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Tytuł:
Long-term effect of climate and air pollution on health status and growth of Picea abies (L.) Karst. peaty forests in the Black Triangle region
Autorzy:
Vacek, Z.
Vacek, S.
Prokůpková, A.
Bulušek, D.
Podrázský, V.
Hůnová, I.
Putalová, T.
Král, J.
Powiązania:
https://bibliotekanauki.pl/articles/2077652.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
Norway spruce
air pollutants
climate factors
nutrients
stress factors
Czech Republic
Opis:
The Jizerské hory Mts. (the Czech Republic) are part of the Black Triangle region strongly af- fected by a decline and dieback of Norway spruce (Picea abies [L.] Karst.) stands since the 1970s. In the studied peaty spruce stands in the summit parts of the Jizerské hory Mts., the health status, radial growth and foliar nutrient content in relation to air pollution (SO2, NOX and O3) and climate factors (temperature, precipitation) were investigated in 1960–2015. A considerable disturbance of the stand structure induced by an increased mortality was observed in 1981–1983 when more than a half of the tree individuals died. Severe defoliation occurred in 1981 as a consequence of the synergic effects of air pollution, winter des- iccation and spruce bark beetle outbreak, as well as in 2015 due to the drought and high temperatures. Tree ring analyses indicated significant growth depression in 1979–1987, a period of the highest SO2 load, and in 2010–2015. Foliation and diameter increment were significantly influenced by SO2 and NOX con- centrations, the maximum daily concentration being the most negative factor; no significant correlation of the ozone exposure was detected, though. Foliar analyses also document significant negative impacts of air pollutants on the nutrient status of forest stands, mainly in the increase of the sulphur level. Since 1990, a significant increase in calcium and magnesium has been observed, as a result of forest liming. Interaction between radial growth and temperature was stronger compared to precipitation. Low temper- atures and high precipitation in growing season were the limiting factors for radial growth in waterlogged mountain areas.
Źródło:
Dendrobiology; 2020, 83; 1-19
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stand dynamics in natural Scots pine forests as a model for adaptation management?
Autorzy:
Vacek, S.
Vacek, Z.
Bilek, L.
Remeš, J.
Hůnová, I.
Bulušek, D.
Král, J.
Brichta, J.
Powiązania:
https://bibliotekanauki.pl/articles/2077666.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
Pinus sylvestris
forest dynamics
stands structure
air pollution
climatic factors
Central Europe
Opis:
The paper deals with the dynamics of structure, diversity and growth of natural pine stands without direct human impact during the ten-year period in Nature Reserve (NR) Kostelecké bory, Czech Republic. The objective was to determine the main characteristics of the spontaneous development of Scots pine (Pinus sylvestris L.) forest stands in relation to their naturalness, ecological stability and adaptation to climate change and air pollution stress. Horizontal and vertical structure and species diversity of the tree layer, dead wood and natural regeneration of each permanent research plot (PRP) were evaluated (n = 6, 50 × 50 m /0.25 ha/, Northern Bohemia, 410–425 m above sea level). The average ring series of PRPs were correlated with the climatic data (precip- itation, temperature) according to individual years from the Doksy climatic station, and the air pollution data (SO2 in 1988–2015, NOX and AOT40F – ozone exposure in 1992–2015) from Radimovice station. In 2016, the stand volume increased by 26.0% to 136 m3 ha−1 (108 m3 ha−1 in 2006) and the volume of dead wood increase by 127.2% to 27 m3 ha−1 (12 m3 ha−1 in 2006). The horizontal structure of tree layer and natural regeneration was predominantly aggregated to random. More distinct changes in biodiversity and structural characteristics occurred in the natural regeneration (21.5%) compared to tree layer (2.8%). The precipitation had a significantly higher effect on radial growth compared to temperature. The lack of pre- cipitation in growing season and high temperature in previous autumn and winter were limiting factors for growth. Climatic factors had significant effect on diameter increment in July of the current year (P < 0.01) and June of the current and previous year (P < 0.05). Radial growth was negatively correlated with SO2 con- centrations (P < 0.01) and ozone exposure (P < 0.05). NOX concentrations had low effect on radial growth. The natural stand dynamics had positive effect on biodiversity and functional integrity of natural pine eco- systems.
