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Physical insight into strains can be gained by observing that a given strain can be decomposed into normal and shear components. The amount of stretch or compression along material line elements or fibers is the normal strain , and the amount of distortion associated with the sliding of plane layers over each other is the shear strain , within ...
The formula to calculate average shear stress τ or force per unit area is: [1] =, where F is the force applied and A is the cross-sectional area.. The area involved corresponds to the material face parallel to the applied force vector, i.e., with surface normal vector perpendicular to the force.
Generally speaking, curves that represent the relationship between stress and strain in any form of deformation can be regarded as stress–strain curves. The stress and strain can be normal, shear , or a mixture, and can also be uniaxial, biaxial, or multiaxial, and can even change with time.
The shear modulus is one of several quantities for measuring the stiffness of materials. All of them arise in the generalized Hooke's law: . Young's modulus E describes the material's strain response to uniaxial stress in the direction of this stress (like pulling on the ends of a wire or putting a weight on top of a column, with the wire getting longer and the column losing height),
The strain rate can also be expressed by a single number when the material is being subjected to parallel shear without change of volume; namely, when the deformation can be described as a set of infinitesimally thin parallel layers sliding against each other as if they were rigid sheets, in the same direction, without changing their spacing.
The strains associated with length, i.e., the normal strain and the shear strains and (if the length is the 3-direction) are constrained by nearby material and are small compared to the cross-sectional strains. Plane strain is then an acceptable approximation.
Stresses in a contact area loaded simultaneously with a normal and a tangential force. Stresses were made visible using photoelasticity.. Contact mechanics is the study of the deformation of solids that touch each other at one or more points.
Cauchy observed that the force across an imaginary surface was a linear function of its normal vector; and, moreover, that it must be a symmetric function (with zero total momentum). The understanding of stress in liquids started with Newton, who provided a differential formula for friction forces (shear stress) in parallel laminar flow.