Thermal Buckling of a Bimetallic Beams

A study is made of the buckling or snapping characteristics of a rigidly supported, pin-ended bimetallic beam, as influenced by the mean coefficient of expansion and difference in coefficients of expansion of the bimetallic beam elements. It is found that the snapping or sudden buckling that is attributed to a bimetallic beam thermostat is difficult to achieve. The results of the present analysis are compared to the well-known Timoshenko analysis which allows the supports to separate an amount equal to the mean expansion of the beam. It is found that only very large differences in the coefficients of expansion of the bimetallic materials will cause sudden buckling or snapping to occur. However, quasi-stable deflected positions exist which are not attained by heating, from the initially deflected mode. The bimetallic beam may be manually deflected into the quasi-stable mode, when it is at elevated temperature, and snapping will then take place into the stable equilibrium mode at some temperature, during the cooling of the beam.