摘要
为研究玉米收获机车架振动特性及其优化方法,该文通过振动测试与模态分析方法,分析车架田间振动特性,并以提高1阶扭转频率为目标优化车架结构。首先,通过有限元建模及模态分析,提取车架固有频率与振型,其次,通过整机田间振动试验,获取车架4个测点处振幅统计特征及功率谱,分析其对车架振动特性的影响,最后,研究车架壁厚和刚度与固有频率的关系,以提高车架1阶扭转频率为目标优化车架。研究结果发现,测点振幅大小依次为:车架后桥上方、发动机横梁位置、发动机纵梁位置、车架前桥上方,其中车架后桥上方振幅已超过发动机振幅,发生共振;模态振型与田间振动试验对比发现,1阶扭转和2阶弯曲模态对车架振动影响较大,引起车架共振主频为9.79 Hz,接近1阶扭转共振频率;发现优化后车架1阶扭转振型位移由7.778下降到3.768,1阶弯曲振型位移由6.83下降到3.651,显著改善了车架振型,1阶扭振频率由15.9927提高到22.4595 Hz,提高车架1阶扭转频率。田间耐久试验表明优化后车架无故障时间由20提高到60 h。该研究可为农机装备的振动特性分析与减振设计提供参考。
The low level of Chinese corn harvest seriously has restricted the corn harvest mechanization. Modal analysis is a very important and useful method for various engineering applications, such as design and dynamic test. There are few researches on vibration test and modal analysis of corn combine harvester frame, which is a key part of the corn harvester. During the harvester＇s operation, the frame carries and supports the assembly and components, such as engine, cutting header, cab, picking mechanism, elevator, granary, tank, and all alternating loads will eventually pass to the frame. When the vibration frequency is caused by the external excitation and closed to the natural frequency of the frame, it will produce resonance phenomenon, which accelerates the frame strength failure, and therefore affects the dynamic performance and reliability of the frame structure. Using the method of combining the vibration test and modal analysis, this paper studies the vibration characteristics and optimizes the frame, which has the guiding significance for the corn combine harvester design and optimization. Firstly, the paper studies the finite element modeling and analysis method of the frame, and obtains the natural frequency and vibration mode based on the theory of modal analysis. Secondly, using the method of time domain and power spectrum analysis, the paper analyzes the field road test data, and gets amplitude characteristics and power spectrum at 4 measuring points of the frame, as well as attains the excitation frequency of road roughness which is concentrated in the range from 0 to 2.4 Hz, and the whole machine key components＇ excitation frequency, and studies the influence of the frame. Eventually, this paper studies the influence of discontinuous change of the interval of frame wall thickness and stiffness on the frequency and mode, improves the first-order frequency based on the fundamental frequency optimization method, and then puts forward the improvement scheme and optimized frame structure. The result shows that the vibration frequency of the rear bridge above the frame is 9.79 Hz, close to first-order resonance frequency, which has caused resonance and strength failure. At the same time, the vibration amplitude of the frame from high to low is as follows： the rear bridge above the frame, the engine beam position, the engine longitudinal beam position, and the front bridge above the frame. The vibration amplitude of the rear bridge above the frame exceeds the engine amplitude, which illustrates the resonance has occurred. After the optimization, the first-order natural frequency of frame keeps away from the external excitation, which increases from 15.9927 to 22.4595 Hz, and at the same time, after the optimization of vibration shape, the first-order torsional eigen mode magnitude decreases from 7.778 to 3.768; the first-order bending eigen mode magnitude decreases from 6.83 to 3.651, which has improved the mode shape. The durability test shows that the failure rate of optimized frame is reduced, and the mean time without failure increases from 20 to 60 h. This paper presents the modeling analysis, vibration test, data processing and structure optimization method, and provides a good reference for corn combine harvester vibration control and performance optimization.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第19期46-53,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
现代农业装备与技术协同创新中心资助项目(NZXT01201401)
教育部博士学科点专项科研基金资助项目(20130008110043)
关键词
农业机械
振动
优化
玉米收获机
车架
模态分析
agricultural machinery
vibrations
optimization
corn combine harvester
frame
modal analysis
