斜裂纹悬臂梁非线性振动特性分析

Nonlinear vibration characteristics analysis of a cantilever beam with slant crack

针对工程中悬臂杆件可能出现的斜裂纹故障,基于ANSYS软件对斜裂纹悬臂梁的非线性动力学特性进行了分析。仅考虑悬臂梁的弯曲振动,采用混合单元建立了斜裂纹悬臂梁的有限元模型,该模型在裂纹位置采用平面单元(Plane183)来模拟,采用接触单元来模拟裂纹的呼吸效应,在远离裂纹位置采用梁单元(Beam188)来模拟,通过与纯平面单元的振动响应对比,首先验证了模型的精度,其次对比了该模型相对于纯平面单元模型的计算效率;随后还分析了裂纹角度和激振力幅值对系统振动响应的影响。研究表明随着裂纹角度的增加,裂纹导致的系统非线性特性更为明显;系统响应产生的基频及倍频成分幅值与激振力幅值具有线性关系。

Aiming to investigate the slant crack fault of a cantilever bar or beam,this paper analyzes the nonlinear dynamic characteristics of a cantilever beam with a slant crack based on ANSYS software. Assuming that only a bending vibration of the cantilever beam is considered,a finite element( FE) model is established using mixed elements. In the model,the plane elements( Plane 183) are adopted in the crack region and the contact elements are used to simulate the breathing effect of the slant crack. Moreover,beam elements are utilized in the regions that are far away from the crack region. By comparing this with the FE model composed by full plane elements,the accuracy of the developed model is verified; in addition,the calculation efficiency is evaluated. Finally,the effects of crack angles and the amplitude of the excitation force on the vibration responses of the system are also analyzed. The results show that the nonlinear characteristics caused by a slant crack are more obvious with the increasing crack angles. Among the vibration responses,the amplitudes of the base frequency and its multiple frequencies have a linear relationship with the amplitudes of the excitation force.