Отработка методов моделирования зубчатых шестерен планетарного редуктора с применением объемной постановки конечноэлементного анализа в рамках пакета ANSYS

В статье проведен модальный анализ ведущего колеса (эпицикла) планетарной зубчатой передачи и рассмотрен возможный алгоритм анализа процесса зацепления в квазистатической постановке. По результатам модального анализа и после построения резонансных диаграмм получили, что наиболее опасной для эпицикла оказалась формаколебания с тремя узловыми диаметрами и менее опасной с четырьмя узловыми диаметрами при условии вращения вала двигателя в рабочем диапазоне частот. Возникновение резонансных колебаний может привести к разрушению зубчатого колеса, которое начинается от впадины между зубьями, развивается в диафрагму и приводит к поломке шестерни. В процессе статического анализа была произведена попытка проверить подход, применяемый для расчета зубчатых передач, а именно определение напряженнодеформированного состояния (НДС) во впадине зубьев ведущего зубчатого колеса авиационного двигателя при приложении рабочих нагрузок. Предложенный подход не претендует на точные количественные значения и может рассматриваться как метод, который должен впоследствии сам подвергнуться тщательному анализу с учетом практических результатов испытаний

Comparison of Phases Formation Process in Initial and Mechanically Activated Ceramic Batches with Pyrochlore Formulations

Formation of two pyrochlore ceramics with formulations CaZr0.25U0.75Ti2O7 and CaUTi2O7 within the temperature range 1000-1500 C from batches prepared by grinding of oxide powders in a mortar and an activator with hydrostatic yokes AGO-2U as well as soaking of a Ca, Zr, and Ti oxide mixture with uranylnitrate solution was studied. The pyrochlore ceramics are produced through intermediate calcium uranate formation. Phase formation reactions in the batch pre-treated in the AGO-2U unit were completed within the temperature range 1000-1100 C that is lower than in the batches prepared by two other methods

Forecast of 241Am migration from a system of deep horizontal boreholes

Highly radioactive materials classified as high-level nuclear waste (HLW) of atomic power engineering should be disposed of deeply underground in special geological disposal facilities (GDFs), which can be of either shaft or borehole type. The advantages of borehole-type GDFs result from smaller volumes of mining operations, a simpler construction technology, shorter construction time and cost. This allows us to consider them as an alternative to shaft-type GDFs. The parts of the boreholes in which waste containers should be placed can be both vertical and horizontal. Computer simulation of the migration of radionuclides from a group of parallel horizontal boreholes into the biosphere made it possible to conclude that horizontal GDF boreholes have significant advantages over vertical ones. We determined a forecast of 241Am migration by a method of mathematical modelling of 241Am release from vitrified HLW disposed of in several horizontal drillholes. The maximum concentrations of americium in the near-surface groundwater above the repository are calculated depending on the number of boreholes, the depth of their location and the distance between them, the permeability of rocks and the time of waste storage prior to disposal. Influence of different conditions on the safety of a GDF of borehole type is estimated. Calculations show that the heat generated by HLW causes a weaker groundwater convection near horizontal boreholes compared to vertical boreholes of the same capacity. In addition to that, at an equal thickness of the rock layer separating the HLW from the surface, the geothermal temperature of the host rocks in the near field of a horizontal borehole will be lower than the average geothermal temperature near a vertical borehole. As a result, the rate of radionuclides leaching from the waste forms by groundwaters will also be lower in the case of horizontal boreholes

Phase partitioning and uranium speciation in brannerite-based ceramics

Branneritecontaining ceramics were produced by cold pressing and sintering (CPS) and cold crucible inductive melting (CCIM) methods and examined by X-ray diffraction and absorption and by scanning electron microscopy. Brannerite content in the ceramics ranged between ∼20 and 90 vol.%. Uranium is mainly partitioned between brannerite and minor mixed U/RE oxide but since brannerite is a dominant phase, it takes up to 90% of total U. Uranium in the ceramics is present as U(IV) and U(V). In the low-brannerite ceramics U occurs as U(IV) whereas in the ceramics with brannerite as major phase U(V) dominates over U(IV). Ce in the brannerite ceramics is mainly trivalent. The first coordination shell of U in ceramics produced by CPS is split into two sub-shells with U-O distances of 1.7–1.9 Å and ∼2.1 Å while in the melted ceramics this interatomic distance is 2.1–2.2 Å. The next three atoms (Ti) are positioned at a distances of 3.1–3.2 Å