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.

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.

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 Effects of Machined Surface Integrity on High-Temperature Low-Cycle Fatigue Life and Process Parameters Optimization of Turning Superalloy Inconel 718

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2428
Author(s):  
Xiaoping Ren ◽  
Zhanqiang Liu ◽  
Xiaoliang Liang ◽  
Pengcheng Cui
Keyword(s):  
Residual Stress ◽  
High Temperature ◽  
Fatigue Life ◽  
Process Parameters ◽  
Surface Integrity ◽  
Inconel 718 ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Machined Surface ◽  
Machined Surface Integrity

Machined surface integrity characteristics, including surface stresses, physical-mechanical properties and metallographic structures, play important roles in the fatigue performance of machined components. This work aimed at investigating the effects of machined surface integrity on high-temperature low-cycle fatigue life. The process parameters were optimized to obtain required surface integrity and fatigue life of the turning superalloy Inconel 718. The relationships between low-cycle fatigue life and machined surface integrity characterization parameters were established based on the low-cycle fatigue tests at a high temperature (650 °C). The sensitivities of turning process parameters to high-temperature low-cycle fatigue life were analyzed, and the optimization parameters were proposed with the goal of antifatigue manufacturing. Experimental results indicated that the impact order of the characterization parameters of machined surface integrity on the high-temperature low-cycle fatigue life were the degree of work hardening RHV, the residual stress in the cutting speed direction S22, the fatigue stress concentration factor Kf, the degree of grain refinement RD and the residual stress in the feed direction S33. In the range of turning parameters of the experiments in this research, the cutting speeds could be 80~110 m/min, and the feed rate could be 0.10~0.12 mm/rev to achieve a longer high-temperature low-cycle fatigue life. The results can be used for guiding the fatigue-resistant manufacturing research of aeroengine superalloy turbine disks.

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.

Experimental study of surface integrity and fatigue life in the face milling of inconel 718

2017 ◽  
Vol 13 (2) ◽  
pp. 243-250 ◽  
Author(s):  
Xiangyu Wang ◽  
Chuanzhen Huang ◽  
Bin Zou ◽  
Guoliang Liu ◽  
Hongtao Zhu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Fatigue Life ◽  
Surface Integrity ◽  
Inconel 718 ◽  
Face Milling ◽  
The Face

scholarly journals Effect Tool Wear During End Milling on the Surface Integrity and Fatigue Life of Inconel 718

Procedia CIRP ◽  
2014 ◽  
Vol 14 ◽  
pp. 546-551 ◽  
Author(s):  
W. Li ◽  
Y.B. Guo ◽  
M.E. Barkey ◽  
J.B. Jordon
Keyword(s):  
Fatigue Life ◽  
Tool Wear ◽  
Surface Integrity ◽  
Inconel 718 ◽  
End Milling

Life enhancement of fatigue-aged fastener holes using the cold expansion process

2000 ◽  
Vol 214 (5) ◽  
pp. 281-293 ◽  
Author(s):  
J Gaerke ◽  
X Zhang ◽  
Z Wang
Keyword(s):  
Fatigue Life ◽  
Experimental Test ◽  
Load Transfer ◽  
Test Results ◽  
Expansion Process ◽  
Cold Expansion ◽  
Final Failure ◽  
Low Load ◽  
Open Hole ◽  
Life Enhancement

This paper examines the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint. The specimens were pre-cycled to 25, 50 and 75 per cent of the baseline fatigue life of a non-expanded specimen and then cold expanded prior to cycling to final failure. The experimental test was designed to provide a close comparison with standard maintenance practices for aircraft structures and used the FALSTAFF spectrum which was derived from actual flight loading. The test results have indicated that part-life cold expansion can provide substantial improvements in fatigue life, but the actual benefit is dependent upon the degree of precycling and he length of existing cracks when the specimen is cold expanded. Additionally, tests on open hole specimens of the same material and thickness were also carried out, with attempts being made to predict the crack growth lives of these specimes.

scholarly journals Influence of turning tool wear on the surface integrity and anti-fatigue behavior of Ti1023

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110112
Author(s):  
Li Xun ◽  
Wang Ziming ◽  
Yang Shenliang ◽  
Guo Zhiyuan ◽  
Zhou Yongxin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Tool Wear ◽  
Surface Integrity ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Machined Surface ◽  
Deformation Layer

Titanium alloy Ti1023 is a typical difficult-to-cut material. Tool wear is easy to occur in machining Ti1023, which has a significant negative effect on surface integrity. Turning is one of the common methods to machine Ti1023 parts and machined surface integrity has a direct influence on the fatigue life of parts. To control surface integrity and improve anti-fatigue behavior of Ti1023 parts, it has an important significance to study the influence of tool wear on the surface integrity and fatigue life of Ti1023 in turning. Therefore, the effect of tool wear on the surface roughness, microhardness, residual stress, and plastic deformation layer of Ti1023 workpieces by turning and low-cycle fatigue tests were studied. Meanwhile, the influence mechanism of surface integrity on anti-fatigue behavior also was analyzed. The experimental results show that the change of surface roughness caused by worn tools has the most influence on anti-fatigue behavior when the tool wear VB is from 0.05 to 0.25 mm. On the other hand, the plastic deformation layer on the machined surface could properly improve the anti-fatigue behavior of specimens that were proved in the experiments. However, the higher surface roughness and significant surface defects on surface machined utilizing the worn tool with VB = 0.30 mm, which leads the anti-fatigue behavior of specimens to decrease sharply. Therefore, to ensure the anti-fatigue behavior of parts, the value of turning tool wear VB must be rigorously controlled under 0.30 mm during finishing machining of titanium alloy Ti1023.

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