Future increase in the unit capacity of hydraulic turbines and in hydroelectric-station heads are making it necessary to increase in the turbine-penstock characteristic P x D (product of pressure and penstock diam.), which basically determines the required strength of the penstock material [i, 2]. For the penstocks of modern high-capacity hydraulic turbines, the strength properties of the usual low-carbon and low-alloy steels are practically exhausted because the shell thickness of turbine penstocks in this case reaches critical values (60-70 ram). A further increase in penstock wall thickness is associated with a reduction in the technological and brittle strength of welded joints and the reliability of welded construction, in general, also with a sharp increase in the labor required for assembly and welding work.

A technique is proposed that makes it possible to simulate the stress-strain state of threads with a certain bending stiffness under the action of a transverse short-term dynamic load. The studies were carried out on the basis of the general theorem of dynamics, namely the law of conservation of energy, as well as the provisions of the resistance of materials, mathematical modeling using the apparatus of differential and integral calculus of functions of one and several variables. As a result of the calculation, in addition to the distribution of stresses and strains along the length of the thread, the value of the equivalent static load to the impact arising from the kinetic energy of the impacting body interacting with the structure is determined. This load is limited by the initial amount of kinetic energy of the body, and its value and the law of change with time depend on the physical and geometric parameters of the thread of finite rigidity. The use of the developed methodology in design and development will allow to correctly solve the problems of calculating elements, the model of which is a thread with a certain bending stiffness. This will increase the reliability of products designed using such elements. At the same time, it can lead to a wider introduction of structures operating mainly in tension with partial perception of bending moments while ensuring the overall strength of a particular mechanical system under external influence.

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Since a pumped-storage plant operates briefly in a power generation regime its capacity can be increased by increasing the parameter P. D (product of the pressure and penstock diameter) of the penstocks with a comparatively small vohime of the reservoir. However, an increase in diameter and pressure leads to an increase in the thickness of the penstock walls and consequently to a decrease in the reliability of the structure and to complications in manufacture and assembly. The thickness of the penstock walls can be reduced by using higher strength steels. The experience of a number of countries shows that the most promising in hydropower construction are the low alloy steels and, in particular, high-strength, heat-treated low-alloy steels in the highest pressure parts of penstocks [1-3].The 200,000-kW Kiev pumped-storage plant, whose construction was completed in 1972, includes six penstocks with a diameter of 3800 mm and wall thickness of 14-30 mm made of steel Mt6CS (GOST 6713-53). The working pressure in the penstock is 6.4 arm. During construction of the sixth penstock two 10.5-m links of high-strengthsteel 14Kh2GMR (ChMTU-1-645-69) with a wall thickness of 20 mm were installed in place of steel M16$ with a wall thickness of 28 mm in the lower, most loaded section of the penstock. The links of steel Ivi168 were replaced by steel 14Kh2GMR for conducting experimental welding of large-diameter, high-strength steel penstocks and for studying the design strength of the experimental links during operation of the plant. Observation of the experimentalconstruction work during operation of the Kiev plant revealed no difficulties, since the penstock was laid on the ground surface.The high-strength, low-alloy steel 14Kh2GMR is one of the most promising, since it combines high strength characteristics with sufficient weldability, cold resistance, and comparatively low cost.The rolled sheet products for the experimental links of the Kiev plant penstock were hardened and tempered when delivered. The chemical composition and main mechanical properties of the 20-mm-thick steel sheet are presented in Table 1.In fabricating the cylindrical sections of steel 14Kh2GMR V, grooving for welding the circular joints was done mechanically. Gas cutting with subsequent dressing by an emery stone was used for X-grooving forwelding the longitudinal joints when assembling the cylinders into sections. Each section was made up of two cylinders, the length of the section was 1500 mm. Connection of the cylinders into sections and enlargement of the sections into ]inks were done by automatic submerged arc welding. Welding was done without preheating.The root welds during automatic welding were made with a 3-mm-diameter Svl0GA electrode (GOST 2246-70). FilLing of the grooves was done with a 3-mm-diameter high-strength Svl0KhGN2MYu electrode (TU 43-71). Flux AN17M was used during welding (TU IE5 26F-69). Electrodes UONI-13/45 (type 342A) and ANP-2 (type ET0) with a diameter of 4 mm were used for assembling the elements of the penstock and welding...

Аннотация. Объектом исследования выступало мобильное заграждение, образованное железобетонными блоками соединенными между собой и предназначенное для создания физического препятствия для автотранспортного средства. Предметом исследования настоящей работы являлись внутренние усилия в элементах связей мобильного заграждения, возникающие в результате действия кратковременной динамической нагрузки, а также деформации заграждения, характеризующиеся углом поворота ударяемого блока вокруг его продольной оси. Исследование проведено с помощью коммерческой системы компьютерного моделирования SolidWorks «Анализ движения». Расчет связанных дифференциальных и алгебраических уравнений, определяющих движение модели механической цепи при наезде автотранспортного средства, производился с помощью интегратора переменного порядка и шага WSTIFF. Проведен анализ по влиянию коэффициента трения скольжения на характер изменения реакций, возникающих в элементах связей между отдельными блоками, а также на поведение конструкции. Выявлена значительная обусловленность возникающих внутренних усилий в элементах связей, а также углов поворота блоков вокруг продольной оси заграждения от указанного параметра. Полученные данные дают возможность принимать эффективные технические решения по снижению коэффициента трения скольжения в паре «мобильное заграждение -основание для его установки» при разработке и применении подобных устройств.Ключевые слова: цепь, изгибно-жесткая нить, мобильное заграждение, удар, коэффициент трения.