【作者】 王晓宁；

【导师】 孙胜；

【作者基本信息】 山东大学 ， 材料加工工程， 2008， 硕士

【摘要】 随着我国现代化建设进程的不断推进,工程机械行业的发展得到极大的促进,对工程机械的结构提出了越来越高的要求,不仅要求有较高的承载能力、高的疲劳寿命,还要求减少原材料的使用,降低生产成本;在满足强度的前提下,求得最优设计。装载机工作装置是承受载荷的基础构件,研究工装机构的实际受力情况,将为不断改进挖掘机械设计和制造方法提供理论依据。搞清了工装机构的受力情况,不仅奠定了对其进行有限元或结构强度分析的基础,而且也有助于对其进行加工材料、加工方法及结构形状等的合理选定。材料力学方法的长处是可以快捷地获得特定区域(特别是边界区域)上的综合力学量,为进一步的细致分析提供依据。但是,由于其在几何建模和力学模型建模方面,往往作出很多假设,造成与实际情况较大的差异。而使用有限元模拟技术可以建立与实际结构和受力情况相吻合的有限元模型,对结构进行全面而准确的应力、变形分析。根据装载机的作业方式、作业过程和外载施加特点,搞清工作装置的受力特点,计算工作装置各构件的受力情况,其结果作为有限元分析时的外载荷。同时,在此计算结果的基础上,用材料力学方法计算各构件的内力,进行危险断面的强度校核,与有限元分析结果进行分析比较。用UG软件建立与该工作装置实际情况相吻合的数字模型,为下一步进行有限元分析做好准备。动臂是工作装置中最重要的部件,它受力复杂,自重较大。国内外装载机的动臂都有发生过动臂破坏现象。本文首先以动臂处于最低位置,工作机构的最大受力工况为模型,对工作装置的动臂框架进行静态结构分析,得到整个动臂框架在正载、偏载情况下的应力、应变、变形分布。改变动臂框架的位置,重复上述分析,根据分析,选取以下四种工况:(1)动臂与地面成30°角的位置;(2)动臂与地面成15°角的位置;(3)动臂抬升至卸载位置;(4)装载机卸料时。通过这几种不同工况的分析结果,了解动臂框架在整个工作过程中最大应力、最大应变和最大变形的位置变化,为今后动臂框架的设计及优化提供参考。记录动臂框架各工况下最大应力、最大应变和最大变形的位置及其数值,作出静力载荷谱即动臂时间—应力载荷谱,时间—应变载荷谱,时间—位移载荷谱。了解动臂框架各工况下应力、应变、变形值最大处在整个工作过程中的数值变化,更清楚地了解容易发生破坏处的受力情况。最后,根据有限元分析结果以及疲劳累积损伤原理,对动臂框架进行疲劳寿命预估,能在其发生破坏之前及早发现问题并进行补救工作,减少疲劳断裂事故的发生,同时,对于指导装载机的设计、制造、检验与管理也具有十分重要的意义。更多还原

【Abstract】 With the development of modernization, the industry of engineering machine has gained huge promotation,higher requirement has been needed for the structure of engineering machine,such as high bearing capacity,long fatigue life,and low production cost .On the presupposition of meeting its strength and stiffness,optimal design should be obtained. Working device of the loader is one of the main bearing parts,studying its practical bearing circs will provide academic gist for the designation of loaders. Knowing the bearing circs of working device,you can make the finite element method analysis and structural intensity analysis,making right choose for machining material,machining method and structural shape.The strongpoint of material mechanics is you can shortcut gain the resultant force of the location(especially the boundary area)to do farther particulary analysis.However,there is big difference with the fact because of the hypothesis in geometric modeling and mechanical modeling. The finite element model can be build according to its main character by the finite element simulation to analyze its stress and distortion completely and exactly.Beating out the bearing circs of working device,baced on the loader’s working mode,working process and the outside force to load,calculating the bearing circs of each component of working device to do the finite element analysis. At the same time, calculateing the internal force of each component by material mechanics to compare with the finite element analysis result. Building the figure model according to its main character by UG for the next finite element analysis.Active arm is one of the main parts of working device,its bearing circs is complex and its deadweight is large. In the past,damage has occurred in loaders in home and overseas. In this dissertation,we first choose the most bearing case to do static structural analysis,the stress,strain and displacement ditributions of wholly active arm are obtained. Changing the place of active arm to do the same analysis,we choose four cases to analyze: (1)the angle of active arm and the floor is 30;(2)the angle of active arm and the floor is 15;(3)active arm is in the unload position;(4)the loader unloads. Analyzing the results of the four cases ,we know the place of the maximum of stress, strain and displacement of active arm in the whole working process,which may be used as reference in the optimization of active arm.Noting the place and numerical value of the maximum of stress, strain and displacement,the static load spectrum is obtained ,namely time-stress load spectrum, time-strain load spectrum and time-displacement load spectrum. Understanding the change of place of the maximum,we can know the bearing circs of the easy destroyed position much more clearly.At last,estimating the fatigue life in advance based on the finite element analysis results and fatigue damage accumulation theory,we can find problem before breakage and repair it to reduce fatigue rupture accident. At the same time,it is of great meaning for the design, produce, checkout and manager of loader.更多还原