽  
Fast Fracture

Methods are described for assessing acceptable defect sizes for plant in high temperature service. At one extreme of behavior, that of creep ductile response, failure is governed by continuum damage mechanics which may be analyzed using finite element methods or more approximately by reference stress techniques. In less ductile cases failure can occur through the initiation and growth of a dominant creep crack. For this case the paper outlines how the assessment requirements may be based on an estimate of the initiation time and a method for calculating this initiation time is given. When the initiation time is small, the assessment also requires an estimate of the time taken in the creep crack growth stage and both empirical correlation and statistical approaches for analyzing this stage are described. Finally the paper outlines how fast fracture and ductile instability can be included in determining repair criteria for use with the various assessment methods.

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