Elasto-Plastic Analysis of a Functionally Graded Rotating Disk Under Cyclic Thermo-Mechanical Loadings Considering Continuum Damage Mechanics

2015 ◽  
Vol 07 (02) ◽  
pp. 1550026 ◽  
Author(s):  
Ali Nayebi ◽  
Ali Tirmomenin ◽  
Mohsen Damadam
Keyword(s):  
Damage Mechanics ◽  
Volume Fraction ◽  
Yield Criterion ◽  
Kinematic Hardening ◽  
Numerical Procedure ◽  
Rotating Disk ◽  
Continuum Damage Mechanics ◽  
Back Stress ◽  
Functionally Graded ◽  
Continuum Damage

The goal of this work is to study the influence of continuum damage mechanics on a functionally graded rotating disk subjected to cyclic temperature gradient loading through nonlinear kinematic hardening rule employed to model the back stress. The formulations have been developed on the basis of von Mises' yield criterion. The material properties are assumed to be independent of temperature and vary according to a power law volume fraction relation but Poisson's ratio is assumed to be constant. Return mapping algorithm (RMA), an incremental method, has been used in the numerical procedure. Material behaviors such as elastic shakedown, plastic shakedown and ratcheting were specified in the existence of continuum damage mechanics to obtain the Bree's interaction diagram for different temperatures and angular velocities.

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.

Shakedown-Ratcheting Analysis of a Spherical Pressure Vessel by Anisotropic Continuum Damage Mechanics

2018 ◽  
Author(s):  
Ali Nayebi ◽  
Azam Surmiri ◽  
Hojjatollah Rokhgireh
Keyword(s):  
Pressure Vessel ◽  
Damage Mechanics ◽  
Kinematic Hardening ◽  
Continuum Damage Mechanics ◽  
Mapping Method ◽  
Anisotropic Damage ◽  
Continuum Damage ◽  
Interaction Diagram ◽  
Plastic Shakedown ◽  
Spherical Pressure

In cyclic loading and when plastic flow occurs, discontinuities grow. In this research, interaction diagram of Bree has been developed when the spherical pressure vessel contains discontinuities such as voids and microcracks. Bree’s diagram is used for ratcheting assessment of pressurized equipment in ASME III NH. Nature of these defects leads to an anisotropic damage. Anisotropic Continuum Damage Mechanics (CDM) is considered to account effects of these discontinuities on the behavior of the structure. Shakedown – ratcheting response of a hollow sphere under constant internal pressure and cyclic thermal loadings are studied by using anisotropic CDM theory coupled with nonlinear kinematic hardening of Armstrong-Frederick m’s model (A-F). Return mapping method is used to solve numerically the developed relations. Elastic, elastic shakedown, plastic shakedown and ratcheting regions are illustrated in the modified Bree’s diagram. Influence of anisotropic damage due to the plastic deformation is studied and it was shown that the plastic shakedown region is diminished because of the developed damage.

scholarly journals On continuum damage mechanics

2019 ◽  
Vol 52 (3) ◽  
pp. 125-147
Author(s):  
Kari Juhani Santaoja
Keyword(s):  
Stress Tensor ◽  
Effective Stress ◽  
Elastic Strain ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Strain Tensor ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
The Matrix ◽  
Elastic Strain Tensor

A material containing spherical microvoids with a Hookean matrix response was shown to take the appearance usually applied in continuum damage mechanics. However, the commonly used variable damage D was replaced with the void volume fraction f , which has a clear physical meaning, and the elastic strain tensor \Bold {ε}^e with the damage-elastic strain tensor \Bold {ε}^{de}. The postulate of strain equivalence with the effective stress concept was reformulated and applied to a case where the response of the matrix obeys Hooke’s law. In contrast to many other studies, in the derived relation between the effective stress tensor \Bold {\Tilde{σ}} and the stress tensor \Bold {σ}, the tensor \Bold {\Tilde{σ}} is symmetric. A uniaxial bar model was introduce for clarifying the derived results. Other candidates for damage were demonstrated by studying the effect of carbide coarsening on creep rate.

CONTINUUM DAMAGE MECHANICS ANALYSIS OF THIN-WALLED TUBE UNDER CYCLIC BENDING AND INTERNAL CONSTANT PRESSURE

2013 ◽  
Vol 05 (04) ◽  
pp. 1350038 ◽  
Author(s):  
H. YAZDANI ◽  
A. NAYEBI
Keyword(s):  
Internal Pressure ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Cyclic Bending ◽  
Thin Walled Tube ◽  
Thin Walled

Ratcheting and fatigue damage of thin-walled tube under cyclic bending and steady internal pressure is studied. Chaboche's nonlinear kinematic hardening model extended by considering the effect of continuum damage mechanics employed to predict ratcheting. Lemaitre damage model [Lemaitre, J. and Desmorat, R. [2005] Engineering Damage Mechanics (Springer-Verlag, Berlin)] which is appropriate for low cyclic loading is used. Also the evolution features of whole-life ratcheting behavior and low cycle fatigue (LCF) damage of the tube are discussed. A simplified method related to the thin-walled tube under bending and internal pressure is used and compared well with experimental results. Bree's interaction diagram with boundaries between shakedown and ratcheting zone is determined. Whole-life ratcheting of thin-walled tube reduces obviously with increase of internal pressure.

