Stability of Peripheral Milling Operations with Long End Mills

AbstractThis paper presents dynamic modelling of peripheral milling systems with axially varying dynamics. The end mill is divided into differential elements along the cutter axis, and discrete nodes are assigned along the axial depth of cut. The cutting forces, which include regenerative and process damping components, are distributed to nodes. The equation of motion is transformed into modal space as periodic, delayed differential equations which cover one tooth period for regular, and one spindle period for variable pitch cutters. The directional coefficients are averaged and the stability is solved in frequency domain using Nyquist criterion. The presented model is experimentally verified in peripheral milling tests with low radial and high axial depth of cut

Estimated stress and friction distributions on tool rake face in the medium density fiberboard cutting process

This paper presents a model of load distribution on the cutting edge of a tool during machining Medium Density Fibreboard (MDF). A series of cutting tests has been carried out with tools having designated rake face contact lengths. Utilising the experimental data and a mechanics approach developed earlier by the third author, a model to estimate the distribution of stresses and friction on the rake face is developed. The model provides an essential step in the design and development of cutting edge geometry to prevent early edge failure and to control and reduce thermal/mechanical loading of the tool wedge

Разработка нанокомпозита MgAl2O4 - Ag с использованием установки распылительной сушки

В процессе исследования проводились обзор литературы, посвящённый методам синтеза, свойствам и применению наночастиц серебра как антибактериального препарата; получение оценка антибактериальных свойств наночастиц системы Al2O3-MgO–Ag, полученных с применением экстракта берёзы и без него.В результате исследований синтезированы и исследованы композиционные порошки MgAl2O4 на установке Nano Spray Dryer B-90 при различном соотношении магния и алюминия. Проведено осаждение наночастиц серебра на носитель. Показана противогрибковая активность полученных систем.In the course of the study, a literature review was carried out on the methods of synthesis, properties and use of silver nanoparticles as an antibacterial drug; obtaining an assessment of the antibacterial properties of nanoparticles of the Al2O3-MgO-Ag system obtained with and without birch extract. As a result of the research, composite powders of MgAl2O4 were synthesized and investigated using a Nano Spray Dryer B-90 at various ratios of magnesium and aluminum. The deposition of silver nanoparticles on a support has been carried out. The antifungal activity of the obtained systems has been shown

Виды микросинтаксических моделей при переводе терминов нефтедобывающего оборудования с русский языка на китайский

Ключевые слова: микросинтаксис, микросинтаксическая модель, словообразовательная модель, термин, терминологическая единица. Объектом исследования стали виды микросинтаксических моделей в китайском языке. Предмет изучения составляют структура, функции и реализация микросинтаксических моделей при переводе с русского языка на китайский на примере статей-аннотаций нефтедобывающего оборудования. Цель работы – выявление особенностей реализации микросинтаксических моделей при переводе терминов с русского языка на китайский. Для достижения поставленной цели необходимо решение ряда конкретных задач: изучить основные понятия, касающиеся микросинтаксиса в китайском языке, проанализировать виды микросинтаксических моделей при переводе терминов нефтедобывающего оборудования с русского на китайский.Key words: microsyntax, microsyntactic model, word-building pattern, term, terminology unit. The objects of this research are the types of microsyntactic models in Chinese. The subjects of this research are structure, functions and realization of microsyntactic models in the translation of the oil-production equipment articles from Russian to Chinese. The purpose of this study is to identify the features of realization of microsyntactic models in translation of the oil-production equipment terms from Russian to Chinese. The research requires realization of the following objectives: to explore the basic terms of the microsyntax in Chinese, to examine various classifications of microsyntactic models in Chinese, to analyze types of microsyntactic models in the translation of terms

Highly Stable, Near-Unity Efficiency Atomically Flat Semiconductor Nanocrystals of CdSe/ZnS Hetero-Nanoplatelets Enabled by ZnS-Shell Hot-Injection Growth

Colloidal semiconductor nanoplatelets (NPLs) offer important benefits in nanocrystal optoelectronics with their unique excitonic properties. For NPLs, colloidal atomic layer deposition (c-ALD) provides the ability to produce their core/shell heterostructures. However, as c-ALD takes place at room temperature, this technique allows for only limited stability and low quantum yield. Here, highly stable, near-unity efficiency CdSe/ZnS NPLs are shown using hot-injection (HI) shell growth performed at 573 K, enabling routinely reproducible quantum yields up to 98%. These CdSe/ZnS HI-shell hetero-NPLs fully recover their initial photoluminescence (PL) intensity in solution after a heating cycle from 300 to 525 K under inert gas atmosphere, and their solid films exhibit 100% recovery of their initial PL intensity after a heating cycle up to 400 K under ambient atmosphere, by far outperforming the control group of c-ALD shell-coated CdSe/ZnS NPLs, which can sustain only 20% of their PL. In optical gain measurements, these core/HI-shell NPLs exhibit ultralow gain thresholds reaching approximate to 7 mu J cm(-2). Despite being annealed at 500 K, these ZnS-HI-shell NPLs possess low gain thresholds as small as 25 mu J cm(-2). These findings indicate that the proposed 573 K HI-shell-grown CdSe/ZnS NPLs hold great promise for extraordinarily high performance in nanocrystal optoelectronics

Slip-line field model of microcutting process with round tool edge effect

a b s t r a c t This paper presents a slip-line field model which considers the stress variation in the material deformation region due to the tool edge radius effect. The Johnson-Cook constitutive model is applied to obtain the shear flow stress and hydrostatic pressure as functions of strain, strain-rate, and temperature in the primary shear zone. The friction parameters between the rake face and chip are identified from cutting tests. The sticking and sliding contact zones between the tool and chip are considered in the secondary shear zone. The total cutting forces are evaluated by integrating the forces along the entire chip-rake face contact zone and the ploughing force caused by the round edge. The proposed model is experimentally verified by a series of cutting force measurements conducted during micro-turning tests. Micro-cutting process is analyzed from a series of slip-line field simulations

Alptunc Comak Stability of Milling Operations With Asymmetric Cutter Dynamics in Rotating Coordinates

High-speed machine tools have parts with both stationary and rotating dynamics. While spindle housing, column, and table have stationary dynamics, rotating parts may have both symmetric (i.e., spindle shaft and tool holder) and asymmetric dynamics (i.e., twofluted end mill) due to uneven geometry in two principal directions. This paper presents a stability model of dynamic milling operations with combined stationary and rotating dynamics. The stationary modes are superposed to two orthogonal directions in rotating frame by considering the time-and speed-dependent, periodic dynamic milling system. The stability of the system is solved in both frequency and semidiscrete time domain. It is shown that the stability pockets differ significantly when the rotating dynamics of the asymmetric tools are considered. The proposed stability model has been experimentally validated in high-speed milling of an aluminum alloy with a two-fluted, asymmetric helical end mill