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

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

3D finite element modelling of drilling: the effect of modelling method

A comprehensive benchmarking study has been carried out to determine the influence of the mesh formulation and chip separation methods on the reliability and accuracy of finite element modelling of large diameter drilling operations. The Coupled Eulerian–Lagrangian and the updated-Lagrangian (with element deletion) formulations available in ABAQUS/Explicit, together with the updated-Lagrangian (with re-meshing) formulation in DEFORM 3D are compared by simulating through-coolant drilling of AISI 1045. The Johnson–Cook damage model was implemented by a sub-routine in DEFORM 3D to ensure a consistent damage model is implemented across the formulations. Experimentally measured drilling thrust force, torque, and chip thickness values were used to compare the models performance and assess the accuracy of the predictions. The updated-Lagrangian with dynamic re-meshing was found to be the best performing methodology concerning the accuracy of predictions, whilst the Coupled Eulerian–Lagrangian methodology significantly under-predicted the drilling thrust force and torque. Due to numerical instabilities and computational cost, the updated-Lagrangian with element deletion method is not recommended to model large diameter drilling

Determination of PVD coating mechanical properties by nanoindentations and impact tests at ambient and elevated temperatures

The performance of physical vapour deposition (PVD) films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of cemented carbides and high speed steel specimens, coated with various films, at temperatures up to 400 °C. Nanoindentations were conducted by a nanoindentation device, enabling measurements at room and elevated temperatures in an inert gas atmosphere. The obtained results were evaluated using appropriate FEM algorithms for determining the film stress-strain curves, at the temperatures of the conducted nanoindentations. The lesuits reveal a nonlinear temperature dependence of the coating properties. Moreover, perpendicular impact tests on the coated specimens were carried out up to 400°C, for investigating the film impact behaviour. T he developed impressions were recorded by scanning electron microscopy and white light confocal measurements. The attained results demonstrate a non-linear dependence of the film fatigue properties versus temperature, whereas a significant impact resistance improvement at approximately 150°C develops. Finally, a convergence between the yield and the fatigue endurance stress versus the temperature was revealed

Correlation between PVD coating strength properties and impact resistance at ambient and elevated temperatures

The performance of PVD films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of a TiAlN coating at temperatures up to 400°C. Nanoindentations were conducted by a nanoindentation device, enabling measurements at room and elevated temperatures in an inert gas atmosphere. The obtained results were evaluated using appropriate FEM algorithms for determining the film's stress-strain curves, at the temperatures of the conducted nanoindentations. Moreover, perpendicular impact tests on the coated specimens were carried out up to 400°C, for investigating the film's impact behaviour. The developed impressions were recorded by scanning electron microscopy and white light confocal measurements. The attained results demonstrate a non-linear dependence o f the film fatigue properties versus the temperature, whereas a significant impact resistance improvement at approximately 150°C develops. Finally, a convergence between the yield and the fatigue endurance stress versus the temperature was revealed