Measurements of Strain-Free Temperature and Parr End Correction Factor in Solid Propellant Grains
MORTON THIOKOL INC BRIGHAM CITY UT WASATCH OPERATIONS
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The structural analysis of a rocket motor propellant grain subjected only to thermal loads involves the fundamental assumption that a small thermomechanical reference state exists at which the grain stress and strains disappear. Substantial evidence now exists which shows that the grain stresses and strains do not necessarily vanish at the same reference state, i.e. the stress-free and strain-free temperatures are significantly different. The primary cause of the strain-free temperature shifts was found to be movements of the grain ends, which were experimentally identified through measured changes in the Parr factor.
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