Temperature changes occurring during the compression and recompression of solids

Abstract

Measurements of the temperature rise occuring on compression, recompression and relaxation of compacts formed from Asagran, sodium chloride and boric acid have been made by means of thermocouples inserted into the compressed materials. There are marked differences in temperature rise for the different compacts when compressed to a final force of 50 kN (5 tons). With all compacts there was a rise in temperature on initial compression and a fall in temperature on relaxation. The rise could be separated into two components—that due to compact formation plus a further rise due to its elastic compression. The fall in temperature is thought to result on release of the strain energy stored in the compact. The rise in temperature on recompression followed by the fall of relaxation could be repeated many times on the same compact. Both rise and fall were directly proportional to the final compression force used. The fall on relaxation appeared to be numerically less than the rise on recompression for compacts of boric acid and Asagran. Lubrication of Asagran with magnesium stearate had little effect on the temperature rises.