When fused quartz is heated, its elastic constants for stretch shear and bulk change all increase, a sharp distinction in behaviour from that of most other elastic solids. An elastically-stretched fibre becomes shorter upon heating, and a strained torsion member reduces its twist for a given twisting effort; and so forth. The changes of shear modulus with temperature have been studied in detail (22 to 98° C.) by Threlfall and later by Horton to about 1000° C., who used methods of experiment based upon the changes in period upon heating, of a torsional pendulum having fused quartz as the elastic member. The results of Horton's experiments showed a continuous increase in modulus up to about 880° C. beyond which temperature the modulus rapidly diminished. At 880° C. the modulus was 5·9 per cent, greater than at 15° C. and the mean rate of increase up to 500° C. was 0·85 × 10
-4
per degree Centigrade. The increase is more rapid at lower temperatures, thus, in the interval 20 to 100° C. mean rate of increase per degree Centigrade was found by Horton to be 1·25 × 10
-4
, which is in good agreement with the earlier determinations made by Threlfall. At still lower temperatures, and using the same method of torsional oscillation, Guye and Einhorn-Bodzechowski showed that the mean temperature coefficient in the interval —194° C. to 0° C. is 1·46 × 10
-4
per degree Centigrade, and that there is no major discontinuity in behaviour in this range.
Elastic constants of fused quartz. Change of young's modulus with temperature
