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Continuous relaxation spectrum - its advantages and methods of calculation

100%

Malkin A. Y.

2006

tom Vol. 11, no 2

235-243

Some advantages in treating experimental data on viscoelastic properties of polymeric materials in terms of a continuous spectrum instead of generally used fitting these data by means of a discrete relaxation times spectrum were demonstrated. The proposed continuous spectrum of a power-like type contains only three adjustable parameters. They can be found from integral characteristics of viscoelastic material, such as instantaneous modules, Newtonian viscosity, areas under shear and normal stress relaxation curves. The proposed continuous spectrum correctly reflects main peculiarities of viscoelastic properties of real polymeric materials in a wide frequency range.

Non-linear elasticity of spiral springs

51%

Goncharenko V. V. , Goncharenko M. V. , Malkin A. Y.

2008

tom Vol. 13, no 2

373-381

Drawing of a cylindrical spiral spring with indexes in the range 50-100 at the high extension domain results in the non-linear behavior of a spring, the Young modulus of the material being constant. The equation describing the non-linear relationship between the drawing force and draw ratio was obtained and compared with experimental data. The origin of non-linearity is explained as the continuous transition from uncoiling of a spring to extension of its material.

The rheokinetics of a fast-curing polyurethane

38%

Polushkin E. , Polushkina O. , Malkin A. Y. , Blaurock J. , Kleba I. , Michaeli W.

1999

tom Vol. 4, no spec.

85-90

A viscosity build-up of various fast curing polyurethane compositions has been investigated under isothermal conditions. A diisocyanate (DI) and a polyol (PO) forming the polyurethane in course of the exothermic reaction were mixed with an original single-screw mixer in the mass ratios from 1:3 to 3:1. The rheokinetic measurements were carried out with a modified cone-plate rheometer in range of shear rates from 0.025 to 6.2 s-1 at temperatures from 22 to 114oC. It has found that the maximal rate of viscosity growth is observed for the polyurethanes with the ratio of DI:PO falling in the narrow range between 1:1 and 1.5:1. It is interesting that these curing systems have shown the Newtonian behaviour up to the viscosity value of 105 Pa*s at the shear range of 0.04 to 0.6 s-1. The obtained curves can be fitted with the equation 'eta'='eta'0*exp(k*t) on the initial stage of the viscosity rise only. For more precise fitting of the entire rheokinetic curve a modified exponential equation with the parameter k depending on the time t is proposed.

Hydrodynamic model of the srim-process and its verification

38%

Polushkin E. , Kuznetsov V. , Polushkina O. , Malkin A. Y. , Kleba I. , Blaurock J. , Michaeli W.

1999

tom Vol. 4, no spec.

297-302

A two-dimentional hydrodynamic model of a rheokinetic fluid during filling a thin and long mold packed with reinforcement materials are proposed. A core layer of the mold is a porous and rather thick spacer mat. The location of other denser and thinner reinforcement materials into the mold was symmetrical with respect to the spacer mat. During mold filling the fluid easily flows along the core spacer mat and simultaneously impregnates the peripheral reinforcement mats. The model allows to simulate the flow front propagation of the fluid and pressure rise inside the mold during filling. In order to verify the model an original glass mold has been designed and built. The experimental results for the flow front propagation of the fluid were compared with the model predictions and a good coincidence between them has been obtained. For correct comparison of the experimental pressure profiles with the calculated data, the pressure losses in the mold gate must be taken into consideration. These losses can essentially exceed the pressure level into the mold.