‘Firmness’ in Compression and Tension

Abstract

ATTENTION was directed some time ago¹ to the applicability of Scott-Blair's equation, ψ = s^βσ^-1tk (s is shearing stress, σ is strain, t is time, ψ is firmness, κ and β are constants) for the ‘firmness’ of soft materials² to tests in tension as well as to tests in compression. This applicability was later extended to tests in torsion³. Some actual experimental figures were published showing the comparison between tension and torsion tests results, but no figures have been given for comparative tension and compression tests. These were omitted as no good agreement was obtained, apparently indicating the existence of experimental errors. It is now believed, however, that the apparent anomalies are due to a fundamental cause and not to experimental error.