scholarly journals Impact of Load Retention on Aircraft Engine Parts Under Real Flight Cycle Conditions in Service Life Monitoring

2021 ◽  
Vol 2021 (3) ◽  
pp. 47-57
Author(s):  
Sergiy Yepifanov ◽  
Andrii Brunak
Keyword(s):  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Cycle Fatigue ◽  
Non Linear Equation ◽  
Accumulation Of Damage ◽  
Static And Dynamic Loading ◽  
Theoretical Results ◽  
Maximum Stresses

Abstract One of the major problems in the development of algorithms for monitoring the life of aircraft gas turbine engines is that the character of loading in real flight cycles is crucially different from the character of the static and dynamic loading during the testing of samples. This paper proposes a method for taking into account the effect of retentions at maximum stresses and cycle temperatures on the low-cycle fatigue (LCF) of the heat-resistant alloys used in engine parts. Regularities in repeated-static loading (RSL) are used in combination with the method of linear accumulation of damage due to the LCF and RSL, with retentions of a variable length. A non-linear equation is derived for the summation of these damages, the solution of which determines the durability (life) of the part while taking into account the retention duration. The theoretical results were verified by using the experimental characteristics of the GS-6K and EI-437B nickel-based alloys, previously reported by other researchers.

Coating Pre-Cracking Effect in Combined Cycle Fatigue Tests of Superalloys for Gas Turbine Blades

2010 ◽  
Author(s):  
Mauro Filippini ◽  
Stefano Foletti ◽  
Giuseppe Pasquero
Keyword(s):  
Gas Turbine ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Nickel Superalloy ◽  
Combined Cycle ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Cycle Fatigue ◽  
Polycrystalline Nickel

In gas turbine engines for aerospace propulsion, the application of coatings on HP and LP stage blading where the highest temperatures are experienced is a common practice to prevent environmental degradation. However, since the strength of the coating is lower than that of the substrate material, upon loading the static strength of the coating may be exceeded and coating cracking may occur. In order to assess the effect of cracking in the coating on polycrystalline nickel superalloy MAR-M002, a number of combined cycle fatigue (CCF) and low cycle fatigue (LCF) tests with and without dwell have been carried out, at temperatures up to 870 °C. In order to experimentally assess the potential detrimental effect of coating cracking, controlled cracking in the coating prior to fatigue testing has been generated by using a special procedure. CCF tests have carried out by superimposing to strain controlled zero to maximum LCF cycles with dwell time stress controlled smaller HCF cycles, simulating the high loading ratio vibrations occurring in the blades. The loading mode applied in the CCF tests, even if much simpler than effective service conditions, is sufficiently representative of the loading experienced by the materials in correspondence of critical geometrical features of the turbine blades, where HCF amplitudes due to blade vibrations are superimposed to major (ground-air-ground) LCF cycles occurring during the regular service of the gas turbine engines. Comparison of the CCF and of the LCF tests with dwell with conventional LCF tests is presented herein, with special consideration of the effect of coating cracking.

Practical Implications of Integrating Turbomachinery Into the Air Turborocket

2004 ◽  
Author(s):  
Joshua A. Clough ◽  
Mark J. Lewis
Keyword(s):  
Gas Turbine ◽  
Aircraft Engine ◽  
Launch Vehicle ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Gas Turbine Engines ◽  
Turbine Inlet Temperature ◽  
Turbine Engine ◽  
Space Launch ◽  
Practical Implications

The development of new reusable space launch vehicle concepts has lead to the need for more advanced engine cycles. Many two-stage vehicle concepts rely on advanced gas turbine engines that can propel the first stage of the launch vehicle from a runway up to Mach 5 or faster. One prospective engine for these vehicles is the Air Turborocket (ATR). The ATR is an innovative aircraft engine flowpath that is intended to extend the operating range of a conventional gas turbine engine. This is done by moving the turbine out of the core engine flow, alleviating the traditional limit on the turbine inlet temperature. This paper presents the analysis of an ATR engine for a reusable space launch vehicle and some of the practical problems that will be encountered in the development of this engine.

scholarly journals Design of experiments for verification of computational life prediction methods

2019 ◽  
Vol 18 (3) ◽  
pp. 143-154
Author(s):  
O. V. Samsonova ◽  
K. V. Fetisov ◽  
I. V. Karpman ◽  
I. V. Burtseva
Keyword(s):  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Turbine Engines ◽  
Prediction Methods ◽  
Gas Turbine Engines ◽  
Loading Conditions ◽  
Load History ◽  
Strain Behavior ◽  
Before And After ◽  
Two Stages

