ABSTRACT
In the selection of materials for diaphragms it is important that the designer understand thoroughly the meaning of the terms relating to their mechanical properties. This chapter provides definitions of the most important mechanical properties, usually required for evaluating diaphragm materials. Yield strength is the stress at which a material exhibits a specified deviation from the proportionality of stress and strain. Ultimate strength is the maximum stress, tensile, compressive, or shear, that a material can withstand. Most materials can be stressed slightly above the proportional limit—to the elastic limit—without taking any permanent set. The proof stress is superior to the determination of the elastic limit as it depends on the offset method used in determining the yield strength. The modulus of elasticity in tension is very important in the design of diaphragms as it is one of the Parameters to be considered in calculating the thickness of the diaphragm for a particular deflection.
