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在800℃条件下,对国产压力容器(RPV)用A508-Ⅲ钢分别进行17.5 MPa、20 MPa和27 MPa 3种载荷下的蠕变试验及部分载荷下的蠕变中断试验(20 MPa和27 MPa)。微观组织及蠕变曲线研究表明,随着蠕变时间的增加,试样内空洞及第二相粒子的体积分数近似成线性增长;由此可以推断蠕变空洞萌生、扩展及第二相粒子的粗化是造成蠕变损伤的主要原因。本研究从细观力学思路出发,结合A508-Ⅲ钢蠕变过程中微观损伤机理,通过定义无损相、空洞相和第二相粒子相组成三相复合体作为代表性体积单元,提出考虑微结构损伤及演化的K-R蠕变本构方程。通过归一化处理,最终获得反映空洞及第二相粒子演化的蠕变本构方程和损伤演化方程的形式,建立微观结构损伤与本构方程之间的内在联系。
The creep tests under partial load of 17.5 MPa, 20 MPa and 27 MPa and the creep rupture tests under partial load (20 MPa and 27% respectively) were carried out at 800 ℃ for A508-Ⅲ steel made in domestic pressure vessel (RPV) MPa). The results of microstructure and creep curve show that the volume fraction of cavity and second phase particles increases approximately linearly with the increase of creep time. From this, it can be inferred that the creep cavity is initiated and expanded and the second phase particle Coarsening is the main cause of creep damage. In this paper, starting from the meso-mechanics, combined with the microscopic damage mechanism in the creep process of A508-Ⅲ steel, by defining the three-phase composite of non-destructive phase, hollow phase and second phase particle as the representative volume unit, Damage and Evolution of KR Creep Constitutive Equation. Through the normalization process, the creep constitutive equations and damage evolution equations that reflect the evolution of voids and second-phase particles are finally obtained, and the intrinsic relations between the damage of the microstructure and the constitutive equation are established.