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Principle


37. Thermal Expansion

a. Use expansion or contraction of material by heat
b. Use various materials with different coefficients of heat
expansion

  • Principle Description:  Convert heat energy into mechanical energy or action.

  • Hints on Usage:  A more general form of this principle is to convert one form of energy into another form of energy to create a specific outcome.

  • Consider what materials are used within the system?  Can those materials be affected by heat?  If so, how can the heat-induced change be used to provide a desired function?

  • Be aware of the direction of change.  Thermal expansion can be positive or negative.  Look for ways heat can expand a material or contract it.  Can the same heat contract one material within the system while expanding another?   What happens within the system if heat is removed?  Can that be used?

  • Traditionally, this principle has been used for linear thermal expansion and contraction.  However, it is not limited to thermal fields.  Think about how to use other environmental fields to cause change.  For example, what would the effects of gravity, barometric pressure, altitude, or light be if applied to the system?
    Allow your thinking to expand to include social or psychological phenomena.



Examples:
  • Parts with different thermal expansion coefficients can be separated.  For example:  remove a metal lid from a glass jar by running hot water over them.

  • Thermostats use bi-metal mechanisms.

  • Really small sensors (such as sub-nanometers and micromechanical cantilevers) coated with materials of different thermal expansion coefficients bend due to the bimetallic effect.

  • A bearing mounted on a shaft (the bearing and shaft have unmatched thermal expansion coefficients) will expand slower than the shaft during work, creating a tighter fit and a more efficient joint.

  • Music strongly affects brain function:  Baroque largos enhance learning speed; Mozart’s music can temporarily enhance cognitive performance;  jazz music can create a contemplative mood; modern discordance can create a feeling of agitation.

  • Some materials shrink when heated but often with poor predictability.  Zirconium tungstate (a blend of zirconium, tungsten and oxygen) shrinks uniformly when heated.  This makes it an ideal candidate for use in dental fillings, electronics, metallurgy, and ceramics.

  • Zirconium tungstate can adjust the thermal expansion of circuit boards to match that of silicon.

  • Zirconium tungstate eliminates distortions in optical applications such as telescopes and laser devises so precise focus is maintained even with temperature fluctuations.

  • Experimental materials are processed in space because the lack of gravitational field affects material properties.

  • Depression resulting from lack of regular sunlight may be alleviated by moving to sunny regions.

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