Papers by Author: K. Zarrabi

Abstract: Fracture studies of components involving mode III loading are rare. This paper concentrates on mixed-modes I, II and III fracture testing of brittle PMMA material and summarises an extensive experimental investigation. Karpour and Zarrabi have developed a special pair of grips for which they have received a patent. These grips allow the application of various mixtures of modes, including mode III, using a universal testing machine. To measure the three-dimensional crack-tip opening and sliding displacements, Karpour and Zarrabi have also developed a novel stereo machine vision system whose description is included in the paper. The measured critical crack-opening displacements presented in normalised format with potential of being used to assess the integrity of any component against elastic fracture and they compare well with limited pertinent data available from literature.

Abstract: This paper proposes a new three-layer artificial neural network (ANN) to predict the fatigue crack length under constant amplitude mode I cyclic loading. It is shown that the proposed model predicts the crack length with an error of less than 0.05%, and more accurately than the current commonly-used models.

Abstract: Boilers in power, refinery and chemical processing plants contain extensive range of tube bends. Tube bends are manufactured by bending a straight-section tube. As a result, the crosssection of a tube bend becomes oval. Using the finite element analysis (FEA) and artificial neural network (ANN), the paper presents the relationships between the plastic collapse pressures and tube bend dimensions with various degrees of ovality. It is found that as ovality increases the plastic collapse pressure decreases. Also, the reduction of plastic collapse pressure with ovality is small for a thick tube bend when compared with that for a thin tube bend.