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Crack Branching in Homalite-100 Sheets
WASHINGTON UNIV SEATTLE DEPT OF MECHANICAL ENGINEERING
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Crack branching in Homalite-100 sheets of 18-inch and 38-inch thickness was studied by using dynamic photoelasticity. Dynamic stress intensity factors, crack velocities and branching angles were measured. Corresponding static stress intensity factors were determined by the method of finite element analysis. Dynamic stress intensity factors reached a peak value at branching with a value of three times larger than the fracture toughness of the material and preceded the actual branching. The dynamic stress intensity factor after branching drops and then increases again to the maximum stress intensity at which point branching occurs again. Roughness of the fracture surface can be related to dynamic stress intensity factor and crack velocities near the branching stress intensity factors and terminal crack velocities, respectively. Average branching angle was 26 degrees.
APPROVED FOR PUBLIC RELEASE