Viskosivastus

Viskosivastus is a term used in rheology to denote the viscous component of a material’s response to deformation. It refers to the part of stress that arises from the rate of change of strain and dissipates energy as heat, as opposed to the elastic component, which stores energy. In languages such as Estonian and Finnish, viskosivastus literally combines the ideas of viscosity and response.

In practical terms, viskosivastus is encountered when materials flow or deform under applied forces. For Newtonian fluids, the viscous response is proportional to the shear rate, described by the viscosity coefficient. For viscoelastic materials, the situation is more complex: the total response consists of both viscous and elastic elements, often analyzed through dynamic mechanical tests that separate storage (elastic) and loss (viscous) moduli.

Measurement and modelling typically involve rheometers that perform creep, relaxation, or oscillatory tests. In oscillatory shear, the material exhibits a loss modulus, G’’ (the viscous part), and a storage modulus, G’ (the elastic part). The balance between these components depends on factors such as temperature, frequency, and composition, and determines whether the material behavior is more liquid-like or solid-like.

Applications span many fields, including polymer science, lubricants, food technology, geology, and biomechanics. Understanding viskosivastus helps characterize flow properties, energy dissipation, and processing performance. See also viscosity, viscoelasticity, and rheology.