belastningshastighed

Belastningshastighet is a term used in materials science, biomechanics, and structural engineering that describes the rate at which a load is applied to a specimen, component, or tissue. It includes both the speed of the applied force and the resulting deformation rate. In practice it is commonly described as either the crosshead speed of a testing machine (units: mm/min or mm/s) or as the strain rate (s^-1) in dynamic tests. The exact meaning depends on context and method.

Measurement and control: In a universal testing machine, the crosshead speed sets the loading rate. For dynamic tests, servo-hydraulic or servo-electric actuators enforce a target strain rate. Data is collected to compute instantaneous strain rate ε̇ = dε/dt, expressed as s^-1 or percent elongation per second. Reported values typically include the rate and the specimen geometry.

Significance: Many materials are rate-dependent. Higher loading rates can increase apparent stiffness and strength, while reducing ductility and toughness. Viscoelastic materials, polymers, and composites show pronounced rate effects, and the chosen belastningshastighet can influence failure mode. Therefore, specifying the loading rate is essential for comparing results and for modeling behavior under service or impact conditions.

Standards and context: ISO and ASTM standards often specify recommended loading rates for specific tests to ensure comparability. The rate should reflect the intended application—static, quasi-static, or dynamic—and any dynamic effects relevant to the material.