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

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.

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Experimental and Theoretical Studies on the Creep Behavior of Bayer Red Mud

Advances in Civil Engineering ◽

10.1155/2018/6327971 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Baoyun Zhao ◽

Wei Huang ◽

Zhile Shu ◽

Mengmeng Han ◽

Yanbo Feng

Keyword(s):

Creep Strain ◽

Creep Behavior ◽

Red Mud ◽

Damage Model ◽

Creep Damage ◽

Creep Model ◽

Creep Tests ◽

Accelerated Creep ◽

Bayer Red Mud ◽

Creep Damage Model

Long-term stability and safety of the Bayer red mud (BRM) disposal field is very important for the local residents’ life, which necessitates the knowledge of its creep behavior. In order to investigate the creep behavior of BRM, a series of triaxial drained creep tests were conducted by using an improved triaxial creep apparatus. The results indicate that the creep behavior of BRM is significant with confining and deviatoric stresses being critical factors. The creep strain is in a nonlinear relationship with stress and time, and a larger deviator stress will lead to a larger creep strain. The main failure mechanism of BRM is plastic shear, accompanied by a significant compression and ductile dilatancy. Based on the test results, two well-established creep models, the Burgers creep model and Singh–Mitchell creep model, were used to comparatively analyze the creep behavior of the Bayer red mud under a certain stress level. Then, an improved Burgers creep damage constitutive model with the addition of a damage variable was proposed, whose parameters were also analyzed in detail. The comparison of the calculated values of the creep model and the experimental values shows that the proposed creep damage model can better describe the instant elastic deformation, attenuation creep, steady-state creep, and accelerated creep stages of the Bayer red mud.

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

Materials ◽

10.3390/ma14195518 ◽

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.

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

International Journal of Damage Mechanics ◽

10.1177/1056789520909531 ◽

2020 ◽

Vol 29 (7) ◽

pp. 1117-1137 ◽

Cited By ~ 3

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.

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Statistical Damage Constitutive Model for Concrete under Biaxial Tension

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.438-439.183 ◽

2013 ◽

Vol 438-439 ◽

pp. 183-186

Author(s):

Wei Feng Bai ◽

Jun Hong Zhang ◽

Jun Feng Guan ◽

Ying Cui

Keyword(s):

Constitutive Model ◽

Biaxial Tension ◽

Damage Model ◽

Damage Mechanism ◽

Deformation Properties ◽

Damage Constitutive Model ◽

Strength And Deformation ◽

Statistical Damage Constitutive Model ◽

Damage Theory ◽

Statistical Damage

Based on the statistical damage theory and the experimental phenomena, the statistical damage constitutive model for concrete under biaxial tension is proposed. The two meso-scale damage modes, rupture and yield are considered, and the whole damage evolution process is driven by the principal tensile damage strain. The results show that the proposed statistical damage model can accurately predict the constitutive behavior in the uniform damage phase for concrete under biaxial tension. The damage mechanism is discussed in the view point of biaxial strength and deformation properties.

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Probabilistic Design and Analysis of Pressure Measuring Probes for Creep Behavior

Volume 2: Structures and Dynamics; Renewable Energy (Solar, Wind); Inlets and Exhausts; Emerging Technologies (Hybrid Electric Propulsion, UAV, ...); GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2017-4906 ◽

2017 ◽

Author(s):

Dattatraya Parle

Keyword(s):

Creep Behavior ◽

Probabilistic Approach ◽

Operating Conditions ◽

Model Complexity ◽

Creep Model ◽

Operating Parameters ◽

Secondary Creep ◽

Operating Pressure ◽

Probabilistic Design ◽

Input Parameters

Pressure probes are typically used to measure the pressure of a fluid stream. These probes are designed to serve for 25 years life under operating pressure and temperature conditions. Therefore, such pressure probes are also designed for safe creep behavior. Typically creep is time dependent phenomenon and it can be classified as Primary, Secondary and Tertiary creep. In the literature, the creep phenomenon is studied analytically and numerically. Literature review reveals that creep analysis requires special material models and its selection depends on operating conditions. This work presents FEA based probabilistic design and analysis of pressure measuring probes using ANSYS which has several creep models depending on type of creep phenomenon. Probes in this study are subjected to primary and secondary creep. Therefore, this work proposes combined time hardening creep model. Combined time hardening model has 7 coefficients. This further increases the complexity of the model. Apart from the model complexity, there are various other design and operating parameters which further complicates the creep behavior. Some of the important design and operating parameters are length, diameter and tip dimensions along with pressure and temperature. Thus there are around 16 parameters which controls the creep behavior of pressure measuring probe. Traditional design process of probe is based on deterministic analysis which involves the use of safety factors as a way of accounting for uncertainty in design input parameters. This can often results in overly conservative designs. Moreover, to understand optimal creep behavior of probes under several uncertainties in input parameters becomes a challenging. Therefore, this work presents probabilistic approach as opposed to a deterministic approach to understand the combined effect of several uncertain parameters on creep behavior of probes. This work not only determines probability of probe failure more accurately but also determines the sensitivity of each parameter during creep phenomenon using FEA.

