Research on a New Secondary Creep Model and Creep Damage Evolution for P92 Steel

2013 ◽  
Vol 690-693 ◽  
pp. 157-163 ◽  
Author(s):  
Jun Yuan ◽  
Hong Xu ◽  
Yong Zhong Ni
Keyword(s):  
Experimental Data ◽  
Stress Exponent ◽  
Creep Damage ◽  
Creep Model ◽  
Secondary Creep ◽  
Creep Life ◽  
P92 Steel ◽  
Tertiary Stage ◽  
Creep Constitutive Model ◽  
Damage Equation

In the traditional Norton-Bailey model, the stress exponent is a constant value when the temperature keeps constant, But for some materials, this situation can’t be suitable. Based on the analysis of the experimental data, a secondary creep constitutive model which can be used in the stress exponent changing situation has been proposed. By introducing Kachanov-Rabotnov damage equation, the modified creep model has been established for P92 steel at 610°C and 670°C, which can describe the second and tertiary stage. And the method to determine creep parameters of tertiary stage has been derived. The new model was embedded into ANSYS interface program, and used for calculating the creep life of P92 steel. The results show that the model is in agreement with the experimental data.

scholarly journals Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 623
Author(s):  
Xiaoyan Wang ◽  
Meng Li ◽  
Yuansheng Wang ◽  
Chengjiang Zhang ◽  
Zhixun Wen
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Creep Damage ◽  
Primary Creep ◽  
Single Crystal Superalloy ◽  
Secondary Creep ◽  
Creep Life ◽  
Phase Coarsening ◽  
Damage Repair ◽  
Creep Time

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

Modeling the Temperature-Dependence of Tertiary Creep Damage of a Directionally Solidified Ni-Base Superalloy

2009 ◽  
Author(s):  
Calvin M. Stewart ◽  
Erik A. Hogan ◽  
Ali P. Gordon
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Creep Damage ◽  
Time Estimation ◽  
General Purpose ◽  
Tertiary Creep ◽  
Secondary Creep ◽  
Directionally Solidified ◽  
Estimation Model ◽  
Element Analysis

Directionally solidified (DS) Ni-base superalloys have become a commonly used material in gas turbine components. Controlled solidification during the material manufacturing process leads to a special alignment of the grain boundaries within the material. This alignment results in different material properties dependent on the orientation of the material. When used in gas turbine applications the direction of the first principle stress experienced by a component is aligned with the enhanced grain orientation leading to enhanced impact strength, high temperature creep and fatigue resistance, and improve corrosion resistance compared to off axis orientations. Of particular importance is the creep response of these DS materials. In the current study, the classical Kachanov-Rabotnov model for tertiary creep damage is implemented in a general-purpose finite element analysis (FEA) software. Creep deformation and rupture experiments are conducted on samples from a representative DS Ni-base superalloys tested at temperatures between 649 and 982°C and two orientations (longitudinally- and transversely-oriented). The secondary creep constants are analytically determined from available experimental data in literature. The simulated annealing optimization routine is utilized to determine the tertiary creep constants. Using regression analysis the creep constants are characterized for temperature and stress-dependence. A rupture time estimation model derived from the Kachanov-Rabotnov model is then parametrically exercised and compared with available experimental data.

Investigations on Creep Behavior of P91-Type Steel Using Combined Creep Damage Model

2013 ◽  
Author(s):  
Fujun Liu ◽  
Ping Tang ◽  
Shuai Kong ◽  
Zhangwei Ling ◽  
Muling Zheng ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Creep Behavior ◽  
Power Plants ◽  
Damage Model ◽  
Creep Damage ◽  
Damage Function ◽  
Creep Model ◽  
Secondary Creep ◽  
Type Steel ◽  
Damage Theory

P91-type steel is widely used for the high-temperature pipe work components in advanced power plants. The creep behavior of the P91-type steel has been studied by many researchers during the past years. Since it is well known that the creep behavior of P91-type steel cannot be satisfactorily described by a simple, Arrhenius-type, power-law constitutive model. While Norton-Bailey creep is a deviatoric temperature-dependent creep model, furbished with a time-hardening creep model, which is the most common model for modeling primary and secondary creep together, and Kachanov-Rabotnov creep damage theory described with Norton creep model can be used to model tertiary creep. Both of them based on Norton creep constitutive equation. In this paper, based on the Norton-Bailey creep law and Kachanov-Rabotnov creep damage theory, a new combined constitutive model has been developed, in which the creep and damage function are both considered as nonlinear variables. The damage parameters in the model have clear physical meaning and can be determined from the benchmark experiment. The results indicated that this combined damage model was applicable to describe the full damage evolution for P91-type steel.

