Date of Award

1983

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Dr. Shukla

Abstract

A photoelastic investigation of high speed crack propagation and branching in a brittle polyester material called Homalite 100 was conducted for both uniaxial and biaxial loading conditions. Cross type specimens were loaded in a specially designed loading fixture where loads perpendicular and parallel to the crack could be controlled independently.

The photoelastic data obtained were analyzed to get the stress intensity factor K, the crack tip position a, the crack velocity a and other non-singular stress field coefficients including the stress acting parallel to the crack, a . ox

It was observed that K showed an increasing trend as the crack propagated through the specimens. Tensile stress parallel to the crack gave rise to higher stress intensity factors, compared to the compressive case for the same crack tip positions and .initial normal loads. It was also found that tensile parallel remote stress enhanced branching and branching angle. While branching angles of 22° to 29° were encountered in uniaxial normal loading and biaxial tension-compression loading, angles as high as 45° and 73° were obtained in the tensiontension case.

It was concluded in this study that any crack branching criterion has to take into account the nature of the remote stress parallel to the crack and that crack branching is strongly influenced by non-singular stress field coefficients.

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