THERMAL STRESSES IN AN ABLATING THICK-WALLED SPHERE.
POLYTECHNIC INST OF BROOKLYN N Y DEPT OF AEROSPACE ENGINEERING AND APPLIED MECHANICS
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A theoretical technique for predicting thermal stresses in a thick-walled ablating sphere of a low-conductivity material subjected to point-symmetric aerodynamic thermal and pressure loading is proposed. A previously developed approximate ablation analysis is combined with a known thermal stress solution for multi-layer spheres in order to determine stresses and strains in a material with variable modulus of elasticity and coefficient of linear thermal expansion. The multi-layer analysis is compared with a known thermoelastic solution for the incompressible sphere as a qualitative measure of the accuracy of this approach. The thermoelastic strains predicted are compared to the results of hypersonic wind tunnel strain measurements obtained on tests of ten Plexiglas and Nylon hemispherical models. For four of the models the agreement is good, while agreement for the other six models ranges from fair to poor.