The failure of heavily loaded rotating parts of aviation gas turbine engines may bring about dangerous consequences. The life of such parts is limited with the use of computational and experimental methods. Computational life prediction methods that are used without carrying out life-cycle tests of engine parts or assemblies should be substantiated experimentally. The best option for verifying the computational methods is to use the results of cyclic tests of model disks. These tests make it possible to reproduce loading conditions and surface conditions that correspond to those of real disks, and the data on the load history and material properties make it possible to simulate stress-strain behavior of disks under test conditions by calculation. This paper shows the process of planning such tests. It is assumed that the tests will be carried out in two stages - before and after the initiation of a low-cycle fatigue crack. A number of criteria are formulated that the geometry of model disks and their loading conditions are to satisfy. Based on these criteria, model disks were designed and the conditions for their testing were selected.

scholarly journals Advanced Technology for Reducing Aircraft Engine Pollution

1974 ◽  
Vol 96 (4) ◽  
pp. 1354-1360 ◽  
Author(s):  
R. E. Jones
Keyword(s):  
Gas Turbine ◽  
Aircraft Engine ◽  
Advanced Technology ◽  
Turbine Engines ◽  
Variable Geometry ◽  
Gas Turbine Engines ◽  
Large Reduction ◽  
Final Phase ◽  
Fuel Staging ◽  
Develop Technology

The proposed EPA regulations covering emissions of gas turbine engines will require extensive combustor development. The NASA is working to develop technology to meet these goals through a wide variety of combustor research programs conducted in-house, by contract, and by university grant. In-house efforts using the swirl-can modular combustor have demonstrated sizable reduction in NOx emission levels. Testing to reduce idle pollutants has included the modification of duplex fuel nozzles to air-assisted nozzles and an exploration of the potential improvements possible with combustors using fuel staging and variable geometry. The Experimental Clean Combustor Program, a large contracted effort, is devoted to the testing and development of combustor concepts designed to achieve a large reduction in the levels of all emissions. This effort is planned to be conducted in three phases with the final phase to be an engine demonstration of the best reduced emission concepts.

Engine Test Experience and Characterization of Self Sealing Ceramic Matrix Composites for Nozzle Applications in Gas Turbine Engines

2003 ◽  
Author(s):  
Eric P. Bouillon ◽  
Patrick C. Spriet ◽  
Georges Habarou ◽  
Thibault Arnold ◽  
Greg C. Ojard ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Turbine Engines ◽  
Matrix Composites ◽  
Gas Turbine Engines ◽  
Sic Fiber ◽  
Engine Testing

Advanced materials are targeting durability improvement in gas turbine engines. One general area of concern for durability is in the hot section components of the engine. Ceramic matrix composites offer improvements in durability at elevated temperatures with a corresponding reduction in weight for nozzles of gas turbine engines. Building on past material efforts, ceramic matrix composites using a carbon and a SiC fiber with a self-sealing matrix have been developed for gas turbine applications. Prior to ground engine testing, a reduced test matrix was undertaken to aggressively test the material in a long-term hold cycle at elevated temperatures and environments. This tensile low cycle fatigue testing was done in air and a 90% steam environment. After completion of the aggressive testing effort, six nozzle seals were fabricated and installed in an F100-PW-229 engine for accelerated mission testing. The C fiber CMC and the SiC Fiber CMC were respectively tested to 600 and 1000 hours in accelerated conditions without damage. Engine testing is continuing to gain additional time and insight with the objective of pursuing the next phase of field service evaluation. Mechanical testing and post-test characterization results of this testing will be presented. The results of the engine testing will be shown and overall conclusions drawn.

Smart Structures: Gas Turbine Engine Applications

2001 ◽  
Author(s):  
Sanford Fleeter ◽  
Patrick B. Lawless
Keyword(s):  
Gas Turbine ◽  
Smart Materials ◽  
High Cycle Fatigue ◽  
Smart Structures ◽  
Forced Response ◽  
Smart Structure ◽  
Turbine Engines ◽  
Cost Ratio ◽  
Gas Turbine Engines ◽  
Cycle Fatigue

Abstract This paper is directed at providing the smart structure technology community an introduction to aircraft gas turbine engines issues that might be addressed, i.e. smart/active propulsion systems. Specifically, in gas turbine engines, smart structures can (1) influence performance, stability, noise and high cycle fatigue by providing airfoil aerodynamic control, (2) alleviate or avoid high cycle fatigue due to flutter and forced response by introducing damping intra structures, and (3) provide health monitoring. However, the benefits-to-cost ratio of the added complexity of incorporating smart materials into gas turbine engines must be large as smart materials and actuator/control systems are not a simple solution to complex problems. The prime selling point of smart structure technology to current state-of-the-art gas turbine engines may be adaptability to age, mission, and the environment.

