【作者】 杨昆；

【导师】 徐平；

【作者基本信息】 辽宁工程技术大学 ， 机械设计及理论， 2013， 博士

【摘要】 汽车车架是车辆最主要的承载和吸能部件,其耐撞性及动态特性的优劣直接关系着汽车的舒适性、平顺性和碰撞安全性。为了进一步提高车架结构的耐撞性和动态性能,考虑将新型吸能结构材料泡沫铝填充到车架结构中,以期提高结构耐撞性和动态特性。因此,本文将泡沫铝填充到汽车车架结构中主要的吸能部件——薄壁方管中,以其简化的泡沫铝填充方管模型为研究对象,采用实验、理论分析和数值模拟技术围绕其能量吸收性能和阻尼性能进行了深入研究。在此研究的基础上,利用有限元数值模拟方法对泡沫铝填充汽车车架结构耐撞性和动态性能进行了研究。主要研究的内容和得出的结论如下：综合采用实验、有限元模拟和理论分析的方法,分别对空方管和泡沫铝填充方管结构的轴向压缩和三点弯曲性能进行了研究,建立了泡沫铝填充方管结构静动态压缩和弯曲力学行为和能量吸收性能的理论模型,并利用实验结果验证了有限元模拟结果和理论分析结果。研究结果表明,泡沫铝材料的填充显著提高了方管结构轴向压缩和弯曲的承载能力和能量吸收性能。采用粘胶的连接方式能进一步提高了填充结构的抗弯刚度及承载能力,但使得填充结构在较小的转角就发生了破坏。综合运用实验、有限元模拟的方法,分别对空方管、无粘胶和有粘胶两种形式的泡沫铝填充方管的阻尼性能进行了研究,并分析了其阻尼作用机制。研究结果表明,实验结果与有限元模态分析结果基本一致,泡沫铝材料的填充提高了空方管的阻尼性能,而粘胶的连接方式影响了泡沫铝填充方管阻尼性能的发挥。以某皮卡车的车架结构为原型,设计了泡沫铝填充结构车架。应用Hypermesh软件建立了泡沫铝填充车架的有限元模型。以我国NCAP中正面碰撞刚性壁障的指标为依据,应用LS-DYNA软件对泡沫铝填充车架的整车碰撞安全性进行了模拟分析。分析结果表明,汽车车架结构中填充泡沫铝材料使得车架纵梁吸收了更多的碰撞冲击能,变形幅度减小碰撞加速度降低,从而提高了整车的碰撞安全性。利用有限元仿真的方法对原型车架和泡沫铝填充结构汽车车架的自由模态和约束模态进行了分析,并将模态结果进行对比分析。分析结果表明泡沫铝填充结构车架的自由和约束模态的动态特性参数较原车架有所改善。在车架约束模态分析的基础上,对泡沫铝填充结构车架和原车架在随机路面输入功率谱激励作用下的振动响应进行了有限元分析。分析结果表明,原车架和泡沫铝填充结构车架共振频率分别为其结构对应的第一阶和第九阶固有频率,而泡沫铝填充结构车架的共振响应要低于原车架的响应。填充泡沫铝材料是提高车架的动态特性,并由此提高汽车行驶平顺性的一种有效方法,具有广阔的应用前景。更多还原

【Abstract】 The vehicle frame is the most important bearing and energy-absorbing parts, which crashworthiness and dynamic characteristics is directly related to comfort, ride performance and crash safety of car. In order to further improve the crashworthiness and dynamic characteristic of frame structure, the new type energy-absorption material foam aluminum is considered to fill into the frame structure. Therefore, the foam aluminum is filled into the thin-walled square tube, which is the main energy-absorbing component of automobile frame structure. And square tube filled with foam aluminum is taken as the research object to further research its energy-absorbing and damping performance by using experiment, theoretical analysis and numerical simulation method. Based on the research above, the crashworthiness and dynamic performance of car frame filled with foam aluminum are studied by using finite element numerical simulation method. The main contents and conclusions of this dissertation are as follows:The axial compression and three-point bending performance of square empty tube and square tube filled with foam aluminum are studied by comprehensive using experiment, finite element simulation and theoretical analysis method, respectively. The mechanical behavior and energy absorption property theoretical model of square tube filled with foam aluminum are established under static and dynamic compression and bending. And the results of finite element simulation and theoretical analysis are verified by using experiment results. The results show that the foam aluminum filling can significantly improve the bearing and energy absorption performance of square tube structure under compression and bending deformation. The adhesive connection mode can further improve the bearing capacity of filling structure, but it also make the structure destroyed in a smaller angular easily.The damping properties of empty square tube, two forms of foam aluminum filling square tube (with glue and without glue) are studied by using experiment and finite element simulation method, respectively. And the mechanism of damping is also analyzed. The results show that the experiment and finite element modal analysis results are basically the same. The foam aluminum filling can improve the damping performance of square empty tube. And the adhesive connection mode has a bad influence on the damping performance of square tube filled foam aluminum.By taking a certain type frame structure of pickup truck as a prototype, the frame structure filled with foam aluminum has been designed. And the finite element model of frame filled with foam aluminum is established by using Hypermesh software. Based on the parameters of frontal crash against a rigid wall in C-NCAP, the crash safety of whole vehicle which contains frame filled with foam aluminum is simulated by using LS-DYNA software. The results show that the longitudinal beam filled with foam aluminum can absorb more impact energy than original frame type, and the deformation amplitudes and collision accelerations of filled structure frame are reduced. Thus, the filled structure can improve the crash safety of vehicles. The free and constraint modal of original and foam aluminum filling frame are analyzed by using finite element simulation method. Through the comparison of the modal results of two type structure of frames, it shows that the free and constraint modal dynamic characteristics of frame filled with foam aluminum are better than the original frame structure. Based on the analysis of constraint modal, the vibration responses of original frame and frame filled with foam aluminum are analyzed under the excitations of random road input power spectrum by using finite element analysis. The results show that the resonance frequency of original frame and frame filled with foam aluminum are corresponding to the first and ninth-order natural frequency of its structure. But the resonant response of frame filled with foam aluminum is lower than the original frame. So, the dynamic characteristics of frame can be improved by filling foam aluminum. And it is also an effective method to improve the ride performance of vehicles, which has a broad application prospects.更多还原