Puristusenergia

Puristusenergia, or strain energy, is the energy stored in an elastic body as a result of deformation caused by external forces. It is a form of potential energy that can be recovered when the loads are removed, provided the material remains within its elastic limit. If plastic deformation occurs, part of the energy is dissipated as heat and permanent deformation may occur.

In continuum mechanics, the strain energy density w is defined as the work required to produce a unit volume of strain from zero to the final deformation, w = ∫0^ε σ(ε') dε'. The total puristusenergia U is the integral of w over the body: U = ∫V w dV. In linear elastic isotropic materials, w = 1/2 σ ε = 1/2 E ε^2, where ε is strain and E is Young's modulus, or equivalently w = 1/2 σ^2 / E. In uniaxial loading, the total energy is U = 1/2 V E ε^2 = 1/2 V σ ε.

Examples of applicability include bending of beams, where the energy per unit length is U/L = M^2/(2EI) with M the bending moment, E the modulus, and I the second moment of area. For torsion of a circular shaft, the energy per unit length is T^2/(2GJ), with T the torque, G the shear modulus, and J the polar moment of inertia.

Puristusenergia is central to structural design, fracture mechanics, and finite element analysis, providing a measure of the elastic reserve in a structure. Its use assumes elastic behavior; beyond the yield point, part of the energy becomes plastic work or is dissipated as heat.