In this paper some details are given for the construction of a simple balance for the measurement of stress relaxation at constant elongation. A simple means of obtaining equal strain in two parts of the strained specimen is provided. By means of four typical stocks, covering the widest possible range of aging resistance, it is shown that the stress relaxations give approximately the same estimate of stability as does the normal Geer test using 2-mm. Dumbbell specimens. As a measure for stress relaxation, the time is used that is required to obtain 50 per cent of the value of the interpolated modulus at 200 per cent elongation 6 seconds after the straining zero time at 110° C. The parameter for the aging test is the time in days at 70° C for the 50 per cent value of tensile strengths. The range for the stress relaxation parameter may be estimated to 8–1200 minutes and the aging parameter from 10–600 days. Finally the concordance of temperature coefficient for relaxation and oxidation rates is shown.

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