Turbine Disc Creep And Low Cycle Fatigue Life Reliability Analysis Method

For turbine discs, the hot section components of gas turbine engine, fatigue and creep are two important failure mechanisms. Creep damage and fatigue damage increase with applied loading cycles in a cumulative manner, and the interaction between creep damage and fatigue damage may be significant. So, analysis for creep-fatigue damage plays an important role in the life prediction of turbine discs. Moreover, metallic material under high level stresses at elevated temperature can produce creep deformation significantly. For turbine discs, stress relaxation may be occurred, considering the influence of stress relaxation or not may be leaded to several times or even hundred times difference in the result of life prediction.Considering the problem described above, in this paper, new idea, new method and contribution were described below:1) Creep strain probabilistic model was proposed, this model and creep rupture life probabilistic model were first used in creep rupture life reliability analysis of turbine discs and creep-fatigue life reliability analysis of turbine discs.2) A creep rupture life reliability analysis method of turbine discs with the influence of stress relaxation was proposed. In this method, Central Composite Design Method, included in ANSYS program, was used to sample for each random variables. Then, a damage critical rupture function can be got by fitting the results of finite element creep analyses with stress relaxation, considering the influence of the scatter of material and loading data. Next, Monte-Carlo method was used to obtain the creep rupture life with given reliability. Finally, the influence of stress relaxation and each random variable on creep rupture life was analyzed.3) In this paper, a creep-fatigue damage Second Order approach method for creep-fatigue life estimating of turbine discs was proposed with the influence of stress relaxation. Base on this method and the response surface method, a creep-fatigue life reliability analysis method for turbine discs was proposed with the influence of stress...