Papers by Keyword: Liquid Helium

Abstract: In the elements of structures with a limited resource during operation, significant cyclic stresses can occur, reaching and exceeding the yield strength; the results of an experimental study of the effect of the magnitude of preliminary plastic deformations on the strength and durability of structural alloys under low-cycle loading can be of undoubted interest for practice. The use of experimental planning methods in the study of the influence of the maximum cycle stresses and the magnitude of the preliminary permanent deformation on the low-cycle fatigue of 03Kh13AG19 chromium-manganese steel at T = 4.2 K under pulsating tension showed that these methods can be successfully used.

Abstract: Metallurgy, mechanical engineering, energy, agriculture, food industry, energy, electronics, rocket and space technology – this is a far from complete list of areas of the national economy in which liquid cryogenic products (cryoproducts). The production volumes of such products and the scale of their use are constantly increasing. This is due to the fact that cryogenic temperatures (below 120 K) provide unique opportunities for the implementation of such physical phenomena and processes that do not manifest themselves under normal conditions, but are used very effectively in science and technology. The solution of fundamental scientific problems and applied problems of both promising and current importance is determined by the level of development of cryogenic technology and the degree of its practical application. The continuous expansion of the scale of production of liquid cryogenic products has led in recent years to a significant increase in the volume of production of systems for their storage and transportation. These systems, as a rule, are welded shell structures in execution, they are operated in difficult conditions of temperature and force effects. The share of their production in the total output of cryogenic engineering products is very significant, and the operating conditions are the most stressful in comparison with other types of cryogenic structures. For the manufacture of cryogenic shell structures, expensive non-ferrous alloys and special steels are used, the degree of consumption of which, taking into account the sufficient material consumption of such structures and the expanding scale of their production, is constantly increasing. Therefore, one of the most urgent for cryogenic mechanical engineering at present is the problem of reducing the material consumption of shell structures and increasing their reliability and durability. It is obvious that a solution to this problem for cryogenic engineering products can be achieved by improving the methods of their strength calculations based on taking into account the specific hardening effect of low temperature on structural alloys. The phenomenon of low-cycle fatigue of metals is associated with elastoplastic deformation of their macrovolumes. The kinetics of elastoplastic deformation processes under cyclic loading depends on the loading conditions and material properties, and the nature of these processes and their intensity have a decisive influence on the features of material destruction. If the accumulation of deformation is small, then the destruction, as a rule, is of a fatigue nature; quasi-static fracture (similar in appearance to fracture during static tests for short-term strength) occurs after the realization of the ultimate plasticity of the material. The task of assessing the bearing capacity and durability under cyclic loading conditions is extremely important. Under cyclic loading, a number of specific phenomena and factors that are difficult to take into account analytically arise, which are primarily associated with the development of fatigue damage, with the need to assess the cyclic and structural instability of materials [1]. Since such studies are very laborious and expensive, the problem of minimizing such experiments is currently urgent. In this paper, we investigate the possibility of using mathematical planning methods for experimental studies at cryogenic temperatures. Experiment planning is usually understood as the procedure for choosing the volume and conditions of testing necessary and sufficient to solve the problem with the required accuracy.

Abstract: Introduce the basic concepts of the superconducting and superconducting magnetic separation, the species and properties of superconducting material. Through the current use situation of superconducting magnetic separation machine to explain the advantages and disadvantages about superconducting magnetic separation machine than conventional magnetic separation machine. The paper analyzes the main problems of the superconducting magnetic separation. With a clear direction of superconducting magnetic separation research, improve the superconducting magnet of the critical temperature, especially in liquid nitrogen temperature, even at room temperature, which is a very important research subject.

Abstract: With the development of modern industrial society, the need of measuring the pressure parameters at the ultra-low temperature is proposed. However, there is no developed products of ultra-low pressure sensors at home and abroad, and reports related to ultra-low pressure sensors such as the structural design of and methods of test and calibration are also few. This paper mainly describes a method for test and calibration of the pressure sensor at the ultra-low temperature. Based on the requirements obtained under the ultra-low temperature condition, a calibration device for the pressure sensor at the ultra-low temperature is designed, and the specific calibration instructions of some parameters are given.

Abstract: An efficient and reliable pressurization system for an oxidizer and fuel of a liquid propellant rocket is critical for a successful launch. A liquid helium pressurization system employing a heater can reduce its mass, and be made simpler and more reliable than conventional pressurization systems. The key issue to minimize the total mass of the system is the optimization of the size of the liquid helium tank. In this paper, we describe a method to determine the optimal size of a liquid helium tank, and present one set of results under a given set of requirements. In this pressurization system, the heater design is represented by the heater efficiency. To estimate the heater efficiency, the convection heat transfer coefficient should be known beforehand. The guideline how to estimate this convection heat transfer coefficient based on the preliminary experimental data is also presented in this paper.