Date of Award

2012

Document Type

Campus Access Dissertation

Department

Mechanical Engineering

First Advisor

Yuh Chao

Abstract

Fracture toughness is an important material property used to assess the structural integrity of mechanical components containing cracks. Often, the fracture toughness depends upon the geometry of the component as well as the configuration and level of the applied loading. This dependence is referred to as the constraint effect in fracture. The two parameter J-A2 method is investigated to determine if it can be used to quantify the constraint effect and predict failure of mechanical components. The J-A2 method is a more accurate representation of the stress fields near the crack, as additional terms from the HRR series solution are used. The subject of the current study is to apply the J-A2 method to published fracture toughness data of a variety of cracked specimens, 3-D uniaxial and biaxially loaded cruciform specimens and 3-D uniaxial and biaxial loaded flat plates containing semi-elliptical cracks to determine the constraint effect. The J-A2 results of the plates and cruciform specimens are compared to those of other ASTM standard plane strain specimens, including three point bend and compact tension, to determine if loss of constraint exists. Finite element analysis models were developed for each specimen to determine the constraint parameter A2 for each, as well as Material Failure Curves for the materials and Crack Driving Force curves for each specimen.

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