"We have already derived expressions for the normal and shear stresses acting on inclined sections in both uniaxial stress and pure shear. In the case of uniaxial stress, we found that the maximum shear stresses occur in planes inclines at 45^o to the axis, whereas the maximum normal stresses occur on the cross sections. In the case of pure shear, we found that the maximum tensile and compressive stresses occur on 45^o planes. In an analogous manner, the stresses on inclined sections cut through a beam may be larger than the stresses acting on a cross section. To calculate such stresses, we need to determine the stresses acting on inclined plnes under a more general stress state known as plane stress."

EQUATION
A MATHEMATICAL EQUALITY RELATING PARAMETERS OR MEASUREMENTS

NORMAL
IN MECHANICS, NORMAL OFTEN MEANS PERPENDICULAR OR AT RIGHT ANGLES TO A SURFACE OR A DIRECTION. NORMAL CAN ALSO MEAN NOMINAL OR AVERAGE.

NORMAL STRESS
A COMPONENT OF THE STRESS THAT IS PERPENDICULAR (NORMAL) TO A PLANE OF REFERENCE

PLANE
NORMALLY A FLAT, IMAGINARY SURFACE

PLANE STRESS
A STATE OF STRESS IN WHICH THE STRESSES REMAIN PARALLEL TO A SINGLE PLANE.

SHEAR

SHEAR STRESS

STRESS

STRESS

TRANSFORMATION EQUATIONS FOR PLANE STRESS