On The Study Of Creep Damage Mechanism And Elasticplastic-creep Model Of P92 Steel Notch Specimen

The reason related to creep accidents not only including the material characteristic,but also including the increase of unit parameters.As for the research on creep,the creep life and fracture position will become the most valuable contents.The researches of multi-axial creep are mainly by two methods,that is the experiments and finite element models.The former experimental results can be produced by the qualitative conclusions,but it is difficult to put one result to other samples.The finite element analysis parameters need to use the uniaxial creep experimental datas,and of notch specimens.After fitting the parameters.The simulate including two stages,the first is to experience a very short time process of elastic creep process,then a long time creep process,therefore we call it elastic-creep model.But,with the better fitting parameters,the fitting conclusion of elastic-creep model is not completely corresponding to the experimental conclusion,that is this model should be changed.This paper established the elastic-plastic-creep model under multi-axial stress state,firstly we discuss the applied conditions for different gap shapes.Then respectively using elastic-creep model and elastic-plastic-creep model under multi-axial stress state to simulate the creep process.Focuses on the damage distribution under two models and from the corresponding stress distribution to seekthe reasons.At the same time we make the study of the changes of damage distribution and creep life with different yield limit and stress coefficients.Finally,by the corresponding experiment to find the largest damage location.On the one hand,to search for the creep fracture mechanism.On the other hand,according to the micro fracture cross section and hardness of the related phenomenon to explore the damage distribution.the simulated results can be validated.The results show that under high temperature and stress,the P92 steel specimens in the initial stages is easy to get yield limit,then to produce plastic deformations.So the elasticplastic-creep model simulates better.After the application of elastic-plastic-creep model,the creep life ofsamples reduced with the increase of notch radius,andthe maximum damage locationgradually moved from the roots towards the centreof minimal cross section.This is because the plastic deformation changed the stress distribution of each cross sections,which weaken the stress of the notch root areas at the same time to strengthen the stress of the middle areas.As the change of P92 steel contains trace elements or the rise of temperature,the material yield limit is reduced,which will further increase the plastic deformation and reduce the creep life.By the results of experiments,the hardness minimum position and the most holes position for u-shaped notch specimens,has a distance from the notch root,that is elastic-plastic-creep model is more accurate than elastic-creep model.