Extending the Fatigue Life of Aircraft Engine Components by Hole Cold Expansion Technology

1993 ◽  
Vol 115 (1) ◽  
pp. 165-171 ◽  
Author(s):  
A. C. Rufin
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
Life Extension ◽  
Expansion Process ◽  
Specific Test ◽  
Cold Expansion ◽  
Wide Range ◽  
Engine Components ◽  
Shrink Fit

The split-sleeve cold expansion process has been used successfully for over 20 years to extend the fatigue life of holes in aircraft structures. Cold expansion technology can also be applied to enhance engine low-cycle fatigue (LCF) performance in both production and repair applications. Specific test data are presented showing that fatigue life extension can be attained by cold expansion of holes in a wide range of situations (including nonround hole geometries and low edge margins), and in components subjected to high operating temperatures. A cold expanded bushing system is compared to standard shrink-fit bushing installations. Finally, two case studies are used to illustrate the application of cold expansion to full-scale engine components.

scholarly journals Extending the Fatigue Life of Aircraft Engine Components by Hole Cold Expansion Technology

1992 ◽  
Author(s):  
Antonio C. Rufin
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
Life Extension ◽  
Round Hole ◽  
Specific Test ◽  
Cold Expansion ◽  
Wide Range ◽  
Engine Components ◽  
Shrink Fit

The split-sleeve cold expansion process has been used successfully for over 20 years to extend the fatigue life of holes in aircraft structures. Cold expansion technology can also be applied to enhance engine low-cycle fatigue (LCF) performance in both production and repair applications. Specific test data are presented showing that fatigue life extension can be attained by cold expansion of holes in a wide range of situations (including non-round hole geometries and low edge margins), and in components subjected to high operating temperatures. A cold expanded bushing system is compared to standard shrink-fit bushing installations. Finally, two case studies are used to illustrate the application of cold expansion to full-scale engine components.

Application of Cold Expansion Process to Dovetail Slots of Compressor Disc: A Numerical Study

2017 ◽  
Author(s):  
Anil Kumar Sudhakar ◽  
Mahendra Babu Neelakantanahally Channaiah
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Surface Treatment ◽  
Life Extension ◽  
Expansion Process ◽  
Cold Expansion ◽  
Element Simulation ◽  
Circular Holes ◽  
Compressive Residual Stresses ◽  
Made In

Dovetail slots are essential structural cut-outs made in compressor disc to assemble blades. Under in-service centrifugal loading and inherent vibrations, the root regions of these dovetail slots are prone to fatigue failures. Surface treatment methods like shot peening, low plasticity burnishing and laser shock peening are employed to achieve fatigue life extension of dovetail slots. Another method commonly employed in aerospace industry for fatigue life extension of circular holes is the cold expansion process. This cold expansion process is a proven surface treatment method capable of achieving highest fatigue life enhancement benefits compared to other surface treatment methods, particularly for circular holes. Considering the efficacy of circular hole cold expansion process, an attempt is made in this work to study the suitability of cold expansion process for dovetail slots. In this work, a three dimensional, non-linear Finite Element simulation has been carried out to explore the application of cold expansion process for dovetail slot of a compressor disc. This Finite Element simulation involves two main steps namely, cold expansion of holes and machining process between holes. Two circular holes of appropriate radius at root locations of dovetail slot are cold expanded to introduce beneficial compressive residual stresses and further, portion between the two holes is machined-off to obtain the required dovetail shape. Complete distributions of beneficial compressive residual stresses retained after machining of dovetail slot are captured to assess the efficacy of cold expansion. The predicted results indicate that the proposed cold expansion process for dovetail slots is capable of significantly enhancing the fatigue life of dovetail slots.

scholarly journals Fatigue Strength Enhancement Using Shape Memory Alloy Bushings

1990 ◽  
Author(s):  
Edward R. Buchanan ◽  
Regina B. Celin
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
Turbine Engine ◽  
Innovation Research ◽  
Research Award ◽  
Wide Range ◽  
The Subject

