Document Type

Thesis - Open Access

Award Date

1973

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Abstract

The phenomenon of fracture in solids has intrigued scientists and engineers since almost the early days of the Industrial Revolution in Europe. More and more new facts are coming to light as more and more researchers are engaged in finding out facts about the properties of materials in relation to fracture. After the study of inelastic, and elastic materials, researchers started taking interest in the study of viscoelastic materials. Since this paper mainly deals with viscoelastic materials the discussion and study will be limited to viscoelastic materials only. Maxwell was, probably, among the pioneers in this field and he found that substances like pitch or tar are neither ideal elastic solids nor viscous liquids, but have some characteristics of both. The model he devised was the spring and dashpot elements connected in series, known as the Maxwell element. Then came Boltzmann' s superposition principle which was used in the form of an integral for linear viscoelasticity. Wiechert derived a differential formulation of linear viscoelastic behavior as a generalization of Maxwell's equation which is particularly of interest for describing stress-relaxation experiments. Voigt introduced the Voigt element which is a parallel connection of the spring and dashpot elements. This is of particular interest for describing creep experiments. In this paper, the three-element linearly viscoelastic solid is taken as the working model, and the creep and relaxation behaviors of this model and its responses to different types of loads are also studied. Knauss has studied, both theoretically and experimentally, the problems concerning the failure criteria for viscoelastic materials, taking into consideration the material characteristics, stress analysis of crack geometries under large deformations, and crack propagation in a strip. Frankiewicz, Stankowski and Wnuk have studied the time dependent fracture in viscoelastic materials taking the displacement, energy criterion, and crack movement into consideration. Wruk and Knauss have analysed the stress and strain distributions around the crack, effect of time dependent yield in the case of fracture initiation in viscoelastic materials. Wnuk has constructed a closed form solution valid for a special case of isotropic, incompressible, ideally elastic-plastic solid, weakened by a crack, and subjected to tensile mode of fracture, taking both the plane stress and plane strain cases into consideration.

Library of Congress Subject Headings

Fracture mechanics

South Dakota State University Theses

Format

application/pdf

Number of Pages

113

Publisher

South Dakota State University

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