Non-Local Cyclic Life Prediction for Gas Turbine Components With Sharply Notched Geometries

2007 ◽  
Author(s):  
Roland Mu¨cke ◽  
Holger Kiewel
Keyword(s):  
Test Data ◽  
Gas Turbines ◽  
Life Prediction ◽  
Stress And Strain ◽  
Rotor Steel ◽  
Cyclic Life ◽  
Stress Strain ◽  
Efficient Operation ◽  
Strain Gradients ◽  
Non Local

The safe and efficient operation of modern heavy duty gas turbines requires a reliable prediction of fatigue behaviour of turbine components. Fatigue damage is located in areas where cyclic stress and strain amplitudes are highest. Thus, geometrical notches associated with stress/strain concentrations and stress/strain gradients appear to be the most important sites for fatigue crack initiation. The paper addresses a non-local concept for fatigue life prediction of notched components. In contrary to various local approaches in the field, the proposed method explicitly accounts for stress and strain gradients associated with notches, cooling holes, fillets and other design features with stress raising effect. As a result, empirical analytical expressions for considering either strain or stress gradients on cyclic life prediction are obtained. The method has been developed from cyclic test data on smooth and notched specimens made of a ferritic 1.5CrNiMo rotor steel. The obtained analytical formulations have then been applied to test data on the Nickel base superalloy MAR-M247 CC showing a good agreement between prediction and measurement. Moreover, the proposed non-local lifing concept has been validated by component tests on turbine blade firtrees. The predicted cycles to failure correlates well to the experimental results showing the applicability of the proposed method to complex engineering designs.

Nonlocal Cyclic Life Prediction for Gas Turbine Components With Sharply Notched Geometries

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Roland Mücke ◽  
Holger Kiewel
Keyword(s):  
Test Data ◽  
Gas Turbines ◽  
Life Prediction ◽  
Fatigue Crack Initiation ◽  
Stress And Strain ◽  
Rotor Steel ◽  
Cyclic Life ◽  
Stress Strain ◽  
Efficient Operation ◽  
Strain Gradients

The safe and efficient operation of modern heavy duty gas turbines requires a reliable prediction of fatigue behavior of turbine components. Fatigue damage is located in areas where cyclic stress and strain amplitudes are highest. Thus, geometrical notches associated with stress/strain concentrations and stress/strain gradients appear to be the most important sites for fatigue crack initiation. The paper addresses a nonlocal concept for cyclic life prediction of notched components. Contrary to various local approaches in the field, the proposed method explicitly accounts for stress and strain gradients associated with notches arising from grooves, cooling holes, fillets, and other design features with stress raising effect. As a result, empirical analytical expressions for considering either strain or stress gradients for cyclic life prediction are obtained. The method has been developed from cyclic test data on smooth and notched specimens made of a ferritic 1.5CrNiMo rotor steel. The analytical formulations obtained have then been applied to test data on the nickel base superalloy MAR-M247 CC showing a good agreement between prediction and measurement. Moreover, the proposed nonlocal lifing concept has been validated by component tests on turbine blade firtrees. The predicted number of cycles to failure correlates well with the experimental results showing the applicability of the proposed method to complex engineering designs.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

A Cyclic Life Prediction Approach for Directionally Solidified Nickel Superalloys

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Roland Mücke ◽  
Piyawan Woratat
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Failure Behavior ◽  
Mathematical Framework ◽  
Material Symmetry ◽  
Nickel Superalloys ◽  
Cyclic Life ◽  
Directionally Solidified ◽  
Transverse Isotropic ◽  
Prediction Approach

The performance of heavy duty gas turbines is closely related to the material capability of the components of the first turbine stage. In modern gas turbines single crystal (SX) and directionally solidified (DS) nickel superalloys are applied, which, compared with their conventionally cast version, hold a higher cyclic life and a significantly improved creep rupture strength. SX and DS nickel superalloys feature a significant directional dependence of the material properties. To fully exploit the material capability, the anisotropy needs to be accounted for in both the constitutive and lifing model. In this context, the paper addresses a cyclic life prediction procedure for DS materials with transverse isotropic material symmetry. Thereby, the well-known local approaches to fatigue life prediction of isotropic materials under uniaxial loading are extended toward materials with transverse isotropic properties under multiaxial load conditions. As part of the proposed methodology, a Hill type function is utilized for describing the anisotropic failure behavior. The coefficients of the Hill surface are determined from the actual multiaxial loading, material symmetry, and anisotropic fatigue strength of the material. In this paper we first characterize the anisotropy of DS superalloys. We then present the general mathematical framework of the proposed lifing procedure. Later we discuss a validation of the cyclic life model by comparing the measured and predicted fatigue lives of the test specimens. Finally, the proposed method is applied to the cyclic life prediction of a gas turbine blade.

A Cyclic Life Prediction Approach for Directionally Solidified Nickel Superalloys

2009 ◽  
Author(s):  
Roland Mu¨cke ◽  
Piyawan Woratat
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Failure Behavior ◽  
Mathematical Framework ◽  
Material Symmetry ◽  
Nickel Superalloys ◽  
Cyclic Life ◽  
Directionally Solidified ◽  
Transverse Isotropic ◽  
Prediction Approach

