Rateavhengig

Rateavhengig describes a property or response that changes with the rate at which an input is applied. In contrast to rate-independent behavior, where the outcome depends only on the magnitude of the stimulus, rateavhengig behavior varies with the speed, frequency, or time scale of the loading, forcing, or excitation.

In materials science and rheology, rateavhengighet is common. Polymers and other viscoelastic materials show different stiffness and damping when loaded at different strain rates; metals may exhibit higher flow stress under rapid deformation. Viscoelastic effects lead to phenomena such as creep (time-dependent deformation under constant load) and stress relaxation (decrease in stress under constant deformation), both influenced by how quickly the load is applied.

Rate dependence also emerges in chemical kinetics, diffusion, and biological systems, where reaction rates, transport, or regulatory processes respond to the pace of stimuli or environmental changes. Mechanisms behind rateavhengighet include time-dependent microstructural rearrangements, diffusion-limited transport, dislocation motion with thermal activation, and phase transformations that depend on the duration of exposure to conditions.

Modeling approaches typically incorporate viscous or rate terms in constitutive equations. For example, constitutive relations may include a term proportional to the rate of deformation (eta * d(e)/dt) alongside elastic terms, or use integral and internal-state frameworks to capture history-dependent behavior. Testing at multiple loading rates and time-temperature superposition are common methods to characterize rateavhengighet.

Understanding rateavhengighet is important for design and analysis across engineering, materials science, and process optimization, ensuring accurate prediction of performance under real-world loading conditions.