客车车身骨架有限元建模及优化分析
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摘要
有限元分析是现代工程设计中一种快捷、有效的辅助工具。在汽车结构设计中,它对提高汽车动、静态性能和优化车身、车架结构设计,缩短新车开发周期,节约开发费用,均具有重要意义。将有限元技术应用于客车车身的结构分析,提出改进意见,使结构能够满足强度和刚度要求,己经成为车身设计的重要组成部分。随着计算机及其技术的发展,各种大型有限元软件,如ANSYS,NASTRAN,PARTRAN等纷纷推出,有限元技术广泛被应用于车身结构的静动态特性分析和模态分析等领域。实践证明,利用有限元法对客车车身骨架结构进行分析是有效的,可进行静动态分析,并对结构的承载特性和振动特性进行评价,充分认识其强度和固有振型,了解车身可能会有的应力和变形情况。
以某型国产客车为例,在工程图纸的基础上,首先利用ANSYS软件建立了全车骨架结构的几何模型。然后利用梁单元,建立了供强度计算的有限元模型并进行了简化。在有限元模型的建立过程中,不但考虑了边界条件的处理与简化,还考虑了骨架结构以及作用在其上的载荷的处理方法。结合客车在实际运行中出现的四种典型工况,如直线匀速行驶,路面高低不平出现单轮瞬间悬空,紧急制动及急速转弯等工况,详尽地进行了车身骨架结构的强度计算。然后计算了客车骨架的自由振动模态,研究了如何使用ANSYS软件进行客车车身结构的模态分析,获得了车身的固有频率及相应的振型,为车身结构的改进设计做出了有益的尝试。
优化设计是本文研究的另一个方面。汽车优化不仅可以节省材料,而且有利于提高整车的动力性和经济性并减少排放。本文优化设计是在进行车身骨架强度和动态(模态)CAE分析及静动强度态试验基础上,并结合相关研究及工程实践经验,提出结构优化方案。按照此方案,车身骨架共减轻273kg,达到减重5%以上的目标。CAE分析表明,优化后的车身骨架应力分布没有较大的变化,强度满足要求。
计算结果表明,文中建立的有限元模型是合理的,分析是正确的,所得结果可直接用于指导客车设计的改进和性能评价。
The FEA is an efficient tool of modem engineering. It would bring us dramatic effect inmany aspects, especially in optimizing bus structure shortening the cycle and reducing the cost of developing new models. Applying the finite element technique to analyze the structure, put forward better opinions to satisfy the body's requests in stiffness and strength, become the main part in body designing. Along with the technical development in computer, large software such as ANSYS, NASTRAN, PARTRAN and so on are developed now, the FEA can be applied in the static&dynamic analysis, also the mode analysis of body structure. It has been proved that using FEA in bus body analysis is efficient, the static&dynamic analysis can be proceeded, the bearing capability and vibration characteristic can be evaluated, the stiffness, strength and inherence vibration model can be recognized. It can be also know the possible stress and distortion of the bus body. The FEA has shown its advantages in the application in auto industries.
In the thesis, take a bus as an example, on the basis of two-dimensional project drawings, firstly established a geometry model of the full scale bus skeleton utilizing ANSYS. By using beam element, the finite element model for strength analysis was setup and simplified. The FEA model also involves treatments of boundary conditions, simplified treatment of some skeleton parts and deals with the fixed weight and loading that is put on the structure. Considering four typical operation situation, such as the bus running with the uniform velocity; one of the wheels hang in the air when the bus running on an uneven road; the bus brakes suddenly and the bus steers quickly. The calculation of strength of bus body's structure is expatiated. Then the research calculates the free vibration modes of the bus skeleton. At last, calculate the stress response of it by inputting the road spectrum into the model of it, and attempt to improve the dynamic capability of it.
Optimization analysis design is another aspect of this paper. Car-body frame Optimization analysis is propitious to reduce whole vehicle weight. Reduction of body weight can not only save materials, but also improve acceleration performance and fuel economy of the vehicle and reduce engine emission. The Optimization analysis scheme, discussed in this paper, is based upon the results of CAE analysis and static and dynamic test, and also based upon experience of related research and engineer practice, according to which, 273 Kg of the coach-body frame weight is reduced, which comes up to the goal of 5% weight to decrease, but stress distributing change little and the coach-body frame stiffness performance meets requirements.
The calculating results prove that the finite element model established in the text is rational, the analysis is correct, and the results could directly help to evaluate and improve the design of the passenger car.
