A self-consistent creep damage constitutive model and a finite element model have been developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The m...A self-consistent creep damage constitutive model and a finite element model have been developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The model parameters are determined from the creep test data of a single crystal and a directionally solidified superalloy with a special crystallographic orientation. The numerical analysis shows that the modeled creep damage behaviors of nickel-base directionally solidified super-alloys with different crystallographic orientations are in good agreement with the experimental data.展开更多
In order to study the failure criterion of porous surrounding rock of tunnel in cold regions under the action of low temperature frost heave,the frost heave force and stress intensity factor of surrounding rock are so...In order to study the failure criterion of porous surrounding rock of tunnel in cold regions under the action of low temperature frost heave,the frost heave force and stress intensity factor of surrounding rock are solved based on frozen rock mechanics,fracture mechanics and meso-damage mechanics.The stress corrosion limit of rock instead of fracture toughness is taken as the crack initiation criterion.Under the action of single frost heave,the frost heave failure criterion of surrounding rock is established for the“main-side branch”pore structure which is prone to frost heave failure;Under the action of continuous frost heave,it is regarded as freeze-thaw cycle,the effect of rock debris loss during the cycle is considered,and the frost heave failure criterion of surrounding rock is established.Relying on the verification of the reliability of the instability criterion of a tunnel in a cold region of Tibet,it is found that the stress intensity factor of surrounding rock calculated by traditional fracture mechanics may be quite different from the real value.The above engineering examples are used to analyze the effect of different parameters on the stress intensity factor of surrounding rock.The results show that the stress intensity factor of surrounding rock is proportional to the axis diameter of main hole and water pressure.The growth rate of the stress intensity factor of the former in the initial stage is significantly higher than that in the late stage,while the latter increases almost linearly;It is inversely proportional to the ambient temperature and toughness ratio of surrounding rock,and the effect of temperature on surrounding rock instability is more obvious.The research results can improve the understanding of the frost heave failure characteristics of surrounding rock and improve the theoretical basis for the long-term stability of tunnel engineering in cold regions.展开更多
文摘A self-consistent creep damage constitutive model and a finite element model have been developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The model parameters are determined from the creep test data of a single crystal and a directionally solidified superalloy with a special crystallographic orientation. The numerical analysis shows that the modeled creep damage behaviors of nickel-base directionally solidified super-alloys with different crystallographic orientations are in good agreement with the experimental data.
基金Science and Technology Research Project of Jiangxi Provincial Department of Education(GJJ170562)。
文摘In order to study the failure criterion of porous surrounding rock of tunnel in cold regions under the action of low temperature frost heave,the frost heave force and stress intensity factor of surrounding rock are solved based on frozen rock mechanics,fracture mechanics and meso-damage mechanics.The stress corrosion limit of rock instead of fracture toughness is taken as the crack initiation criterion.Under the action of single frost heave,the frost heave failure criterion of surrounding rock is established for the“main-side branch”pore structure which is prone to frost heave failure;Under the action of continuous frost heave,it is regarded as freeze-thaw cycle,the effect of rock debris loss during the cycle is considered,and the frost heave failure criterion of surrounding rock is established.Relying on the verification of the reliability of the instability criterion of a tunnel in a cold region of Tibet,it is found that the stress intensity factor of surrounding rock calculated by traditional fracture mechanics may be quite different from the real value.The above engineering examples are used to analyze the effect of different parameters on the stress intensity factor of surrounding rock.The results show that the stress intensity factor of surrounding rock is proportional to the axis diameter of main hole and water pressure.The growth rate of the stress intensity factor of the former in the initial stage is significantly higher than that in the late stage,while the latter increases almost linearly;It is inversely proportional to the ambient temperature and toughness ratio of surrounding rock,and the effect of temperature on surrounding rock instability is more obvious.The research results can improve the understanding of the frost heave failure characteristics of surrounding rock and improve the theoretical basis for the long-term stability of tunnel engineering in cold regions.
