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首页> 外文期刊>Journal of Sound and Vibration >Influence of alternating loads on nonlinear vibration characteristics of cracked blade in rotor system
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Influence of alternating loads on nonlinear vibration characteristics of cracked blade in rotor system

机译：交变载荷对转子系统裂纹叶片非线性振动特性的影响

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摘要

As important causes of fatigue and crack failure, alternating loads also affect vibration characteristics of cracked blades in rotor system and probably influence formulation of diagnostic rule. This work carried out analysis of nonlinear vibration of cracked blade in rotor system with crack breathing effects and alternating loads taken into account. Firstly, equations of motion are formed with Finite Element Method (FEM), and breathing crack is modeled with cracked hexahedral element (CHE) where the breathing behavior is load dependent, Secondly, displacement responses of cracked blade are obtained, and the results with CHE and contact element are identical. The stiffness of the cracked blade is obtained with CHE and proved to be time varying and dependent on the alternating loads. Thirdly, natural frequencies of cracked blade in stationary condition are analyzed including normal model, linear model (open crack) and nonlinear model (breathing crack), and the requirement of the inclusion of breathing effects in blades with fatigue crack is proved. Finally, influence of alternating loads on critical frequency of cracked blade in rotating condition is compared. The results show that the critical frequency is significantly affected due to the co-effects of the rotating speed and alternating loads. The proposed method can estimate nonlinear vibration characteristics of crack blade which is beneficial for the formulation of the diagnostic rule. (C) 2015 Elsevier Ltd. All rights reserved.
机译：作为疲劳和裂纹破坏的重要原因，交变载荷还会影响转子系统中裂纹叶片的振动特性，并可能影响诊断规则的制定。这项工作在考虑了裂纹呼吸效应和交变载荷的情况下，对转子系统中裂纹叶片的非线性振动进行了分析。首先，通过有限元方法（FEM）形成运动方程，并使用裂纹六面体元素（CHE）对呼吸裂纹进行建模，其中呼吸行为与载荷有关，其次，获得裂纹叶片的位移响应，并使用CHE进行计算和接触元件相同。裂纹刀片的刚度是通过CHE获得的，并且证明是随时间变化的，并且取决于交变载荷。第三，分析了裂纹叶片在静止状态下的固有频率，包括正常模型，线性模型（开放裂纹）和非线性模型（呼吸裂纹），并证明了疲劳裂纹叶片中包含呼吸效应的要求。最后，比较了交变载荷对旋转条件下裂纹叶片临界频率的影响。结果表明，由于转速和交变载荷的共同影响，临界频率受到显着影响。该方法可以估计裂纹叶片的非线性振动特性，有利于诊断规则的制定。 （C）2015 Elsevier Ltd.保留所有权利。

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