Unified Viscoplasticity Modeling Features Needed for Simulation of Grade 91 Creep and Fatigue Responses

2016 ◽  
Author(s):  
Nazrul Islam ◽  
Dave Dewees ◽  
Tasnim Hassan
Keyword(s):  
Model Simulation ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Primary Objective ◽  
Static Recovery ◽  
Chaboche Model ◽  
Creep Fatigue ◽  
Grade 91

Chaboche unified viscoplasticity model and uncoupled plasticity and creep models (nonunified) are evaluated for their capability in simulating low-cycle fatigue, creep and creep-fatigue responses of Grade 91 steel. The primary objective of this study is to develop a constitutive model incorporating various advanced modeling features for design-by-analysis of elevated temperature power plant components. For validation of the model a broad set of experimental responses of Grade 91 in the temperature range 20–600°C are collected from literature. Performance of the models is demonstrated against simulating these experimental responses. It is demonstrated that the unified Chaboche model simulation capability can be improved through implementing strain range dependence, cyclic hardening through kinematic hardening rule and static recovery modeling features.

Constitutive Modeling of Haynes 230 for High Temperature Fatigue-Creep Interactions

2014 ◽  
Author(s):  
Paul R. Barrett ◽  
Raasheduddin Ahmed ◽  
Tasnim Hassan
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Model Development ◽  
Strain Range ◽  
Uniaxial Stress ◽  
Cycle Fatigue ◽  
Modeling Framework ◽  
Creep Fatigue

Non-linear stress analysis for high temperature cyclic viscoplasticity is increasingly becoming an important modeling framework for many industries. Simplified analyses are found to be insufficient in accurately predicting the life of components; such as a gas turbine engine of an airplane or the intermediate-heat exchanger of a nuclear power plant. As a result, advanced material models for simulating nonlinear responses at room to high temperature are developed and experimentally validated against a broad set of low-cycle fatigue responses; such as creep, fatigue, and their interactions under uniaxial stress states. . This study will evaluate a unified viscoplastic model based on nonlinear kinematic hardening (Chaboche type) with several added features of strain-range-dependence, rate-dependence, temperature-dependence, static recovery, and mean-stress-evolution for Haynes 230database. Simulation-based model development for isothermal creep-fatigue responses are all critically evaluated for the developed model. The robustness of the constitutive model is demonstrated and weaknesses of the model to accurately predict low-cycle fatigue responses are identified. Paper published with permission.

Constitutive Modeling of TMF and Creep-Fatigue of a Ni-Base Alloy

2019 ◽  
Author(s):  
Nathan O’Nora ◽  
Thomas Bouchenot ◽  
Grant Geiger ◽  
Ali P. Gordon
Keyword(s):  
Mechanical Load ◽  
Base Alloy ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Pressure Vessels ◽  
Isotropic Hardening ◽  
Creep Tests ◽  
Static Recovery ◽  
Load Rate ◽  
Creep Fatigue

Abstract Engineering materials are often subjected to high temperatures and varying mechanical load, making them display both creep and fatigue. Viscoplastic models have been an attractive way to simulate the behavior of materials under these conditions due to their ability to capture the hysteresis, load rate, and stress relaxation effect exhibited by materials. Nickel-base alloys experience widespread use throughout pressure vessels and turbomachinery due to their ability to retain high strength at high temperature. In this study, the low-cycle fatigue (LCF), thermo-mechanical fatigue (TMF), and creep-fatigue (CF) of candidate material IN617 is modeled using the Chaboche viscoplasticity model. The Chaboche model is implemented using three non-linear kinematic hardening terms with static recovery included as well as nonlinear isotropic hardening. Methods for finding the kinematic and isotropic hardening from Ramberg-Osgood constants are presented to allow for model development to encompass all available data instead of fitting to specific data sets. A novel method for fitting the static recovery portion of the model from creep data is presented, allowing for the capture of complex loadings such as CF from standard creep tests. New temperature-dependent formulations of the Chaboche constants are presented for IN617. The model is compared to available test data and simulations are presented to show future experiments that could be run to further validate or improve the model.

scholarly journals Constitutive Modeling of High Temperature Uniaxial Creep-Fatigue and Creep-Ratcheting Responses of Alloy 617

2013 ◽  
Author(s):  
P. G. Pritchard ◽  
L. Carroll ◽  
T. Hassan
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Parameter Determination ◽  
Model Framework ◽  
Alloy 617 ◽  
North Carolina State University ◽  
Uniaxial Creep ◽  
Creep Fatigue

Inconel Alloy 617 is a high temperature creep and corrosion resistant alloy and is a leading candidate for use in Intermediate Heat Exchangers (IHX) of the Next Generation Nuclear Plants (NGNP). The IHX of the NGNP is expected to experience operating temperatures in the range of 800°–950°C, which is in the creep regime of Alloy 617. A broad set of uniaxial, low-cycle fatigue, fatigue-creep, ratcheting, and ratcheting-creep experiments are conducted in order to study the fatigue and ratcheting responses, and their interactions with the creep response at high temperatures. A unified constitutive model developed at North Carolina State University is used to simulate these experimental responses. The model is developed based on the Chaboche viscoplastic model framework. It includes cyclic hardening/softening, strain rate dependence, strain range dependence, static and dynamic recovery modeling features. For simulation of the alloy 617 responses, new techniques of model parameter determination are developed for optimized simulations. This paper compares the experimental responses and model simulations for demonstrating the strengths and shortcomings of the model.

