The algorithm for generating the training set for the problem of elastoplastic deformation of the metal rod

The paper proposes an algorithm for forming a small training set, which will provide a reasonable quality of a surrogate ML-model for the problem of elastoplastic deformation of a metal rod under the action of a longitudinal load pulse. This dynamic physical problem is computationally simple and convenient for testing various approaches, but at the same time it is physically quite complex, because it contains a significant range of effects. So, the methods tested on this problem can be further applied to other areas. This work demonstrates the possibility of a surrogate ML-model to provide a reasonable prediction quality for a dynamic physical problem with a small training set size.

Experimental evaluation of rational parameters of pre-acceleration to ensure liquid sustainer engine launch in zero gravity

The paper presents the results of experimental studies of liquid fuel deposition processes in liquid rocket propulsion system tanks under the conditions of free, i.e. unperturbed, orbital and suborbital flight under the influence of small prestart G-load created by auxiliary engines before liquid sustainer engine launch. Having conducted the dimension analysis, we formed the structure of dimensionless groups, which determine the dependence of the time required for fuel deposition to the tank intake, on the g level, the degree of tank filling and the physical properties of the propellant. Experimental studies were carried out on a zero gravity test bench, using the principle of implementing below-G conditions at the free fall of the equipment under test, and on a laboratory aircraft at the "Kepler's parabola" flight. The results of experimental studies have shown that the effect of viscosity on the deposition rate is practically absent. At the same time, in experiments it was found that, starting with Bond numbers exceeding 40 ... 50, the dimensionless separation time does not depend on Bond number, the value of the latter being determined by the minimum radius of free gas inclusions, deformed during when ascending during the separation process. Findings of research show that with a considerable duration of the prestart G load pulse, the movement of gas bubbles in the liquid under the action of a G load pulse becomes quasistationary.

Il-76TD air crash. Aircraft loading evaluation

The purpose of the paper was to study the accidental collision of the Il-76TD aircraft flying at speeds of up to240 m/s with an obstacle, and the condition of dangerous goods being transported. According to the results of calculations, comparisons with the available analytical solutions and data on real accidents, we developed a prediction model of the IL-76TD aircraft, the model reflecting the aircraft mass-dimensional and power characteristics. Furthermore, we estimated the parameters of the load pulse acting on the transported cargo and the impact of the obstacle material on them. The resulting load pulse parameters are the basis for the development of packaging, the design of which should ensure compliance with regulatory safety requirements for the transport of dangerous goods

Research of the anti-resonance pulse forming network and its application in the Marx generator

An anti-resonance pulse forming network (PFN) has been designed, analyzed, and tested for its application in generating quasi-square pulses. According to the circuit simulations, a compact generator based on two/three-section network was constructed. Two-section network is applied in the generator due to its compact structure, while three-section network is employed for generating pulses with higher quality. When two-section network is applied in the generator, the full-width at half-maximum of the load pulse is 400 ns, at the same time, its rise time, flat top and fall time are 90, 180 and 217 ns, respectively. When the three-section network is applied with the same pulse width of the load pulse, the rise time of the output decreases to 60 ns, while the flat top increases to 240 ns and the fall time reduces to 109 ns. Meanwhile, this kind of network could be used to shape the output pulses of generators whose equivalent circuit is LC series discharge network, such as MARX generator, into quasi-square pulses. And the preliminary experiment demonstrates that anti-resonance network could work well on four-stage Marx generators. A sine pulse generated by the four-stage Marx generator is shaped into a quasi-square pulse with voltage of 11.8 kV and pulse width about 110 ns based on two-section anti-resonance network.