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Powder injection moulding of a ceramic part
Hausnerová, B.; Marcaníková, L.; Filip, Petr
2009 - English
The aim of the study is to optimize the production of alumina ceramic parts via Powder Injection Moulding (PIM) technology. As a case study fabric with main demand on surface-roughness tolerances has been selected with the potential of high production quantities for textile machines industry. The process is searched in terms of material tailoring, part design and dimensions, and processing conditions of injection moulding, debinding and sintering steps. Rheological, thermal and pressure-volume-temperature characteristics were measured in order to provide the reliable data for the simulation of injection moulding as well as thermal and thermogravimetric analyses have been carried out to attain non-porous final sintered products.
Keywords:
powder injection moulding; sintering; pressure-volume-temperature
Available at various institutes of the ASCR
Powder injection moulding of a ceramic part
The aim of the study is to optimize the production of alumina ceramic parts via Powder Injection Moulding (PIM) technology. As a case study fabric with main demand on surface-roughness tolerances has ...
Transition from the saltation mode of bed load transport to the rolling mode
Lukerchenko, Nikolay; Ivanova, Irina; Chára, Zdeněk; Vlasák, Pavel
2009 - English
The paper deals with the sediment transport of sand particles conveyed by water in an open channel. A 3D numerical model developed by the authors was used for simulation of the sand particles movement in the channel with rough bed. Similarly to Shields theory of sediment transport incipient motion of the bed load particles the shear stress for the transition process from saltation mode to rolling mode can be defined. The shear stress value can be determined as a function of two dimensionless parameters, particle parameter and equivalent bed roughness. The particle parameter is a function of the particle size and density, and the carrier liquid density and viscosity. The presented numerical solution reveals that the shear stress for the transition process from saltation mode to rolling mode is less than the shear stress for the incipient sediment motion and depends on channel bed roughness. Příspěvek se zabývá sedimentačním pohybem písčitých částic unášených vodou podél dna otevřeného koryta. Pro simulaci pohybu částice v kanále s drsným dnem byl použit 3D model vyvinutý autory. Podmínky změny saltačního pohybu částice na rotační (valivý) podél dna koryta byly určeny obdobně jako podle Shieldsova teorému. Hodnota smykového napětí byla určena jako funkce dvou bezrozměrných parametrů, bezrozměrného průměru částice, který je funkcí velikosti a hustoty částice a hustoty a viskozity vody, a ekvivalentní drsnosti dna. Provedené numerické řešení potvrdilo, že smykové napětí pro přechod ze saltačního do rotačního pohybu je menší než smykové napětí pro počátek pohybu sedimentující částice a je závislé na drsnosti dna koryta.
Keywords:
bed-load transport; particle saltation; particle rolling; numerical modelling
Available in digital repository of the ASCR
Transition from the saltation mode of bed load transport to the rolling mode
The paper deals with the sediment transport of sand particles conveyed by water in an open channel. A 3D numerical model developed by the authors was used for simulation of the sand particles movement ...
Polyvinyl chloride filled with bismuth oxychloride powder
Polášková, M.; Sedláček, T.; Kharlamov, Alexander; Pivokonský, Radek; Saha, P.
2009 - English
Mixing of polymers with radiopaque agents enables the polymers visibility on X-ray images and represents the easiest way to accurately locate the polymeric surgical device during a critical procedure. Medical-grade polyvinyl chloride was compounded with various amounts of bismuth oxychloride, chosen for its unique properties such as high radiopacity, non-toxicity, excellent chemical and physical stability and good dispersibility in the polymeric matrix. Micro-compounder Haake MiniLab II, consisting of a conical co-rotating twin-screw compounder with an integrated backflow channel, was used for melt mixing and simultaneously for rheological measurement. Rheological data received from micro-compounder were supplemented and correlated with the data obtained from Anton Paar rotational rheometer. Structure of prepared composites was studied by scanning electron microscopy, and their thermo-mechanical properties were tested using dynamic mechanical analysis.
