Relation between specific heats - 1
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For thermoelastic materials, show that the specific heats are related by the relation
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Proof:
Recall that
and
Therefore,
Also recall that
Therefore, keeping constant while differentiating, we have
Noting that , and
plugging back into the equation for the difference between the two
specific heats, we have
Recalling that
we get
Relation between specific heats - 2
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For thermoelastic materials, show that the specific heats can also be related by the equations
We can also write the above as
where is the thermal expansion tensor and is the stiffness tensor.
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Proof:
Recall that
Recall the chain rule which states that if
then, if we keep fixed, the partial derivative of with respect
to is given by
In our case,
Hence, we have
Taking the derivative with respect to keeping constant, we have
or,
Now,
Therefore,
Again recall that,
Plugging into the above, we get
Therefore, we get the following relation for :
Recall that
Plugging in the expressions for we get:
Therefore,
Using the identity , we have
Specific heats of Saint-Venant–Kirchhoff material
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Proof:
Recall that,
Plugging the expressions of and into the above
equation, we have
Therefore,