Advanced Experimental and Analytical Investigations on Combined Cycle Fatigue (CCF) of Conventional Cast and Single-Crystal Gas Turbine Blades

2011 ◽  
Author(s):  
Swen Weser ◽  
Uwe Gampe ◽  
Mario Raddatz ◽  
Roland Parchem ◽  
Petr Lukas
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Aircraft Engine ◽  
Combined Cycle ◽  
Rotor Blades ◽  
Blade Design ◽  
Cycle Fatigue ◽  
Predictive Methods

Rotor blades are the highest thermal-mechanical loaded components of gas turbines. Their service life is limited by interaction of creep, low cycle fatigue (LCF), high cycle fatigue (HCF) and surface attack. Because assurance of adequate HCF strength of the rotor blade is an important issue of the blade design the European project PREMECCY has been started by the European aircraft engine manufacturers and research institutes to enhance the predictive methods for combined cycle fatigue (CCF), as a superposition of HCF and LCF. Although today’s predictive methods ensure safe blade design, there are certain shortcomings of assessing fatigue life with Haigh or “modified Goodman diagrams”, such as isolated HCF assessment as well as uni-axial and off-resonant testing. HCF and LCF are considered without taking into account their interaction. PREMECCY is aimed to deliver new and improved CCF prediction methods for exploitation in the industrial design process. Beside development of predictive methods the authors are involved in the design and testing of advanced specimens representing rotor blade features. In this connection the paper presents a novel test specimen type and a unique hot gas rig for CCF feature test at mechanical and ambient representative conditions.

The Testing and Approval of Aircraft Engine Mounted Accessories

1982 ◽  
Vol 196 (1) ◽  
pp. 57-64
Author(s):  
D S Pearson
Keyword(s):  
Gas Turbine ◽  
Aircraft Engine ◽  
Single Frequency ◽  
Turbine Engines ◽  
Severity Assessment ◽  
Gas Turbine Engines ◽  
Shaft Speed ◽  
Unified Approach ◽  
Frequency Excitation ◽  
Environmental Simulation

Vibration measurements on gas turbine engines are normally made using accelerometers. The environment to which engine accessories would be subject has been evaluated by comparing ‘g’ peaks in the frequency spectrum, individually, with empirical yardsticks of severity. Endurance approval testing of accessories to withstand the environment so characterized is normally conducted by applying unidirectional single frequency excitation to simulate engine conditions at a particular shaft speed. These procedures have proved inadequate in predicting failure or verifying corrective measures where accessory problems due to wear phenomena are concerned. This paper analyses reasons for this inadequacy in terms of measurement practice, engine severity assessment, environmental simulation and approval procedures. By recognizing the effect of multi-frequency vibration in three planes it further aims to provide a unified approach to accessory design and development by which service accessory reliability might be improved. Although at first sight more expensive, the approach described will in many cases reduce to previous practice. In cases where greater test expenditure is necessary, loopholes will have been plugged by which many expensive service problems previously escaped.

Impact of Bolt-Nut Interface Modeling Assumptions on the Calculated Low Cycle Fatigue Life of Aircraft Engine Turbine Rotor Bolted Joints

2013 ◽  
Author(s):  
Anil Saigal ◽  
Luke Jensen ◽  
Thomas James
Keyword(s):  
Finite Element ◽  
Stress Analysis ◽  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
High Energy ◽  
Bolted Joint ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Joint Stress ◽  
Interface Modeling

Finite element analysis is used extensively in the aircraft turbine engine industry to predict stresses to calculate low cycle fatigue (LCF) life of life-limited parts (LLP’s). A failure of an LLP can lead to a potentially catastrophic event such as a noncontainment of high energy debris. Under-predicted stress can cause the life limits to be set too high, which is a safety hazard. Over-predicted stress can cause the life limits to be set too low, which adds cost due to the need to replace expensive engine hardware more frequently. As such, high fidelity stress analysis is necessary to appropriately set LCF life limits. This study focuses on the nut-bolt interface modeling assumptions associated with a rotor bolted joint stress analysis for LCF predictions. A 3D finite element model of an actual aircraft engine rotor bolted joint is created. Different cases are analyzed and compared to investigate how the thread modeling assumptions might affect the calculated life in the mated rotor LLP hardware. Walker-adjusted alternating stress, σ0,alt, is used to measure the affect on life impact. It is shown that elastic versus elastic-plastic nut/bolt materials properties and the inclusion of the helical thread shape have minor impact on the calculated stresses. However, inclusion of contact elements with friction at the thread interface instead of couples has a moderate impact on the calculated stresses and therefore expected life.

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