Thermoelastic damping is a source of intrinsic material
damping
Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation. Examples in ...
due to thermoelasticity present in almost all materials. As the name thermoelastic suggests, it describes the coupling between the
elastic
Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rubber used to hold objects togeth ...
field in the structure caused by deformation and the temperature field.
Definition
In any vibrating structure, the strain field causes a change in the internal energy such that compressed region becomes hotter (assuming a positive coefficient of
thermal expansion
Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions.
Temperature is a monotonic function of the average molecular kinetic ...
) and extended region becomes cooler. The mechanism responsible for thermoelastic damping is the resulting lack of
thermal equilibrium
Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be i ...
between various parts of the vibrating structure. Energy is dissipated when irreversible heat flow driven by the temperature gradient occurs.
The earliest study of thermoelastic damping can be found in
Zener’s classical work,
[{{cite journal , last=Zener , first=Clarence , title=Internal Friction in Solids II. General Theory of Thermoelastic Internal Friction , journal=Physical Review , publisher=American Physical Society (APS) , volume=53 , issue=1 , date=1938-01-01 , issn=0031-899X , doi=10.1103/physrev.53.90 , pages=90–99, bibcode=1938PhRv...53...90Z , url=https://hal.archives-ouvertes.fr/hal-03437261/file/Zener1938.pdf ] in 1937, in which he studied thermoelastic damping in
beams undergoing flexural
vibration
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...
s. Flexural vibrations cause alternating tensile and compressive strains to build up on opposite sides of the neutral axis leading to a thermal imbalance. Irreversible heat flow which is driven by the temperature gradient causes vibrational energy to be dissipated.
References
Elasticity (physics)
Mechanical vibrations