| As the heart of an airplane,the aero engine is known as "the flower of industry",and the turbine blade is the brightest one in this flower.Turbine blades work in the most extreme environment of aero gas turbine engines.At present,the turbine inlet gas temperature of the advanced engine has reached about 2000 K,and the turbine speed is tens of thousands,even hundreds of thousands of turns per minute,and the gas flow velocity is up to 150m/s,which makes the turbine blade short life and poor reliability.Its life seriously restricts the whole machine life.In this paper,the turbine blade was used as the research object.Through the finite element simulation analysis,the fatigue-creep test at different temperatures and the theoretical modeling analysis,the multiaxis low cycle fatigue life and the fatigue-creep interaction life of turbine blade were studied.Provide reference and technical support for safety inspection,regular maintenance and subsequent improvement and optimization.The main work of this article was as follows:(1)In view of the problem that the time history of the turbine speed and the exhaust temperature are not true and the amount of data is too large,the cycle load spectrum of the engine was obtained by the false reading elimination,invalid value elimination,peak valley value compression and rain flow counting treatment.The aircraft rise and fall working cycle was divided into one main cycle and four sub cycles,which provided a load basis for subsequent life study.(2)In order to solve the complicated load problem of turbine blade,a thermal-fluid-solid coupling simulation platform was set up by Ansys software.The temperature field and stress-strain field of turbine blade were calculated under the combined action of centrifugal load,pneumatic pressure load and temperature load,and coupling simulation process of the flow-heat transfer-structure integration of the turbine blade was completed under the steady state of each flight load condition.Under the condition 1,the maximum equivalent stress of the blade is 840 MPa at the transition point between the blade and the platform plate,the maximum equivalent elastic strain is 0.8536% at the tail edge of the vents at the middle of the blade,and the highest temperature is 850? at the tail edge of the high exhaust vent of 3/4 leaf.(3)Using the SWT model in the Manson-coffin theory system,the Shang Deguang fatigue damage parameter was introduced,the critical plane method which considers the multi axis effect was modified to improve the fatigue damage parameters.The theoretical model of low cycle-multiaxial fatigue life of the turbine blade was established after the corresponding deduction.The assessment parts of turbine blades were determined by the results of the thermal-fluid-solid coupling simulation and the outfield failure data of the blade,and the simulation samples of the blade were designed: The flange plate simulator and the blade body simulator.The low cycle fatigue tests were carried out on the blade simulators.Based on the test results,the prediction results of various models were compared.The prediction error of the low cycle-multiaxial fatigue life prediction model proposed in this paper was only 3.5%,which showed its rationality.(4)The creep life of the turbine blade was calculated by the heat intensity comprehensive parameter equation.The interaction between creep and fatigue at high temperature was studied by the interaction test of high temperature fatigue-creep.The fatigue-creep interaction life of turbine blades was calculated to be 1552 h,and the results were reduced by 33.4% compared with the fatigue-creep life results based on the linear cumulative damage.Therefore,the effect of fatigue-creep interaction cannot be ignored in the study of the turbine blades life. |
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