Evaluation of Flow and Fracture Propensity of Notched Steel Plates by Means of a Photoelastic Model

The object of this investigation was to gain a better understanding of the flow and fracture propensity of steel plates in which the Wells-type notch served as the fracture initiator. This type of notch is of importance in experimental investigations of the brittle fracture phenomenon because it successfully initiates low-stress brittle fractures in the wide-plate specimen in which it is used. The wide-plate specimen is thought to simulate effectively circumstances associated with known brittle fractures occurring in engineering practice. The magnitude of the brittle fracture problem in steel structures is revievled in general terms, as well as by citing representative case histories. A review of the most notable theoretical investigations of brittle fracture is given, including the Griffith theory, the Orowan-Irwin modification of the Griffith theory to account for notch-brittle materials, and highlights from thefracture mechanics approach to the brittle fracture problem. The factors affecting brittle strength are examined, with an emphasis on the concept of notch-constraint by which normally ductile metals, such as steel, can be induced to fracture in a brittle manner. Experimental brittle fracture studies are reviewed with an emphasis on tests of notched and welded wide-plates, for which representative data are discussed. A model of the vicinity of the Wells notch used in the wide-plate tests was designed and fabricated out of epoxy material into which birefringence was ITfrozen. II The use of three-dimensional