Numerical modelling of crack shape evolution for surface flaws in round bars under tensile loading

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

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Numerical Modelling of Shape Evolution of Tubular Preform in Spray Forming Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.2426 ◽

2011 ◽

Vol 189-193 ◽

pp. 2426-2433 ◽

Cited By ~ 1

Author(s):

Jin Zong Xiang ◽

Yin Zhang ◽

Wen Jun Fan ◽

You Duo He

Keyword(s):

Mathematical Model ◽

Numerical Modelling ◽

Three Dimensional ◽

Spray Forming ◽

Geometrical Shape ◽

Shape Evolution ◽

Effective Algorithm ◽

Forming Process ◽

Movement Parameters

A three-dimensional mathematical model of growth, integrated with a new and effective algorithm for visibility checking, has been established based on a spray forming equipment with three different fixed atomizers in this paper. The model was used to predict the geometrical shape and the thickness profiles of the tubular deposit under various situations. By investigating and discussing the effects of different mandrel movement parameters and spray heights, the optimal atomizer of the equipment to fabricate a tubular preform was identified numerically.

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Constraint Effects on the Prediction of Fatigue Life of Surface Flaws

Journal of Engineering Materials and Technology ◽

10.1115/1.3225646 ◽

1983 ◽

Vol 105 (3) ◽

pp. 215-218 ◽

Cited By ~ 8

Author(s):

M. Jolles

Keyword(s):

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Crack Growth ◽

Stress Field ◽

Crack Growth ◽

Crack Closure ◽

Growth Analysis ◽

Crack Shape ◽

Surface Flaws ◽

Constraint Effects

The effects of the variation of stress field triaxiality on the prediction of the fatigue growth of semielliptic surface flaws are investigated. The concepts of crack closure are used in a fatigue growth analysis to account for constraint variation. The analysis, together with a traditional fatigue crack growth analysis which does not account for constraint variation, is used to predict flaw growth observed in experiments. Significant improvements in predicted fatigue life, as well as predicted crack shape, are obtained by accounting for the variation in constraint.

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