Creep Parameters Determination by Omega Model to Norton Bailey Law by Regression Analysis for Austenitic Steel SS-304

2021 ◽  
Vol 324 ◽  
pp. 188-197
Author(s):  
Mohsin Sattar ◽  
A. Rahim Othman ◽  
Shahrul Kamaruddin ◽  
Mohammad Azad Alam ◽  
Mohammad Azeem
Keyword(s):  
Regression Analysis ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Complete Analysis ◽  
Mechanical Equipment ◽  
Strain Rates ◽  
Secondary Creep ◽  
Creep Data ◽  
Ss 304 ◽  
Omega Model

In the material’s creep failure analysis, the difficulty of assessing the applied thermo-mechanical boundary conditions makes it critically important. Numerous creep laws have been established over the years to predict the creep deformation, damage evolution and rupture of the materials subjected to creep phenomena. The omega model developed by the American Petroleum Institute and Material Properties Council is one of the most commonly used creep material models for numerical analysis over the years. It is good in defining the fitness of mechanical equipment for service engineering evaluation to ensure the reliable service life of the equipment. The Omega model, however, is not readily accessible and specifically incorporated for creep evaluation in FEA software codes and creep data is always scarce for the complete analysis. Therefore, extrapolation of creep behavior was performed by fitting various types of creep models with a limited amount of creep data and then simulating them, beyond the available data points. In conjunction with the Norton Bailey model, based on API-579/ASME FFS-1 standards, a curve fitting technique was employed called regression analysis. From the MPC project omega model, different creep strain rates were obtained based on material, stress and temperature-dependent data. In addition, as the strain rates increased exponentially with the increase in stresses, regression analysis was used for predicting creep parameters, that can curve fit the data into the embedded Norton Bailey model. The uncertainties in extrapolations and material constants has highlighted to necessitate conservative safety factors for design requirement. In this case study, FEA creep assessment was performed on the material SS-304 dog bone specimen, considered as a material coupon to predict time-dependent plastic deformation along with creep behavior at elevated temperatures and under constant stresses. The results indicated that the specimen underwent secondary creep deformation for most of the period.

Effects of Creep Deformation Model of Gr. 91 Steel at 600°C on Creep Fracture Mechanics Parameters

2017 ◽  
Author(s):  
Min-Gu Won ◽  
Nam-Su Huh ◽  
Hyeong-Yeon Lee ◽  
Woo-Gon Kim ◽  
Jae-Boong Choi
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Creep Deformation ◽  
Creep Model ◽  
Deformation Model ◽  
Secondary Creep ◽  
Creep Fracture ◽  
Reference Stress ◽  
Creep Region ◽  
Omega Model

The present paper investigates the effect of creep deformation model of Gr. 91 Steel at 600 °C on creep fracture mechanics parameters. Three types of creep deformation model were considered, i.e. Garofalo’s model and RCC-MRx model for primary-secondary creep region, and modified omega model for primary-secondary-tertiary creep region. The parameters for each creep deformation model were characterized from experiment results. Reference Stress (RS) method was used to estimate creep fracture mechanics parameters, C(t)-integral and COD rate for each creep model. Furthermore, elastic-creep finite element (FE) analyses were carried out to verify the results of RS method. Finally, the effect of creep deformation model was investigated by comparing the results of C(t)-integral and COD rate.

Analysis of the Secondary Creep of a Rotating Flat Disk

1972 ◽  
Vol 1 (4) ◽  
pp. 227-228
Author(s):  
J.G. Lenard
Keyword(s):  
Creep Strain ◽  
Creep Behavior ◽  
Flow Rule ◽  
Strain Rates ◽  
Secondary Creep ◽  
Uniform Thickness ◽  
Hyperbolic Sine ◽  
Flat Disk ◽  
Linear Creep ◽  
Associated Flow Rule

Secondary creep behavior of a rotating hollow disk of uniform thickness is considered. The hyperbolic sine creep law is used to relate stress and creep strain rate; the applicability of Tresca’s criterion and associated flow rule is assumed. The creep strain rates so obtained are compared to results, given by the exponential and linear creep laws. Recommended limits of applicability of the linear and exponential laws are established.

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.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

Investigation on Creep Behavior of Grade 91 Heat-Resistant Steel at 923K

2016 ◽  
Vol 853 ◽  
pp. 163-167
Author(s):  
Fa Cai Ren ◽  
Xiao Ying Tang
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Grade 91

Creep deformation behavior of SA387Gr91Cl2 heat-resistant steel used for steam cooler has been investigated. Creep tests were carried out using flat creep specimens machined from the normalized and tempered plate at 973K with stresses of 100, 125 and 150MPa. The minimum creep rate and rupture time dependence on applied stress was analyzed. The analysis showed that the heat-resistant steel obey Monkman-Grant and modified Monkman-Grant relationships.

The Creep Behavior of a Floating Beam

1983 ◽  
Vol 27 (04) ◽  
pp. 271-280
Author(s):  
Paul C. Xirouchakis
Keyword(s):  
Cross Section ◽  
Creep Behavior ◽  
Failure Time ◽  
Failure Criteria ◽  
Secondary Creep ◽  
Nonlinear Creep ◽  
Double Membrane ◽  
Creep Response ◽  
Distributed Load ◽  
Linear Viscoelastic

The creep response is obtained for an inhomogeneous beam, with simple end supports, resting on a liquid foundation and subjected to a sinusoidally distributed load. The Norton-Bailey constitutive equations are used to describe secondary creep behavior and elastic effects are retained. The liquid foundation is taken as a continuous Winkler support. The beam cross section is replaced by a double-membrane model. The implications are discussed of using stress or deflection failure criteria in determining the magnitude of the instantaneous breakthrough load. The linear viscoelastic as well as nonlinear creep beam response is obtained explicitly. The influence of the beam geometric and material characteristics and of the presence of the liquid foundation on the growth of the deflections with time is discussed. The variation of the breakthrough load with failure time is also explored. Results obtained are compared with available sea ice laboratory test data.

