Age, deformation, and temperature effects of viscoelastic materials under large deformations
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Silicone, two-part polymer and rubberized asphalt are widely used as sealant materials in concrete pavement joints. These materials undergo large stretch under various environmental conditions in service. This experimental study characterizes viscoelastic behavior of these materials. A series of relaxation tests were conduced. Specimens were artificially aged to different levels by being exposed to ultraviolet irradiance before testing. The ambient test temperature ranged from -25 to 60 C and the specimens were stretched to different lengths with an increase ranging from 5 to 100%. It was found that the relaxation modulus curve of each material was age, deformation and temperature dependent. The effects of time and temperature on the relaxation of a viscoelastic material under small deformation has been taken into account through the time-temperature principle. The WLF (Williams, Landel and Ferry) equation proposes a shift factor to relate temperature to time. Our work shows that the shift factor proposed by the WLF equation can be used to relate all the age, deformation and temperature to time in the relaxation modulus for these materials under large deformation, with which Cauchy stress is represented in terms of Lagrangian strain. With shift factors for age, deformation and temperature, the relaxation modulus can be satisfactorily expressed by a single `master relaxation curve.' This master curve is then expressed in the form of generalized Maxwell model in parallel. This model may be easily merged into some commercial finite element package for structural analysis.
