ppl in a plane stress problem, it is assumed that perpendicular to the

plane shear stress and normal stress is zero.

but due to the strain in directions parallel to the plane , there must

be a strain in the direction perpendicular to the plane by poisson's

effect, which will cause a normal stress.

so is the assumption made as normal stresses @ surface is zero ( as

surface is free of loads in one direction and hence there is no

deformations possible in the elements on surface) and by omitting the

stress in the interior

Regards

WOT

- posted 14 years ago