Źródło:
Dendrobiology; 2019, 82; 24-42
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy absorption capability numerical analysis of thin-walled prismatic tubes with corner dents under axial impact
Numeryczna analiza energochłonności cienkościennych słupów pryzmatycznych z przetłoczeniami
Autorzy:
Ferdynus, M.
Kotełko, M.
Kral, J.
Powiązania:
https://bibliotekanauki.pl/articles/301392.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
crashworthiness indicators
energy absorber
thin-walled member
wskaźniki energoabsorbcyjne
absorber energii
konstrukcje cienkościenne
Opis:
The paper presents results of a parametric study into energy absorption capability of thin-walled square section columns with redrawn dents, subjected to axial impact compressive load. Thin-walled aluminum tubes with four dents in the corners were under investigation. The varying parameters were the dent’s depth and distance of the dent to the base. The study was performed using Finite Element numerical code. Three crashworthiness indicators were examined: peak crushing force, crash load efficiency and stroke efficiency. The numerical results are shown in load-shortening diagrams, as well as diagrams and maps of crashworthiness indicators. It was found, that the main factor influencing a crushing mode and, subsequently, energy absorption capability, is a dent depth. The dent distance from the base is of less importance. Also a position of a dent, either at the bottom, or at the top base (the load application point) does not influence the crushing behavior significantly. For the deepest dents the relative increase of crash load efficiency (CLE) amounts 25% in comparison with the column without dents.
W artykule przedstawiono wyniki badań numerycznych zdolności pochłaniania energii energoabsorberów w postaci cienkościennych słupów o przekroju kwadratowym z wgłębieniami, poddanych osiowym obciążeniom udarowym. Badano wpływ parametrów geometrycznych oraz położenia inicjatorów zgniotu w postaci walcowych przetłoczeń w narożach na zachowanie się konstrukcji oraz właściwości energoabsorbcyjne (współczynnik efektywności zgniotu- Ste oraz procentowy stosunek siły średniej do maksymalnej - CLE). Obliczenia numeryczne prowadzono z wykorzystaniem MES, programu Abaqus 6.14. Wyniki przedstawiono w postaci charakterystyk obciążenie – skrócenie oraz diagramów i wykresów. Stwierdzono, że istotny wpływ na zachowanie się konstrukcji podczas uderzenia oraz jej energochłonność ma głębokość przetłoczenia, mniej istotne jest jego położenie. W przypadku słupów z najgłębszymi przetłoczeniami względny wzrost współczynnika CLE, w porównaniu z wynikami uzyskanymi dla słupa gładkiego wynosi 25%.
Źródło:
Eksploatacja i Niezawodność; 2018, 20, 2; 252-259
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
CNC milling machine precision analysis through numerical modelling
Autorzy:
Svetlík, J.
Demeč, P.
Kráľ, J.
Powiązania:
https://bibliotekanauki.pl/articles/102601.pdf
Data publikacji:
2017
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
accuracy of manufacturing machine
virtual prototyping
modal analysis
virtual model
Opis:
The motive behind the effort to make virtual prototyping more sophisticated is first of all cost reduction of manufacturing machine design, followed by reduction of lead time for development, prototyping and testing of the pre-manufacturing machine series. This article deals with the analysis of manufacturing precision of a 3-axial, numerically controlled milling machine. The methodology for precision analysis rests on a selected simplified numerical calculation model of a manufacturing machine on which virtual machining has been conducted. The mechanical inaccuracy itself is calculated by computer via the FEM analysis. The results are processed for visualization by the Excel software.
Źródło:
Advances in Science and Technology. Research Journal; 2017, 11, 2; 212-219
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of eccentricity of load on critical force of thin-walled columns CFRP
Autorzy:
Wysmulski, P.
Kráľ, J.