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Creep Damage Analysis of High Pressurized Steam Pipelines Using Omega Method

Volume 7: Operations, Applications and Components ◽

10.1115/pvp2008-61662 ◽

2008 ◽

Author(s):

Gong H. Jung ◽

Parikh Prashant ◽

Jorge Penso ◽

Dong S. Kim

Keyword(s):

Damage Model ◽

Creep Damage ◽

Element Model ◽

Creep Model ◽

Fe Model ◽

Damage Analysis ◽

Weld Repair ◽

Damaged Material ◽

Omega Method ◽

Pressure Steam

Cracks, bulges and leaks have been found in weld-o-let connections that were installed in high-pressure steam lines. Creep has been known as one of failure mechanisms associated with cracks on the weld-o-let connections. A success of weld repairing of the creep-damaged connections strongly relies on how well the creep-damaged material is removed. The FE (finite element) model was developed to predict the creep damage on the weld-o-let connections. Omega creep model and time fraction damage model were incorporated. The developed FE model successfully explained why cracks were found on the outer surface of saddle point in most of the connections. The results of creep analyses were successfully incorporated into development of a weld repair plan of the creep damaged connections.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.690-693.157 ◽

2013 ◽

Vol 690-693 ◽

pp. 157-163 ◽

Cited By ~ 3

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.

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A Creep Damage Constitutive Model for a Rock Mass with Nonpersistent Joints under Uniaxial Compression

Mathematical Problems in Engineering ◽

10.1155/2019/4361458 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11

Author(s):

Shuran Lv ◽

Wanqing Wang ◽

Hongyan Liu

Keyword(s):

Rock Mass ◽

Constitutive Model ◽

Mechanical Behavior ◽

Uniaxial Compression ◽

Damage Model ◽

Creep Damage ◽

Model Parameters ◽

Damage Constitutive Model ◽

Set Up ◽

Creep Damage Model

As part of the rock mass, both the mesoscopic and macroscopic flaws will affect the creep mechanical behavior of the rock mass with nonpersistent joints. This study focuses on this kind of rock mass and establishes a creep damage model to account for the effect of the joint on its creep mechanical behavior. First, on basis of analyzing the rock element creep mechanism and the typical creep deformation curve, a new creep damage constitutive model for the rock element is set up by introducing the damage theory and Kachanov damage evolution law into the classic creep constitutive model such as J body model. Second, the determination method of the proposed model parameters is studied in detail. Third, the calculation method of the macroscopic damage caused by the joint proposed by others is introduced which can consider the joint geometry, strength, and deformation parameters at the same time. Finally, the creep damage model for the rock mass with nonpersistent joints under uniaxial compression is proposed. The calculation examples indicate that it can present the effect of the joint on the rock mass creep mechanical behavior.

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A Creep-Damage Constitutive Model for Sandstone

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.289 ◽

2012 ◽

Vol 170-173 ◽

pp. 289-294 ◽

Cited By ~ 3

Author(s):

Wei Wang ◽

Jun Lv ◽

Hai Cheng Wang

Keyword(s):

Constitutive Model ◽

Creep Test ◽

Creep Damage ◽

Creep Model ◽

Whole Process ◽

Proposed Model ◽

Accelerated Creep ◽

Damage Constitutive Model ◽

Triaxial Creep ◽

Triaxial Creep Test

Based on the results obtained by the triaxial creep test, a creep-damage constitutive model for sandstone is presented by using the damage theory and by introducing the concept of “the whole process of damage” into Burgers creep model. The parameters of the model are determined by fitting the creep test data. The result shows that the proposed model can not only describe efficiently the variation of decay and steady creep under relatively low stress condition, but also give a satisfied representation of damage behavior in accelerated creep stage.

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