Engineering structures such as wind turbine rotor blades, airplanes, and bridge decks, are subjected to different cyclic loading profiles and in most cases including interrupted loading at high or low stress levels. If such structures are composed of viscoelastic materials, they are sensitive to the type of loading patterns due to their cyclic- and time-dependent mechanical properties. The cyclic-dependent mechanical properties such as fatigue stiffness and hysteresis loop are mainly attributed to high frequency fatigue experiments at zero mean stress level while the time-dependent mechanical properties such as creep strain are related to the rheological deformation of the material when it is subjected to a constant external load. Cyclic-and time-dependent phenomena can interact with each other, and the degree of interaction, but also the dominance of one over the other, depends on the loading spectrum and the material type. The objective of this talk is to (1) introduce the concept of the creep-fatigue interaction as the most known interaction between cyclic-and time-dependent phenomena in viscoelastic materials, (2) present its investigation methods, and (3) study its effect on materials’ mechanical, thermal, and optical properties.
Dr. Vahid Movahedi-Rad
Scientific collaborator at “EPFL”, and R&D scientist at “tobii AB” in Switzerland
Vahid Movahedi-Rad has a PhD degree in materials science from École polytechnique fédérale de Lausanne (EPFL) and he is specialist in production, characterization, and mechanics of different types of materials (polymers, composites, metals). Currently, he is a R&D scientist at tobii AB in Switzerland, which deals with the development of new smart glasses. In addition, he collaborates in several projects at École polytechnique fédérale de Lausanne (EPFL) as Scientific collaborator investigating the effect of loading pattern on fatigue behaviour and damage mechanism of viscoelastic materials.