Improving Simulations for Low Cycle Fatigue and Ratcheting Responses of Elbows

2016 ◽  
Author(s):  
Nazrul Islam ◽  
Tasnim Hassan
Keyword(s):  
Residual Stresses ◽  
Low Cycle Fatigue ◽  
Numerical Technique ◽  
Kinematic Hardening ◽  
Model Development ◽  
Strain Range ◽  
Isotropic Hardening ◽  
Cycle Fatigue ◽  
Chaboche Model ◽  
Modeling Feature

A rate-independent constitutive model is developed incorporating various uniaxial and multiaxial modeling features for improving the simulations of elbow low-cycle fatigue and ratcheting responses. The model development is motivated by the fact that the Chaboche model in ANSYS is unable to simulate the strain ratcheting responses of elbows subjected to internal pressure and opening-closing displacement-controlled cycles. This drawback of the existing model is traced to the isotropic and kinematic hardening modeling features. The isotropic hardening in the Chaboche model can reasonably simulate the material test stress peaks but fails to simulate the hysteresis loop shapes. Incorporation of a strain range dependent modeling feature in evolving the isotropic and kinematic hardening rule parameters improved the simulation of the hysteresis loops both at the material and component levels. The axial and circumferential strain ratcheting simulation of elbow is improved by incorporating a biaxial ratcheting parameter. A modeling feature for nonproportional loading developed by Tanaka is also incorporated in order to simulate the additional cyclic hardening under multiaxial loading. The performance of modified model developed is validated against simulating a broad set of cyclic responses both at the material and component levels. Finally, a numerical technique is developed to simulate the initial and welding residual stresses in elbows, and thereby analytically demonstrate the influence of initial residual stresses on elbow responses.

High Temperature Constitutive Model Development for Alloy 617

2014 ◽  
Author(s):  
Shahriar Quayyum ◽  
Patrick Graham Pritchard ◽  
Tasnim Hassan
Keyword(s):  
Constitutive Model ◽  
Model Development ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Design Code ◽  
Model Framework ◽  
Alloy 617 ◽  
Static Recovery ◽  
Operation Temperature ◽  
Creep Fatigue

One of the most challenging tasks in the design code development for Next Generation Nuclear Plant (NGNP) is the design of intermediate heat exchanger (IHX), whose operation temperature may range from 800°C–950°C (1472°F–1742°F). The ASME design code does not have any design provisions for any material at this temperature range. Hence, different candidate materials are under consideration for IHX and one of the leading candidate materials is Ni based Alloy 617. The operating temperature of IHX will be in the creep regime of Alloy 617 and low-cycle creep-fatigue and creep-ratcheting failure mechanisms of Alloy 617 need to be understood. This study is developing a unified constitutive model (UCM) for Alloy 617 based on a broad set of uniaxial and multiaxial creep-fatigue and creep-ratcheting experiments at high temperatures. The experiments were conducted at different temperatures, loading rates and strain ranges prescribing different loading histories. The unified constitutive model was developed based on the Chaboche viscoplastic model framework. Model improvement was performed by including cyclic hardening/softening, dynamic and static recovery, strain rate and strain range dependence, nonproportional loading parameter and multiaxial ratcheting features. The simulated responses of the modified UCM were compared against the broad range of experimental data to demonstrate the robustness of the improved model. The strengths and shortcomings of the model are discussed. Paper published with permission.

The Effect of Cyclic Hardening Model on Deformation Behavior of Cracked Body Under Creep-Fatigue Loading Condition

2020 ◽  
Author(s):  
Hyun-Woo Jung ◽  
Yun-Jae Kim ◽  
Yukio Takahashi ◽  
Kamran Nikbin ◽  
Catrin M. Davies ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Deformation Behavior ◽  
Kinematic Hardening ◽  
Cyclic Hardening ◽  
Local Deformation ◽  
Hardening Model ◽  
Creep Fatigue ◽  
Creep Fatigue Crack

Abstract In this study, to determine appropriate cyclic hardening model for simulating creep-fatigue crack growth, sensitivity of hardening model on global/local deformation behavior during creep-fatigue crack growth is studied using finite element (FE) debonding analysis method. Three hardening models derived from tensile stress-strain curve to treat large strain near crack are considered in this study: isotropic hardening model, kinematic hardening model and combined hardening model. Simulation results indicate that cyclic hardening model does not make large difference in global deformation behavior but make difference in local deformation behavior. The effect of hardening model on inelastic strain and stress near crack are discussed in detail.

