• Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.12-19
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• 2009

The research for the fatigue analysis is regarded greatly as important in aerospace field. Moreover, a study on the fatigue characteristic is very actively progressing. In this study, the fatigue life estimation was performed for Flaperon Joint which has FCL(fatigue critical location) of tilt-rotor UAV. The Flaperon Joint should be taken the various loads by several missions profiles of UAV. The fatigue load spectrum of Flaperon Joint is generated by the standard mission segment for the tilt-rotor UAV, and this spectrum is used for the fatigue test and analysis. The in-house fatigue analysis program is applied to calculate the fatigue life based on Stress-Life(S-N) method. The S-N curve is generated from the S-N data of Mil-Handbook by second order polynomial regression method. Moreover, the coefficient of determination is used to ensure how accuracy it has. In addition, the Goodman equation is used to consider the mean stress effect for evaluating more accurate fatigue life. Finally, the result of fatigue analysis is verified by comparing with the fatigue test result for the Flaperon Joint.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.654-659
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• 2007

In this paper, the fatigue load spectrum for tilt rotor UAV is developed and fatigue analysis is achieved for flaperon joint. Tilt rotor UAV has two modes which are helicopter mode when UAV is taking off and landing and fixed wing mode when UAV is cruising. To make fatigue load spectrum, FELIX for helicopter mode and TWIST for fixed wing mode are used. And Fatigue analysis of flaperon joint is achieved using fatigue load spectrum we obtained. When S-N test data are analyzed, we use the Kriging meta model to get probability S-N curve for whole range of material life. The result which is life of flaperon joint obtained by suggested fatigue analysis procedure in this paper is compared with that obtained by MSC/Fatigue.

• Journal of Aerospace System Engineering
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• v.3 no.4
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• pp.27-34
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• 2009

This paper deals with the lifetime prediction of Aircraft Flaperon Joint made of AISI 4130 steel. Reviews are performed on the published damage models at first. And three different damage models are used for predicting the fatigue life of the structure subjected to variable amplitude fatigue loading. These models require no increase in complexity of use, nor do they require additional material property or mission loading information to achieve the improved accuracy. Finally a comparison among the fatigue results is performed. It is observed that the Miner's rule could predict longer life than other cumulative damage models which take into account loads below the endurance limit.

• Journal of Aerospace System Engineering
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• v.1 no.2
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• pp.27-36
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• 2007

The Damage Tolerant Design is developed to help alleviate structural failure and cracking problems in aerospace structures. Recently, the Damage Tolerant Design is required and recommended for most of aircraft design. In this paper, the damage tolerant design is applied to tilt rotor UAV. First of all, the fatigue load spectrum for the tilt rotor UAV is developed and fatigue analysis is performed for the flaperon joint which has FCL (fatigue critical location). Tilt rotor UAV has two modes: helicopter mode when UAV is taking off and landing; fixed wing mode when the tilt rotor UAV is cruising. To make fatigue load spectrum, FELIX is used for helicopter mode. TWIST is used for fixed wing mode. Fatigue analysis of flaperon joint is performed using fatigue load spectrum. E-N curve approach is used for picking crack initiation point. The LEFM(Linear Elastic Fracture Method) is considered for analyzing crack growth or propagation. Finally, including the crack initiation and propagation, the fatigue life is evaluated. Therefore the Damage Tolerant Design can be done.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.541-549
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• 2008

The fatigue analysis is performed to avoid structural failure in aerospace structures under repeated loads. In this paper, the fatigue life is estimated for the design of tilt rotor UAV. First of all, the fatigue load spectrum for tilt rotor UAV is generated. Fatigue analysis is done for the flaperon joint which may have FCL(fracture critical location). Tilt rotor UAV operates at two modes: helicopter mode such as taking off and landing; fixed wing mode like cruising. To make overall fatigue load spectrum, FELIX is used for helicopter mode and TWIST is used for fixed wing mode. The other hand, the Kriging meta model is used to get S-N regression curve for whole range of material life when S-N test data are analyzed. And then, the second order of S-N curve is accomplished by the least square method. In addition, the coefficient of determination method is used to ensure how accuracy it has. Finally, the fatigue life of flaperon joint is compared with that obtained by MSC. Fatigue.