Spannkraft

Spannkraft is a term used in German engineering to describe the force that acts in tension along a member or component. It denotes the axial pulling force transmitted by elements such as cables, ropes, rods, or springs, and is measured in newtons. In design, Spannkraft is balanced against opposing forces such as external loads, self-weight, and friction. It is closely related to the concepts of axial load and tensile stress, with the basic relation F = σA, where F is the Spannkraft, σ the normal stress, and A the cross-sectional area.

Spannkraft can also refer to the clamping or gripping force produced by fasteners, vises, or clamping devices. In this context, it must be sufficient to prevent slip and maintain contact between surfaces, especially under varying loads and conditions. The required Spannkraft depends on factors such as desired friction, surface finish, temperature, and safety requirements; designers often apply a factor of safety to account for uncertainties, wear, and imperfect materials.

In engineering practice, the maximum usable Spannkraft is limited by material properties, notably tensile strength and yield strength, to avoid permanent deformation or failure. Fatigue behavior under cyclic loading further constrains usable Spannkraft in many applications. Technical literature typically specifies Spannkraft together with related parameters such as load duration, temperature, pretension, and environmental conditions.