Stored energy in creep deformed graphite

ABSTRACT GRAPHITE which has been strained in tensile creep releases a very large amount of stored energy when the creep stress is reduced, as happens in the dip test1. The very large amount

of negative creep (actual shrinkage of the specimen while it is still under an appreciable applied tensile force) that takes place after a stress reduction is shown graphically in Fig. 1.

Three individual stress reduction tests are shown. The work the specimen does against gravity in lifting the hanging weights is measured by the distance the specimen shrinks in negative

creep multiplied by the remaining applied force. In a series of tests on ZTA graphite, the largest measured amount of energy released was 1.1 × 106 ergs/cm3 (0.17 calories/g atom). This was

released when one specimen was strained almost to fracture (20 per cent elongation) at 3,200 pounds inch−2, at which point the applied stress was reduced to 1,600 pounds inch−2. The negative

creep strain after the load reduction was 1.2 per cent. In time the negative creep period ended, but additional negative creep, some four times greater than that already measured, then

occurred after complete removal of the applied stress. If the total energy release were proportional to that measured after the initial stress reduction, it would have been about 5.5 × 106

ergs/cm3. It was probably less than this. For further calculations, however, let us assume that the released energy was somewhere between 1.1 × 106 and 5.5 × 106 ergs/cm3. Access through

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California, Los Alamos Scientific Laboratory, Los Alamos, New Mexico, 87544 W. V. GREEN & E. G. ZUKAS Authors * W. V. GREEN View author publications You can also search for this author

inPubMed Google Scholar * E. G. ZUKAS View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE

CITE THIS ARTICLE GREEN, W., ZUKAS, E. Stored Energy in Creep Deformed Graphite. _Nature_ 225, 628–629 (1970). https://doi.org/10.1038/225628a0 Download citation * Received: 21 August 1969 *

Revised: 01 December 1969 * Issue Date: 14 February 1970 * DOI: https://doi.org/10.1038/225628a0 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this

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