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Formula for Creep Curves of Metals

1951; Nature Portfolio; Volume: 168; Issue: 4284 Linguagem: Inglês

10.1038/1681007a0

1476-4687

E. N. DA C. ANDRADE,

Computational Physics and Python Applications

I WAS somewhat surprised to read in Nature of October 20 the letter of Prof. R. R. Hasiguti and his collaborator. Prof. Hasiguti sent me a copy of this letter in April and I replied to him on May 25, by air mail, pointing out that the only reason that he found that the four-constant formula, put forward by him, gave a better fit to his experimental results than my three-constant formula was that he had taken unfavourable values for the constants in my formula. I sent him the correct values of the constants, found by the method of Dr. A. J. Kennedy1, which are l0 = 49.57 cm.; β = 1.1006 × 10−2 sec.-1/3; ϰ = 1.4713 × 10−4 sec.−1. With these values, the “Length calculated from Andrade's formula” in Table 1 given in his letter come out to be 50.71, 51.35, 53.16, 57.30, 65.00. Prof. Hasiguti sent me in his original letter a much fuller list of values than that given in his Table 1, and, except at 7 sec., where the experimental reading cannot possibly be accurate (in view of the difficulty of deciding to within a second the moment of imposition of the load, inertia effects and the rapid rate of flow in the first ten seconds), the greatest difference between the values given by my equation and the experimental values was 0.08 per cent as against a greatest difference of 0.10 per cent with his equation. In fact, with the constants given above, my three-constant formula shows a better fit than his four-constant formula.