On the Determination of the a-K Relationship for Birefringent Polymers

Methods of utilizing dynamic photoelasticity with fracture-type to simultaneously determine the stress-intensity factor K sub I and the crack-tip velocity are reviewed. Problems associated with data analysis to obtain K sub I from isochromatic-fringe loops are discussed. Errors resulting from the use of static near-field equations in the method of analysis are considered and a correction method is developed. The invariance of K sub Im (the min. K required to maintain a finite crack is noted and evidence is provided to indicate that K sub Im can be as a material property.16 refs.--AA