An Energy-Based Uniaxial Fatigue Life Prediction Method for Commonly Used Gas Turbine Engine Materials

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Onome E. Scott-Emuakpor ◽  
Herman Shen ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Life Prediction ◽  
Prediction Method ◽  
Gas Turbine Engine ◽  
Turbine Engine ◽  
Bending Fatigue ◽  
Al 6061 ◽  
Stress Ratios

A new energy-based life prediction framework for calculation of axial and bending fatigue results at various stress ratios has been developed. The purpose of the life prediction framework is to assess the behavior of materials used in gas turbine engines, such as Titanium 6Al-4V (Ti 6Al-4V) and Aluminum 6061-T6 (Al 6061-T6). The work conducted to develop this energy-based framework consists of the following entities: (1) a new life prediction criterion for axial and bending fatigue at various stress ratios for Al 6061-T6, (2) the use of the previously developed improved uniaxial energy-based method to acquire fatigue life prior to endurance limit region (Scott-Emuakpor et al., 2007, “Development of an Improved High Cycle Fatigue Criterion,” ASME J. Eng. Gas Turbines Power, 129, pp. 162–169), (3) and the incorporation of a probabilistic energy-based fatigue life calculation scheme to the general uniaxial life criterion (the first entity of the framework), which is capable of constructing prediction intervals based on a specified percent confidence level. The precision of this work was verified by comparison between theoretical approximations and experimental results from recently acquired Al 606-T6 and Ti 6Al-4V data. The comparison shows very good agreement, thus validating the capability of the framework to produce accurate uniaxial fatigue life predictions for commonly used gas turbine engine materials.

A New Energy-Based Uniaxial Fatigue Life Prediction Method for a Gas Turbine Engine Material

2007 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
M.-H. Herman Shen ◽  
Tommy George ◽  
Charles Cross ◽  
Jeffrey Calcaterra
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Life Prediction ◽  
Prediction Method ◽  
Fatigue Life Prediction ◽  
Turbine Engine ◽  
Bending Fatigue ◽  
New Energy ◽  
Stress Ratios ◽  
Materials Used

A new energy-based fatigue life prediction framework for calculation of axial and bending fatigue life at various stress ratios has been developed. The purpose of the life prediction framework is to account for materials used in gas turbine engines, such as Titanium 6Al-4V, which experience an endurance stress limit as the number of cycles increase towards infinity. The work conducted to develop this energy-based framework consist of the following entities: (1) A new life prediction criterion for axial and bending fatigue at various stress ratios for Aluminum 6061-T6, (2) use of the previously developed improved uniaxial energy-based method to acquire fatigue life prior to endurance limit behavior [1], (3) and the incorporation of a statistical energy-based fatigue life calculation scheme to the uniaxial life criterion (the first entity of the framework), which is capable of constructing prediction intervals based on a specified percent confidence level. The exactitude of this work was verified by comparison between theoretical approximations and experimental results from recently acquired Al 606-T6 and Ti 6Al-4V data. The comparison shows very good agreement, thus validating the capability of the framework to produce accurate fatigue life predictions.

A New Finite Element Approach to Biaxial Fatigue Life Prediction in Gas Turbine Engine

2010 ◽  
Author(s):  
Wasim Tarar ◽  
M.-H. Herman Shen
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Gas Turbine ◽  
Life Prediction ◽  
Gas Turbine Engine ◽  
Constitutive Law ◽  
Fatigue Life Prediction ◽  
Turbine Engine ◽  
Number Of Cycles ◽  
Cycles To Failure

High cycle fatigue is the most common cause of failure in gas turbine engines. Different design tools have been developed to predict number of cycles to failure for a component subjected to fatigue loads. An energy-based fatigue life prediction framework was previously developed in recent research for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. A finite element approach for uniaxial and bending fatigue was developed by authors based on this constitutive law. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop a new QUAD-4 finite element for fatigue life prediction. The newly developed QUAD-4 element is further modified to obtain a plate element. The Plate element can be used to model plates subjected to biaxial fatigue including bending loads. The new QUAD-4 element is benchmarked with previously developed uniaxial tension/compression finite element. The comparison of Finite element method (FEM) results to existing experimental fatigue data, verifies the new finite element development for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can predict the number of cycles to failure at each location in gas turbine engine structural components. The new finite element provides a very useful tool for fatigue life prediction in gas turbine engine components. The performance of the fatigue finite element is demonstrated by the fatigue life predictions from Al6061-T6 aluminum and Ti-6Al-4V. Results are compared with experimental results and analytical predictions.

