Dispersion Characteristics of Charpy Impact Values and a Proposal on the Estimation Standard of the Notch-Toughness

Abstract

In the methods for estimation of the Charpy impact values, proposed up to now, the average value of a few specimens and the deviations from it (σ²), etc. are mainly considered. The authors have made a large number of impact tests with steel plates to clarify the physical meaning of the distribution of testing values. As the result of these experiments it has been found that the distri-bution of the Charpy-impact values seems to be not a normal, but a skewed one. The theory for such a skewed distribution was established.
Proposal was made of a standard for the estimation of the notch-toughness of weld-metals ba-sed on the theory. According to this proposal the average value, the theoretical lowest value and σ², etc. cand be obtained comparatively exactly by using a definite number of specimens, and the method of estimation seems to be reasonable.