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1、曲轴扭振分析哈尔滨工业大学本科毕业论文（设计）摘要在发动机工作过程中，曲轴上各曲拐所承受转矩的大小周期性变化的,而曲轴后端的飞轮具有大的惯量，转速可以看成是均匀的，所以各曲拐相对于飞轮就会发生大小和方向作周期性变化的相对扭转振动，产生曲轴轴系的扭转振动。曲轴的扭转振动时，扭转变形的幅度大大超过正常允许值，轻则产生很大的噪声，是磨损加剧，重则使曲轴断裂。因此在设计内燃机时，必须对轴系的扭振特性进行分析，以确定其临界转速、振型、振幅、扭转应力，以及据是否需要采取减振措施进而设计减振器。本文中首先用pro/E软件对所要分析的曲轴进行建模，用其模型分析功能求取曲轴当量转动惯量，用其Mecha
2、nica模块求取曲轴的当量刚度；用矩阵法和霍尔茨法计算曲轴的自由振动，确定曲轴的固冇频率和振型；通过对曲轴激振力矩的简谐分析，确定曲轴的单缸转矩振幅；通过对轴系强迫振动计算，确定曲轴的临界转速、共振时的幅值以及曲轴的扭振应力；判别扭振应力的大小是否超过允许应力，如果扭振应力接近或超过允许零件允许值，则对曲轴采取减振措施，设计合适的减振器。关键词：曲轴；扭振；扭振减振器I哈尔滨工业大学本科毕业论文（设计）AbstractIntheprocessofengineworking’cranktorqueofthecrankshaftisperiodicallychanging,whileth
3、eflywheelisapproximatelyinuniformrotationbecauseofthebigmomentofinertiaoftheflywheel.Therefor,theerankhavearelativemotioncomparedtotheflywheel.,then,thetorsionalvibrationofthecrankshaftoccurs.Whenthedeformationamplitudeofthecrankshaftconsiderablymorethanthenormalvalue,theenginewillproducenoisin
4、gnoise,andtheabrasionincreased?worsemore,theerankshaftmaycrackevenbroken.Therefore,inthedesignoftheinternalcombustionengine?theshaftingtorsionalvibrationcharacteristicsareanalyzedtodetermineitscriticalspeed,mode,amplitude,torsionalstress,aswellasdesigningtorsionalvibrationdamper.Firstly,modelth
5、eerankshafttobeanalyzedwithpro/Esoftware,then,wecangettheequivalentinertiaofthecrankshaftandtheequivalentstiffness;Secondly.calculatethefreevibrationoftheerankshaftusingmatrixmethodandHoltzmethod,anddeterminethenaturalfrequenciesandmodeshapes;Thirdly?determinetheamplitudeofthesingle-cylinderera
6、nkshafttorque,throughanalyzingtheexcitingmomentofthecrankshaft;Then,determinethecriticalspeedoftheerankshaft,crankshafttorsionalvibrationamplitudeandstressbycalculatingtheforcedvibrationoftheerankshaft;Finallyjudgewhetherthesizeofawkwardvibrationstressexceedstheallowablestress.Ifthetorsionalstr
7、essclosetoorexceedstheallowablevalueoftheerankshaftparts,dampingmeasuresmustbetaketoconsiderationanddesignthesuitabletorsionalvibrationdamper.Keywords:erankshaft,torsionalvibration,torsionalvibrationdamperII哈尔滨工业大学本科毕业论文（设计）目录摘要IA
