Optimization of end mills periphery milling

Розроблена математична модель для оптимізації процесу периферійного фрезерування, яка містить чисельний метод визначення сили різання, а також рівняння, що зв'язують обмеження з керованими параметрами режиму різання: частотою обертання шпинделя і подачею. Доведено, що шорсткість поверхні не залежить від геометричної складової профілю, що утворюється при переміщенні зубів фрези за траєкторією квазітрохоїди, а визначається максимальною амплітудою і частотою спектру сили різання, а також частотними характеристиками технологічної оброблювальної системи. Оптимальний режим різання формується в області допустимих значень фазового простору «частота обертання – подача» в основному двома обмеженнями: за стійкістю інструменту і за шорсткістю. Створена прикладна програма для автоматизованого визначення оптимального режиму різання при периферійному фрезеруванні сталей, чавунів та легких сплавів на основі алюмінію.A mathematical model is developed for optimization of process of the peripheral milling, which contains the digital method of determination of cutting force, and also equalizations relating limitations with the guided parameters of the cutting mode: by frequency of rotation of spindle and feed-rate. It is well-proven that the roughness of surface does not depend on the geometrical constituent of type, appearing at moving of points milling cutter on a cvasytrohoid, and determined maximal amplitude and frequency of spectrum of cutting force, and also by frequency descriptions of the technological processing system. The optimum mode of cutting is formed in area of legitimate values of phase space «frequency of rotation – feed-rate» mainly by two limitations: on firmness of instrument and on a roughness. The application program is created for the automated determination of the optimum mode of cutting at the peripheral milling of steels, cast-irons and easy alloys on the basis of aluminum.Разработана математическая модель для оптимизации процесса периферийного фрезерования, которая содержит численный метод определения силы резания, а также уравнения связывающие ограничения с управляемыми параметрами режима резания: частотой вращения шпинделя и подачей. Доказано, что шероховатость поверхности не зависит от геометрической составляющей профиля, образующейся при перемещении зубьев фрезы по квазитрохоиде, а определяется максимальной амплитудой и частотой спектра силы резания, а также частотными характеристиками технологической обрабатывающей системы. Оптимальный режим резания формируется в области допустимых значений фазового пространства «частота вращения – подача» в основном двумя ограничениями: по стойкости инструмента и по шероховатости. Создана прикладная программа для автоматизированного определения оптимального режима резания при периферийном фрезеровании сталей, чугунов и легких сплавов на основе алюминия

Simulation of end mills milling

Розроблена математична модель і алгоритм моделювання фрезерування контуру кінцевими фрезами. Математична модель ураховує повну геометричну конфігурацію інструмента, а саме, забезпечує можливість зміни кута нахилу спіральної канавки, кількості зубів, можливість використання довільних контурів деталі і заготовки. Створене програмне забезпечення дозволяє не тільки моделювати процес фрезерування, а й визначати управління подачею для стабілізації сили різання. Результати моделювання підтверджені експериментами на верстаті VF-3 фірми HAAS.A mathematical model and algorithm of simulation of contour milling by end mills is developed. A mathematical model takes into account complete geometrical configuration of instrument, namely, provides possibility of change of angle of slope of spiral ditch, amounts of points, possibility of the use of arbitrary contours of detail and workpiece. The created software allows not only to simulate a milling process but also determine a control of feed for stabilizing of cutting force. Design results are confirmed experiments on the CNC-machine VF-3 HAAS.Разработана математическая модель и алгоритм моделирования фрезерования контура концевыми фрезами. Математическая модель учитывает полную геометрическую конфигурацию инструмента, а именно, обеспечивает возможность изменения угла наклона спиральной канавки, количества зубьев, возможность использования произвольных контуров детали и заготовки. Созданное программное обеспечение позволяет не только моделировать процесс фрезерования, но и определять управление подачей для стабилизации силы резания. Результаты моделирования подтверждены экспериментами на станке VF-3 фирмы HAAS

Запасы льда в ледниках на Земле Норденшельда (Шпицберген) и их изменения за последние десятилетия