Powiązania:
https://bibliotekanauki.pl/articles/102239.pdf
Data publikacji:
2017
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
finite element method
buckling
eccentricity load
thin-walled structures
laminate
composite CFRP
Opis:
The subject of study was a thin-walled C-section made of carbon fiber reinforced polymer (CFRP). Column was subjected to eccentric compression in the established direction. In the computer simulation, the boundary conditions were assumed in the form of articulated support of the sections of the column. Particular studies included an analysis of the effects of eccentricity on the critical force value. The research was conducted using two independent research methods: numerical and experimental. Numerical simulations were done using the finite element method using the advanced system Abaqus®. The high sensitivity of the critical force value corresponding to the local buckling of the channel section to the load eccentricity was demonstrated.
Źródło:
Advances in Science and Technology. Research Journal; 2017, 11, 3; 109-113
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of the technological conditions of plane surface machining on a triangular milling cutter on the residual hysteresis of the movement axis of the machine
Autorzy:
Stejskal, T.
Kráľ, J.
Rudy, V.
Melko, J.
Rjabušin, A.
Pavliková, L.
Powiązania:
https://bibliotekanauki.pl/articles/957896.pdf
Data publikacji:
2017
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
machine tools
laser interferometer
hysteresis
Opis:
The paper deals with the possibilities of measuring the residual displacement or hysteresis on the lateral direction of the movement forces caused by the cutting forces of the machining. A special adjustment of laser interferometry assemblies was used for measurement. The measurement results indicate that the positioning accuracy in addition to the cutting forces also influences the position of the displaced moving substances and the temperature. The complex effect of these parameters is greatly dependent on the design of the machine.
Źródło:
Advances in Science and Technology. Research Journal; 2017, 11, 3; 240-245
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural diversity and production of alder stands on former agricultural land at high altitudes
Autorzy:
Vacek, Z.
Vacek, S.
Podrazsky, V.
Kral, J.
Bulusek, D.
Putalova, T.
Balas, M.
Kalouskova, I.
Schwarz, O.
Powiązania:
https://bibliotekanauki.pl/articles/41581.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
structural diversity
stand structure
alder stand
agricultural land
black alder
Alnus glutinosa
grey alder
Alnus incana
afforestation
succession
Sudetes Mountains
Opis:
The paper deals with the structural diversity and production of a less frequently studied type of alder stands originated on former agricultural lands in the 1950s, established partly by plantation and partly by natural succession in the area of the Krkonoše Mts. and the Orlické hory Mts. (Czech Republic). Four permanent research plots (PRP) were established at sites where Black alder (Alnus glutinosa L. Gaertn.) and Grey alder (Alnus incana L. Moench.) naturally occurs, each plot of 0.25 ha in size. The aim of the study was to evaluate the structure and development of the alder stands with respect to biodiversity, horizontal, vertical and species structure, diameter increment with emphasis on climate factors, and the quantity and quality of timber production. The results document low diversification of the studied stands in the PRPs. The horizontal structure is defined as random and clumped at sites at the highest altitude with high water table. The number of living trees with DBH ≥ 4 cm ranges between 556 to 828 trees ha-1 with the relative stand density index (SDI) 0.67–0.77. The stand volume ranges from 247 to 393 m3 ha–1, and decreases with higher altitudes. Low temperatures is limiting factor for radial growth in the high mountain areas, respectively low precipitation in the middle lands. Owing to a rather specific site character, as especially the spring area, the stands exhibit only average production, but the production quality is generally high. The quality timber is suitable for industrial use; the rot-affected trunk base parts usable for fuel represent only approximately 16%.
Źródło:
Dendrobiology; 2016, 75
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of σ-phase formation on long-term durability of welding joints in SUPER 304H steels
Autorzy:
Horváth, J.
Král, P.
Janovec, J.
