Abstract
Many mathematical formulas have so far been proposed to represent the stress-strain curve in the plastic range. However of these formulas, there are many that are not fit to express the actual curves accurately and are too complicated for convenient application, and it is often difficult to determine the constants in these formulas.
In this paper, the following stress-strain formula which contains three constants is proposed for the plastic range.
σ/E=εy+k2/εy+a-k2/ε+a,
where σ: the true stress, E: the modulus of elastisity, ε: the natural strain and k, a, εy: the constants.
As a result, the experimental values of several materials which have been obtained by tension and compression test agree well with this formula within 10% strain.
It is shown, furthermore, that this formula can be applied to the prestrained materials as well as to the fully annealed materials, and the constants in it have well-defined physical meanings. The term k is the constant which suggests the characteristic of strain-hardening, a the constant which is varied by the magnitude of prestrain, and εy the yield strain.
