Shear stress
From Wikipedia, the free encyclopedia
Shear stress is a stress state where the stress is parallel to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. The variable used to denote sheer stress is τ (tau).
The definition of sheer stress is:
- <math> \tau = {F \over A}</math>
where F is the shear force and A is the area. The true shear stress of a material is calculated with A being the instantaneous area, but because this is difficult to calculate engineering shear stress is more often used.
Engineering shear stress uses the same equation, except A is the initial area (the area of the material before the shear force is applied). Engineering shear stress is usually a very good approximation of true shear stress because the shear force will cause infinitesimally small changes in the area of the material.
Structural members in pure shear stress are the torsion bars and the driveshafts in automobiles. Riveted and bolted joints may also be mainly subjected to shear stress. Cantilevers, beams, consoles and column heads are subject to composite loading, consisting of shear, tensile and compressive stress.
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; e.g., the weight of an earth-filled dam or dike may cause the subsoil to collapse, like a small landslide.
Shear stress is relevant to the motion of fluids upon surfaces, which result in the generation of shear stress. Particularly, the laminar flux on a surface has a zero velocity and shear stress occurs between the zero-velocity surface and the higher-velocity flow away from the surface.
[edit] See also
- Geotechnical engineering
- Shear
- Shear rate
- Shear modulus
- Shear strength
- Strength of materials
- Tensile stressde:Scherung
it:Taglio es:tensión cortante he:מאמץ גזירה nl:Schuifspanning sl:Strig sv:Skjuvspänning zh:剪應力