Data on thickness and area of 16 glaciers on the Nordenskiöld Land (Svalbard) were obtained in 1999 and 2010–2013. These data were used to determine volume of the glaciers and to establish statistical local relationship between the volume V and the area A (V–A scaling) in the form of the power function V = cAγ, and then to calculate the total ice volume of all 202 glaciers in this area and its changes during the period since 1936 to 2002–2008. The total area of 16 glaciers was 129.9±0.35 km2, 14 of which had areas from 0.2 to 8.1 km2. The two largest ones, the Fridtjof and the West Grenfjord, had the areas 17.5 and 47.3 km2, respectively, and thus occupied about 50% (64.8 km2) of the total area of 16 glaciers. These two glaciers account for 67% of the total measured volume (10,034 km3) of the 16 glaciers. A nonlinear least-squares method was used to estimate ice reserves in all 202 glaciers from data on the volume and area of 16 glaciers. The relation between volume V and area A of the  glaciers (V–A scaling) was obtained as the ratio V = 0.03637A1,283 with 95%‑th confidence intervals of the coefficients с and γ, (0.02303–0,4971) and (1.184–1.381), respectively. This made possible to calculate total volume of 202 glaciers as of 2002-2008 state using data from RGI v.6.0, and that prove to be equal to 32.89 (16.75–56.63) km3. To verify this estimation, we applied the bootstrapping method for chosen 43 glaciers and calculated the volume by means of sequential use of data for large and smaller glaciers. According to this estimate, the total volume of 202 glaciers amounted to 30.34 km3 with a 95% confidence interval of 15.42–44.27 km3, that turned out to be slightly smaller than the volume calculated by nonlinear least squares method basing on measurements on 16 glaciers. Despite the large error (on the average, from −49% to +84%) in estimating the total volume of 202 glaciers in the Nordenskiöld Land, the data obtained were used for assessment of relative changes in the total volume of glaciers in this area over different time intervals. During the period from 1936 to1990 (54 years), the total area of all glaciers reduced from 738.1 to 546.7 km2, and the total volume decreased from 49,205 to 34,857 km3. Similar results for the period 1990–2002–2008 (~15 years) are the total area changes from 546.7 to 507.9 km2 and their total volume - from 34.857 to 32.890 km3. The rate of decrease of the volume for the period 1936–1990 was equal to −0.266 km3/year, for the period 1990–2002–2008 – minus 0.131 km3/year, and as a whole for the studied period (since 1936 to 2002–2008) – minus  0.236 km3/year. The average mass balance in the first period was equal to −0.372 m w.e./year, in the second one −0.224 m w.e./year, and for the whole time −0.342 m w.e./year. Приведены результаты наземных радиолокационных измерений в 1999 и 2010–2013 гг. толщины и объёма 16 ледников на Земле Норденшельда (Шпицберген) с применением статистической связи между объёмом и площадью ледников. Оценены запасы льда во всех 202 ледниках этого района и их изменения за последние десятилетия с использованием данных о площади ледников по состоянию на 1936, 1990, 2002–2008 гг. и на годы радиолокационных измерений

Сравнение гидротермической структуры двух ледников Шпицбергена и Тянь-Шаня по данным радиозондирования

The distribution of cold and temperate ice and water in polythermal glaciers significantly affects their dynamics, thermal and hydrological regime. Radar techniques are an effective remote method of their studies that allows one to determine a glacier thickness by the delay time and to estimate the water content in temperate ice and at bedrock by the intensity of reflections from the interface between cold and temperate ice and the glacier bed. In case study of Austre Grønfjordbreen in Spitsbergen and Central Tuyksu glacier in Tien Shan we consider the features of their hydrothermal structure in spring and summer periods using the data of ground-based radio-­echo sounding at frequency of 20 MHz. To estimate the relative water content, we used data from measurements of relative power reflections from the cold-temperate ice interface, at the bedrock, and from the temperate ice body. In these glaciers (Austre Grønfjordbreen and Central Tuyksu), the average thickness of cold and temperate ice is, respectively, 61 ± 6 and 27 ± 2 m, and 39 ± 4 and 20 ± 2 m, the volume of cold ice is 0.466 ± 0.005 km3 and 0.044 ± 0.002 km3, and volume of temperate ice is 0.104 ± 0.001 and 0.034 ± 0.001 km3. Warm ice contains 2080 × 103 and 680 × 103 m3 of water, respectively, with an average content of 2%. Measurements along the longitudinal profiles of these glaciers showed that in some parts on Austre Grønfjordbreen in the spring period the average intensity of reflections from the cold­temperate ice interface and the bedrock is −0.02 – −26.3 and −6.0 – −11.8 dB, respectively, and at the whole profile this is −13.36 dB. At Central Tuyuksu glacier the spring values are −14.5 – −32.4 and −29.6 dB, respectively. We attribute such differences of glaciers to the different water content in the temperate ice below and above these boundaries, to the specific distribution of the ice facies zones and glacial nourishment, to the different intensity of surface melting in the spring and summer periods, and to the different crevassing and velocity of glaciers.Рассмотрены особенности распределения толщины холодного и тёплого льда и воды в политермических ледниках на Шпицбергене (Земле Норденшельда) и Тянь-Шане (Заилийский Алатау) по данным наземных радиолокационных измерений на частоте 20 МГц, выполненных соответственно весной 2010 и 2019 гг. и летом 2013 г. По времени запаздывания и интенсивности отражений от поверхности раздела холодного и тёплого льда из толщи тёплого льда и от ложа определены толщина и объём холодного и тёплого льда, оценено содержание воды в тёплом льду и показана связь этих характеристик с особенностями строения и режима ледников в весенний и летний периоды, до и после начала таяния

