Estimation of longevity index for flying vehicles structures under random loadings

Аuthors

Zareckiy M. V.^*, Sidorenko A. S.^**

Izhevsk Electromechanical plant "KUPOL", 3, Pesochnaya str., Izhevsk, 426033, Russia

*e-mail: iemz@kupol.ru
**e-mail: k906@mai.ru

Abstract

Operation reliability is one of the basic requirements to flying vehicles carried by launcher aircrafts. An intensive vibration causes high-level stresses in the areas of structural irregularity so that results the fatigue damages accumulation. These stresses must be considered to estimate accurately the strength and reliability of both carrier and carried vehicle, therefore the correct estimation of loading levels and of the durability of structures is one of the most practically important problems of aircrafts design.
The main goal of the presented investigation is the mathematical modeling of the dynamic stress and strain state of cinematically excited aircrafts’ structures and the estimation of their durability.
The random excitation caused by the flight loadings is transferred from the carrier to the carried vehicle through the suspension brackets.
The SolidWorks software is used to simulate the dynamic stress state. The stationary kinematic excitation is defined by several types of the acceleration spectral density. The properties of the random vibrations of the carried flying vehicle are computed using the constructed numerical models. The areas of the maximum amplitudes of vibration are found as well as the zones of the maximum stresses, and both the spectral properties and stresses are computed. It is shown that the maximum stress dispersion corresponds to two lowest eigenfrequencies.
The random stress processes corresponding to various spectral densities of stresses are computed using the statistical simulation algorithms as the harmonic series with random parameters for each time value. The obtained random processes are reduced to the sets of regular stress cycles that are equivalent by damaging capacity to the random ones on the basis of the standard algorithms. The repeatability diagrams for the regular cycles are calculated using the linear hypothesis of damage summation, and the fatigue damageability of the structure is estimated.
The developed models of random forced vibrations can be used to estimate the dynamic stress state, the vibration strength, and the durability of various carried flying vehicles.

Keywords:

airplane, design, oscillations, finite element method, shell, dynamic response, vibration stress, stationary vibration, spectral density, statistical simulation, fatigue damageability

References

1. Gudkov A.I., Leshakov P.S. Vneshnie nagruzki i prochnost’ letatel’nyh apparatov (External loads and strength of aircraft), Moscow, Mashinostroenie, 1968, 470 p.
2. Figurovskij V. I. Raschet na prochnost’ bespilotnyh letatel’nyh apparatov (Calculation for strength of unmanned flight vehicles), Moscow, Mashinostroenie, 1973, 360 p.
3. BolotinV.V. Vibracii v tehnike (Vibration in engineering), Moscow, Mashinostroenie, 1978, vol. 1, 352 p. Dimentberg F.M., Kolesnikov K.S. Kolebanija mashin, konstrukcij i ih jelementov (Vibrations of machines, structures and their elements), 1980, vol. 3, 544 p.
4. Sidorenko A.S., Rodionov G.L. Elektronnyi zhurnal «Trudy MAI», 2007, no. 26, available at: http://www.mai.ru/science/trudy/published.php?ID=29685 (accessed 31.01.2007)
5. Zareckij M.V., Sidorenko A.S. Elektronnyi zhurnal «Trudy MAI», 2011, no. 46, available at: http://www.mai.ru/science/trudy/published.php?ID=29685 (accessed 07.07.2011).
6. Zareckij M.V., Sidorenko A.S. Elektronnyi zhurnal «Trudy MAI», 2012, no. 58, available at: http://www.mai.ru/science/trudy/published.php?ID=29685 (accessed 26.09.2012).
7. Raschety i ispytanija na prochnost’. Metody shematizacii sluchajnyh processov nagruzhenija jelementov mashin i konstrukcij i staticheskogo predstavlenija rezul’tatov, GOST 25.101-83 (Calculations and strength tests. Methods of schematization of random processes of loading of machine elements and structure and statistical representation of the results, State Standart 25.101-83), Moscow, Standarty, 1984, 21 p.
8. Troshhenko V.T., Sosnovskij L.A. Soprotivlenie ustalosti metallov i splavov (Fatigue resistance of metals and alloys), Kiev, Naukova dumka, 1987, vol.1, 510 p., vol. 2, 825 p.

Download