以某型国产客车为例,在工程图纸的基础上,首先利用ANSYS软件建立了全车骨架结构的几何模型。然后利用梁单元,建立了供强度计算的有限元模型并进行了简化。在有限元模型的建立过程中,不但考虑了边界条件的处理与简化,还考虑了骨架结构以及作用在其上的载荷的处理方法。结合客车在实际运行中出现的四种典型工况,如直线匀速行驶,路面高低不平出现单轮瞬间悬空,紧急制动及急速转弯等工况,详尽地进行了车身骨架结构的强度计算。然后计算了客车骨架的自由振动模态,研究了如何使用ANSYS软件进行客车车身结构的模态分析,获得了车身的固有频率及相应的振型,为车身结构的改进设计做出了有益的尝试。
优化设计是本文研究的另一个方面。汽车优化不仅可以节省材料,而且有利于提高整车的动力性和经济性并减少排放。本文优化设计是在进行车身骨架强度和动态(模态)CAE分析及静动强度态试验基础上,并结合相关研究及工程实践经验,提出结构优化方案。按照此方案,车身骨架共减轻273kg,达到减重5%以上的目标。CAE分析表明,优化后的车身骨架应力分布没有较大的变化,强度满足要求。
计算结果表明,文中建立的有限元模型是合理的,分析是正确的,所得结果可直接用于指导客车设计的改进和性能评价。
The FEA is an efficient tool of modem engineering. It would bring us dramatic effect inmany aspects, especially in optimizing bus structure shortening the cycle and reducing the cost of developing new models. Applying the finite element technique to analyze the structure, put forward better opinions to satisfy the body's requests in stiffness and strength, become the main part in body designing. Along with the technical development in computer, large software such as ANSYS, NASTRAN, PARTRAN and so on are developed now, the FEA can be applied in the static&dynamic analysis, also the mode analysis of body structure. It has been proved that using FEA in bus body analysis is efficient, the static&dynamic analysis can be proceeded, the bearing capability and vibration characteristic can be evaluated, the stiffness, strength and inherence vibration model can be recognized. It can be also know the possible stress and distortion of the bus body. The FEA has shown its advantages in the application in auto industries.
In the thesis, take a bus as an example, on the basis of two-dimensional project drawings, firstly established a geometry model of the full scale bus skeleton utilizing ANSYS. By using beam element, the finite element model for strength analysis was setup and simplified. The FEA model also involves treatments of boundary conditions, simplified treatment of some skeleton parts and deals with the fixed weight and loading that is put on the structure. Considering four typical operation situation, such as the bus running with the uniform velocity; one of the wheels hang in the air when the bus running on an uneven road; the bus brakes suddenly and the bus steers quickly. The calculation of strength of bus body's structure is expatiated. Then the research calculates the free vibration modes of the bus skeleton. At last, calculate the stress response of it by inputting the road spectrum into the model of it, and attempt to improve the dynamic capability of it.
Optimization analysis design is another aspect of this paper. Car-body frame Optimization analysis is propitious to reduce whole vehicle weight. Reduction of body weight can not only save materials, but also improve acceleration performance and fuel economy of the vehicle and reduce engine emission. The Optimization analysis scheme, discussed in this paper, is based upon the results of CAE analysis and static and dynamic test, and also based upon experience of related research and engineer practice, according to which, 273 Kg of the coach-body frame weight is reduced, which comes up to the goal of 5% weight to decrease, but stress distributing change little and the coach-body frame stiffness performance meets requirements.
The calculating results prove that the finite element model established in the text is rational, the analysis is correct, and the results could directly help to evaluate and improve the design of the passenger car.
引文
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[6]中国客车市场分析及展望,中国经贸报,2002,2.12
[7]杨丽华,张景坤,林革.21世纪汽车发展的趋势,汽车技术.2001,1:1-3
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[11]Hyungyil Lee,Heon Seo,Gyung-Jin Park.Design enhancements for relaxation in automotive multi-shell-structures,International of Solids and Structure 40(2003):5319-5334
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[13]马迅,过学迅.工程分析在车身结构设计中的应用与前景.汽车技术,2001,4:4-6(31)
[14]刘竹清.客车车身结构优化研究,北京航天大学硕士学位论文,2003,3
[15]卢金火,赵百灵,黄迪民.并行工程在汽车车身开发上的应用,汽车工程:1997(Vol19),3:134-138(159)
[16]傅立敏编.汽车新技术.长春吉林科学技术出版社,2000
[17]Kim T,卢耀祖等.机械与汽车结构的有限元分析.上海:同济大学出版社,2003
[18]谢庆生,李少波,楚甲良.虚拟样机中的有限元方法,系统仿真学报,2003,4:508-511(515)
[19]杨华,曹立波.特征建模在汽车车身覆盖件设计中应用,客车技术与研究,2002,4:11-12
[20]屈求真.轿车车身开发中的计算机辅助设计与辅助工程,汽车技术,1995,11:1-3
[21]李玉璇,林忠钦,金先龙.客车车身外形虚拟开发系统的建立及其应用,汽车研究与开发,2002,2:19-22
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