Fatigue life evaluation method for low-pressure turbine shaft

Abstract

The invention provides a fatigue life evaluation method for a low-pressure turbine shaft, and the method comprises the steps: obtaining a stress amplitude equivalent factor C1 = F1(Nf)/F2(Nf) according to a smooth SN curve sigma max = F1(Nf) and a tau-N curve equation tau max = F2(Nf) under the condition that the stress ratio R of a material used by the low-pressure turbine shaft at a given temperature is equal to -1; calculating an average stress equivalent factor C2 = sigma b/tau b according to the tensile strength sigma b and the shear strength tau b of the material used by the low-pressureturbine shaft at the given temperature; according to the stress amplitude equivalent factor C1, the bending stress sigma u, the vibration torque shear stress delta tau, the bending stress concentration coefficient K sigma and the torsional stress concentration coefficient K tau, calculating an equivalent stress amplitude sigma a by utilizing a formula; according to the average stress equivalent factor C2, the axial stress sigma z, the main torque shear stress tau, the bending stress concentration coefficient K sigma and the torsional stress concentration coefficient K tau, calculating an equivalent stress amplitude sigma a by utilizing a formula; converting the equivalent stress amplitude sigma a and the equivalent stress amplitude sigma m into symmetrical cyclic stress sigma-1; and evaluating the fatigue life of the low-pressure turbine shaft according to the symmetric cyclic stress sigma-1.

Description

technical field [0001] The present application relates to the field of engines, in particular to a method for evaluating the fatigue life of a low-pressure turbine shaft. Background technique [0002] The main loads on the low-pressure turbine bearings of aero-engines include: main torque, axial force, vibration torque and bending moment generated by maneuvering overload. The main torque and axial force are low-frequency fatigue loads. High frequency fatigue loading. The main torque and vibration torque act on the low-pressure turbine shaft in the form of shear stress, and the axial force and bending moment act on the low-pressure turbine shaft in the form of tensile stress. The main torque and axial force belong to the steady state load, generally take the maximum value of each working state of the engine, the vibration torque takes 10% of the main torque, and the bending moment is generated by the motor overload. [0003] Take the life analysis of continuous work for 15s...

AI Technical Summary

Problems solved by technology

Conventional Analysis Methods Reduce Accuracy of Fa

Images