PVD Coatings’ Strength Properties at Various Temperatures by Nanoindentations and FEM Calculations Determined

Nanoindentation is usually applied on thin films at ambient temperatures for hardness determination. Recently, instruments for conducting nanoindentation at elevated temperatures have been developed facilitating measurements up to 700 oC. Both indenter and specimen, if necessary, are heated in an inert atmosphere to avoid film oxidations. In the described investigations, nanoindentations were conducted on cemented carbides and high speed steel specimens, coated with various films, up to 400 oC. The obtained results were subjected to statistical analysis to estimate their reliability. Moreover, the results were evaluated by appropriate FEM (Finite Element Method) algorithms for determining the coatings’ elasticity modulus, yield and rupture stress as well as hardness at various temperatures. The results reveal a non-linear temperature dependence of the coating properties

Краткий обзор балансирующих устройств активного типа

Balancing active type scheme was shown. Self-balancing device's classification was reported. Keynotes were explored of each mechanism. Mechanism's developing was trained to moving time

Равновесие и динамика адсорбции паров воды на металлорганическом каркасе MOF-801

В работе представлены результаты исследования равновесия и динамики адсорбции паров воды на металлоорганическом каркасе MOF-801 с целью оценки потенциала его применения в системах адсорбционного охлаждения. Показано, что адсорбция воды на MOF-801 характеризуется S-образными изобарами IV типа по классификации ИЮПАК. В условиях типичного рабочего цикла адсорбционного холодильника (АХ) MOF-801 обменивает 0,21 г/г и может быть регенерирован при 80-85°С, что позволяет использовать источники низкотемпературной теплоты (солнечная энергия). Динамика адсорбции на гранулах MOF-801 в условиях рабочего цикла АХ происходит в режиме, при котором скорость процесса определяется отношением S/m площади поверхности теплопереноса S к массе адсорбента m. Эффективность и удельная мощность АХ с использованием пары "MOF-801-вода" достигают 0,67 и 2 кВт/кг соответственно, что представляет большой практический интерес

Применение сверточной нейронной сети U-Net для сегментации текстовых областей на изображениях реальных сцен

Micro-blasting on PVD films has been documented, among others, as an efficient method for inducing compressive stresses, thus for increasing the coating hardness and potentially tool life of coated tools. Since contradictory results have been registered concerning the efficiency of wet micro-blasting on coated tools for improving the wear behaviour, the paper aims at explaining how this process can be successfully applied for post-treatment of PVD films. In this context, the employed conditions such as pressure and grain size affect significantly the wear resistance of the micro-blasted coated tools.In the described investigations, TiAlN coatings were post-treated through wet micro-blasting by Al2O3 abrasives of various grains' diameter. Abrasion mechanisms after micro-blasting were investigated by roughness measurements. Nanoindentations on micro-blasted film surfaces at various pressures revealed the influence of this process on coating superficial hardness. The relat ed residual stress changes were estimated considering the film yield stress alterations, which were analytically determined, based on nanoindentation results. Nano-impact tests were conducted for investigating the effect of the developed film compressive stresses at certain micro-blasting pressures and grain sizes on the film's brittleness. To monitor film thickness and cutting edge radius changes of coatings subjected to micro-blasting, ball cratering tests and white light scans were carried out respectively. In this way, micro-blasting conditions for improving the film hardness, without revealing the substrate in the cutting edge region, were detected. Finally, the wear behaviour of coated and variously wet micro-blasted tools was investigated in milling of hardened steel

Математическое моделирование теплового воздействия низового лесного пожара на фрагмент корневой системы дерева

В настоящей работе представлены результаты численного моделирования теплопереноса в слоистой структуре корневого ответвления при воздействии повышенной температуры от очага лесного пожара. Задача решена методом конечных разностей в цилиндрической системе координат с использованием одномерной постановки. Рассматриваются типичные времена воздействия и температуры во фронте лесного пожара. Представлены распределения температуры в системе "фрагмент корня-почва-ЛГМ-воздух". Выявлены характер распределения температуры и глубина прогрева слоя почвы до значений опасных для корневой системы хвойного дерева.We present the numerical simulation results of heat transfer in a layered structure of the root branch when exposed to a high temperature from a forest fire in this paper. The problem is solved by the method of finite differences in a cylindrical coordinate system using a one-dimensional formulation. Typical exposure times and temperatures in the forest fire front are considered. The temperature distributions are presented for the system "root fragment-soil-forest fuel-air". We revealed the character of the temperature distribution and the depth of the soil layer heating to the values which are dangerous for the coniferous tree root system

Çile

Aka Gündüz'ün İleri'de tefrika edilen Çile adlı romanıTelif hakları nedeniyle romanın tam metni verilememiştir

Разработка алгоритма для выполнения операции обратного проецирования

High Power Pulsed Magnetron Sputtering (HPPMS) techniques jointly with the deposition of a graded Cr/CrN-nanointerlayer on cutting inserts can increase the film adhesion and consequently the tool life. These improvements depend on the roughness of the employed cemented carbide substrates. The investigations described in the present paper intend to explain the effect of Cr/CrN-interlayer thickness and substrate roughness on the coating adhesion and cutting performance. To attain various roughnesses, the applied cemented carbide inserts were superficially treated. These treatments were grinding at a medium roughness level, or grinding with subsequent polishing for enhancing the surface integrity and finally, in all cases, micro-blasting by fine Al2O3 grains. After Ar-ion etching, graded Cr/CrN adhesive layers with different thicknesses were deposited by HPPMS technology on the variously pretreated substrates. Subsequently, an approximately 3m thick (Ti,Al)N film was depos ited by HPPMS PVD on all used inserts. Rockwell C indentations and inclined impact tests were performed to assess qualitatively and quantitatively the films' adhesion. The cutting performance of the coated tools was investigated in milling of 42CrMo4 QT. FEM supported calculations of the developed stresses during the material removal process contributed in explaining the obtained tool wear results. In these calculations, the adhesion, dependent on the substrate roughness characteristics and on the adhesive interlayer thickness, was taken into account. The results revealed that the effectiveness of HPPMS adhesive graded Cr/CrN-nanointerlayer strongly depends on the substrate surface integrity and on the interlayer thickness. Thus, the film adhesion and consequently the cutting performance can be significantly improved if the interlayer thickness is adapted to the substrate roughness

A critical review of FEM models to simulate the nano-impact test on PVD coatings

Nano-impact test is a reliable method for assessing the brittleness of PVD coatings with mono- or multi-layer structures. For the analytical description of this test, a 3D-FEM Finite Element Method (FEM) model and an axis-symmetrical one were developed using the ANSYS LS-DYNA software. The axis-symmetrical FEM simulation of the nano-impact test can lead to a significantly reduced computational time compared to a 3D-FEM model and increased result's accuracy due to the denser finite element discretization network. In order to create an axis symmetrical model, it was necessary to replace the cube corner indenter by an equivalent conical one with axis-symmetrical geometry. Results obtained by the developed FEM models simulating the nano-impact test on PVD coatings with various structures were compared with experimental ones. Taking into account the sufficient convergence between them as well as the reduced calculation time only in the case of an axis-symmetrical model, the latter introduced numerical procedure can be effectively employed to monitor the effect of various coating structures on their brittleness