There are two or three equations in the past on the relation between the percentage of elongation and area contraction, but we showed, basing on by another idea, certain new equations expressing the relation between the both on the 4th test piece defined in JIS. That is, a General Contraction ψ
g% was considered in addition to a minimum contraction ψ
m%. It is the area contraction of a section that lies at a distance of 3/2 D
0 mm from the minimum sectional area on the longer piece after the test, where D
0 is a diameter before the test. Then we have obtained three equations on the relation between δ and ψ
m, ψ
g, where δ is the percentage of elongation, and it has been found that the calculated values of elongation by these equations coincide well with the measured values. In the three, the following equation is easily applicable to determination of elongation.[numerical formula]
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