Papers by Keyword: Nonlinear Creep

Abstract: The article deals with the processing of shear creep curves for foamed polymers, as well as a technique for calculating three-layer beams, taking into account the nonlinear creep of the aggregate. The Maxwell-Gurevich equation is used as the creep law. An example of calculation of a three-layer panel with a middle layer of polyurethane foam is given.

Abstract: The article gives the differential equation of bending of a thin plate at nonlinear creep. This equation is suitable for arbitrary dependencies between stresses and creep deformations. Derivation of the equation is based on simplifying hypotheses Kirchhoff-Loves technical theory of plate bending. Solution is made numerically by finite difference method. Calculations were performed in mathematical package MATLAB. As the material was taken epoxy polymer EDT-10, for which is valid the physical law of Maxwell-Gurevich. It is shown that with the growth of displacements the maximum stresses in the polymer plate decrease.

Abstract: The uniaxial tensile creep of a commercial grade Poly(methyl methacrylate) was measured for 4000 seconds under various temperatures and stress levels ranging from 14 oC to 26 oC and 6 MPa to 32 MPa. The resultant creep compliance curves depart from each other for stresses beyond a critical value which varies with temperature, indicating nonlinear viscoelastic behavior. The time-temperature-stress superposition principle (TTSSP) was used to construct a smooth master compliance curve with a much longer time-scale interval from the short-term tests at higher stresses and temperatures. It is shown that the master curve covers a period of over 290 days, which is nearly 3.9 decades longer than the test duration. Moreover, it is verified that the time-temperature shift factors are dependent on stresses at which the shifts are applied, and that the time-stress shift factors are dependent on reference temperatures.