Multi-axial Fatigue Life Prediction And Test Verification For Typical Landing Gear Components

Fatigue life predictions of structure under complex loads have been the key point of fatigueresearch in recent years. Multi-axial fatigue research is relatively complicated because of theinfluence of more factors.The great majority of machines and engineering structures serve undermulti-axial stress states.Uniaxial fatigue theory can not meet the needs of anti-fatigue design forhigh-tech products, so people pay more attention to multi-axial fatigue study. As the main bearingparts the leading gear suffers multiple loads in the rollout and landing situations.The research offatigue life udnder the complex loading conditions has a great important meaning in practicalengineering.The effect of the surface deformation strengthening on the workpiece structure fatigueperformance was analysed in this dissertation,then the mechanism of how the deformationstrengthening technology of shot peening、rolling and spurling to improve the fatigue limit andengineering application were elaborated in detail. We studied the crack initiation and propagationmechanism under multi-axial proportion loads and fracture surface, and steady state cyclic stressstrain relationship under multi-axial proportional load, as well as multi-axial fatigue damageparameters, and then summarized some prediction methods of multi-axial low-cycle fatigue life andestimation accuracy;built the low-cycle fatigue life estimation method under multi-axial proportionalloading based on the concept of critical plane; estimated the fatigue life of a certain type of aircraftmain landing gear typical structure on the basis of the proposed model, and obtained the low-cyclefatigue life under proportional loads.The compared test on the typical landing gear structures with and without surface strengtheningtreatment has been finished. It is concluded that under the some conditions the fatigue life of shotpeening is better than the general one. The research of the fatigue life of structure under multi-axialproportional loads provided optimization design reference to the weak point of the typical leadinggear structure.