For metals that experience the gradual elastic-plastic transition, the point of yielding is determined as the initial departure from linearity of the stress-strain curve and this is sometimes called the proportional limit.

• 对于金属逐步的弹塑性形变转变，其屈服点确定为应力－应变曲线非线性关系的开始，这个点也被称为比例极限。