Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Engineering Science and Mechanics

First Advisor

Loren W. Zachary


The stress field at the roots of mathematically sharp notches has singularities of order r[superscript][lambda] -1, where [lambda] depends on the notch angle between the two stress-free boundaries. The purpose of this study was to determine Mode I and Mode II stress intensity factors associated with 90° re-entrant notches;To determine the stress intensity factors an experimental study using photoelasticity combined with digital image analysis was undertaken. A digital image analysis system was used to collect photoelastic data ([theta], r, and N) for the stress field near the corner. To take advantage of whole-field photoelasticity and reduce the experimental error, the overdeterministic least square algorithm of Sanford (1) in conjunction with Newton-Raphson iterative method was used;Three different models, machined from a single sheet of PSM-1 photoelastic material, with 90° corners were used. One of the models used was a plate with a 90° V-notch. The experimentally obtained stress intensity factors for this model agreed well with theoretical and numericals results. Stress intensity factors for the other two models follow the same trend as two previous numerical investigations. Because of the difference in definitions of K[subscript] I and K[subscript] II, the results from this study and the two numerical investigations can not be compared with each other. Once the stress intensity factors for a specimen at a given load condition were determined, they were used to back plot (regenerate) the fringe pattern. If the regenerated fringe pattern matched or came close in matching the original fringe pattern, the stress intensity factors were accepted as the representative values. And if the match was not satisfactory the experiment was repeated to obtain a new set of stress intensity factors which would give a satisfactory match.



Digital Repository @ Iowa State University,

Copyright Owner

Mohammad Mahinfalah



Proquest ID


File Format


File Size

128 pages