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Wyświetlanie 1-10 z 18
Tytuł:
Experimental and numerical investigation of friction coefficient effects on defects in horizontal tube bending process
Autorzy:
Taheri Kahnamouei, J.
Fattahi, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/279854.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
tube bending
wrinkle
simulation
friction
wall thickness change
Opis:
The aim of this paper is to investigate defects in a thin-walled tube bending process (without using mandrel and booster) and effects of friction between the dies and tube on wrinkles. In the tube bending process, there are several effective parameters such as wall thickness, outer diameter-to-wall thickness ratio, centerline bending radius-to-outer diameter ratio and friction coefficient. Any mismatch in the selection of the process parameters would cause defects inducing undesirable variations in wall thickness and cross-section distortion. In this work, firstly, tubes with several wall thickness values are bent, and the final depths of wrinkling and wall thickness change are reviewed. Then, to study the process numerically, numerical simulations are carried out. Then, a series of experimental tests are carried out to verify the simulation results. A comparison between numerical and experimental results shows a reasonable agreement. Finally, in order to obtain a suitable friction condition, the effects of friction coefficients on defects are studied. For this purpose, a series of simulations has been carried out. It shows that at a certain friction coefficient, a minimum wrinkling depth can be observed and variations in the friction coefficient between the dies and tube has no effective influence on wall thinning and thickening.
Źródło:
Journal of Theoretical and Applied Mechanics; 2015, 53, 4; 837-846
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An experimental study on wall thickness distribution in thermoforming
Autorzy:
Karabeyoglu, S. S.
Ekşi, O.
Erdoğan, S.
Powiązania:
https://bibliotekanauki.pl/articles/103237.pdf
Data publikacji:
2017
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
geometric element analysis (GEA)
wall thickness distribution
polystyrene
thermoforming
Opis:
In this work, Polystyrene (PS) sheets were thermoformed in predetermined conditions. Wall thickness distributions obtained by experimental method in PS thermoformed products. Then the same thickness distributions were predicted by using Geometric Element Analysis (GEA). The thickness results were obtained experimentally, compared to thickness distributions which were predicted by GEA. It has been found that GEA does not precisely reveal thickness distributions.
Źródło:
Advances in Science and Technology. Research Journal; 2017, 11, 3; 139-142
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasound measurement of the gallbladder wall thickness in the assessment of the risk of conversion from elective laparoscopic cholecystectomy to open surgery — Olkusz county experience
Autorzy:
Kania, Dariusz
Powiązania:
https://bibliotekanauki.pl/articles/1393735.pdf
Data publikacji:
2016
Wydawca:
Index Copernicus International
Tematy:
laparoscopic cholecystectomy
conversion
gall-bladder wall thickness
gall-bladder ultrasound
Opis:
The aim of the study was to assess the risk of intraoperative difficulties, conversion and biliaryintestinal fistula during laparoscopic cholecystectomy on the basis of an ultrasound-measured gallbladder wall thickness. Material and methods. A prospective study was conducted in 50 patients undergoing laparoscopic cholecystectomy for chronic gallstone-induced cholecystitis. To calculate the relationships between categorical variables, a chi-square (χ2 ) independence test was used, and the results were interpreted for the significance threshold of α = 0.05. Results. The relationship between the gall-bladder wall thickness and the occurrence of intraoperative difficulties in the analysed set is deterministic (AUC = 1), and the wall thickness of ≥ 5 mm allows to predict their occurrence as soon as at the stage of diagnostic evaluation (p < 0.001). In addition, the ultrasound-measured GB wall thickness is a good predictor of conversion (AUC = 0.976; 95% CI 0.444–0.975; p < 0.001) and biliary-intestinal fistula (AUC = 0.935; 95% CI 0.121–0.738; p = 0.001). Conclusions. The results allow prediction of technically difficult laparoscopic cholecystectomies in patients with CCh, and selection of the right surgical team helps to reduce the number of conversions and possible complications. In addition, bearing in mind the above results in everyday practice should facilitate planning and increase effectiveness in the operating room.
Źródło:
Polish Journal of Surgery; 2016, 88, 6; 587-607
0032-373X
2299-2847
Pojawia się w:
Polish Journal of Surgery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimisation of the deoxidation degree and modification on the cast steel properties improvement at low temperature
Optymalizacja stopnia odtleniania i modyfikacji na poprawę własności w niskich temperaturach
Autorzy:
Sierant, Z.
Powiązania:
https://bibliotekanauki.pl/articles/351224.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
steel castings
minus temperatures
wall thickness
odlewy stalowe
niskie temperatury
grubość ścianki
Opis:
Industrial conditions of obtaining thick-walled and shaped castings intended for operations at temperatures: minus 40÷60°C are presented in the paper. The selection of a cast steel grade is based on known studies [1,10,14], however due to castings wall thickness (70-240mm), the way of preparing liquid metal (deep deoxidation and modification, argon stirring in a ladle) and conditions of filling mould cavities (gating system assuring quiet filling, directional solidification and avoiding a formation of inessential heat centres), were developed to assure the required impact strength. Maintaining these parameters as well as the selection of heat treatments for the produced massive castings allowed to achieve the impact strength over 50 J/cm2 at minus 40°. This value was obtained for walls of various thickness.