Реконструкция баланса массы ледника Гарабаши (1800–2005 гг.) по дендрохронологическим данным

The exploration whether tree-ring data can be effectually applied for the mass balance reconstruction in Caucasus was the main goal of this research. Tree-ring width and maximum density chronologies of pine (Pinus sylvestris L.) at seven high-elevation sites in Northern Caucasus were explored for this purpose. As well as in other places of the temperate zone tree- ring width has complex climate signal controlled both temperature and precipitation. Instrumental mass balance records of Garabashi Gglacier started at 1983s. It is well known that Caucasus glaciers intensively retreat in the last decades and according to instrumental data mass balance variations are mostly controlled by the ablation, i.e. summer temperature variations. Maximum density chronology has statistically significant correlation with mass balance due to summer temperature sensitivity and great input of ablation to total mass balance variations. To include in our reconstruction different climatically sensitive parameters, stepwise multiple regression model was used. The strongest relation (r = 0.88; r2 = 0.78; p < 0.05) between two ring-width and one maximum density chronologies was identified. Cross-validation test (r = 0.79; r2 = 0.62; p < 0.05) confirmed model adequacy and it allowed to reconstruct Garabashi Glacier mass balance for 1800–2005ss. Reconstructed and instrumental mass balance values coincide well except the most recent period in 2000s, when the reconstructed mass balance slightly underestimated the real values. However even in this period it remained negative as well as the instrumental records. The bias can be explained by the weak sensitivity of the chronologies to winter precipitation (i.e. accumulation). The tree-ring based mass balance reconstruction was compared with one based on meteorological data (since 1905s). Both reconstructions have good interannual agreement (r = 0.53; p < 0.05) particularly for the period between 1975 and 2005. According to the reconstruction two distinct periods of positive mass balance occurred in 1830s and 1860s. They agree well with early historical data and the tree-ring of moraines of Kashkatash Glacier in Central Caucasus. Выполнена первая реконструкции баланса массы ледника Гарабаши по дендрохронологическим данным с 1800 по 2005 г. Лучше всего модель воспроизводит изменчивость годового баланса ледника при использовании хронологий по ширине годичных колец и по максимальной плотности поздней древесины. Изучен вклад каждой древесно-кольцевой хронологии в модель и её климатический отклик. Установлена высокая согласованность реконструкции баланса массы ледника по дендрохронологическим данным с реконструкциями, полученными ранее по метеорологическим рядам

Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th century

South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia–New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions

Гляциоклиматические исследования Института географии РАН в кратере Восточной вершины Эльбруса в 2020 г.

During the field campaign in August 18–30, 2020 the meteorological regime and heat balance of the glacier surface were investigated in the crater of Mt Elbrus Eastern Summit (5600 m a.s.l.) together with the GPR measurements of the ice thickness and seasonal snow cover. Preliminary data analysis allowed the following features: the predominance of synoptic fluctuations over the diurnal ones; the high values of average and maximum wind speed associated with the impact of jet streams and with influence of leeward storms; extremely high temporal variability of relative humidity and its very high deficit in cloudless conditions conducive to intensive evaporation and sublimation from the snow surface. The maximum thickness of ice in the crater reaches 100 m, and the average is 34 m. A new ice core with a length of 96.01 m from the glacier surface to its bed had been obtained. The drilling speed varied from 11 to 1 m/h, decreasing with depth from 4.5 to 4.0 m/h on average. The thickness of the snow-firn mass is about 20 m, which is three times less than on the Western Plateau of Mt Elbrus. According to measurements in the borehole, temperature at the glacier bed is −0.6 °C. The calculated heat flux is 0.39 W/m2. Air sampling was carried out in the crater of the Eastern Summit of Elbrus and on the Garabashi glacier. Repeated measurements of the soil temperature in the fumarole field on the outer edge of the crater of the Elbrus Eastern Summit allow the conclusion that the temperature regime is stable.С 18 по 30 августа 2020 г. в кратере Восточной вершины Эльбруса впервые проводились наблюдения за метеорологическим режимом и тепловым балансом ледника. Выполнена также радиолокационная съёмка толщины льда и сезонного снежного покрова, пробурена скважина от поверхности до ложа с получением керна льда, измерены температуры в скважине, в шурфе из сезонной снежной толщи отобраны образцы для изотопного, химического и спорово-пыльцевого анализа, на поверхности фумарольного поля и в атмосфере над ледником взяты образцы газа, продолжен мониторинг температуры грунта на фумарольной площадке

