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Expanding heat source model for thermal spalling of TiB2 in electrical discharge machining

Published online by Cambridge University Press:  31 January 2011

A.M. Gadalla  and
B. Bozkurt
A.M. Gadalla
Affiliation:
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
B. Bozkurt
Affiliation:
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
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Abstract

A model is presented to explain the recently reported mechanism of thermal spalling for shaping high melting point ceramics by electrical discharge machining. Since previous models fail to explain the experimental observations completely, an expanding circular heat source created by growth of plasma is assumed to act on the surface. Erosion of materials by spalling is caused by thermally induced compressive stresses during heating-up periods and tensile stresses during cooling-down periods. This model explains material removal for anodic erosion in general (wire-cutting machines) and for cathodic erosion (die-sinking machines) whenever long pulse duration is used. Simulation of the model for TiB2 provides a local melt front that penetrates to a depth of submicrometer, then recedes as pulse duration increases. Spalling develops flakes with thickness correlated to pulse duration. The results were verified by the experimental observations which showed that large flakes having the predicted maximum thickness as well as few quenched spherical droplets containing titanium were obtained.

Type
Articles
Information
Journal of Materials Research , Volume 7 , Issue 10 , October 1992 , pp. 2853 - 2858
Copyright
Copyright © Materials Research Society 1992

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References

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