ABSTRACT
A fundamental assumption of mechanics of materials is that plane sections remain plane. This hypothesis can be shown to be exact for axially loaded prismatic bars, circular torsion members, and beams, plates, and shells subjected to pure bending [1-3]. It is approximate for other stress analysis problems. Note, however, that there are extraordinarily many cases where applications of the basic formulas of mechanics of materials lead to useful results for slender members under any type of loading. According to St. Venant’s principle, the actual stress distribution closely approximates that given by these formulas, except near the restraint or geometric discontinuities on the member.