Modeling the Creep Damage of P91 Steel Using Peridynamics

2019 ◽  
Author(s):  
Shank S. Kulkarni ◽  
Alireza Tabarraei ◽  
Xiaonan Wang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Structural Integrity ◽  
Creep Damage ◽  
Creep Model ◽  
Creep Tests ◽  
P91 Steel ◽  
Damage Models ◽  
Modeling Creep ◽  
Non Local

Abstract Creep is an important failure mechanism of metal components working at a high temperature. To ensure the structural integrity and safety of systems working at high temperature it is essential to predict failure due to creep. Classical continuum based damage models are used widely for modeling creep damage. A more recently developed non-local mechanics formulation called peridynamics has displayed better performance in modeling damage with respect to classical local mechanics methods. In this paper, the peridynamic formulation is extended to model creep in metals. We have chosen Liu-Murakami creep model for developing a peridynamic formulation for modeling creep. The proposed formulation is validated by simulating creep tests for P91 steel and comparing the results with experimental data from the literature.

A Modified Microstructure-Based Creep Damage Model for Considering Prior Low Cycle Fatigue Damage Effects

2018 ◽  
Author(s):  
Wei Zhang ◽  
Xiaowei Wang ◽  
Jianming Gong
Keyword(s):  
Creep Behavior ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Creep Damage ◽  
Martensite Lath ◽  
Creep Model ◽  
Cycle Fatigue ◽  
P92 Steel ◽  
Damage Mechanisms ◽  
State Variable

A modified continuum damage mechanics (CDM) model was proposed to predict the creep behavior of P92 steel with prior low cycle fatigue (LCF) damage. In order to investigate the damage mechanisms of prior LCF, microstructural observations of P92 steel after various prior LCF and subsequent creep exposures were performed. Results show that the key creep degradation is associated with the martensite lath recovery. Based on the physics of microstructural evolutions, three state variable formulas which represent damage mechanisms related to martensite lath recovery were employed to account for the prior LCF damage. The three state variable formulas which describe the damage evolution with prior LCF cycles were coupled with Hayhurst CDM model. The main advantage of the modified CDM creep model lies in its ability to directly predict creep behavior with different levels of prior LCF damage. The only parameter needed to be known for the prediction is the martensite lath width after prior LCF. Comparison of the predicted and experimental results shows that the proposed model can give a reasonable prediction for creep behavior. Moreover, this model also shows good predictive ability at different strain amplitudes of prior LCF.

Effects of Secondary Creep Formulation on API 579-1 Residual Life Evaluation

2017 ◽  
Author(s):  
Lorenzo Scano ◽  
Luca Esposito
Keyword(s):  
Life Prediction ◽  
Ad Hoc ◽  
Residual Life ◽  
Creep Damage ◽  
International Standards ◽  
Secondary Creep ◽  
Creep Life ◽  
Life Evaluation ◽  
Level 3 ◽  
The Impact

Although several ad hoc procedures are codified into main international standards, the creep life prediction remains a critical phase of each Fitness-For-Service assessment. Commonly, either a time-fraction or a ductility exhaustion approach can be used. In both cases, conservative predictions within a factor of 2 or 3 are expected [1]. However, since the procedures to determine the creep damage are based upon the results of a stress analysis, the residual life evaluation can be affected by the adopted creep formulation. The choice to use a simple modeling, only accounting for the dislocational creep range, could lead to overestimate the component creep life at low stresses, and this is also subtly true even at concentration points if triaxiality or deformation-controlled loading lead to marked stress relaxation over time. In this paper, the tube to header and the header to hemispherical end joints of a HRSG assembly were assessed by the API 579-1/ASME FFS-1 [2] Level 3 procedure, via inelastic FEA, changing the creep formulation to compare the results. The classical Nortons law was replaced by more sophisticated secondary creep models to account for the complex time-dependent stress-field. In particular, the primary and secondary stress re-distribution/relaxation in the creep range were investigated in order to evaluate the impact of the steady-state creep constitutive equation on the residual life prediction.

scholarly journals Curve Fitting for Damage Evolution through Regression Analysis for the Kachanov–Rabotnov Model to the Norton–Bailey Creep Law of SS-316 Material

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5518
Author(s):  
Mohsin Sattar ◽  
Abdul Rahim Othman ◽  
Maaz Akhtar ◽  
Shahrul Kamaruddin ◽  
Rashid Khan ◽  
...  
Keyword(s):  
Creep Behavior ◽  
Creep Deformation ◽  
Curve Fitting ◽  
Elevated Temperatures ◽  
Creep Behaviour ◽  
Creep Damage ◽  
Tertiary Creep ◽  
Creep Model ◽  
Secondary Creep ◽  
Dog Bone

