MecMovies 4.0 : M1.11: Inclined Plane Stresses: Theory

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The figure shows a section of a prismatic bar. The stresses labeled sigma on a section labeled a a are directed rightwards. The load on the left end of the bar is directed leftwards.

This internal force distribution is called stress. Since the area exposed at section $a - a$ is perpendicular to the line of action of force $P$ , the stress is called normal stress (denoted by the symbol $σ$ ).

The normal stress acting on the cut surface may be calculated from $σ = P / A$ , provided that the stress is uniformly distributed. The stress will be uniform in this case since the cross section is constant and the force $P$ is applied at the centroid.