This paper presents the results of experiments conducted with extracted human and bovine teeth. The teeth were subjected to thermal cycling at temperatures between 140 and 90 F. The results offer conclusive evidence that thermal fracture may be induced by the thermal stresses caused by the temperature cycling. Less than 3,000 thermal cycles cause severe cracking or the propagation of cracks previously existing in the teeth, or both.

Experiments were conducted to determine the thermal resistance between food and teeth during mastication processes and the drinking of beverages. It was found that the assumption of negligible resistance between food and teeth overestimates greatly the resulting temperature gradients. Also, heat transfer coefficients (reciprocal thermal resistance) during drinking and mastication are below 7.0 X 10 -2 calorie/cm2 second°C.

A B S T R A C T A viscoelastic fracture analysis has been developed for rocket grain fracture predictions. The fracture analysis uses a stress intensity factor technique to predict crack velocity histories under thermal and pressurization loading conditions. The theory is compared with two-dimensional pressurized tests of two typical rocket motor geometries using the viscoelastic material, Solithane 113.

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