Simple description of thermoelastic inversion

If the temperature coefficient is calculated under the condition that the degree of elongation eo measured relative to the equilibrium length at the reference temperature To is constant, it is 

The critical degree of elongation at which the sign changes is found to be 

The tension reduces on heating in the small elongation region below this critical value. For instance, if we take 7b = 293 K, T = 343 K, and = 6.6 x the critical 

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