【作者】 陈渊博；

【导师】 郝志勇；

【作者基本信息】 浙江大学 ， 动力机械及工程， 2011， 硕士

【摘要】 本文以车用柴油机为研究对象,对其曲柄连杆机构的动力学特性进行了分析,在此基础上对曲轴进行了强度分析和改进,并优化了活塞对气缸套的动态敲击性能。分别运用传统当量化方法和有限元技术计算分析了曲轴轴系的扭转振动特性,结果表明传统当量化方法是计算曲轴轴系扭振的有效方法,并且能够对硅油减振器参数进行优化设计。从优化结果可知,硅油减振器阻尼在一定范围内对减振器的性能影响较小,而改变减振器的转动惯量能有效改善减振器的工作性能。在充分考虑曲轴的弹性体变形和摩擦阻尼的情况下,有限元技术使用多体动力学方法计算曲轴轴系的扭振,其结果相对准确。曲轴扭振试验验证了上述两种方法的准确性。运用半自动拓扑方法划分曲轴六面体单元网格,做出精细曲轴有限元模型。在动力学仿真的基础上计算了曲轴动态应力。在谐振式弯曲疲劳试验台上进行了曲轴弯曲疲劳试验,通过仿真试验过程,获取准确的疲劳计算参数。在考虑弯扭耦合作用下对曲轴进行多轴疲劳寿命计算,并对曲轴结构进行了优化。结果表明子模型法可以有效优化曲轴圆角结构,提高曲轴疲劳强度。另外更换疲劳性能更好的曲轴原材料,曲轴的疲劳可靠性也可以得到较大提升。对于钻孔深度误差产生的曲轴后端断裂事故,详细分析了其破坏原因。采用仿真计算和试验相结合的方法,获取了活塞的冷热态型面以及活塞体径向刚度等边界条件。通过调整活塞销偏置、配缸间隙和优化活塞裙部型线来提高活塞的二阶运动性能,结果表明原有的中凸桶形裙部型线能够保证良好的活塞运动特性。通过对比有无活塞对缸套的动态敲击力时机体头部主推力侧的表面振动加速度响应的不同,表明活塞的动态敲击力主要包含中高频冲击成分。本文从工程应用的角度分析研究了曲柄连杆机构性能优化设计的新方法,取得了一系列具有工程实用价值的成果,对工程实际具有一定的指导意义。更多还原

【Abstract】 This paper analyzed dynamic characteristics of the crank-connecting rod mechanism in the vehicle diesel engine. Further more it researched dynamic stress of the crankshaft and optimized the dynamic slap performance of the piston on the cylinder liner.Both the traditional discretization method and finite element technique were used to calculate torsional vibration characteristics of the crankshaft system. The results show traditional discretization method is effective which can also optimize the silicone oil damper. Besides the damping value of the silicone oil damper has little effect to the damper’s performance and rotational inertia value of the damper can change the work performance of the silicone oil damper. With sufficient consideration of elastic deformation and friction damping, multibody dynamics simulation can calculate amplitude of torsional vibration more accurately. Torsional vibration test of crankshaft system verifies the accuracy of the two methods above.Semi-automatic topological method was used to make the hexahedral mesh model of the crankshaft. The dynamic stress was obtained by multibody dynamics simulation. Based on the fatigue test data, material parameters of the crankshaft were obtained by simulating the bending fatigue testing process. Multiaxial fatigue life was analyzed by coupling bending and torsional vibrations. Further the crankshaft structure was optimized. The results show the substructure method can be used to improve the fatigue reliability of the crankshaft. Besides the fatigue reliability can improve effectively by using better material of crankshaft. Then fracture accident of crankshaft back end was analyzed in detail for the error of drilling depth.Boundary conditions such as thermal profile and radial stiffness of piston were obtained by combining simulation and test. The secondary motion characteristic of piston was improved by adjusting piston pin offset and clearance between piston and cylinder liner, as well as optimizing piston skirt profile. The result shows original middle-convex bucket skirt profile can keep well motion characteristics of piston. The difference of vibration acceleration of thrust side on block head was analyzed by whether having dynamic slap force of the piston on the cylinder liner in simulation. The result shows that dynamic slap force of the piston on the cylinder consists of mainly medium and high frequency.This paper developed the related new method of analysis of crank-connecting rod mechanism from the view of engineering application. It has gained a series of results with practical engineering value to direct engineering application.更多还原