![]() The engineering shear strain is defined as the tangent of that angle, and is equal to the length of deformation at its maximum divided by the perpendicular length in the plane of force application which sometimes makes it easier to calculate. The true shear strain is defined as the change in the angle (in radians) between two material line elements initially perpendicular to each other in the undeformed or initial configuration. Measures of strain are often expressed in parts per million or microstrains. Where e is the engineering normal strain, L is the original length of the fiber and l is the final length of the fiber. In the case of elastic deformations, the response function linking strain to the deforming stress is the compliance tensor of the material. Another type of irreversible deformation is viscous deformation, which is the irreversible part of viscoelastic deformation. One type of irreversible deformation is plastic deformation, which occurs in material bodies after stresses have attained a certain threshold value known as the elastic limit or yield stress, and are the result of slip, or dislocation mechanisms at the atomic level. They exist even after stresses have been removed. On the other hand, irreversible deformations remain. In this case, the continuum completely recovers its original configuration. Deformations which cease to exist after the stress field is removed are termed as elastic deformation. ![]() The relation between stress and strain is expressed by constitutive equations, e.g., Hooke's law for linear elastic materials. ![]() In a continuous body, a deformation field results from a stress field due to applied forces or because of some changes in the temperature field of the body. Different equivalent choices may be made for the expression of a strain field depending on whether it is defined with respect to the initial or the final configuration of the body and on whether the metric tensor or its dual is considered. Strain is related to deformation in terms of relative displacement of particles in the body that excludes rigid-body motions. muscle contraction), body forces (such as gravity or electromagnetic forces), or changes in temperature, moisture content, or chemical reactions, etc. A configuration is a set containing the positions of all particles of the body.Ī deformation can occur because of external loads, intrinsic activity (e.g. In physics and continuum mechanics, deformation is the transformation of a body from a reference configuration to a current configuration.
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