Dynamic deformation of structural elements of flying vehicles at their emergency impacts with barriers
Aviation technics and technology
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
An emergency disconnection of a flying vehicle from a carrier vehicle is often caused by destruction of connection points or by an abnormal function of launching device. The emergency disconnection at stages of landing or starting runs results the impact of the flying vehicle to a runaway surface. To predict the impact’s effect and the explosion or ignition danger, the dynamics, the deforming state, and destruction of the vehicle have to be estimated.
The technique and the results of the numerical simulation of the dynamic deformed state of the flying vehicle structure are performed for the medium velocity impact with the rigid flat barrier after the emergency separation from the carrier at starting and landing run stages. The problem of transient dynamics is solved by the finite elements method using the LS-DYNA system and the explicit integration approach. The finite elements of shell type with one point of integration are used; the deformation curve is by the bilinear function approximated. An initial velocity and an incidence angle are used as input data for the dynamics problem for the structure with known geometrical, mass, and stiffness properties.
The eigenfrequencies and eigenmodes of the existing vehicle as well as the accelerations for some structural elements in the transient process resulted by the impact are computed and compared with the semi-nature tests data. The numerical simulation has shown that the structure destruction occurs on compartments’ joints so that corresponds to the experimentally observed destruction. The obtained correlation between the computational and experimental values of eigenfrequencies and impact accelerations confirms the usability of the developed numerical technique for the simulation of impact interaction of flying vehicles structures and barriers.
The developed numerical simulation technique allows one to estimate the dynamic stress state parameters for various flying vehicles at emergency impacts.
Keywords:airplane, aircraft, accident, finite element method, dynamic response, acceleration, impact, barrier, bilinear material model
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