Przedstawiono przemysłowe warunki otrzymywania grubościennych i kształtowych odlewów, przeznaczonych do pracy w temperaturze minus 40÷60°. Dobór gatunku staliwa oparto o znane prace [1,10,14], jednak ze względu na grubość ścianek odlewów (70-240 mm), opracowano sposób przygotowania ciekłego metalu (głębokie odtlenianie i modyfikacja, argonowanie w kadzi) oraz warunki zapełnienia wnęki formy (układ wlewowy zapewniający spokojne wypełnianie, kierunkowe krzepnięcie i unikanie tworzenia zbędnych węzłów cieplnych), dla zapewnienia wymaganej udarności. Zachowanie tych parametrów jak również dobór obróbki cieplnej dla produkowanych masywnych odlewów, pozwoliły na uzyskanie udarności w minus 40° wynoszącej powyżej 50 J/cm2. Wartość tą otrzymano dla ścianek o różnej grubości.
Źródło:
Archives of Metallurgy and Materials; 2013, 58, 3; 763-767
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Derivation of relations and analysis of tube bending processes using discontinuous fields of plastic strains. Part I. Derivation of geometric-analytic relationships
Autorzy:
Śloderbach, Z.
Powiązania:
https://bibliotekanauki.pl/articles/264482.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
bending tubes
three simplifications
strains
wall thickness
discontinuous strain fields
naprężenia
kinematyka
gięcie rur
Opis:
The generalized strain scheme in bending metal tubes at bending machines with the use of a mandrel presented in Śloderbach (1999; 2002; 20131,2; 2014) satisfies initial and boundary kinematic conditions of bending, conditions of continuity and inseparability of strains. This paper introduces three formal simplifications gradually imposed into forms of principal components of the generalized strain model giving suitable simplifications of the 1st, 2nd and 3rd types. Such mathematical simplifications cause that the obtained strain fields do not satisfy the condition of consistency of displacements and strain continuity. The simplified methods determine safer values of the wall thickness than those from the generalized continuous strain scheme. The condition of plastic incompressibility was used for the derivation of an expression for distribution of Wall thickness of the bent elbow in the layers subjected to tension and compression for three examples of discontinuous kinematic strain fields.
Źródło:
International Journal of Applied Mechanics and Engineering; 2015, 20, 2; 417-426
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Derivation of relations and analysis of tube bending processes using discontinuous fields of plastic strains. Part II. Discussion and analysis of the obtained results
Autorzy:
Śloderbach, Z.
Powiązania:
https://bibliotekanauki.pl/articles/955329.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
three simplifications
strains
wall thickness
allovable strains and ovalization
odkształcenia plastyczne
gięcie rur
naprężenia
Opis:
This paper presents the calculation results obtained on the basis of three formal simplifications (derived in Part I) gradually led into the main components of the generalized model of strain where suitable simplifications of the 1st, 2nd and 3rd type have been obtained. The paper also presents the results of considerations on the wall thickness distribution in the vertex point of the elongated layers of the bent elbow, and values of main components of the strain state and intensity of the strain (equivalent strain) depending on the bending angle for the generalized strain scheme and three simplified methods. The results are shown in the form of graphs and table.
Źródło:
International Journal of Applied Mechanics and Engineering; 2015, 20, 2; 427-435
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Casting Wall Thickness on Crystallisation Under Pressure
Autorzy:
Pastirčák, R.
Ščury, J.
Brůna, M.
Bolibruchová, D.
Jakubski, J.
Powiązania:
https://bibliotekanauki.pl/articles/353947.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
squeeze casting
AlSi7Mg0.3 alloy
AlSi12 alloy
pressure
wall thickness
Opis:
The paper deals with squeeze casting technology. For this research a direct squeeze casting method has been chosen. The influence of process parameters variation (casting temperature, mold temperature, pressure) on mechanical properties and structure will be observed. The thicknesses of the individual walls were selected based on the use of preferred numbers and series of preferred numbers (STN ISO 17) with the sequence of 3.15, 4.00, 5.00, 6.00 and 8.00 mm. The width of each wall was 22 mm with a length of 100 mm. As an experimental material was chosen the AlSi12 and AlSi7Mg0.3 alloys. The mechanical properties (UTS, E) for individual casting parameters and their individual areas of different thicknesses were evaluated. In the structure the influence of pressure on the change of the eutectic morphology, the change of the volume of eutectic and the primary alpha phase, the effect of the pressure on the more fine-grain and the regularization of the structure were evaluated.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 4; 1889-1893
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact assessment of the uniformity mixing recycled and virgin polymers on the technical extrusion blow molding efficiency
Autorzy:
Pepliński, K.
