The material constitutive relation at high temperature was related to time and could be indicated by isochronous stress-strain curve.Experiments on P91 steel,such as instantaneous tensile tests at 600℃,high-temperature instantaneous tensile tests after 100,500 and 900 h creep tests,and creep rupture tests,were performed respectively.The results showed that the isochronous stress-strain curve was extremely conservative to describe the material constitutive relation of P91 steel after high-temperature creep damage.By defining creep damage under high temperature based on life fraction parameter,the relation of tensile strength of P91 steel with creep damage was obtained,and the isochronous stress-strain curve at high temperature was modified,therefore,the constitutive relation equation of P91 steel with creep damage at high temperature was established.%高温下材料的本构关系和时间相关,可以由高温等时应力-应变曲线表示.对P91钢分别进行高温(600℃)短时拉伸实验,高温蠕变100、500和900 h实验之后的高温短时拉伸实验,以及完整的蠕变断裂实验.结果表明:用高温等时应力-应变曲线描述P91钢高温蠕变损伤后的本构关系极为保守.由此,引入寿命分数参数定义材料的高温蠕变损伤,获得了P91钢发生高温蠕变损伤后材料抗拉强度与蠕变损伤的关系,修正了高温等时应力-应变曲线,建立了基于蠕变损伤的P91钢应力-应变本构方程.
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