Shear (fluid)

A shear stress, often denoted τ (Greek: tau), is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section. Normal stress, on the other hand, arises from the force vector component perpendicular to the material cross section on which it acts.

The formula to calculate average shear stress is force per unit area.:

where:

Pure shear stress is related to pure shear strain, denoted γ, by the following equation:

where G is the shear modulus of the isotropic material, given by

Here E is Young's modulus and ν is Poisson's ratio.

Beam shear is defined as the internal shear stress of a beam caused by the shear force applied to the beam.

where

The beam shear formula is also known as Zhuravskii shear stress formula after Dmitrii Ivanovich Zhuravskii who derived it in 1855.

Shear stresses within a semi-monocoque structure may be calculated by idealizing the cross-section of the structure into a set of stringers (carrying only axial loads) and webs (carrying only shear flows). Dividing the shear flow by the thickness of a given portion of the semi-monocoque structure yields the shear stress. Thus, the maximum shear stress will occur either in the web of maximum shear flow or minimum thickness

Also constructions in soil can fail due to shear; , the weight of an earth-filled dam or dike may cause the subsoil to collapse, like a small landslide.