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Computational and experimental studies of a pressure pulsation damper for pipeline systems

A generalized-structure analytical model of a pressure pulsation damper for pipeline systems is presented. The model was obtained using the four-pole method. The model is obtained in lumped and distributed parameters. The distributed-element model and finite element model are used for calculating the inherent characteristics of the pressure pulsation damper. The analytical distributed-element model takes into account the distribution parameters of the central inertial channel by introducing into the analytical model a matrix for the distributed element instead of the matrix of inertial resistance. A finite element parametric model of a two-stage reactive-type oscillation damper is developed in the Ansys software. Pulsation processes in the damper are modeled using acoustic analysis. The frequency-dependent coefficients of the damper transfer matrix are calculated for three models using three numerical experiments with a section of the pipeline system with the dynamic characteristics known in advance. The characteristic parameters of the pressure pulsation damper are calculated. These are the wave input impedance, wave output impedance and the inherent vibration damping. The calculation was carried out using analytical and finite element models. A single-stage reactive pressure pulsation damper is developed. The damper is designed in such a way that its settings such as the resistance of the jets and resonance tubes, the length of the central channel and the capacity of the expansion cavity can be changed. The results of experimental and numerical research of the inherent characteristics of a single-stage reactive of a vibration damper are presented.

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Model of interaction between laser radiation and metal powder composition during direct laser growth

This paper presents a model for analyzing the interaction of laser radiation and a metal-powder composition in the process of direct laser growing of large-sized combustion chambers of gas turbine engines. The metal-powder composition is fed into the melting zone coaxially with laser radiation; the task is to completely melt the powder with laser radiation before it enters the melt bath on the construction platform. The laser radiation is absorbed as it passes through the gas-powder jet, and its energy is also used to melt the construction platform or the previous layer. Thus, in order to determine the parameters of the operating conditions that provide the possibility of melting powder particles, it is necessary to determine the boundaries of the parameters at which each particle of the metal-powder composition completely melts in a gas-powder jet. To simulate heat transfer inside a particle, the Beer – Lambert laser radiation absorption law was used using the lumped parameter approach. The required energy for melting the powder material was determined through enthalpy. The resulting one-dimensional differential equation of enthalpy increment is solved numerically by the Euler method. Using this model, the distance from the point of origin of the interaction of the laser beam with a metal-powder composition to the zone of its complete melting was determined and the effect of the velocity of the gas-powder jet, the power of laser radiation, the bulk density of the metal-powder composition and the average radius of the powder particles on the distance to the zone of complete melting was studied.

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Method of testing the software of spacecraft electronic equipment based on fault injection in the algorithms of orientation and stabilization

The purpose of the work is to develop and describe a new method of testing spacecraft electronic equipment. The article substantiates the relevance of developing new methods and means of testing on-board electronic equipment of spacecraft based on the intentional introduction of faults for the purpose of testing survivability algorithms. It was shown that carrying out such tests makes it possible to increase the completeness of control and reliability of on-board electronic equipment of spacecraft while simultaneously reducing testing costs. A new method for testing spacecraft software based on fault injection is proposed, which is used to solve the specific task of checking orientation and stabilization modes. The proposed method makes it possible to develop semi-natural models of on-board electronic equipment of increased adequacy and reconfigurability due to the use of programmable logic integrated circuits as the basis of hardware and software complexes. The proposed method is implemented on the hardware and software of a ground-based debugging complex for on-board electronic equipment and is distinguished by the ability to simulate a wide range of on-board electronic equipment, low cost and mobility. All technical solutions described in the article were introduced into the production process when creating modern spacecraft for communications, radio navigation and geodesy.

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Thermocycling test of a titanium-carbon fiber adhesive joint produced using laser texturing technology

In spacecraft load-bearing structures, adhesive bonding of titanium alloy and composite material parts is often used. To increase the strength of the adhesive bond of the titanium-carbon fiber reinforced plastic pair, preliminary treatment of the bonded surfaces is necessary. In this paper, it is proposed to use laser texturing to process the metal surface. The main objective of the study is to experimentally determine the strength characteristics of the adhesive bond of carbon fiber reinforced plastic and titanium alloy with different modes of laser processing of the metal surface and to determine the effect of thermal cycling on the samples of the adhesive bond. The surface of the OT-4 titanium alloy was laser processed in different modes, after which the samples were glued with VK-9 and LOCTITE® EA 9394 AERO glue. The glued samples were subjected to thermal cycling in a vacuum chamber in the temperature range from –150 to +150 °C. Shear testing of adhesive bond samples showed that laser texturing increases bond strength by an average of 60% for LOCTITE® EA 9394 AERO adhesive and by 142% for VK-9 adhesive. Samples with laser texturing have a cohesive nature of failure on carbon fiber. During thermal cycling, most samples show a slight decrease in adhesive bond strength by an average of 6...8%. The results show that the use of laser processing to prepare titanium alloy before bonding with composite material is a promising method for increasing the strength of adhesive bonds for spacecraft components.

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