Powiązania:
https://bibliotekanauki.pl/articles/2073653.pdf
Data publikacji:
2015
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
technical extrusion blow molding
plastics mixing recyclate
virgin plastics
mixing uniformity
part weight
wall thickness
Opis:
Extrusion blow molding of technical products (EBM-TP) is a significant technological polymer manufacturing process ex. for the automotive branch. Implementation of the extrusion blow molding process in an operating arrangement of polymer technology is a component of many technological factors, but also of factors related to feedstock material. The products can be manufacturing with the participation of plastics recyclate. The homogeneity of the recyclate-virgin polymer mixture strongly influences the distribution of spreading the wall thickness of the final products. For this type product wall thickness distribution should be uniform and very close to each other or determined in a specific range of values. Work presents the mixture influence (HDPE recyclate-virgin polymer,) with different characteristics of mixing degree defined as homogeneous and heterogeneous, on the part features (the intake manifold airflow in a motor vehicle) with respect to the weight of the weight and wall thickness in reference required by the customer of the product. Mixtures of HDPE were prepared via a specialized gravimetric mixer, which is directly connected to the feed circuit extruder blow molding. They began to manufacture defined types of test specimen (actual Products of) and their evaluation according to criteria adopted burden of weight and wall thickness.
Źródło:
Journal of Polish CIMEEAC; 2015, 10, 1; 127--132
1231-3998
Pojawia się w:
Journal of Polish CIMEEAC
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Different Wall Thicknesses of the Casting in the Direct Squeeze Casting
Autorzy:
Pastirčák, R.
Brůna, M.
Bolibruchová, D.
Powiązania:
https://bibliotekanauki.pl/articles/381032.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
squeeze casting
wall thickness
mechanical properties
structure
aluminium alloy
odlew
grubość ścianki
właściwości mechaniczne
struktura
stop aluminium
Opis:
The paper deals with squeeze casting technology. For this research a direct squeeze casting method has been chosen. As an experimental material, the AlSi12 and AlSi7Mg0.3 alloys were used. The influence of process parameters variation (pouring temperature, mold temperature) on mechanical properties and structure will be observed. For the AlSi7Mg0.3 alloy, a pressure of 30 MPa was used and for the AlSi12 alloy 50 MPa. The thicknesses of the individual walls were selected based on the use of preferred numbers and series of preferred numbers (STN ISO 17) with the sequence of 3.15 mm, 4 mm, 5 mm, 6.3 mm and 8 mm. The width of each wall was 22 mm and length 100 mm. The mechanical properties (Rm, A5) for individual casting parameters and their individual areas of different thicknesses were evaluated. For the AlSi7Mg0.3 alloy, the percentage increase of the tensile strength was up to 37% and the elongation by 400% (at the 8 mm thickness of the casting). For the AlSi12 alloy, the strength increased from 8 to 20% and the tensile strength increased from 5 to 85%. The minimum thickness of the wall to influence the casting properties by pressure was set to 5 mm (based on the used casting parameters). Due to the effect of the pressure during crystallization, a considerable refinement and uniformity of the casting structure occured, also a reduction in the size of the eutectic silicate-eliminated needles was observed.
Źródło:
Archives of Foundry Engineering; 2019, 1; 19-24
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic sensor for the control of pipe wall thickness
Elektromagnetyczny czujnik do kontroli grubości ścianek rur
Autorzy:
Avramenko, A.
Garmash, A.
Gorkunov, B.
Lvov, S.
Tyshchenko, A.
Powiązania:
https://bibliotekanauki.pl/articles/209202.pdf
Data publikacji:
2015
Wydawca:
Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
Tematy:
electromagnetic converter
sensor
magnetic flux
wall thickness
tubular product
przetwornik elektromagnetyczny
czujnik
strumień magnetyczny
grubość ścianki
produkty rurowe
Opis:
Calculation of the primary inductive converter with magnetic core is problematic because of the difficulty in determining the various fluxes inside and outside the magnetic core. Observance of certain requirements for structural and scheme-related decisions makes is possible to substantially simplify theoretical expressions for description of work in such type of converters. The paper presents problems in the theory, design, and schematic layout of universal surface sensor with magnetic core, used for controlling wall thickness in tubular conductive products. The proposed construction of the sensor will allow using it to control wall thickness in a wide assortment of pipes.
Obliczenie podstawowego przetwornika indukcyjnego z rdzeniem magnetycznym jest problematyczne z powodu trudności w określeniu wewnętrznych i zewnętrznych strumieni rdzenia magnetycznego. Stosowanie pewnych wymagań dotyczących struktury i schematu przetwornika umożliwia zasadnicze uproszczenie teoretycznych wyrażeń opisujących pracę tego typu przetworników. Artykuł przedstawia problemy teorii i projektowania oraz schematyczny układ uniwersalnego czujnika powierzchni z rdzeniem magnetycznym stosowanego do kontroli grubości ścian elektro-przewodzących wyrobów rurowych. Proponowana konstrukcja czujnika pozwoli na zastosowanie go do szerokiego asortymentu rur.
Źródło:
Biuletyn Wojskowej Akademii Technicznej; 2015, 64, 2; 35-43
1234-5865
Pojawia się w:
Biuletyn Wojskowej Akademii Technicznej
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 18

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