【作者】 刘萌；

【导师】 张维峰；

【作者基本信息】 长安大学 ， 车辆工程， 2009， 硕士

【摘要】 汽车行驶时,作用在汽车各部件上的载荷都是动载荷。车架作为汽车结构的主要部分,承受着来自路面和其上各种部件的复杂动载。若这些动载荷的频率与车架的某阶固有频率接近时,车架将产生强烈的振动,这种共振现象不仅会影响汽车的舒适性,还会引起结构很高的动应力,造成较早的疲劳破坏或产生不允许的变形。为使车架在使用中避免共振、确保安全可靠,需要深入了解其动态特性,必要时进行合理的动力修改。模态分析技术是研究构件动态特性的一种行之有效的试验方法,通过试验模态分析技术可以较为准确地得到结构的固有频率和模态振型等模态参数。本文以某车架为研究对象,在综合考虑悬挂条件、激励方式及位置对试验结果影响的基础上,对其进行试验模态分析,得到车架前五阶模态参数;之后,利用路面谱采集试验得到的路面激励信号作为输入,对车架进行动力响应模拟,以得到车架在典型路面上的响应特性;最后,在研究质量和刚度的改变对车架动态特性影响的基础上,探索一种提高车架固有频率的结构动力修改方法,为车架的结构优化提供理论依据。更多还原

【Abstract】 All the loads that act on the automobile’s parts belong to dynamic loads when the vehicle runs on the road. As one part of the automobile structure, the frame withstands the complex dynamic loads coming from the road surface and the other parts that fixed on it. If the frequency of these dynamic load close with some the natural frequency of the frame, the frame will be caused the intense vibration which will not only affect automobile’s comfortableness, but also cause the very high dynamic-load stress, and make the early fatigue failure or the un-allowed distortion happened .In order to prevent the frame’ resonating and make sure the safety and the reliableness in the use, its dynamic characteristic need to be studied deeply and the dynamic modification should be carried on if necessary . The modal analysis is an effective method which studies the dynamic characteristic of the component and structure. The modal parameters such as natural frequency and vibration mode, can be obtain through the modal test exactly.One type automobile frame is regarded as the studied object in this paper. Based on the overall evaluation of the influence on the result by the hanging condition, the excitation method and the point arrangement, the first five modal parameters are obtained through the modal test firstly. Then the simulation force response analysis of the frame is carried on under the typical road surface condition. The simulation force signal is obtained through the road testing for some typical road surface. Finally, a structural dynamic modification method which is going to raise the natural frequency of the frame is explored based on the studying of the dynamic characteristic which influenced by the change of its mass and rigidity. It provided one helpful method for frame structure optimization.更多还原