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Identification of the Process of Dynamic Stretching of Threads in Warp-Knitting Technology

Prążyńska A., Mikołajczyk Z.

Autex Research Journal

2017

Vol. 17, no. 4

334--343

The publication presents a theoretical study of the susceptibility of rheological models of threads to dynamic stretching in the context of modern, highly efficient textile technologies. Input parameters of the four analyzed models, the Kelvin-Voigt model, the Maxwell model, Standard model 2, and the Zener model, corresponded to the actual values of the coefficients of viscosity, elasticity, kinematic and dynamic loading, and stretching speed for the analyzed polyester silk threads produced in a knitting process, with knitting speeds from 700 to 1,600 courses/min. The research proves that the tested thread models behave differently in the stretching process-the Kelvin-Voigt model is sensitive to both the increases in kinematic loading and viscosity coefficient, Standard model 2 is only susceptible to dynamic stiffness, and the Zener model is significantly sensitive to kinematic loading. All responses of the models increase with the increase in stretching speeds. The obtained results indicate substantial “accuracy tolerance” in setting input parameters while identifying dynamics of the knitting process on warp-knitting machines.

Niektóre błędy wyznaczania parametrów modelu reologicznego na podstawie testu relaksacji naprężeń na przykładzie bulwy ziemniaka

Stropek Z., Gołacki K.

Inżynieria Rolnicza

2005

R. 9, nr 4

291--297

Artykuł prezentuje procedury oszacowania niektórych błędów wyznaczania parametrów modelu Maxwella opisującego zachowanie się walcowych próbek w teście relaksacji naprężeń na przykładzie tkanki ziemniaka odmiany Irga. Wyznaczono błędy zarówno toru pomiarowego jak i wynikające z niedokładności wykonania próbek. Uwzględniono także zmienny w funkcji siły reakcji próbki błąd systematyczny przy wyliczaniu współczynników sprężystości i lepkości dynamicznej modelu.

This paper presents the estimation procedures of Maxwell’s model parameters describing the behaviour of potato samples during stress relaxation test. Into consideration were taken errors resulting from an inaccuracy of sample preparation, as well as the used measurement device (defined, limited precision). Moreover systematic error depending on sample reaction force, at calculation of elastic and viscosity coefficients was taken into account.

Experimental solution for viscosity coefficient of solid alloy material

Luo Y. S., Dohda K., Wang Z.

International Journal of Applied Mechanics and Engineering

2003

Vol. 8, no spec.

271-276

This paper deals with the experimental method and solution for viscosity coefficient of solid alloy materials, such as, solid aluminum alloy Lc4. Standard creep specimen of f10mm with male screw ends were adopted, and groups of creep tests were carried out under high-temperature on RD2-3 type creep-machines. Tests under a constant temperature but different stress levels, and under a constant stress but different temperature levels were carried out. The effects of temperature and stress on strain and strain rate were analyzed. By putting the experimental data into the constitutive equation of the rheological model of viscoplastic material, the viscosity coefficients of the solid alloy materials under different temperature levels and stress levels were derived easily. They are similar to viscosity coefficient of non-Newtonian fluid. This experiment is simply to be operated, and the calculation is conveniently to be solved.