| How to accurately predict the life of structure under the complex multiaxial stress has been thefocus of academic circles. But the multiaxial fatigue problem is very complicated, although there hasbeen some progress on the multiaxial fatigue research, but the theory is still immature. Therefore tosolve multiaxial fatigue prediction method has the important theory significance and the practicalsignificance.Proportional and nonproportional tension-torsion fatigue tests were conducted on thin-walledtubular specimens of45steel. Axial tension-compression, torsion, in-phase,45°out-of-phase and90°out-of-phase loading paths were selected. The paper analysised all specimens of hysteresis loop,and the damage ratio circulation ratio rule. Another series of biaxial two-path variable mode loadingtests were conducted. Several popular damage accumulation rules are examined with the test dataobtained in this study. A new nonlinear damage mode based on Manson mode was proposed. Themodel adopts45steel path multiaxial fatigue test results, LY12CZ aluminum alloy variable pathmultiaxial fatigue test results,304stainless steel variable path multiaxial fatigue life prediction andexperimental results, and the Miner model, Manson model and Ye Duyi model are compared with theresults.The paper verified this new nonlinear damage mode, and the predicted results show goodagreement with experimental results.Respectively applied uniaxial and multiaxial approach, the aircraft horizontal tail connectorservice life was predicted. Multiaxis method mainly adopts the maximum shear stress near theinterface method. On the maximum shear stress critical plane concept of fatigue life analysis, thepaper used Dang Van high cycle fatigue failure criterion on dangerous points of damage calculation,finally using the Miner linear cumulative damage theory of damage accumulation, to get the finalstructure life. The results show that, uniaxial stress method for prediction of life is much higher thanthat of multi axis method. |
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