Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
D. Gustafsson ◽  
J. J. Moverare ◽  
K. Simonsson ◽  
S. Sjöström
Keyword(s):  
Inconel 718 ◽  
Kinematic Hardening ◽  
Fatigue Crack Initiation ◽  
Model Fit ◽  
Cyclic Plasticity ◽  
Rigorous Analysis ◽  
Hardening Law ◽  
Hot Environment ◽  
Turbine Disks ◽  
Mean Stress Relaxation

Turbine disks are of large importance to turbine designers as they are exposed to hot environment and subjected to high loads. In order to analyze such components with respect to fatigue crack initiation, the work generally starts with a rigorous analysis of the first few cycles, during which an important stress redistribution will always take place in an inelastic structure. In this work, the nonlinear kinematic hardening law by Ohno and Wang (1998, “Constitutive Modeling of Cyclic Plasticity With Emphasis on Ratchetting,” Int. J. Mech. Sci., 40, pp. 251–261) has been used in combination with an isotropic softening law for describing the initial stress-strain distribution for strain controlled uniaxial tests of the material Inconel 718. Focus has been placed on finding a simple model with few material parameters and to describe the initial softening and the comparatively small mean stress relaxation observed during the material testing. The simulation results obtained by using the model fit the experimental results well.

Prediction of Fatigue Crack Initiation Life Based on the Extended Cyclic Plasticity Model

2012 ◽  
Author(s):  
Seiichiro Tsutsumi
Keyword(s):  
Cyclic Loading ◽  
Kinematic Hardening ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Carbon Steels ◽  
Cyclic Plasticity ◽  
Plasticity Model ◽  
Hardening Law ◽  
Crack Initiation Life ◽  
Cyclic Plasticity Model

In order to simulate mechanical fatigue phenomena under macroscopically elastic condition, the plastic stretching within a yield surface has to be described, whilst the plastic strain is induced remarkably as the stress approaches the dominant yielding state. In this study, a phenomenological plasticity model, proposed for the description of the cyclic loading behavior observed for typical carbon steels during the high-cycle fatigue subjected to stresses lower than the yield stress, is applied for the prediction of fatigue initiation life. The model is formulated based on the unconventional plasticity model and is applied for materials obeying isotropic and kinematic hardening law. The mechanical responses under cyclic loading conditions are examined briefly. Finally, the initiation life of fatigue cracking is discussed based on the proposed model with the damage counting parameter.

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.

Description of Closure of Cyclic Stress-Strain Loop and Ratcheting Based on Y-U Model

2016 ◽  
Vol 725 ◽  
pp. 351-356
Author(s):  
Fusahito Yoshida ◽  
Hiroshi Hamasaki ◽  
Takeshi Uemori
Keyword(s):  
Hysteresis Loop ◽  
Kinematic Hardening ◽  
Cyclic Stress ◽  
Cyclic Plasticity ◽  
Plasticity Model ◽  
Stress Strain ◽  
Additional Material ◽  
Material Parameters ◽  
Hardening Law ◽  
Cyclic Plasticity Model

This paper proposes a cyclic plasticity model to describe the closure of a cyclic stress-strain hysteresis loop based on the Y-U model. In this model, the backstress moves in a cyclic memory surface following a newly proposed kinematic hardening law. For this model just the same Y-U parameters can be used, and no additional material parameters are needed. By using a supplementary rule, this model is also able to describe ratcheting.

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

2004 ◽  
Author(s):  
A. M. P. De Jesus ◽  
A. S. Ribeiro ◽  
A. A. Fernandes
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Kinematic Hardening ◽  
Fatigue Crack Initiation ◽  
Continuum Damage Mechanics ◽  
Cyclic Plasticity ◽  
Continuum Damage ◽  
Fatigue Model ◽  
Non Linear

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 non-linear 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 non-linear isotropic and kinematic hardenings. In order to enhance the description of the cyclic elastoplastic behaviour, is suggested the superposition of several non-linear kinematic hardening variables. 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.

Modeling of Fatigue Crack Propagation

2004 ◽  
Vol 126 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Yanyao Jiang ◽  
Miaolin Feng
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Cyclic Plasticity ◽  
R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

A Continuum Model for Single Crystal Cyclic Plasticity

2003 ◽  
Vol 779 ◽  
Author(s):  
Biqiang Xu ◽  
Yanyao Jiang
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Kinematic Hardening ◽  
Strain Curve ◽  
Cyclic Behavior ◽  
Cyclic Plasticity ◽  
Amplitude Dependence ◽  
Slip Systems ◽  
Stress Strain ◽  
Copper Single Crystals

AbstractA constitutive model was developed to bridge the cyclic plasticity behavior of single crystals and the corresponding characteristic dislocation structures. Yield and flow were built on the individual slip systems. The Armstrong-Frederick kinematic hardening rule was invoked to capture the Bauschinger effect. A material memory parameter was introduced to consider the amplitude dependence of cyclic hardening. Latent hardening considering the interactions among the slip systems was used to describe the anisotropic cyclic behavior. The experimental results of copper single crystals were used to validate the model developed. It was found that the model was able to adequately describe the well-known three distinctive regions in the cyclic stress-strain curve of the FCC single crystal oriented for single slip and the associated dislocation substructures. The model was capable of capturing the enhanced hardening observed in copper single crystals in multi-slip orientations. For a given loading history, the model can predict not only the saturated stress-strain response but also the detailed evolution of the transient cyclic behavior. The characteristic dislocation structures can be featured with the slip evolution.

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