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Damping capacity is the ability of a material to absorb energy by converting mechanical energy into heat.
Overview
A large damping capacity is desirable for materials used in structures where unwanted vibrations are induced during operation such as machine tool bases or crankshafts. Materials like brass and steel have small damping capacities allowing vibration energy to be transmitted through them without attenuation. An example of a material with a large damping capacity is gray cast iron.
An understanding of this effect can be gained from observation of a stress-strain diagram with exaggerated features. The units of stress are force per unit area, while strain has units of length per length. Any area covered by integrating each instant of a loading and unloading cycle will then be in terms of force times length per volume, which is equivalent to energy per unit volume. This energy represents the amount of mechanical energy being converted to heat in a volume of material resulting in damping.