National Repository of Grey Literature 3 records found  Search took 0.04 seconds. 
Reologická charakterizace LDPE materiálů pomocí diferenciálních konstitučních rovnic
Pivokonský, Radek ; Zatloukal, M. ; Filip, Petr
For rheological description of branched LDPE melts (Escorene LD165BW1 a Bralen RB0323) the following differential constitutive equations were used: eXtended Pom-Pom, Phan Thien-Tanner-XPP, and modified Leonov models. There was carried out quantitative and qualitative comparison of efficiency of the predictions determined by these models with the experimental data measured at 200oC. For both materials there were measured linear viscoelastic properties, shear and uniaxial extensional viscosities.
Empirický model zohledňující lokální extrém průběhu viskozity
Filip, Petr ; David, Jiří ; Pivokonský, Radek
Almost all empirical models dealing with the flow curves of non- Newtonian fluids can be applied only in the case of monotonous course of these curves. Exceptionally it is possible to model viscosity behaviour of rheologically more complex materials if there appears, in the course of a flow curve, a global extreme. The 8-parameter model proposed enables a description of viscosity behaviour in dependence on shear rate or shear stress also for the case when an extreme (maximum or minimum) is only local.
Vztah viskozita vs. rychlost smykové deformace v procesu stárnutí emulsí
Filip, Petr ; David, Jiří ; Pivokonský, Radek
The aim of this contribution is to present an empirical model taking into account ageing of highly concentrated emulsions. This model enables smooth passage from modelling of viscoelastic fluid (shear-thinning behaviour)corresponding to a "fresh" material to a description of viscoplastic fluid (viscoplastic behaviour) corresponding to an "aged" material including yield stress modelling.

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