Statistical investigations by means of frequency curves are often made in mental tests, researches of social phenomena, &c. Industrial researches, however, have hitherto been confined almost only to the so-called laboratory tests. As the uniformity of products is a matter of utmost importance in the works operation where mass production is made, it is very useful to investigate statistically the daily works operation by means of frequency curves. The author has shown, in the present paper, the results of investigation, by this method, of the mechanical properties of two certain steels A and B manufactured in the Steel Department, Kure Naval Arsenal.
The chief points arrived at in the present investigation are as follows: (i) The frequency curves for the tensile strength and the yield point of steel A have almost symmetrical forms, the former having a smaller deviation or in other words a higher uniformity than the latter. (ii) The frequency curves for the elongation and the reduction of area of steel B have unsymmetrical forms, the cause of which in the former case may be attributed to the position and the state of fracture, and in the latter case chiefly to the state of fracture. (iii) The frequency curves for the Brinell hardness number and the impact value have almost symmetrical forms. (iv) The frequency curves for the ratios of yield point to tensile strength and of tensile strength (kg/mm
2) to Brinell hardness number have almost symmetrical forms, the former having a mode of 83% with 33.8% of the whole results and the latter a mode of 0.33 with 29.6% of the whole results.
The results are also shown by the brief methods giving several representative numerical values or straight line diagrams.
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