Numerical-analytical method to calculate plate response and durability under broadband acoustic loads and its verification

Deformable body mechanics


Аuthors

Denisov S. L.1*, Medvedskiy A. L.2**

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), Zhukovsky, Moscow region, Russia

*e-mail: stl.denisov@gmail.com
**e-mail: medvedskyal@nrczh.ru

Abstract

New ICAO requirements for external aviation noise reduction draw increasing attention to the new types of airframe design/layout to use airframe as shield from engine noise. While targeting external noise reduction, the wingbody layout looks like the most promising. This layout places engines over the airframe. It is necessary to note that this layout leads to increase of the airframe area which suffers from acoustic loads. In turn, these loads produce the stresses which can lead to fatigue airframe failure. So despite of significant progress in aviation engine noise reduction, the discussions about acoustic fatigue and durability of aircraft structures (for example, plates and shells) gain back their popularity.

In this paper we proposed the hybrid numerical-analytical method to calculate the response and durability of isotropic metal plate under broadband acoustic loads with four different acoustic field spatial distributions: fully correlated, partially correlated, delta-correlated and diffuse field distribution. For the simple-supported metal plate, mean square stresses and durability obtained by the proposed hybrid method were compared with the exact analytical solution. It is necessary to note, that proposed hybrid method may be applied for the plate with clamped-clamped or clamped-simple supported edges. The mean square stresses, calculated by the hybrid method, fit well the exact analytical solution but are highly sensitive to acoustical field spatial distribution, external acoustic field frequency spectrum and number of eigen modes taken into account.

We calculated durability by using four different approaches providing the mean square stresses as input data. Calculations performed by Wirsching-Light method (for narrowband Gaussian process) and Kowalewski method (for wideband Gaussian process) give, correspondingly, lower and upper estimations of the plate durability. Miles and Rajcher methods (both are for wideband Gaussian process) produce relatively close values located between the results of Wirsching-Light and Kowalewski methods.

Keywords:

spatial correlation function, cross correlation function, isotropic plates, acoustic fatigue, acoustic endurance

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