Powiązania:
https://bibliotekanauki.pl/articles/1112347.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.70.Jb
68.37.Ma
81.30.Mh
81.20.Vj
62.20.mj
Opis:
Article presents results on the analysis of secondary phases formed in the medium-term static isothermal ageing welding joints of a SUPER 304H (675°C/2×10⁴ h). The investigations of the precipitates were focused on the occurrence of σ-phase because its formation leads to significant deterioration of mechanical properties. The microstructure was investigated on microscopic level by scanning/transmission electron microscopy. The distribution and quantification of brittle σ-phase were studied on macroscopic level by color etching method using light optical microscopy. The effect of microstructural changes (σ-phase formation) on the impact strength of an aged base material was investigated. For comparison impact tests on received state material were also performed. The results showed that long-term ageing led to the significant reduction of impact strength as a result of the formation of the σ-phase. It was found that the σ-phase distribution is influenced by welding process. The influence of brittle σ-phase on long-term durability of the degraded steel regarding its insufficient impact strength has been discussed.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 960-962
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The use of industrial metrotomography in the field of maintenance and reliability of rubber-textile conveyor belts in closed continuous transport systems
Wykorzystanie przemysłowego metrotomografu w utrzymaniu i niezawodności taśm przenośnikowych tkaninowo-gumowych w przenośnikach taśmowych z zamkniętą taśmą
Autorzy:
Fedorko, G.
Molnár, V.
Dovica, M.
Husáková, N.
Král' jr., J.
Ferdynus, M.
Powiązania:
https://bibliotekanauki.pl/articles/946069.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
metrotomography
closed transport systems
conveyor belt
laboratory tests
metrotomografia
zamknięty system transportowy
przenośnik taśmowy
testy laboratoryjne
Opis:
Closed transport systems have been widely implemented in various areas of bulk solid handling because of their advantages. The unique character of these systems stems from the fact that transported material is fully enclosed by a conveyor belt. To ensure their operational reliability and efficient maintenance during operation, processes occurring inside the belt must be monitored. Early damage identification is very important, if not crucial, for reliable functioning of transport systems. One way to do this is by applying the industrial metrotomography method. The paper presents the research methodology of conveyor belt damage using computer metrotomography. It reports the experimental results for two samples: one with a damaged belt matrix and the other with cracks in the upper surface layer of rubber. The damage in the form of puncture of the transporting belt is also described in the paper.
Z powodu swych zalet, systemy transportowe zamknięte, zostały szeroko wprowadzone i zastosowane w różnych dziedzinach transportu materiałów sypkich. Wynika to z unikalnych cech tych systemów, gdzie transportowany materiał jest w pełni otoczony taśmą. Aby zagwarantować niezawodność operacyjną i skuteczną konserwację w trakcie eksploatacji, procesy zachodzące wewnątrz taśmy przenośnikowej muszą być monitorowane. Identyfikacja uszkodzeń we wczesnym stadium, jest bardzo ważna, jeśli nie rozstrzygająca, dla przyszłego niezawodnego funkcjonowania systemu transportowego. Jednym ze sposobów identyfikacji uszkodzeń, jest zastosowanie metody metro-tomografii przemysłowej. W pracy przedstawiono metodykę badań uszkodzeń taśm przenośnikowych tkaninowo- gumowych z wykorzystaniem metro-tomografii. Zaprezentowano wyniki badań doświadczalnych dwóch próbek, gdzie zniszczeniu uległa osnowa taśmy oraz kolejnej, gdzie zaobserwowano pęknięcia w warstwie wierzchniej gumy. Zostało również opisane zniszczenie w postaci przebicia pasa transportowego.
Źródło:
Eksploatacja i Niezawodność; 2016, 18, 4; 539-543
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Long-term Annealing and Hot Bending on Creep of P92 Pipe
Autorzy:
Kral, P.
Dvorak, J.
Kvapilova, M.
Kucharova, K.
Sklenicka, V.
Svobodova, M.
