Influence of Mission Variability on Fracture Risk of Gas Turbine Engine Components

2012 ◽  
Author(s):  
Michael P. Enright ◽  
Jonathan P. Moody ◽  
Ramesh Chandra ◽  
Alan C. Pentz
Keyword(s):  
Fracture Risk ◽  
Gas Turbine ◽  
Life Prediction ◽  
Damage Tolerance ◽  
Gas Turbine Engine ◽  
Fatigue Life Prediction ◽  
Turbine Engine ◽  
Risk Of Fracture ◽  
Failure Data ◽  
Engine Components

The need for application of probabilistic methods to fatigue life prediction of gas turbine engine components is being increasingly recognized by the U.S. Military. A physics-based probabilistic approach to risk assessment provides improved accuracy compared to a statistical assessment of failure data because it can be used to (1) predict future risk and (2) assess the influences of both deterministic and random variables that are not included in the failure data. Probabilistic risk and fatigue life prediction of gas turbine engine fracture critical components requires estimates of the applied stress and temperature values throughout the life of the component. These values are highly dependent upon the mission type and may vary from flight to flight within the same mission. Currently, standard missions are specified and used during the engine design process, but the associated stresses can differ significantly from stress values that are based on flight data recorder (FDR) information. For this reason, efforts are made to periodically update the standard missions and to assess the impact on component structural integrity and associated risk of fracture. In this paper, the influence of mission type and variability on fracture risk is illustrated for an actual gas turbine engine disk subjected to a number of different mission loadings. Disk stresses associated with each mission were obtained by scaling finite element model results based on RPM values obtained from engine flight recorder data. The variability in stress values throughout the life of the component was modeled using two different approaches to identify the upper and lower bound value influences on the risk of fracture. The remaining variables were based on default values provided in FAA Advisory Circular (AC) 33.14-1 “Damage Tolerance for High Energy Turbine Engine Rotors”. The risk of fracture was computed using a probabilistic damage tolerance computer code called DARWIN® (Design Assessment of Reliability With Inspection) and compared for each mission type to illustrate the maximum influence of mission type on fracture risk. The results can be used to gain insight regarding the influence of mission type and associated variability on the risk of fracture of realistic engine components.

A Probabilistic Framework for Risk Prediction of Gas Turbine Engine Components With Inherent or Induced Material Anomalies

2005 ◽  
Author(s):  
Michael P. Enright ◽  
R. Craig McClung ◽  
Luc Huyse
Keyword(s):  
Risk Assessment ◽  
Gas Turbine ◽  
Gas Turbine Engine ◽  
Turbine Engines ◽  
Manufacturing Processes ◽  
Gas Turbine Engines ◽  
Probabilistic Framework ◽  
Turbine Engine ◽  
Risk Of Fracture ◽  
Engine Components

Rare anomalies may be introduced during the metallurgical or manufacturing processes that may lead to uncontained failures of aircraft gas turbine engines. The risk of fracture associated with these anomalies can be quantified using a probabilistic fracture mechanics approach. In this paper, a general probabilistic framework is presented for risk assessment of gas turbine engine components subjected to either inherent or induced material anomalies. A summary of efficient computational methods that are applicable to this problem is also provided.

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.

Damage Tolerance Based Life Prediction in Gas Turbine Engine Blades Under Vibratory High Cycle Fatigue

1997 ◽  
Vol 119 (1) ◽  
pp. 143-146 ◽  
Author(s):  
D. P. Walls ◽  
R. E. deLaneuville ◽  
S. E. Cunningham
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Gas Turbine ◽  
Life Prediction ◽  
High Cycle Fatigue ◽  
Damage Tolerance ◽  
Gas Turbine Engine ◽  
Cycle Fatigue ◽  
Turbine Engine ◽  
Aspect Ratios

A novel fracture mechanics approach has been used to predict crack propagation lives in gas turbine engine blades subjected to vibratory high cycle fatigue (HCF). The vibratory loading included both a resonant mode and a nonresonant mode, with one blade subjected to only the nonresonant mode and another blade to both modes. A life prediction algorithm was utilized to predict HCF propagation lives for each case. The life prediction system incorporates a boundary integral element (BIE) derived hybrid stress intensity solution, which accounts for the transition from a surface crack to corner crack to edge crack. It also includes a derivation of threshold crack length from threshold stress intensity factors to give crack size limits for no propagation. The stress intensity solution was calibrated for crack aspect ratios measured directly from the fracture surfaces. The model demonstrates the ability to correlate predicted missions to failure with values deduced from fractographic analysis. This analysis helps to validate the use of fracture mechanics approaches for assessing damage tolerance in gas turbine engine components subjected to combined steady and vibratory stresses.

scholarly journals Damage Tolerance Based Life Prediction in Gas Turbine Engine Blades Under Vibratory High Cycle Fatigue