A New Hex-8 Finite Element for Gas Turbine Engine Fatigue Life Prediction

2011 ◽  
Author(s):  
Wasim Tarar ◽  
M.-H. Herman Shen
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Gas Turbine ◽  
Life Prediction ◽  
Gas Turbine Engine ◽  
Constitutive Law ◽  
Fatigue Life Prediction ◽  
Turbine Engine ◽  
Number Of Cycles ◽  
Cycles To Failure

High cycle fatigue is the major governing failure mode in aerospace structures and gas turbine engines. Different design tools are available to predict number of cycles to failure for a component subjected to fatigue loads. An energy-based fatigue life prediction framework was previously developed in recent research for prediction of axial, bending and torsional fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. A 1-D ROD element for unixial fatigue, a BEAM element for bending fatigue and a QUAD-4 element for biaxial fatigue were developed by authors based on this constitutive law. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop a new HEX-8 BRICK finite element for fatigue life prediction. The newly developed HEX-8 BRICK element has 8 nodes and each node has 3 degrees of freedom (DOF) in x, y and z directions. This element is further modified to add the rotational and bending DOFs for application to real world three dimensional (3D) structures and components. HEX-8 BRICK fatigue finite element has capability to predict the number of cycles to failure for 3-D objects subjected to multiaxial stresses. The new HEX-8 element is benchmarked with previously developed uniaxial tension/compression finite element in order to verify the new development. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite element development for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can predict the number of cycles to failure at each location in gas turbine engine structural components. The new finite element provides a very useful tool for fatigue life prediction in gas turbine engine components as it provides a complete picture of fatiguing process. The performance of the HEX-8 fatigue finite element is demonstrated by comparison of life prediction results for A16061-T6 to previously developed multiaxial fatigue life prediction approach by the authors. Another set of comparison is made to results for type 304 stainless steel data.

Life Prediction Method of CC and DS Ni Base Superalloys Under High Temperature Biaxial Fatigue Loading

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Takashi Ogata
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Life Prediction ◽  
Compressive Strain ◽  
Prediction Method ◽  
Strain Range ◽  
Fatigue Loading ◽  
Normal Strain ◽  
Biaxial Fatigue

Polycrystalline conventional casting (CC) and directionally solidified (DS) Ni base superalloys are widely used as gas turbine blade materials. It was reported that the surface of a gas turbine blade is subjected to a biaxial tensile-compressive fatigue loading during a start-stop operation, based on finite element stress analysis results. It is necessary to establish the life prediction method of these superalloys under biaxial fatigue loading for reliable operations. In this study, the in-plane biaxial fatigue tests with different phases of x and y directional strain cycles were conducted on both CC and DS Ni base superalloys (IN738LC and GTD111DS) at high temperatures. The strain ratio ϕ was defined as the ratio between the x and y directional strains at 1/4 cycle and was varied from 1 to −1. In ϕ=1 and −1. The main cracks propagated in both the x and y directions in the CC superalloy. On the other hand, the main cracks of the DS superalloy propagated only in the x direction, indicating that the failure resistance in the solidified direction is weaker than that in the direction normal to the solidified direction. Although the biaxial fatigue life of the CC superalloy was correlated with the conventional Mises equivalent strain range, that of the DS superalloy depended on ϕ. The new biaxial fatigue life criterion, equivalent normal strain range for the DS superalloy was derived from the iso-fatigue life curve on a principal strain plane defined in this study. Fatigue life of the DS superalloy was correlated with the equivalent normal strain range. Fatigue life of the DS superalloy under equibiaxial fatigue loading was significantly reduced by introducing compressive strain hold dwell. Life prediction under equibiaxial fatigue loading with the compressive strain hold was successfully made by the nonlinear damage accumulation model. This suggests that the proposed method can be applied to life prediction of the gas turbine DS blades, which are subjected to biaxial fatigue loading during operation.

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

scholarly journals Comparison of Coriolis and Turbine Type Flow Meters for Fuel Measurement in Gas Turbine Testing

1993 ◽  
Author(s):  
J. D. MacLeod ◽  
W. Grabe
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
Gas Turbine Engine ◽  
Turbine Engine ◽  
Turbine Flowmeter ◽  
Turbine Performance ◽  
Coriolis Flowmeter ◽  
Project Objectives

The Machinery and Engine Technology (MET) Program of the National Research Council of Canada (NRCC) has established a program for the evaluation of sensors to measure gas turbine engine performance accurately. The precise measurement of fuel flow is an essential part of steady-state gas turbine performance assessment. Prompted by an international engine testing and information exchange program, and a mandate to improve all aspects of gas turbine performance evaluation, the MET Laboratory has critically examined two types of fuel flowmeters, Coriolis and turbine. The two flowmeter types are different in that the Coriolis flowmeter measures mass flow directly, while the turbine flowmeter measures volumetric flow, which must be converted to mass flow for conventional performance analysis. The direct measurement of mass flow, using a Coriolis flowmeter, has many advantages in field testing of gas turbines, because it reduces the risk of errors resulting from the conversion process. Turbine flowmeters, on the other hand, have been regarded as an industry standard because they are compact, rugged, reliable, and relatively inexpensive. This paper describes the project objectives, the experimental installation, and the results of the comparison of the Coriolis and turbine type flowmeters in steady-state performance testing. Discussed are variations between the two types of flowmeters due to fuel characteristics, fuel handling equipment, acoustic and vibration interference and installation effects. Also included in this paper are estimations of measurement uncertainties for both types of flowmeters. Results indicate that the agreement between Coriolis and turbine type flowmeters is good over the entire steady-state operating range of a typical gas turbine engine. In some cases the repeatability of the Coriolis flowmeter is better than the manufacturers specification. Even a significant variation in fuel density (10%), and viscosity (300%), did not appear to compromise the ability of the Coriolis flowmeter to match the performance of the turbine flowmeter.

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