Research On Stress Relaxation Behavior And Finite Element Simulation Of GH4169 Alloy

GH4169 alloy is a precipitation hardening nickel-based superalloy.Due to its high yield strength,good oxidation resistance,radiation resistance,fatigue resistance and corrosion resistance at high temperatures,GH4169 alloy is widely used in spacecraft,Such as turbine disks,blades,casings,fasteners,etc.Metal stress relaxation phenomena are common in high-temperature structural components.The occurrence of stress relaxation will cause the preload force inside the component to attenuate over time,which in turn will cause leakage or loosening of the seal.Under space environmental conditions,various fasteners in the engine are under high load and temperature conditions,so the material will produce slack failure.However,based on comprehensive domestic and foreign studies,there are few studies on the stress relaxation behavior of GH4169 alloy.In addition,the relationship between the material's anti-relaxation performance and temperature and initial stress is lacking.In this paper,the effects of temperature and initial stress on the stress relaxation behavior of GH4169 alloy under different temperature(600?,650?,680?)and initial stress(580 MPa,680 MPa,780 MPa)were studied.The test results show that the stress relaxation curve of GH4169 alloy exhibits typical characteristics of periodic stress relaxation,and temperature has a greater influence on stress relaxation.In addition,the first,second,and third decay functions were used to mathematically characterize the stress relaxation process of GH4169 alloy.The results show that the second and third decay functions have a better fitting effect,and the third decay function has a higher degree of fitting.Based on the relationship between stress relaxation and creep,this paper studies the effects of temperature and initial stress on creep rate.The results show that there is a threshold stress that divides the stress relaxation process into a high-stress phase and a low-stress phase.The relaxation rate in the high-stress phase is high and stable,the plastic strain rate in the low-stress phase decreases rapidly,and both the temperature and the initial stress increase Threshold stress increases.When the temperature increased from 600? to 680? and the initial stress increased from 580 MPa to 780 MPa,the creep rate of GH4169 alloy in the initial stage increased from 0.01×10-3h-1 to 3.35×10-3h-1,and the initial creep rate increased by about 350 times.The steady-state creep process was used to indirectly reflect the dynamic changes of GH4169 alloy in the stress relaxation test,and the stress relaxation constitutive equation of GH4169 alloy was established.The stress relaxation process of GH4169 alloy is simulated by ABAQUS finite element simulation software.From the comparison between the simulation results and the experimental results under different temperatures and initial conditions,it can be seen that the stress relaxation limit value and stress relaxation changes after stress relaxation based on ABAQUS finite element software The rate is close to the test result,which conforms to the law of test change,and the error between the two is small,not exceeding 4%,which also shows that the finite element simulation results are in good agreement with the experimental results,and also proves the established stress The correctness of the relaxation constitutive model has laid the foundation for the hot forming process of GH4169 alloy.