Damage accumulation in multilayer thin films on gamma titanium aluminides

The present paper involves comprehensive investigations towards an understanding on how aggressive environments, high service temperatures and long dwell times affect damage growth and lifetime reduction of different components of automotive combustion engines and aero-engines made out of gamma titanium aluminides with protective coatings. The outcome of this paper is related to the practical recommendations on how damage growth at high temperatures in multilayer thin films on gamma titanium aluminides under thermal cyclic conditions and multiaxial stress state may be controlled in order to reduce environmental degradation, optimize the protective coating and extend lifetime of a component for automotive, energy and aerospace applications.Настоящая статья включает в себя всеобъемлющие исследования, направленные на понимание того, как агрессивные среды, высокие температуры и время цикла нагружения влияют на рост повреждаемости и сокращение долговечности различных компонентов автомобильных двигателей внутреннего сгорания и авиационных двигателей, изготовленных из гамма алюминидов титана с защитными покрытиями. В результате этих исследований установлено, как рост поврежденности при высоких температурах в многослойных тонких пленках на основе гамма алюминидов титана в условиях теплового циклического нагружения и многоосного напряженного состояния можно контролировать с целью снижения деградации под влиянием окружающей среды, оптимизации защитного покрытия и увеличения срока службы элементов конструкций для автомобильной, энергетической и аэрокосмической промышленности

Multi-domain Boundary Element Method in Nonlinear Liquid Sloshing Analysis for Fuel Tanks

The boundary element method is used for analysis of the non-linear sloshing response of liquid in cylindrical baffled and un-baffled fuel tanks. The liquid is supposed to be an ideal and incompressible one and its flow introduced by the vibrations of a shell is irrotational. The potential formulation is considered for the liquid domain. In this paper the free vibration analysis of the liquid sloshing in the cylindrical shell is carried out in non-linear statement. The non-linear Cauchy-Lagrange integral is involved in the problem statement and the boundary conditions were assigned on the free surface changing in time. Here we use reduced boundary element method. The problem was solved using the single-domain and multi-domain reduced boundary element methods. The fourth-order Runge-Kutta method is employed to advance the solution in the time domain. The rigid baffled tanks with different annular orifices were considered. The time-dependencies of the free surface flood level were obtained numerically for vibrations of the fluid-filled tanks with and without baffles in linear and non-linear statements

Benchmark creep tests for thermal barrier coatings

The topic of this paper involves a number of benchmark creep tests and reference solutions that give the possibility to verify the finite element analysis of stress redistribution in thermal barrier coatings related to commercial software packages. The numerical results have been compared in the benchmark tests with the results obtained by other methods and by other authors. The results of creep studies revealed the magnitudes of the local stresses that correlate with the residual stresses determined in the thermally grown oxide by the luminescence spectroscopy method. The creep properties of Ni-based superalloy substrate have strong influence on the stress state and subsequent failure of EB-PVD thermal barrier coatings. The obtained numerical results demonstrate that the future EB-PVD thermal barrier coatings should be developed simultaneously with the Ni-based superalloy substrate, because the effectiveness of coating is influenced by the composition and properties of the substrate.Тема цієї статті включає в себе ряд тестів на повзучість та еталонні рішення, які дають можливість перевірити аналіз методом скінченних елементів перерозподілу напружень в теплозахисних покриттях, пов'язаний з комерційними пакетами програмного забезпечення. Чисельні результати були порівняні у тестах з результатами, отриманими іншими методами та іншими авторами. Результати досліджень повзучості показали величини локальних напружень, які корелюють із залишковими напруженнями, визначеними в термічно вирощеному оксиді методом люмінесцентної спектроскопії. Повзучість нікелевих жароміцних сплавів підкладки має сильний вплив на напружений стан і подальше руйнування EB-PVD теплозахисних покриттів. Отримані чисельні результати показують, що майбутні EB-PVD теплозахисні покриття повинні бути розроблені одночасно з нікелевою підкладкою, оскільки ефективність покриття залежить від складу і властивостей підкладки

Structural and phase transformations in the thiourea/zinc acetate system

Using differential thermal analysis and thermogravimetry, we have studied thermal decomposition of a mechanical mixture of thiourea and zinc acetate, resulting in the formation of a composite material consisting of graphitic carbon nitride and zinc acetate, g-C3N4/ZnS, and possibly containing zinc oxide (ZnO) inclusions. In the case of a mixture containing the stoichiometric sulfur:zinc ratio for zinc sulfide synthesis, one can obtain a material containing only ZnS semiconductor crystals embedded in a g-C3N4 matrix. ZnS is formed in the temperature range 317–367 °C as a result of decomposition of zinc complexes with thiourea. Heating the mixture to above 560 °C increases the rate of the thermal decomposition of g-C3N4, which reaches completion between 720 and 740 °C. The presence of oxygen in the reaction atmosphere also accelerates this process, without significantly changing the temperature range of synthesis or decomposition of reaction products. The proposed technique can be used for the synthesis of g-C3N4-based composite materials and other semiconducting metal sulfides