scholarly journals Fatigue–Creep Interaction of P92 Steel and Modified Constitutive Modelling for Simulation of the Responses

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 307
Author(s):  
Tianyu Zhang ◽  
Xiaowei Wang ◽  
Wei Zhang ◽  
Tasnim Hassan ◽  
Jianming Gong
Keyword(s):  
Fatigue Life ◽  
Constitutive Model ◽  
Dwell Time ◽  
Kinematic Hardening ◽  
Model Development ◽  
Strain Range ◽  
Peak Stress ◽  
Constitutive Modelling ◽  
P92 Steel ◽  
Static Recovery

Fatigue–creep interaction (FCI) responses of P92 steel are investigated experimentally and numerically. A series of isothermal FCI experiments with tensile dwell time ranging from 60 to 600 s were conducted at two temperatures under strain-controlled trapezoidal waveform. The experimental responses demonstrate that the peak stress is influenced by temperature and dwell time. In other words, creep-mechanism-influenced stress relaxation during dwell time influences the peak stress and fatigue life (Nf). In addition, effects of strain range on peak stress and fatigue life under fatigue–creep loading are evaluated. Towards developing a simulation-based design methodology for high temperature components, first a conventional unified constitutive model is evaluated against the P92 steel experimental responses. Based on the simulation deficiency of the conventional model, a modified static recovery term incorporated in the kinematic hardening rule is proposed and satisfactory simulations of the P92 steel FCI responses are demonstrated. The experimental responses of P92 steel and strengths and deficiencies of the conventional and modified Chaboche models are elaborated identifying the important FCI phenomena and progress in constitutive model development for FCI response simulation.

High-Temperature Low-Cycle Fatigue Behavior of MarBN at 600 °C

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Richard A. Barrett ◽  
Eimear M. O'Hara ◽  
Padraic E. O'Donoghue ◽  
Sean B. Leen
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Material Model ◽  
Cyclic Softening ◽  
Cyclic Strength ◽  
Cycle Fatigue ◽  
Viscoplastic Material

This paper presents the high-temperature low-cycle fatigue (HTLCF) behavior of a precipitate strengthened 9Cr martensitic steel, MarBN, designed to provide enhanced creep strength and precipitate stability at high temperature. The strain-controlled test program addresses the cyclic effects of strain-rate and strain-range at 600 °C, as well as tensile stress-relaxation response. A recently developed unified cyclic viscoplastic material model is implemented to characterize the complex cyclic and relaxation plasticity response, including cyclic softening and kinematic hardening effects. The measured response is compared to that of P91 steel, a current power plant material, and shows enhanced cyclic strength relative to P91.

Low Cycle Fatigue Behavior of a New Type of Zircaloy Material

2011 ◽  
Vol 80-81 ◽  
pp. 788-791
Author(s):  
Wei Wei Yu ◽  
Fei Xue ◽  
Xin Ming Meng ◽  
Lei Lin
Keyword(s):  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Cycle Fatigue ◽  
Fatigue Lifetime ◽  
Softening Behavior ◽  
New Type

To investigate the property of a new type of Zircaloy material, a low cycle fatigue (LCF) test has been performed at room temperature (RT) and 375°C. Results show that the new alloy generally displays cyclic hardening followed by a continuous softening behavior. Fatigue lifetime curves as a function of strain range imply that the new alloy has a nearly same lifetime than that of Zr-4 at RT, and superior than that at 375°C.

Isothermal Fatigue Responses and Constitutive Modeling of Haynes 230

2012 ◽  
Author(s):  
Paul Ryan Barrett ◽  
Mamballykalathil Menon ◽  
Tasnim Hassan
Keyword(s):  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Strain Range ◽  
Thermal Recovery ◽  
Material Behavior ◽  
Accurate Estimation ◽  
Experimental Database ◽  
Macroscopic Models ◽  
Physically Based

Constitutive models are an integral part of a lifing system because it allows for accurate estimation of stresses and strains at failure locations of interest. Constitutive models can be properly defined in a material subroutine of a finite element code. The computational capabilities of today are far higher, allowing for more comprehensive models that can provide more accurate results. Macroscopic models that are physically based, phenomenological models characterize the material behavior on a larger scale that provides invaluable insights even at such length scales which are compatible for industrial application. A unified viscoplastic model based on nonlinear kinematic hardening (Chaboche type) with several added features such as nonproportionality, multiaxiality, strain range dependence, and thermal recovery is being implemented in ANSYS through the User Programmable Features. The simulation capability of the model will be experimentally validated on a nickel based superalloy, HA230. The experimental database encompasses a broad set of low cycle fatigue, symmetric, uniaxial strain-controlled loading histories which include isothermal with and without hold times, with and without a mean strain, at temperatures ranging from 75°F to 1800°F. Simulations from the modified model compared to the experimental responses will be presented to demonstrate the strengths and weaknesses.

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