Cmakal, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402074.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.-t
81.40.-z
62.20.Hg
68.37.Hk
Opis:
This work is focused on the creep behaviour of the thick-walled hot bended P92 pipe, with an outer diameter of 350 mm and wall thickness of 39 mm, in its different parts, namely in straight parts and bends. Selected creep specimens machined from axial section of pipe were thermally aged at 650°C to simulate microstructure degradation typical for long-term service conditions. Subsequent tensile creep tests at constant load were performed at 600°C under 140 MPa and creep behaviour of various structure states was compared. Microstructure was investigated by scanning electron microscopy equipped with electron backscatter diffraction. It was found that ageing at 650°C for 10⁴ h caused the significant reduction of creep resistance down to about 10% of initial state and an additional slight reduction of creep resistance after longer ageing for 2×10⁴ h. Further, creep behaviour was significantly influenced by specimen position in the extrados and intrados parts of bends. Microstructure investigation revealed that long-term annealing has negligible effect on high-angle grain boundary spacing and misorientation. By contrast, creep deformation of long-term annealed specimens led to significant decreasing in high-angle grain boundary spacing and caused a change in the misorientation distribution of boundaries.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 543-547
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation of the shape of tool cutt ing edge for production of involute worm
Autorzy:
Kráľ jr, J.
Kráľ, J.
Powiązania:
https://bibliotekanauki.pl/articles/103210.pdf
Data publikacji:
2013
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
shape
edge
algorithm
worm gear
operations
Opis:
The article deals with theoretical analysis of the production of worm gears and also the calculation of the tool cutting edges for their production. Based on the design parameters of worm and worm wheel, it is possible to calculate the coordinates of the shape of the tool cutting edge. The exact calculation of the coordinates or parameters requires mathematical formulations and applying mathematical relationships we can transform the design of worm screw profile to the profile of tool. Worms of different types can be produced in various ways, e.g. with a lathe and the plane to set a tool is either axial or normal. In this article we consider their production on the lathe and tool setting in the normal plane. Axial profile of worm is a curve which is the intersection of worm surface and the plane passing through its axis, and normal profile is perpendicular in a selected point to worm profile. This normal profile in more accurately way characterizes the shape of the worm profile, therefore, the calculation of the shape of the tool cutting edge is designed with a tool set to the normal plane. Based on the analyses, the new computation equations were obtained, flowchart compiled and, according to a given regulation, the computer aided calculation of the coordinates can be implemented.
Źródło:
Advances in Science and Technology. Research Journal; 2013, 7, 17; 1-5
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Grinding of shaped tools on CNC tool grinder
Autorzy:
Kráľ, J.
Kráľ jr, J.
Powiązania:
https://bibliotekanauki.pl/articles/103053.pdf
Data publikacji:
2013
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
shape
profile
tool grinder
worm gear
operation
Opis:
Worm gears are special gears consisting of a worm wheel and a worm. Worm gears can be produced in different ways, depending on the size of the transmission, the number of courses, the pitch angle of worm profile, the number of units produced, the purpose of application, etc. As cylindrical worm gears we consider the cylindrical worms with globoid gears, globoid worm with globoid worm gear and globoid worm with cylindrical worm gearing. This paper deals with the evolvent worm whose curve of the tooth side in the front plane is evolvent. The production of worm with an optimal profile for optimal meshing conditions is an increasingly frequent focus of worm gear manufacturers. The problem of designing the tool cutting edge can be divided into several steps. This article deals with the problems of optimum design of a tool shape for the production of worms; and the problems of calculating the coordinates of the transition cutting edge shape, and thus the path of grinding wheel for sharpening the tool cutting edge shape are solved. By grinding tool of grinding machine we can complete the worm shape and also sharpen the cutting edges of tools for production of worm surface. The problems of calculation of the coordinates are solved with regard to the functioning of the KON 250 CNC grinding machine logic.
Źródło:
Advances in Science and Technology. Research Journal; 2013, 7, 17; 6-9
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Creep Behavior of a Zirconium Alloy Processed by Equal-Channel Angular Pressing
Autorzy:
Sklenicka, V.
Dvorak, J.
Kral, P.
Svoboda, M.
Kvapilova, M.
Kopylov, V.
Nikulin, S.
Dobatkin, S.