Creep deformation and stress analysis in a transversely material disk subjected to rigid shaft

2019 ◽  
Vol 25 (1) ◽  
pp. 17-25
Author(s):  
Pankaj Thakur ◽  
Monika Sethi
Keyword(s):  
Stress Analysis ◽  
Creep Deformation ◽  
Radial Stress ◽  
Hoop Stress ◽  
Rotating Disk ◽  
Angular Speed ◽  
Transition Theory ◽  
Strain Rates ◽  
Maximum Value ◽  
Inner Surface

The purpose of this paper is to present a study of creep deformation and stress analysis in a transversely material disk subjected to the rigid shaft by using Seth’s transition theory. It has been observed that radial stress has the maximum value at the inner surface of the rotating disk made of isotropic material as compared to the hoop stress and this value of radial stress further increases with the increase in the value of angular speed. Strain rates have maximum values at the inner surface for the disk made of transversely material.

Creep in Ordered Nickel Base Alloys

1984 ◽  
Vol 39 ◽  
Author(s):  
P. R. Strutt ◽  
B. H. Kear
Keyword(s):  
Creep Behavior ◽  
Creep Deformation ◽  
Crystallographic Orientation ◽  
Deformation Behavior ◽  
Strong Influence ◽  
Deformation Mode ◽  
Two Phase ◽  
Effects Of Temperature ◽  
Nickel Base ◽  
Relative Creep

ABSTRACTThis paper examines the fundamentals of deformation behavior in ordered y′ (Ni3Al), β (NiAl) and β′ (Ni2AITi) phases, and specific two phase y/y′ and B/B′ alloys. The relative creep strengths of these ordered nickel-base alloys are discussed. Differences in creep behavior are explained in terms of the effects of temperature, crystallographic orientation and alloying on creep deformation mode. In particular, it is shown that trace additions of boron and carbon to y/y′ alloys, or deviations from stoichiometry in β′ -type alloys can exert a strong influence on creep behavior.

On the Interrupted Creep Test Under Low Stress Levels for the Power Law Parameter Extraction

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Bin Yang ◽  
Fu-Zhen Xuan ◽  
Wen-Chun Jiang
Keyword(s):  
Creep Strain ◽  
Stress Level ◽  
Creep Test ◽  
Creep Deformation ◽  
Parameter Extraction ◽  
Tertiary Creep ◽  
Secondary Creep ◽  
Creep Stage ◽  
Strain Data

Abstract Low stress interrupted creep test, as an interim compromise, can provide essential data for creep deformation design. However, there are no clear guidelines on the characterization of the terminating time for interrupted low-stress creep test. To obtain a suitable terminating time in terms of economy and effectiveness, long-term creep strain data of 9%Cr steels are collected from literatures and their creep deformation characterization is analyzed. First, the variations of normalized time and strain of each creep stage with the stress level are discussed. Then, the effect of the terminating time on final fitted results of Norton–Bailey equation is estimated. Third, the relationship between demarcation points at different creep stages and minimum/steady-state creep rate is analyzed. The results indicate that when the creep rupture life is considered as an important factor for creep design, the tertiary creep stage is of greatest significance due to the largest life fraction and creep strain fraction at low stress level. However, the primary and secondary creep stages are of great significance for design due to their larger contribution to 1% limited creep strain. And the long-term secondary creep data could be extrapolated by combining the primary creep strain data obtained from interrupted creep tests with the time to onset of tertiary creep derived from a similar Monkman–Grant relationship.

Modification of the MPC Omega Model to Predict Primary and Tertiary Creep

2019 ◽  
Author(s):  
Mohammad Shafinul Haque
Keyword(s):  
Creep Deformation ◽  
Work Hardening ◽  
Primary Creep ◽  
Deformation Curve ◽  
Tertiary Creep ◽  
Suitable Model ◽  
Hyperbolic Tangent ◽  
Natural Logarithm ◽  
Wide Range ◽  
Omega Model

Abstract The MPC Omega model has become popular in recent years for the prediction of creep deformation. Successful predictions of the tertiary creep for a wide range of materials are available. The Omega model relates the strain as a linear function of the natural logarithm of strain-rate. It is assumed that the primary creep is a short-lived phenomenon and can be neglected. The Omega model is unable to predict the primary creep deformation. Often primary creep is a long-lived phenomenon and cannot be neglected. A mathematical modification can be performed to incorporate the primary creep curve in the Omega model. A common approach is by adding a work hardening function to the original constitutive model. Approaches using power, or exponential, or logarithmic work-hardening function are available. However, it is difficult to discern which function is the best for accurate prediction. In this study, the Omega model is modified to predict the primary and tertiary creep deformation curve by adding a hyperbolic tangent work hardening function. A metamodel incorporating the four modified Omega sub-models (power, exponential, logarithmic and hyperbolic tangent) is developed. The metamodel enables the determination of the most suitable model for a given material and avoids the force fit of a preselected model. Short, medium, and long-term creep deformation data for alloy P91 (pipe) and G91 (plate) at two isotherms of 600°C and 650°C are used to calibrate the metamodel. The data include five stress levels ranging from 70 to 160 MPa including creep life from 233 to 1.1 × 105 hrs. A detail calibration process is provided. A numerical analysis is performed to compare the four submodels. It is observed that the selection of the most suitable function depends on the loading condition and material properties. Based on the analysis, a recommendation to select the suitable work-hardening function to predict the primary and tertiary creep deformation curve is presented.

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