Surface tractions, or stresses acting on an internal datum plane, are typically decomposed into three mutually orthogonal components. One component is normal to the surface and represents direct stress. The other two components are tangential to the surface and represent shear stresses.
Direct stresses tend to change the volume of the material (e.g. hydrostatic pressure) and are resisted by the body's bulk modulus (which depends on the Young's modulus and Poisson ratio). Shear stresses tend to deform the material without changing its volume, and are resisted by the body's shear modulus
the stress state at point P can be represented by an infinitesimal cube with three stress components on each of its six sides
nine stress components from three planes are needed to describe the stress state at a point P.
These nine components can be organized into a matrix as seen in the picture.
As a mechanical eng. student at NDU i wanted to found something that relates matrices with eng. application ,that is why i did my post on stress matrices.
site used: http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/stress.cfm
Elie Kassab
Thanks very much Elie..for this great post i found it useful and interesting ...especially to my cource mechanics one..:)
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