МЕТОД ПІДТВЕРДЖЕННЯ РЕСУРСНИХ ХАРАКТЕРИСТИК МЕТАЛЕВОЇ ЛОПАТІ НЕСУЧОГО ГВИНТА ВЕРТОЛЬОТА ЗА РЕЗУЛЬТАТАМИ ВИПРОБУВАНЬ

Abstract

The helicopter main rotor blade is the basic product that determines the reliability and service life of the helicopter as a whole. The problem of predicting and ensuring the specified blade life is an urgent problem considered at the stage of its design. The analysis of the design, structural materials and design and technological solutions of the main rotor blade (RB) of the Mi-8 helicopter has been carried out. A brief description of the main rotor blade of the Mi-8 helicopter is presented. The analysis was carried out and a standard flight cycle (SFC) of the helicopter was developed. The type of bench equipment for carrying out bench fatigue tests of the blade has been selected and justified. The loads on the main rotor blade for the SFC are determined. To determine the fatigue life of a blade, it is necessary to know the characteristics of the stress-strain state. The calculation of the stress-strain state (SSS) of a blade by the finite element method (FEM) using the ANSYS system is presented. The characteristics of the stress-strain state of the spar of the regular and irregular parts of the rotor blade of a helicopter are determined using the ANSYS system. The use of numerical methods for calculating the characteristics of the stress-strain state can significantly reduce the time and cost of designing a blade. The paper presents the results of calculating the regular part of the main rotor blade of the Mi-8 helicopter in the hover mode in the case of its loading with aerodynamic and inertial load from rotation, as well as the force from its own weight. With the help of the ANSYS system, a finite element model of the regular part of the blade was developed, consisting of a set of beam elements of variable section, a calculation was carried out taking into account the geometric nonlinearity of the structure's behavior, and an analysis of the results obtained was carried out. To describe the response of materials to an external action, a model of an elastically deformable isotropic body was used with the assignment of the corresponding elastic constants of the material. The analysis of the calculation results includes the determination of reactions at the attachment points, the values of the maximum displacements of structural elements and stresses in dangerous sections. Dangerous sections are determined and the values of the longitudinal force and bending moment in these sections are calculated. The assessment of the static strength of the blade by the safety factor was carried out. When evaluating the static strength, the equivalent stresses according to Mises were considered as the maximum design stresses. To assess the fatigue strength, we analyzed the distribution of the main tensile stresses in the power elements over typical stress concentrators. The maximum level of the main tensile stresses in the dangerous section indicates that the blade material operates in the zone of high-cycle fatigue. A technique for calibrating strain gauge channels has been developed. The calculation of the characteristics of the rotor blade of a helicopter is based on the requirements set forth in the technical literature, regulatory documents. When performing work, the requirements of the Aviation Rules, Part 29 (AP - 29) were taken into account. These studies were the basis for the development of a method for confirming the resource characteristics of a helicopter main rotor blade based on the results of flight and bench tests.