Бурение осадков оз. Каракель (долина р. Теберда) и перспективы реконструкции истории оледенения и климата голоцена на Кавказе

Lacustrine sediments represent an important data source for glacial and palaeoclimatic reconstructions. Having a number of certain advantages, they can be successfully used as a means of specification of glacier situation and age of moraine deposits, as well as a basis for detailed climatic models of the Holocene. The article focuses on the coring of sediments of Lake Kakakel (Western Caucasus) that has its goal to clarify the Holocene climatic history for the region, providing the sampling methods, lithologic description of the sediment core, obtained radiocarbon dating and the element composition of the sediments. The primary outlook over the results of coring of the sediments of the Lake Karakyol helped to reconsider the conventional opinion on the glacial fluctuations in the valley of Teberda and to assume the future possibility for high-definition palaeoclimatic reconstruction for Western Caucasus.Озёрные отложения – важный источник данных для реконструкции колебаний ледников и изменений климата. Рассмотрены первые результаты бурения осадков оз. Каракель (долина р. Теберда, Западный Кавказ), выполненного для реконструкции голоценовой истории оледенения и климата в регионе. Описаны методика отбора образцов и особенности стратиграфии керна донных отложений оз. Каракель, приведены три радиоуглеродные датировки, позволившие оценить скорости осадконакопления в верхней части толщи (поздний голоцен). Датировка нижнего слоя озёрных отложений – 11 700 л.н. (календарный возраст) – одновременно представляет собой оценку минимального возраста морены, подпруживающей оз. Каракель

Reconstructing 800 years of summer temperatures in Scotland from tree rings

We thank The Carnegie Trust for the Universities of Scotland for providing funding for Miloš Rydval’s PhD. The Scottish pine network expansion has been an ongoing task since 2007 and funding must be acknowledged to the following projects: EU project ‘Millennium’ (017008-2), Leverhulme Trust project ‘RELiC: Reconstructing 8000 years of Environmental and Landscape change in the Cairngorms (F/00 268/BG)’ and the NERC project ‘SCOT2K: Reconstructing 2000 years of Scottish climate from tree rings (NE/K003097/1)’.This study presents a summer temperature reconstruction using Scots pine tree-ring chronologies for Scotland allowing the placement of current regional temperature changes in a longer-term context. ‘Living-tree’ chronologies were extended using ’subfossil’ samples extracted from nearshore lake sediments resulting in a composite chronology > 800 years in length. The North Cairngorms (NCAIRN) reconstruction was developed from a set of composite blue intensity high-pass and ring-width low-pass chronologies with a range of detrending and disturbance correction procedures. Calibration against July-August mean temperature explains 56.4% of the instrumental data variance over 1866-2009 and is well verified. Spatial correlations reveal strong coherence with temperatures over the British Isles, parts of western Europe, southern Scandinavia and northern parts of the Iberian Peninsula. NCAIRN suggests that the recent summer-time warming in Scotland is likely not unique when compared to multi-decadal warm periods observed in the 1300s, 1500s, and 1730s, although trends before the mid-16th century should be interpreted with some caution due to greater uncertainty. Prominent cold periods were identified from the 16th century until the early 1800s – agreeing with the so-called Little Ice Age observed in other tree-ring reconstructions from Europe - with the 1690s identified as the coldest decade in the record. The reconstruction shows a significant cooling response one year following volcanic eruptions although this result is sensitive to the datasets used to identify such events. In fact, the extreme cold (and warm) years observed in NCAIRN appear more related to internal forcing of the summer North Atlantic Oscillation.Publisher PDFPeer reviewe