In a number of circumstances, the Kachanov–Rabotnov isotropic creep damage constitutive model has been utilized to assess the creep deformation of high-temperature components. Secondary creep behavior is usually studied using analytical methods, whereas tertiary creep damage constants are determined by the combination of experiments and numerical optimization. To obtain the tertiary creep damage constants, these methods necessitate extensive computational effort and time to determine the tertiary creep damage constants. In this study, a curve-fitting technique was proposed for applying the Kachanov–Rabotnov model into the built-in Norton–Bailey model in Abaqus. It extrapolates the creep behaviour by fitting the Kachanov–Rabotnov model to the limited creep data obtained from the Omega-Norton–Bailey regression model and then simulates beyond the available data points. Through the Omega creep model, several creep strain rates for SS-316 were calculated using API-579/ASME FFS-1 standards. These are dependent on the type of the material, the flow stress, and the temperature. In the present work, FEA creep assessment was carried out on the SS-316 dog bone specimen, which was used as a material coupon to forecast time-dependent permanent plastic deformation as well as creep behavior at elevated temperatures and under uniform stress. The model was validated with the help of published experimental creep test data, and data optimization for sensitivity study was conducted by applying response surface methodology (RSM) and ANOVA techniques. The results showed that the specimen underwent secondary creep deformation for most of the analysis period. Hence, the method is useful in predicting the complete creep behavior of the material and in generating a creep curve.

Creep Life Prediction of Aircraft Turbine Disc Alloy Using Continuum Damage Mechanics

2017 ◽  
Vol 38 (1) ◽  
pp. 25-30
Author(s):  
Yan-Feng Li ◽  
Zhisheng Zhang ◽  
Chenglin Zhang ◽  
Jie Zhou ◽  
Hong-Zhong Huang
Keyword(s):  
Numerical Analysis ◽  
Test Data ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Creep Model ◽  
Continuum Damage ◽  
Creep Life ◽  
Creep Life Prediction ◽  
Turbine Disc

Abstract This paper deals with the creep characteristics of the aircraft turbine disc material of nickel-base superalloy GH4169 under high temperature. From the perspective of continuum damage mechanics, a new creep life prediction model is proposed to predict the creep life of metallic materials under both uniaxial and multiaxial stress states. The creep test data of GH4169 under different loading conditions are used to demonstrate the proposed model. Moreover, from the perspective of numerical simulation, the test data with analysis results obtained by using the finite element analysis based on Graham creep model is carried out for comparison. The results show that numerical analysis results are in good agreement with experimental data. By incorporating the numerical analysis and continuum damage mechanics, it provides an effective way to accurately describe the creep damage process of GH4169.

An improved nonlinear damage model of rocks considering initial damage and damage evolution

2020 ◽  
Vol 29 (7) ◽  
pp. 1117-1137 ◽  
Author(s):  
Wenlin Feng ◽  
Chunsheng Qiao ◽  
Shuangjian Niu ◽  
Zhao Yang ◽  
Tan Wang
Keyword(s):  
Damage Evolution ◽  
Least Squares Method ◽  
Damage Model ◽  
Creep Damage ◽  
Secondary Creep ◽  
Nonlinear Creep ◽  
Creep Failure ◽  
Initial Damage ◽  
Nonlinear Damage Model ◽  
Creep Damage Model

The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage.

Impact of Operating Conditions and Design Parameters on Gas Turbine Hot Section Creep Life

2010 ◽  
Author(s):  
S. Eshati ◽  
M. F. Abdul Ghafir ◽  
P. Laskaridis ◽  
Y. G. Li
Keyword(s):  
Gas Turbines ◽  
Performance Model ◽  
Operating Conditions ◽  
Creep Model ◽  
Design Parameters ◽  
Gas Temperature ◽  
Creep Life ◽  
Cooling Effectiveness ◽  
Radial Temperature ◽  
The Impact

This paper investigates the relationship between design parameters and creep life consumption of stationary gas turbines using a physics based life model. A representative thermodynamic performance model is used to simulate engine performance. The output from the performance model is used as an input to the physics based model. The model consists of blade sizing model which sizes the HPT blade using the constant nozzle method, mechanical stress model which performs the stress analysis, thermal model which performs thermal analysis by considering the radial distribution of gas temperature, and creep model which using the Larson-miller parameter to calculate the lowest blade creep life. The effect of different parameters including radial temperature distortion factor (RTDF), material properties, cooling effectiveness and turbine entry temperatures (TET) is investigated. The results show that different design parameter combined with a change in operating conditions can significantly affect the creep life of the HPT blade and the location along the span of the blade where the failure could occur. Using lower RTDF the lowest creep life is located at the lower section of the span, whereas at higher RTDF the lowest creep life is located at the upper side of the span. It also shows that at different cooling effectiveness and TET for both materials the lowest blade creep life is located between the mid and the tip of the span. The physics based model was found to be simple and useful tool to investigate the impact of the above parameters on creep life.

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