Numerical Simulation And Experiment Investigation Of Creep-fatigue Crack Growth Of P92 Steel

In the aerospace,petrochemical,thermal power and other industries,many components which serve in high temperature conditions will not only bear a constant working load,but also undergo the machine start-stop controlling,load fluctuations and other changes in the load.Therefore,these components are subjected to the combined action of high temperature creep and high temperature fatigue.Creep-fatigue failure is one of the main failure modes of high temperature components which is an essential subject to research.Therefore,in this paper,the creep-fatigue crack growth behavior of P92 steel was studied by numerical simulation,and the relevant experimental verification was also carried out.The main contents are as follows:(1)Based on continuum damage mechanics,this paper has proposed a creepfatigue damage model on the basis of creep toughness dissipation theory and thermodynamics theory,and it considers the creep-fatigue interaction by adding the third term.The damage model and stress strain constitutive equation constitute the creep-fatigue crack propagation model together.(2)By finite element simulation of creep-fatigue crack propagation of P92 steel,the effects of different holding time,crack depth and specimen dimension on creepfatigue crack growth behavior were investigated.It was found that the crack growth rate increased as the hold time reduced.At initial stage,the crack growth rate of 60 s hold time condition is approximately four times of that for 600 s hold time condition,and as crack grows the crack growth rates of different hold time tends to become the same.Under the same stress level,the increases of crack depth and specimen dimension would enhance the crack propagation.That is induced by the constraint effects caused by the increase of crack length and specimen dimension.(3)The effects of different holding time and different crack depth on the crack growth behavior were studied by the creep-fatigue crack growth experiments of P92 steel at 630 ?.It was found that the crack growth rate increased with the reduction of hold time and the increase of crack length.By comparison,the predictions agree well with experimental results,which shows that the creep-fatigue crack growth simulation method is reliable and effective.