Powiązania:
https://bibliotekanauki.pl/articles/1418491.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.40.Lm
62.20.Hg
81.05.-t
81.07.Bc
81.70.Bt
Opis:
A Zr-2.5 wt%Nb alloy was processed by equal-channel angular pressing and then tested under creep conditions at 623 K using a tensile stress within the range from 120 to 300 MPa. The results show conventional power-law creep with a stress exponent of n > 3 which is consistent with an intragranular dislocation process involving the glide and climb of dislocations. It is demonstrated that diffusion creep is not important in these tests. For comparison purposes, the experiments were conducted using both the unprocessed alloy and after processing by equal-channel angular pressing. It was found that under same testing conditions the measured minimum creep rates in the pressed alloy with ultrafine grain sizes were faster than in the same alloy in a coarse-grained unprocessed condition.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 485-489
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Grinding tools and grinding wheels for shaping CNC grinding machine
Narzędzia szlifierskie i tarcze szlifierskie do szlifierek kształtujących CNC
Autorzy:
Kráľ, J.
Spišák, E.
Kráľ jr, J.
Józwik, J.
Powiązania:
https://bibliotekanauki.pl/articles/395549.pdf
Data publikacji:
2012
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
kształtowanie
profilowanie
ostrzarka
przekładnia ślimakowa
operacja
shape
profile
tool grinder
worm gear
operation
Opis:
Production of screws with the optimal profile in terms of mesh properties is still in focus of worm gear manufacturers. The overall problem of tool edge designing is divided in few parts. This post only partly solves the problem of optimal tool shape design to produce the screws. In this paper is solved the problem of the abrasive wheel forming to produce screws with the logic operation of management system of tool grinder and calculation of profile curve on tooth heel.
Produkcja ślimaków o optymalnym profilu pod względem właściwości siatki pozostaje wciąż w centrum uwagi producentów przekładni ślimakowych. Ogólny problem projektowania ostrzy narzędzi jest podzielony na kilka części. Artykuł ten tylko częściowo rozwiązuje problem optymalnego projektowania kształtu narzędzi do produkcji ślimaków przekładni ślimakowej. W pracy rozwiązano problemu formowania tarczy ściernej do produkcji ślimaka i obliczenie krzywej profilu na stopie zęba.
Źródło:
Postępy Nauki i Techniki; 2012, 15; 221-227
2080-4075
Pojawia się w:
Postępy Nauki i Techniki
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure Mechanisms Governing the Creep Life of Ultrafine-Grained Cu-0.2 wt%Zr Alloy
Autorzy:
Kral, P.
Svoboda, M.
Dvorak, J.
Kvapilova, M.
Sklenicka, V.
Powiązania:
https://bibliotekanauki.pl/articles/1418438.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.-t
61.66.Dk
62.20.Hg
68.37.Lp
Opis:
Equal-channel angular pressing was conducted at room temperature and extrusion was performed up to 12 passes using route where the billets were rotated by 90° in the same sense between consecutive passes. Tensile creep tests were performed at 473, 573 and 673 K at different constant applied stresses. It was observed that the original coarse grain size of unprocessed alloy was reduced to 0.3 μm after 8 equal-channel angular pressing passes and the grain growth during creep was restricted by precipitates with the mean diameter ≈ 4.0 nm. No significant effect on creep resistance was found after one equal-channel angular pressing pass at 473 and 573 K. However, the longest time to fracture was exhibited by alloy after 2 equal-channel angular pressing passes at 573 and 673 K but with further increasing number of equal-channel angular pressing passes a decrease in the time to fracture was observed. Nevertheless, the beneficial effect of equal-channel angular pressing on creep resistance was still documented after 8 passes for temperatures of 473 and 573 K. By contrast, creep tests performed at 673 K showed that the time to fracture of ultrafine-grained material is shorter as compared with that for as-received state. The 3D laser measurement of surface showed that the creep fracture process is accelerated by formation of vertical surface step relief and cavitation at the intersection of the shear bands during creep.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 457-460
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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