In recent years, there have been a number of failures of aircraft engine and structural components which are believed to have resulted from the accumulation of fatigue damage. The treatment of such damage is therefore of great significance from the standpoints of increased reliability and extended usage. This paper presents the initial results of a program to evaluate a new process for the repair of fatigue-damaged aircraft engine components. In this process, the fatigue-damaged area is drilled out and replaced with a bushing manufactured from a new class of material called a ‘shape memory’ alloy. This material has the capability to expand in place following insertion, thus placing the surrounding material into compression. A significant improvement in low cycle fatigue life was observed at 288°C in Ti-6Al-4V specimens treated with the above technique. The degree of improvement is about twice that which was obtained with a mechanical cold expansion technique used commercially to extend fatigue life. The degree of improvement of the subject process is greater at high numbers of cycles than at low numbers of cycles. The subject project was funded as a Phase I Small Business Innovation Research award administered by the U.S. Naval Air Propulsion Center. Additional work in this area is planned which will a) identify the process parameters which will optimize the properties of shape memory alloy bushings, b) define the properties of shape memory alloy bushings over a wide range of temperature and loading conditions, and c) evaluate the effect in actual turbine engine hardware in a simulated engine environment.

A novel cold expansion process for improving the surface integrity and fatigue life of small-deep holes in Inconel 718 superalloys

2022 ◽  
Vol 154 ◽  
pp. 106544
Author(s):  
Shu-Lei Yao ◽  
Xue-Lin Lei ◽  
Run-Zi Wang ◽  
Cen-Yao He ◽  
Xian-Cheng Zhang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Surface Integrity ◽  
Inconel 718 ◽  
Expansion Process ◽  
Cold Expansion

scholarly journals Cold Expansion Process with Multiple Balls—Numerical Simulation and Comparison with Single Ball and Tapered Mandrels

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5536
Author(s):  
David Curto-Cárdenas ◽  
Jose Calaf-Chica ◽  
Pedro Miguel Bravo Díez ◽  
Mónica Preciado Calzada ◽  
Maria-Jose Garcia-Tarrago
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Life ◽  
Experimental Tests ◽  
The Finite Element Method ◽  
Expansion Process ◽  
Cold Expansion ◽  
Hoop Stresses ◽  
Element Method

Cold expansion technology is an extended method used in aeronautics to increase fatigue life of holes and hence extending inspection intervals. During the cold expansion process, a mechanical mandrel is forced to pass along the hole generating compressive residual hoop stresses. The most widely accepted geometry for this mandrel is the tapered one and simpler options like balls have generally been rejected based on the non-conforming residual hoop stresses derived from their use. In this investigation a novelty process using multiple balls with incremental interference, instead of a single one, was simulated. Experimental tests were performed to validate the finite element method (FEM) models and residual hoop stresses from multiple balls simulation were compared with one ball and tapered mandrel simulations. Results showed that the use of three incremental balls significantly reduced the magnitude of non-conforming residual hoop stresses and the extension of these detrimental zone.

The Influence of Corrosion Pits and Cold Expanded Fastener Holes on the Fatigue Life Aluminium 7075-T651

2014 ◽  
Vol 891-892 ◽  
pp. 87-92 ◽  
Author(s):  
Benjamin Withy ◽  
Stephen Campbell ◽  
Glenn Stephen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Air Force ◽  
Fatigue Tests ◽  
Expansion Process ◽  
Cold Expansion ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Corrosion Pits

The Royal New Zealand Air Force (RNZAF) utilised the split sleeve cold expansion process to increase the fatigue life of fastener holes in the wings of the C130 transport fleet. As part of the validation of the fatigue improvements offered by the process the Defence Technology Agency conducted a series of fatigue tests on cold expanded fastener holes in aluminium 7075-T651, including specimens with corrosion induced after the cold expansion process had been performed. This research conducted an analysis of fatigue crack origins and modelled the stress concentration factors generated as a result of the corrosion pits. These results were used to explain the differing fatigue life and s-n curves produced by corroded and non-corroded fatigue specimens and the location of crack initiation sites around corroded cold expanded fastener holes.

Application of Damage Tolerance Approach for Turbine Disk Life Extension

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1916-1921 ◽  
Author(s):  
Seung Hoon Nahm ◽  
Chang Min Suh ◽  
Min Woo Jung ◽  
Jong Yup Kim ◽  
Chang Hwan Yang
Keyword(s):  
Fatigue Life ◽  
Residual Life ◽  
Fatigue Crack Initiation ◽  
Aircraft Engine ◽  
Turbine Disk ◽  
Life Extension ◽  
Evaluation Procedure ◽  
Growth Data ◽  
Life Management ◽  
Creep Fatigue

