局部裂纹悬臂梁结构动力学特性试验研究和有限元分析

Experimental Study and Finite Element Analysis on Dynamic Characteristic of Local-crack Cantilever Beam Structure

研究局部带裂纹悬臂梁结构的动力学特性,考虑带有2条贯通裂纹的悬臂梁结构,首先建立3种不同状态下带裂纹悬臂梁有限元模型,通过模态分析,仿真得到振动频率和三阶振型图。然后,将3种状态下的悬臂梁制成试验试件,并进行模态分析试验,将仿真计算结果与试验结果进行了对比,发现有限元数值仿真模型以及方法的准确性,基于验证后的模型和数值仿真方法,通过对大量不同参数模型的计算分析不同裂纹深度和不同裂纹位置对缺陷悬臂梁动力学特性的影响,并发现一定规律:带裂纹悬臂梁振动频率受裂纹的影响较大,阶数越高对频率的影响越大,然而对振型幅度的影响越小;随着裂纹的加深,对悬臂梁振动频率影响也越显著;裂纹距离对悬臂梁动力学特性也有一定影响,当距离悬臂端越近,悬臂梁第一阶和第二阶振动频率将受到较大的影响,而当裂纹远离悬臂端时,第三阶振动频率受到较大影响;对比三阶振动,裂纹对悬臂梁第一阶振动的影响最为显著,且当裂纹深度较小时,三阶振动频率随裂纹位置的变化均不明显。

This paper studies dynamic characteristic of local-crack cantilever beam structure.Taking two long cracks on the steel girder into consideration,three finite element models of local-crack cantilever beam were built in three different states.Based on model analysis,vibrational frequency and three-order vibration chart were put forward through simulations.Then,the steel girder was made into test sample to conduct modal analysis.Compared simulation results with test results,the accuracy of finite element simulation model and its method were both verified.Based on validated model and numerical simulation method,through a lot of various parametric model calculations,this paper analyzes the effect of different crack depths and different crack locations on dynamic characteristics of the defective cantilever beam.Besides,a certain rule was found that the cantilever beam with cracks had more effects on vibrational frequency.The higher the order was,the bigger the effect was,while the smaller the modal amplitude was.With the deepening of the crack,the effect on vibrational frequency of the cantilever beam was becoming more and more significant.What’s more,the crack distance also had certain effect on vibrational frequency.If the crack was close to the end,the first-order and the second-order vibrational frequency had been greatly affected.However,if the crack was far away to the end,it turned to be the third-order vibration frequency.By comparing three-order vibrations,the crack had more significant effect on the first-order vibration of the steel girder.While the crack depth is small,the effect of crack location on all three-order vibration frequency is not obvious.