The performance of heavy duty gas turbines is closely related to the material capability of the components of the 1st turbine stages. In modern gas turbines single crystal (SX) and directionally solidified (DS) nickel superalloys are applied which, compared to their conventionally cast (CC) version, hold a higher cyclic life and a significantly improved creep rupture strength. SX and DS nickel superalloys feature a significant directionally dependence of material properties. To fully exploit the material capability, the anisotropy needs to be accounted for in both, the constitutive and the lifing model. In this context, the paper addresses a cyclic life prediction procedure for DS materials with transverse isotropic material symmetry. Thereby, the well-known local approaches to fatigue life prediction of isotropic materials under uniaxial loading are extended towards materials with transverse isotropic properties under multiaxial load conditions. As part of the proposed methodology, a Hill type function is utilized for describing the anisotropic failure behavior. The coefficients of the Hill surface are determined from the actual multiaxial loading, the material symmetry and the anisotropic fatigue strength of the material. In the paper we first characterize the anisotropy of DS superalloys. We then present the general mathematical framework of the proposed lifing procedure. Later we discuss a validation of the cyclic life model by comparing measured and predicted fatigue lives of test specimens. Finally, the proposed method is applied to the cyclic life prediction of a gas turbine blade.

scholarly journals A Mathematical Framework for Cyclic Life Prediction of Directionally Solidified Nickel Superalloys

2011 ◽  
Vol 278 ◽  
pp. 363-368
Author(s):  
Roland Mücke
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Rupture Strength ◽  
Orthotropic Materials ◽  
Mathematical Framework ◽  
Nickel Superalloys ◽  
Cyclic Life ◽  
Directionally Solidified ◽  
Transverse Isotropic ◽  
Direction Dependence

Modern gas turbines utilize single crystal (SX) and directionally solidified (DS) nickel superalloys which hold a higher cyclic life resistance and an improved creep rupture strength compared to their conventionally cast (CC) version. Both, SX and DS materials feature a significant direction dependence of material properties, which needs to be considered in the constitutive and lifing models. In this context, the paper presents a mathematical framework of cyclic life prediction. Although the method is developed for DS nickel alloys with transverse isotropic material behaviour, a generalisation to common orthotropic materials inclu¬ding SX is straightforward. The proposed procedure is validated by two examples. Moreover, an application to turbine components is shown.

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.

Analytical stress-strain relation for soils

2021 ◽  
Author(s):  
Kristian Krabbenhoft ◽  
J. Wang
Keyword(s):  
Test Data ◽  
Narrow Range ◽  
Strain Range ◽  
Data Sets ◽  
Soil Tests ◽  
Stress Strain ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Typical Test ◽  
Typical Soil

A new stress-strain relation capable of reproducing the entire stress-strain range of typical soil tests is presented. The new relation involves a total of five parameters, four of which can be inferred directly from typical test data. The fifth parameter is a fitting parameter with a relatively narrow range. The capabilities of the new relation is demonstrated by the application to various clay and sand data sets.

scholarly journals Infarcted Left Ventricles Have Stiffer Material Properties and Lower Stiffness Variation: Three-Dimensional Echo-Based Modeling to Quantify In Vivo Ventricle Material Properties

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Longling Fan ◽  
Jing Yao ◽  
Chun Yang ◽  
Dalin Tang ◽  
Di Xu
Keyword(s):  
Wall Thickness ◽  
Material Properties ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain ◽  
Material Stiffness ◽  
The Mean ◽  
Lv Volume ◽  
Parameter Values

Methods to quantify ventricle material properties noninvasively using in vivo data are of great important in clinical applications. An ultrasound echo-based computational modeling approach was proposed to quantify left ventricle (LV) material properties, curvature, and stress/strain conditions and find differences between normal LV and LV with infarct. Echo image data were acquired from five patients with myocardial infarction (I-Group) and five healthy volunteers as control (H-Group). Finite element models were constructed to obtain ventricle stress and strain conditions. Material stiffening and softening were used to model ventricle active contraction and relaxation. Systolic and diastolic material parameter values were obtained by adjusting the models to match echo volume data. Young's modulus (YM) value was obtained for each material stress–strain curve for easy comparison. LV wall thickness, circumferential and longitudinal curvatures (C- and L-curvature), material parameter values, and stress/strain values were recorded for analysis. Using the mean value of H-Group as the base value, at end-diastole, I-Group mean YM value for the fiber direction stress–strain curve was 54% stiffer than that of H-Group (136.24 kPa versus 88.68 kPa). At end-systole, the mean YM values from the two groups were similar (175.84 kPa versus 200.2 kPa). More interestingly, H-Group end-systole mean YM was 126% higher that its end-diastole value, while I-Group end-systole mean YM was only 29% higher that its end-diastole value. This indicated that H-Group had much greater systole–diastole material stiffness variations. At beginning-of-ejection (BE), LV ejection fraction (LVEF) showed positive correlation with C-curvature, stress, and strain, and negative correlation with LV volume, respectively. At beginning-of-filling (BF), LVEF showed positive correlation with C-curvature and strain, but negative correlation with stress and LV volume, respectively. Using averaged values of two groups at BE, I-Group stress, strain, and wall thickness were 32%, 29%, and 18% lower (thinner), respectively, compared to those of H-Group. L-curvature from I-Group was 61% higher than that from H-Group. Difference in C-curvature between the two groups was not statistically significant. Our results indicated that our modeling approach has the potential to determine in vivo ventricle material properties, which in turn could lead to methods to infer presence of infarct from LV contractibility and material stiffness variations. Quantitative differences in LV volume, curvatures, stress, strain, and wall thickness between the two groups were provided.

Gas turbine engine disk cyclic life prediction

1975 ◽  
Vol 12 (4) ◽  
pp. 360-365 ◽  
Author(s):  
S. A. Sattar ◽  
C. V. Sundt
Keyword(s):  
Gas Turbine ◽  
Life Prediction ◽  
Gas Turbine Engine ◽  
Cyclic Life ◽  
Turbine Engine
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