Keywords:
olyvinyl chloride; bismuth oxychloride; radiopaque agents
Available at various institutes of the ASCR
Polyvinyl chloride filled with bismuth oxychloride powder
Mixing of polymers with radiopaque agents enables the polymers visibility on X-ray images and represents the easiest way to accurately locate the polymeric surgical device during a critical procedure. ...
Measurement of elongational viscosity of PE materials
Švrčinová, Petra; Kharlamov, Alexander; Filip, Petr
2009 - English
This contribution aims at the measurements of elongation viscosity for polyethylene materials. The approach is analysed from the viewpoint of possible degradation of materials tested and the emphasis is paid to admissible acceleration of the whole measuring process. There is presented a hint how to simplify (and accelerate) the measurements for a suitable class of materials. Je provedeno měření elongační viskozity vybraných polyetylénových materiálů a ukázána možnost zefektivnění klasického postupu.
Keywords:
elongational viscosity; SER Universal Testing Platform
Available in digital repository of the ASCR
Measurement of elongational viscosity of PE materials
This contribution aims at the measurements of elongation viscosity for polyethylene materials. The approach is analysed from the viewpoint of possible degradation of materials tested and the emphasis ...
Flow behaviour of highly concentrated slurries
Vlasák, Pavel; Chára, Zdeněk
2009 - English
The paper describes results of experimental investigation of the highly concentrated fine-grained slurry. The flow behaviour of the slurry was experimentally investigated for the laminar and turbulent regimes with respect to the effect of solid concentration and flow velocity. The re-circulation pipe loop with smooth stainless steel pipe of the inner diameter D = 17.5 mm was used. Stony dust from Mistrovice quarry (d50 = 8 μm, ρs = 2 701 kg/m3) was used as a solid phase, water was used as a carrier liquid. Volumetric concentration and slurry velocity reached up to 44% and 6 m/s, respectively. Příspěvek se zabývá experimentálním výzkumem vysoce koncentrovaných jemnozrnných suspenzí složených z kamenného prachu z lomu Mistrovice (d50 = 8 μm, ρs = 2 701 kg/m3) a vody. Objemová koncentrace pevné fáze dosahovala hodnot až 44%, rychlost proudění až 6 m/s. Tokové chování těchto suspenzí bylo zkoumáno na recirkulační experimentální trase s hladkým nerezovým potrubím o vnitřním průměru D = 17,5 mm pro laminární i turbulentní režim s ohledem na vliv koncentrace pevné fáze a rychlosti proudění.
Keywords:
dense fine-grained slurry; experimental investigation; effect of concentration; effect of flow velocity; pressure drop
Available in digital repository of the ASCR
Flow behaviour of highly concentrated slurries
The paper describes results of experimental investigation of the highly concentrated fine-grained slurry. The flow behaviour of the slurry was experimentally investigated for the laminar and turbulent ...
A note to the tube theory
Kharlamov, Alexander; Filip, Petr; Švrčinová, Petra
2009 - English
The classical Doi-Edwards (DE) model represents a basic issue for tube theories. The model describes dynamics of polymer strands between entanglements and predicts stress in linear polymers. In this contribution there is considered the dynamics of the whole molecules within the same tube picture. When the molecule end-to-end vector is considered as a Hookean spring the damping function shows weaker thinning. The presented model describes one of the possible mechanisms leading to weaker damping exhibited by branched polymers.
Keywords:
tube theory; damping function; branched polymers; Doi-Edwards model
Available at various institutes of the ASCR
A note to the tube theory
The classical Doi-Edwards (DE) model represents a basic issue for tube theories. The model describes dynamics of polymer strands between entanglements and predicts stress in linear polymers. In this ...
