Dynamic Reliability Modeling And Analysis Of An Aero-engine Turbine Blade

Turbine blade，as one of the key components of aero-engine, can decide the meritsof performance of the engine and also whether its work is reliable or not to the verylarge degree. In running state, turbine blade not only withstand the alternating forceincluding the tremendous centrifugal force, the temperature stress produced by thechanges of temperature and the effect of aerodynamic load caused by high temperatureand high pressure gas, but also as the change of operating temperature and frequency ofloading actions, the turbine blade working under high temperature is very likely tobecome creep damage and fatigue damage. With the rise of operating temperature, themechanical properties of blade reduce gradually and the safety margin decline in thegreater degree, further cause the fatigue failure of the blade.To solve the above problem, this paper takes the low pressure turbine blade ofsome aero-engine for the research object. On the basis of the thorough analysis of thefailure mode of blade, and the consideration of the influence offrequency of loading actions, the dynamic reliability model of turbine blade in somefailure mode is set up according to the stress-strength interference mode1. The maincontents of the paper are as follows:(1) Taking the influence of frequency of loading actions on reliability into account,the dynamic reliability model of the parts in a single or multiple failure modes isanalyzed and discussed under the circumstance that the strength of mechanical partsdoes not change over time.(2) According to the spatial data point of turbine blade obtained by the scan ofnon-contact measurement equipment, the data acquisition of blade is processed by useof the reverse modeling software Imageware, the corresponding curve and curvedsurface are constructed, and also the diagnosis and quality evaluation are conducted.Only the precision of curved surface meets the requirements of the corresponding users,then certain operation can be imposed to build the complete blade shells. In UGthree-dimensional modeling software, the three-dimensional entity model of blade isstructured by use of the corresponding operation. (3) The finite element analysis model of turbine blade is established based onANSYS Workbench. Owing to that turbine blade mainly endure the action of threekinds of load such as centrifugal force, thermal stress and aerodynamic force, firstly thetemperature field and the stress field of the blade are obtained through the conduction offlow field simulation to the turbine blade by use of fluid analysis module Fluid Flow(CFX), then the thermal stress can be calculated according to the corresponding module.In different operating conditions, the blade is applied the corresponding rotational speed,loads and boundary conditions. Finally, the calculation and analysis of blade stress andstrain are completed in the Static Structural Static analysis module.(4) According to the working characteristics of the engine, the working conditionof the engine “start-operation-stop” every time is regard as one-time loading action andthe distribution of the equivalent load is established when the load cycle n times.According to the dynamic reliability model of mechanical parts, on the basis of the onlyconsideration of low cycle fatigue of blade, the dynamic reliability of turbine blade willbe computed under single failure mode and multiple failure modes, consideringdifferent failure mode of blade.