A Technique of Stress Reduction in a Conical Shell of the Head Radio-Transparent Fairing of the Aircraft
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CTURAL MECHANICS AND STRENGTH OF FLIGHT VEHICLES
A Technique of Stress Reduction in a Conical Shell of the Head Radio-Transparent Fairing of the Aircraft Yu. I. Vinogradova, A. I. Maslovb, and G. B. Men’kovc, * a
Bauman Moscow State Technical University, ul. Vtoraya Baumanskaya 5, Moscow, 105005 Russia AO VPK “NPO Mashinostroeniya”, ul. Gagarina 33, Reutov, Moskovskaya oblast, 143966 Russia c ZAO NVP “Bolid”, ul. Pionerskaya 4, Korolev, Moskovskaya oblast, 141074 Russia *e-mail: [email protected]
b
Received October 19, 2019; revised December 18, 2019; accepted July 2, 2020
Abstract—The paper considers a conical shell of the head fairing of a hypersonic aircraft that is connected through the frame with the cylindrical shell. Possibilities of reducing the maximum stresses at the connection are analyzed. DOI: 10.3103/S1068799820030022 Keywords: conical shell, stress concentration, analytical parametric analysis.
The stress concentration that is due to the connection of the conical fairing to the cylindrical body of the aircraft is investigated depending on the geometric parameters of the frame, physical properties of the material of the fairing, and the aircraft frame and body. The structure is loaded by the external pressure in heating conditions (the uniform temperature over the thickness, up to 1500 °C). The issues of flow around aerospace products at supersonic speeds were considered in [1, 2]. The maximum stresses arise in the connection zone of the cylindrical and conical shells, as well as when reinforced with a frame. Another zone of stress concentration is in the area of the apex of the cone. The thermally stressed state of thin-walled structures under local loading was analyzed in [3–13]. Connection of structural elements, modeling of boundary conditions were considered in [14, 15]. The connection of conical and cylindrical shells, the frame and the reinforced part of the conical shell in the area of the frame are shown in Fig. 1. The shell thickness is h; R2 = 0.2R1. The dimensions of the reinforced part of the conical shell and the frame vary during the study. LE bf 2R2
α
2R1
0.6 L
L Fig. 1.
The study is intended to reduce the maximum stresses in the fairing (cone) and to determine the elastic modulus E of the transition section, when the stresses are minimal. A change of the mechanical 377
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characteristics of the conical shell material in the area of contact with the frame or an increase of the strength of the shell material are investigated. Variants of a design solution for different lengths of the section with the modified modulus of elasticity E are considered. Similarly to [16], we perform a complex transformation of a system of differential equations for the axisymmetric loading of the conical shell. The system includes equations of equilibrium, the strain compatibility equations, and the elasticity relations. The temperature-related strains and elastic strains of the structure are summed up. We get a resolving equation (1) [ δ(δ + 2) − z ] T1 = D + F2 z 2 ,
where
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