Liquid Vibrations in Cylindrical Tanks with and Without Baffles Under Lateral and Longitudinal Excitations

The paper is devoted to issues of estimating free surface elevations in rigid cylindrical fluid-filled tanks under external loadings. The possibility of baffles installation is provided. The liquid vibrations caused by lateral and longitudinal harmonic loadings are under consideration. Free, forced and parametrical vibrations are examined. Modes of the free liquid vibrations are considered as basic functions for the analysis of forced and parametric vibrations. The modes of the free liquid vibrations in baffled and un-baffled cylindrical tanks are received by using single-domain and multi-domain boundary element methods. Effects of baffle installation are studied. The problems of forced vibrations are reduced to solving the systems of second order ordinary differential equations. For parametric vibrations the system of Mathieu equations is obtained. The numerical simulation of free surface elevations at different loadings and baffle configurations is accomplished. Beat phenomena effects are considered under lateral harmonic excitations. The phenomenon of parametric resonance is examined under longitudinal harmonic excitations

Liquid vibrations in cylindrical tanks with and without baffles under lateral and longitudinal excitations

The paper is devoted to issues of estimating free surface elevations in rigid cylindrical fluid-filled tanks dunder external loadings. The possibility of baffles installation is provided. The liquid vibrations caused by lateral and longitudinal harmonic loadings are under consideration. Free, forced and parametrical vibrations are examined. Modes of the free liquid vibrations are considered as basic functions for the analysis of forced and parametric vibrations. The modes of the free liquid vibrations in baffled and un-baffled cylindrical tanks are received by using single-domain and multi-domain boundary element methods. Effects of baffle installation are studied. The problems of forced vibrations are reduced to solving the systems of second order ordinary differential equations. For parametric vibrations the system of Mathieu equations is obtained. The numerical simulation of free surface elevations at different loadings and baffle configurations is accomplished. Beat phenomena effects are considered under lateral harmonic excitations. The phenomenon of parametric resonance is examined under longitudinal harmonic excitations

The study of consistent properties of gelatinous shampoo with minoxidil

The aim of the work is the study of consistent properties of gelatinous shampoo with minoxidil 1% for the complex therapy and prevention of alopecia. This shampoo with minoxidil was selected according to the complex physical-chemical, biopharmaceutical and microbiological investigations. Methods and results. It has been established that consistent properties of the gelatinous minoxidil 1% shampoo and the «mechanical stability» (1.70) describe the formulation as exceptionally thixotropic composition with possibility of restoration after mechanical loads. Also this fact allows to predict stability of the consistent properties during long storage. Conclusion. Factors of dynamic flowing for the foam detergent gel with minoxidil (Кd1=38.9%; Kd2=78.06%) quantitatively confirm sufficient degree of distribution at the time of spreading composition on the skin surface of the hairy part of head or during technological operations of manufacturing. Insignificant difference of «mechanical stability» for the gelatinous minoxidil 1% shampoo and its base indicates the absence of interactions between active substance and the base

Improving the Abrasive Resistance of a Slide Frame in a Mortar Mixer

A method has been proposed for machining the outer and inner conical surfaces of the wrist pin and insert, which represent a sliding friction pair on the mortar mixer frame. The machining implies the application on the conical surface of parts, preliminary prepared through turning, of a wear-resistant material in the form of a hard alloyed nickel-based powder. It is applied with a special burner with a hopper-dispenser filled with powder. The result of mixing a combustible gas (acetylene and oxygen) in the burner with the powder from the hopper is melting.In the course of implementing a given technological process, by using mathematical modeling methods, we have determined the optimal mode parameters (PG10N-01 powder consumption is 33.5 g/min.; oxygen flow rate is 7.0 l/min; acetylene pressure is 0.043 MPa) for the gas-flame surfacing, which ensured maximum effect, that is, the greatest strength of adhesion (45 MPa) for the surfaced coating. The surfaced coating quality was checked by using a pin method for determining the adhesion strength between the new coating and the base on a tensile testing machine.A series of experimental studies into the enhancement of abrasive resistance of a sliding frame, namely a comparison of the surfaced coating with other well-known wear-resistant materials such as steel ShKh15, KhVG, were carried out at a specially designed experimental bench. Its structure is based on a vertically drilling desktop machine adjusted to the conditions of a working process that occurs inside the body of a mortar mixer. These include an abrasive medium, and the radial and axial efforts. To determine the axial load on a frame, we have proposed a structure of the hydraulic device, which includes a pressure gauge, a piston, a sleeve, and a ball. The axial load has been found for the most unfavorable conditions of mixer operation. Its value was implemented at an experimental wear bench. In addition, we have performed a series of experimental studies to determine an optimum angle of the cone at the apex of the wrist pin and insert in a conical slide frame for the minimal wear.Using the proposed technique of a gas-flame surfacing could significantly improve the abrasive and corrosion resistance of a slide frame, thereby prolonging the lifespan of a mortar mixer in general, as well as the overhaul cycle for equipment designed to prepare soluble mixtures used for constructio