1995 ◽  
Author(s):  
David P. Walls ◽  
Robert E. deLaneuville ◽  
Susan E. Cunningham
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Gas Turbine ◽  
Life Prediction ◽  
High Cycle Fatigue ◽  
Damage Tolerance ◽  
Resonant Mode ◽  
Gas Turbine Engine ◽  
Cycle Fatigue ◽  
Turbine Engine

A novel fracture mechanics approach has been used to predict crack propagation lives in gas turbine engine blades subjected to vibratory high cycle fatigue (HCF). The vibratory loading included both a resonant mode and a non-resonant mode, with one blade subjected to only the non-resonant mode and another blade to both modes. A life prediction algorithm was utilized to predict HCF propagation lives for each case. The life prediction system incorporates a boundary integral element (BIE) derived hybrid stress intensity solution which accounts for the transition from a surface crack to corner crack to edge crack. It also includes a derivation of threshold crack length from threshold stress intensity factors to give crack size limits for no propagation. The stress intensity solution was calibrated for crack aspect ratios measured directly from the fracture surfaces. The model demonstrates the ability to correlate predicted missions to failure with values deduced from fractographic analysis. This analysis helps to validate the use of fracture mechanics approaches for assessing damage tolerance in gas turbine engine components subjected to combined steady and vibratory stresses.

Prognostics/Diagnostics for Gas Turbine Engine Bearings

2003 ◽  
Author(s):  
Rolf F. Orsagh ◽  
Jeremy Sheldon ◽  
Christopher J. Klenke
Keyword(s):  
Gas Turbine ◽  
Critical Role ◽  
Aircraft Engine ◽  
Gas Turbine Engine ◽  
Sensor Data ◽  
Turbine Engine ◽  
Model Based ◽  
Failure Data ◽  
Oil Debris ◽  
Engine Components

Development of robust in-flight prognostics or diagnostics for oil wetted gas turbine engine components will play a critical role in improving aircraft engine reliability and maintainability. Real-time algorithms for predicting and detecting bearing and gear failures are currently being developed in parallel with emerging flight-capable sensor technologies including in-line oil debris/condition monitors, and vibration analysis MEMS. These advanced prognostic/diagnostic algorithms utilize intelligent data fusion architectures to optimally combine sensor data, with probabilistic component models to achieve the best decisions on the overall health of oil-wetted components. By utilizing a combination of health monitoring data and model-based techniques, a comprehensive component prognostic capability can be achieved throughout a components life, using model-based estimates when no diagnostic indicators are present and monitored features such as oil debris and vibration at later stages when failure indications are detectable. Implementation of these oil-wetted component prognostic modules will be illustrated in this paper using bearing and gearbox test stand run-to-failure data.

Optimal Automated Fracture Risk Assessment of 3D Gas Turbine Engine Components

2016 ◽  
Author(s):  
Michael P. Enright ◽  
Jonathan P. Moody ◽  
James C. Sobotka
Keyword(s):  
Risk Assessment ◽  
Finite Elements ◽  
Fracture Risk ◽  
Gas Turbine ◽  
High Energy ◽  
Gas Turbine Engine ◽  
Fracture Risk Assessment ◽  
Turbine Engine ◽  
Engine Components ◽  
2D And 3D

High-energy rotating components of gas turbine engines may contain rare material anomalies that can lead to uncontained engine failures. A zone-based risk assessment approach can be used to estimate component fracture risk based on groupings of finite elements (FEs) called zones. Creating zones manually is time consuming and requires human judgment. Algorithms have been developed to automatically create zones based on individual FEs, but the associated computation times increase exponentially with the number of FEs. 3D FE models typically contain millions of finite elements. Computation of component risk using individual FE-based automated zoning algorithms may take days or even weeks to complete. An improved optimal autozoning methodology has been developed that substantially reduces the computation time associated with fracture risk assessments. It combines finite elements with similar properties (i.e., stress, temperature, proximity to the surface) into groups called “pre-zones”. An automated zone creation algorithm is applied to pre-zones rather than individual FEs, reducing the overall number of computations. In this paper, the optimal autozoning methodology is presented and illustrated for FE geometries in both 2D and 3D gas turbine engine components. Based on the demonstration problem results, it is shown that the computation speed associated with the optimal autozoning algorithm is expected to be three to four orders of magnitude faster than a previous algorithm that created zones at individual FEs. The pre-zoning-based algorithm also requires less memory than previous algorithms, enabling it to solve much larger models. The resulting algorithm provides a feasible and realistic solution for fracture risk assessment of 2D and 3D component finite element models.

Flexible manufacturing in repair of gas turbine engine components

1992 ◽  
Author(s):  
KIRK D ◽  
ANDREW VAVRECK ◽  
ERIC LITTLE ◽  
LESLIE JOHNSON ◽  
BRETT SAYLOR
Keyword(s):  
Gas Turbine ◽  
Flexible Manufacturing ◽  
Gas Turbine Engine ◽  
Turbine Engine ◽  
Engine Components
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