What the design engineer needs to know about materials variations and specifications

Misperceptions about mechanical properties of common materials are prevalent among design engineers. In addition, many design engineers make assumptions about mechanical property correlations which may be valid for teaching concepts of design to student engineers, but are inadequate in the physical world of stressed structures. The most common mechanical property "myths" held by design engineers will be described, as will common specification mistakes. Some of the sources of "unsuspected" material property variations will be described. Strategies for ensuring that the manufactured assembly actually has the assumed strength characteristics will also be presented.