For gas turbine engines, the safe life methodology has historically been used for fatigue life management of failure critical engine components. The safe retirement limit is necessarily determined by a conservative life evaluation procedure, thereby many components which have a long residual life are discarded. The objective of this study is to introduce the damage tolerant design concept into the life management for aircraft engine component instead of conservative fatigue life methodology which has been used for both design and maintenance. The residual lives of turbine disk component under various temperatures and conditions using creep-fatigue crack initiation and growth data were estimated. As the result of analysis, it was confirmed that retirement for cause concept was applicable to the evaluation of residual life of retired turbine disk which had been designed based on the conventional fatigue life methodology.

scholarly journals Parametric Analysis of the Mandrel Geometrical Data in a Cold Expansion Process of Small Holes Drilled in Thick Plates

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4105 ◽  
Author(s):  
Jose Calaf-Chica ◽  
Marta María Marín ◽  
Eva María Rubio ◽  
Roberto Teti ◽  
Tiziana Segreto
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Parametric Analysis ◽  
Expansion Process ◽  
Forming Process ◽  
Zone Length ◽  
Cold Forming ◽  
Cold Expansion ◽  
Geometrical Data ◽  
Small Holes

Cold expansion technology is a cold-forming process widely used in aeronautics to extend the fatigue life of riveted and bolted holes. During this process, an oversized mandrel is pushed through the hole in order to yield it and generate compressive residual stresses contributing to the fatigue life extension of the hole. In this paper, a parametric analysis of the mandrel geometrical data (inlet angle straight zone length and diametric interference) and their influence on the residual stresses was carried out using a finite element method (FEM). The obtained results were compared with the conclusions presented in a previous parametric FEM analysis on the influence of the swage geometry in a swaging cold-forming process of gun barrels. This process could be considered, in a simplified way, as a scale-up of the cold expansion process of small holes, and this investigation demonstrated the influence of the diameter ratio (K) on the relation between the mandrel or swage geometry and the residual stresses obtained after the cold-forming process.

A Procedure for Low Cycle Fatigue Life Prediction for Various Temperatures and Strain Rates

1990 ◽  
Vol 112 (4) ◽  
pp. 422-428 ◽  
Author(s):  
Ange Zhang ◽  
T. Bui-Quoc ◽  
R. Gomuc
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Low Frequency ◽  
Strain Range ◽  
Strain Rates ◽  
Total Strain Range ◽  
Wide Range ◽  
Experimental Values

This paper describes a procedure that permits the calculation of the fatigue life over a wide range of temperatures and strain rates. The isothermal fatigue life is expressed in terms of the total strain range by an equation previously obtained from a continuous damage concept. Additional new terms are introduced to take into account the effect of the temperature and of the strain rate. For a given material, a multiple regression analysis is carried out using some experimental results in order to evaluate the material constants involved. Once these constants are known, the life prediction can be made for other specified values of temperature and strain rate. The approach is applied to available data obtained from several stainless steels (AISI 304, 316, 348, and some SUS materials) under several combinations of temperatures and strain rates. The deviation of the calculated lives from the experimental values is reasonably acceptable. The extension of the proposed procedure to cases of cycling with a very low frequency, usually involving hold times, is examined and discussed.

Low Cycle Fatigue of 9-12% Cr Steel at Elevated Temperature: Cyclic Deformation Behavior and Life Assessment

2016 ◽  
Author(s):  
Peng Zhao ◽  
Fu-Zhen Xuan ◽  
De-Long Wu
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Life Assessment ◽  
Control Mode ◽  
Cycle Fatigue ◽  
Wide Range

Fatigue testing for an important turbine rotor material (X12CrMoWVNbN10-1-1 steel) was carried out over a wide range of strain and stress amplitudes at 873K. Particular attention was paid to the effect of control mode on the cyclic deformation behavior and life assessment at elevated temperature. Two main domains were observed depending both on the strain and stress amplitudes, where the effect of control mode was different. In the micro plastic deformation domain, the cyclic softening is slight and there is no clear difference in fatigue behavior between the stress and strain modes. In the plastic damage regime, stress cycling causes more significant softening or damage than strain cycling. The dependence of damage behavior on the evolution of dislocation substructure was focused. On the other hand, it is not possible to use strain based life model to predict fatigue life with the test results under a different control mode. A unified energy-based model is proposed based upon the deformation mechanism and the experimental results, which can assess the low cycle fatigue life with different control modes. The results obtained in this study could have significant implications in the design of structures.

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