A note to the measurement of extensional viscosity using SER Universal Testing Platform with different shapes of polymer samples
Švrčinová, Petra; Filip, Petr; Kharlamov, Alexander
2009 - English
For polymer melts, with respect to their numerical simulations, there were recommended to apply polymer samples (rectangles) with a width not exceeding 8 mm and a thickness less than 0.4 mm. The aim of this contribution is to document - for material used (LDPE Escorene, Exxon, USA) - the invariantness of the elongational viscosity measured with respect to sample dimensions including its width and thickness. The width of the samples used consecutively attained 12.7, 11.0, 9.3, and 7.4 mm; the thickness also ranged across a sufficiently broad interval (0.3-1.1mm). Temperature was set to 180, 190, and 200oC. For the measurements there were used the SER Universal Testing Platform from the Xpansion Instruments; the model SER-HV-P01 was applied with a Physica MCR501 rotational rheometer host system. The results obtained justify usage of a 'classical' width 12.7 mm (1/2") more suitable for better manipulation with a sample, especially its fixing to both drums perpendicularly to the clamps.
Keywords:
extensional viscosity; SER Universal Testing Platform; LDPE
Available at various institutes of the ASCR
A note to the measurement of extensional viscosity using SER Universal Testing Platform with different shapes of polymer samples
For polymer melts, with respect to their numerical simulations, there were recommended to apply polymer samples (rectangles) with a width not exceeding 8 mm and a thickness less than 0.4 mm. The aim ...
Electrical response of multiwall carbon nanotubes (MWCNT) "buckypaper" on deformation
Slobodian, P.; Říha, Pavel; Olejník, R.; Kimmer, D.; Sáha, P.
2009 - English
The network of entangled multiwall carbon nanotubes is shown to be a conductor whose resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles are imposed. The cycles at first lead at to the resistance decrease but with a higher number of cycles they fade away.
Keywords:
Carbon nanotubes network; electrical resistance; compressive deformation
Available at various institutes of the ASCR
Electrical response of multiwall carbon nanotubes (MWCNT) "buckypaper" on deformation
The network of entangled multiwall carbon nanotubes is shown to be a conductor whose resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles ...
Polyvinyl chloride catheters with repressed migration of plasticizers
Sedláček, T.; Polášková, M.; Kašpárková, V.; Filip, Petr; Sáha, P.
2009 - English
Impart flexibility and desired softness of polyvinylchloride (PVC) – one of the most widely used polymeric materials for medical device production – is achieved by addition of appropriate amount of plasticizer, usually di(2-ethylhexyl phthalate) (DEHP), into polymer matrix. DEHP is not chemically bonded to PVC and migrates to the surrounding media such as saliva, blood, plasma, or serum resulting in several toxic effects. Migration of DEHP can be significantly suppressed by embedding PVC into another polymer preventing its direct contact with surrounding liquid media. Coextruded TPU-PVC-TPU catheters were prepared with various thicknesses of TPU layers to evaluate its repressing effect on DEHP releasing. Releasing kinetic of DEPH from both three layered catheters and PVC catheters into the acetonitrile was observed in various time intervals and determined using reverse-phase liquid chromatographic technique.
Keywords:
Polyvinyl chloride; catheter; repressed migration of plasticizers
Available at various institutes of the ASCR
Polyvinyl chloride catheters with repressed migration of plasticizers
Impart flexibility and desired softness of polyvinylchloride (PVC) – one of the most widely used polymeric materials for medical device production – is achieved by addition of appropriate amount of ...
A remark to the reptation theory
Kharlamov, Alexander; Filip, Petr; Švrčinová, Petra
2009 - English
Avoiding the Independent Alignment (IA) approximation in the classical Doi-Edwards model causes the computation extremely time and hardware consuming. Nevertheless some flow situations cannot be modelled with the IA approximation. This contribution presents a probabilistic approach not taking into account the IA approximation. Neuvažování IA aproximace v klasickém Doi-Edwardsově modelu způsobuje značné výpočetní potíže, nicméně některé tokové situace nemohou být modelovány pomocí této aproximace, kterou také nově presentovaný přístup nebere v potaz.
Keywords:
tube model; reptation theory; probabilistic approach
Available in digital repository of the ASCR
A remark to the reptation theory
Avoiding the Independent Alignment (IA) approximation in the classical Doi-Edwards model causes the computation extremely time and hardware consuming. Nevertheless some flow situations cannot be ...
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