ABSTRACT
The equivalent viscous damping coefficient that was used in the chapters on the forced response of shell structures is a function of several effects. While there may truly be a motion-resisting force proportional to velocity, we may also have turbulent damping proportional to velocity squared caused by the surrounding media; boundary damping either because of friction in the boundary joints themselves (rivets, clamps, etc.) or because of the elasticity of the boundary (we have to allow for a certain amount of energy to be converted to wave action of the boundary material which is lost to the system that is being investigated); and internal damping of the material. Internal damping is characterized by a hysteresis loop. There is also the possibility that damping is introduced by friction between two shell surfaces. For example, to dampen the hermetically sealed shells of refrigeration machinery, a ring of the same sheet material is loosely pressed inside the main shell so that the two surfaces can work against each other when vibrating.