Finite Element Modeling of Fatigue Damage Using a Continuum Damage Mechanics Approach

2005 ◽  
Vol 127 (2) ◽  
pp. 157-164 ◽  
Author(s):  
Abı´lio M. P. De Jesus ◽  
Alfredo S. Ribeiro ◽  
Anto´nio A. Fernandes
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Kinematic Hardening ◽  
Fatigue Crack Initiation ◽  
Continuum Damage Mechanics ◽  
Cyclic Plasticity ◽  
Continuum Damage ◽  
Elastoplastic Behavior ◽  
Fatigue Model

In this paper, a fatigue model formulated in the framework of the continuum damage mechanics (CDM) is presented. The model is based on an explicit definition of fatigue damage and introduces a kinematic damage differential equation formulated directly as a function of the number of cycles and the stress cycle parameters. The model is initially presented for uniaxial problems, which facilitates the identification of its constants. An extension of the fatigue model to multiaxial problems is also proposed. This model was implemented in a nonlinear finite element code in conjunction with a constitutive model for cyclic plasticity. The cyclic plasticity model considered is based on a J2-plasticity theory with nonlinear isotropic and kinematic hardenings. In order to enhance the description of the cyclic elastoplastic behavior, the superposition of several nonlinear kinematic hardening variables is suggested. Both fatigue and plasticity models are identified for the P355NL1 (TStE355) steel. Finally, the numerical model is used to predict the fatigue crack initiation for a welded nozzle-to-plate connection, made of P355NL1 steel, and results are compared with experimental fatigue data.

Evaluation of the Effects of Inclusion Distribution on the Local Ductility of DP Steel

2012 ◽  
Vol 706-709 ◽  
pp. 1527-1532 ◽  
Author(s):  
Y. Suwa ◽  
T. Matsuno ◽  
S. Hirose ◽  
N. Fujita ◽  
A. Seto
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Analysis ◽  
Dp Steel ◽  
The Difference ◽  
Inclusion Distribution

In the present study, the effects of inclusions on the local ductility of DP steel are investigated using finite element analysis (FEA). In order to evaluate local ductility, a continuum damage mechanics (CDM) model has been incorporated into the Abaqus/Explicit® commercial finite element code. Furthermore, three-dimensional representative volume elements (RVEs) with ferrite, martensite, and inclusion phases have been used to evaluate the stress-strain response. Simulation results show that the volume fraction of the martensite as well as the difference in hardness between the ferrite and the martensite phases dominates the effect of inclusions on local ductility.

A precipitate evolution-based continuum damage mechanics model of creep behaviour in welded 9Cr steel at high temperature

2018 ◽  
Vol 233 (1) ◽  
pp. 39-51
Author(s):  
C Ó Murchú ◽  
SB Leen ◽  
PE O’Donoghue ◽  
RA Barrett
Keyword(s):  
Damage Mechanics ◽  
Volume Fraction ◽  
Creep Behaviour ◽  
Continuum Damage Mechanics ◽  
Time To Failure ◽  
Continuum Damage ◽  
State Variable ◽  
9Cr Steel ◽  
Mechanics Model ◽  
Physically Based

A multiaxial, physically based, continuum damage mechanics methodology for creep of welded 9Cr steels is presented, incorporating a multiple precipitate-type state variable, which simulates the effects of strain- and temperature-induced coarsening kinematics. Precipitate volume fraction and initial diameter for carbide and carbo-nitride precipitate types are key microstructural variables controlling time to failure in the model. The heat-affected zone material is simulated explicitly utilising measured microstructural data, allowing detailed investigation of failure mechanisms. Failure is shown to be controlled by a combination of microstructural degradation and Kachanov-type damage for the formation and growth of creep cavities. Comparisons with experimental data demonstrate the accuracy of this model for P91 material.

Evaluating Fracture Toughness of Ductile Materials: A Critical Indentation Energy Model Based on Continuum Damage Mechanics

2005 ◽  
Author(s):  
Jung-Suk Lee ◽  
Eui-Hyun Kim ◽  
Dongil Kwon
Keyword(s):  
Fracture Toughness ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Continuum Damage Mechanics ◽  
Fracture Toughness Test ◽  
Continuum Damage ◽  
Test Results ◽  
Ductile Materials ◽  
Good Agreement ◽  
Critical Void

A new model for determining fracture toughness of ductile materials is presented that uses indentation and is based on continuum damage mechanics (CDM) and the concept of critical void volume fraction. Fracture toughness evaluated using the model showed good agreement with standard fracture toughness test results.

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