ABSTRACT
The nonlinearity of the diaphragm is accompanied by the gradual shift of the inflection circle of the diaphragm, outwardly toward its perimeter. The theory based on perfect bending locates the inflection circle of the diaphragm at 57.73% of the radius. Flexible membranes with a rigid center plate are sometimes used as diaphragms or force-summing devices in low-pressure-range applications. It is important to note that the tensile stresses in a membrane increase with the square of the deflection and not linearly as is the case with a diaphragm. There are no stresses in the medial plane of the diaphragm at small deflections; however, the bending stresses increase linearly over the thickness of the diaphragm to the outer surfaces where they reach their maximum values. The equations for stress and deflection derived for flat plates are usually expressed for one or the other ideal conditions of support—either simply supported or fixed edges.
