The calculation of energy dissipation in fasteming zone of the landing gear strut at dynamic analysis of aircraft landing

At definition of loads, acting on the airframe and the landing gear strut at landing, the important role plays the damping of oscillations, as in computational cases the determining peaks of loads may are not first, but second or third. As an example, on fig. 1 the computational dependence of the force Py by the time t, acting on the plane frome the main landing gear version of the aircraft Tu-204 in one of landings, is presented. At definition of repeatability of loads and resource in computation some peaks of loads, arising at airframe oscillations are taken. In accepted estimations of damping, the real description of the landing gear shock absorption work [ 11, aerodynamic and constructional damping of the airframe are taken into account. The reckoning of aerodynamic damping in accordance with linear theory of a wing and use of the stationary flow around hypothesis can be found, for exzample, in work [2]. Usually, the logarithmic decrement of oscillations, describing damping property of a plane construction and energy emanation in immobile air environment define at frequent tests in following assumptions: the researched tone of oscillations is well allocated; the damping force are possible approximate by forces of viscous fristion; the damping is sufficiently small. At such assumptions the decrement of oscillations takes by constant size for given tone of oscillations. In present paper the contribution in damping at landing of the energy dissipation in the landing gear fasteming places, in that zone of a wing (or fuselage), in which concentrated forces from the landing gear are distributed on power elements of a composition, is discussed. This kind of damping is away in the flight and cannot be investigated in frequent tests. The model of the indicated kind of damping, taking into account , that it damping is essential at rough landings, when loads on planer are close to maximum operational loads, is propounded. Airframe is represented by system of beams, corresponding to a wing, fuselage and tail unit. However, in zone not far from the fastening of the landing gear the distribution in construction elements the force factors, dependent from the force in the landing gear shock-absorber, differs from srain disrtibution in beam. With regard to plane beams such zones are possible to consider as zones of local deformation, with sizes in several building heights of a beam. For description of the behaviour of some number of constructional elements in zones of local deformation we shall take the following model (fig. 2). Before of determinate strain level the element is deformed as elastic, and higher of this level in element the sliding platform, on which force of dry friction works is arisen. The model of such kind is a special case of Voigt model [3]. For simplification of model we shall assume, that stiffness 2 is small in comparison with stiffness 1. Then the beginning of sliding does not practically change the common stiffness of E element and the law of deformation at sliding can be recorded so: