Vol 61, No 4 (2018)

An approximate solution of the problem of dynamic deformation of an elongated thinshell structure with a fracturing thermal protection coating is given. The paper investigates how the structure frequencies change over the entire process of fracture. Examples are given.

The aeroelastic stability of a medium length cantilever cylindrical shell stiffened by an edge ring with the outer surface exposed to supersonic gas flow is investigated. The shell motion is described by the equations of the semi-membrane theory for laminated shells and considered with various end conditions. The dependences of the critical flutter speed on the dimensions of the ring cross-section, the value of the structural damping coefficient, the flow parameters, and the type of boundary conditions are obtained.

The stress-strain state for the torsion bar of the helicopter main rotor under the action of flight and test bench loads is analyzed. The technique of estimating the ultimate state by phenomenological strength criteria and maximum stresses is described. The close agreement between calculation results and experimental data is observed.

An aircraft seat unit under static and dynamic types of loading is simulated. The technique offers the possibility to determine stressed state and strength of the unit under conditions corresponding to the certification tests of passenger seats. It takes into account the energy absorber (damper) and kinematic connections between load-bearing elements.

A technique of multiobjective robust controller synthesis for airborne electro-optical device line-of-sight stabilization system is developed. The multiobjective synthesis of the robust control law for the stabilization system being considered is performed.

The method is obtained for the optical device axis stabilization by pitch and yaw angles at sliding modes in the conditions of nonlinearity, unsteadiness, cross-coupled and non-invariance to uncertainties. The quality of transients is formed by rotations and displacements of two sliding planes relative to the origin. Accuracy is achieved by adjusting the control parameters and reducing uncertainty with increasing accuracy of its identification and compensation.

In order to determine the rotary derivatives of forces and moments with respect to the angular velocity components, a method of their estimation is developed based on calculations of distributed static aerodynamic characteristics of aircraft under the assumption of smallness of its angular motion perturbations. To estimate the derivatives with respect to the transverse component of the angular velocity, calculations by discrete vortex method are additionally used. Examples of estimates for the passenger aircraft model in a wide range of angles of attack are given.

The results of experimental studies are presented that describe the propagation and orientation of reverse jets in the air cross flow in order to determine design parameters of deflection vane cascade for preventing the ingress of reverse jets in the own or nearby engine.

Four different approaches have been proposed to account for flexibility of the bearing rings and the neighboring parts of the shaft and the housing in computing the radial contact forces acting onto the rolling elements. A numerical example is presented to demonstrate efficacy and performance of the developed models. Their applicability is estimated for various conditions.

To determine the transport factors in multicomponent gaseous media, the authors used an approach based on the molecular-kinetic theory of gases. A mathematical model of the interaction potential of molecules in multicomponent media is proposed. This model takes into account elastic and geometric parameters of molecules as well as an algorithm for determining the parameters in it.

This paper considers the nonlinear transverse vibrations of the rotor of the low-power electric motor fastened with radial ball bearings. Amplitude-frequency characteristics are obtained that determine the resonance conditions. It is shown that it is the nonlinear stiffness characteristic of the rotor ball bearings that determines the rotor compound vibrations appearing due to emergence of subharmonic vibrations.

The approaches to integration of a high-pressure super-reaction turbine of an aircraft gas turbine engine and a gas-dynamic laser are considered.

A new approach to solving the problem of expanding the functionality of the rotor vibratory gyroscope is presented. Its motion equations are analyzed under modulated damping. Numerical solutions and analytical dependences are obtained, on the basis of which recommendations on technical improvement of the device are proposed.

The features of design and structural-functional scheme of the vortex air data system for a subsonic aircraft are considered. Mathematical models are revealed and procedure aerodynamic errors of the system measuring channels are quantitatively estimated.

The task of adjusting and maintaining the shape of the radio-reflective network of a largesized space-based reflector is considered. The possibility of using piezo actuators to solve this problem is estimated. The urgency of the actuator control problem for a wide range of tasks related to the space and aircraft equipment is shown. Different types of control for the chosen mathematical model of a piezo actuator are compared.

In the paper, an algorithm for optimal estimation of the parameters of pseudo-random signals of nonlinear dynamic systems is proposed in order to develop an optimal receiver for broadband systems. The basis of the algorithm being proposed is the maximum likelihood method as well as a presentation of nonlinear dynamic equation system as stochastic differential ones.

The efficiency of the aircraft alternating current (AC) machine with multifunction winding of stator with Y and delta connection of the half-windings with 18 slots per pair of poles is analyzed. The criterion is the amplitude of the first spatial harmonic of the magnetomotive force (MMF) under the fixed loss power in winding.

This paper considers the problem of community noise for an aircraft with contra-rotating open rotors. Main noise sources are described. Basic methods of noise reduction are considered. A noise reduction method by increasing the axial spacing between propellers is proposed from the test results.

The structure of panels for spacecraft solar batteries is analyzed. The production technology of high-strength carbon fiber polymeric composites and the structural members of solar panels produced from composites are considered. The paper also presents data on practical use of a number of composites.