薄壁管数控弯曲成形过程失稳起皱及成形极限的研究

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1、西北工业大学硕士学位论文二竺巴二二二巴二二二二巴巴巴巴竺芯棒间摩擦、管材与弯曲模摩擦等。(s)结合薄壁管数控弯曲过程的成形特点，定义了基于失稳起皱的薄壁管数控弯曲成形极限的概念;基于起皱预测系统TBWS-3D，提出了成形极限的搜索算法，得到了不同工艺参数下的成形极限，建立了初步的成形极限库;通过成形参数对失稳起皱影响规律的研究，获得了提高成形极限的方法;在此基础上提出了基于成形极限与数值模拟的参数确定与优化方案，使薄壁管数控弯曲过程成形的参数快速确定与优化成为可能。最后对今后的进一步研究方向进行了探讨。本研究对提高薄壁弯管制品的质量、缩短产品开发周期、降低生产成本、充分发挥数控弯管设备的

2、优势，从而实现薄壁管数控弯曲精密成形具有重要意义，同时也丰富了薄壁件塑性成形失稳起皱理论。关键词薄壁管;失稳起皱;成形极限:NC弯曲:FEM模拟—11—西北工业大学工学硕士学位论文AbstractNCprecisionbendingprocessofthin-walledtubeisshowinganinevitabletendencytoimproveanddeveloptubebendingprocessintoadvancedplasticformingtechnology.However,itisacomplexastableprocesswithcouplinginteract

3、ivemulti-factorefectsandwrinklingphenomenonasacompressinstabilityoftenoccurring，whentheprocessparametersareinappropriate,especiallyfortubeswithlargediameterandthinwall-thickness.Thus,thewrinklingandforminglimithavebecomeonedifficultandkeyproblemurgentlytoberesolvedintheR&Doftheprocess.Inthisdisse

4、rtation,asystematicalandthoroughinvestigationonthewrinklingandtheforminglimitoftheprocesshasbeencarriedoutbyusingrigid-plasticFEMsimulationcombiningwithanalyticalandexperimentmethods.Themainachievementsoftheprojectmadeareasfollowing:(1)Someofthekeytechniquesrelatedtothe3Drigid-plasticFEMsimulatio

5、nandwrinklingpredictionofthin-walledtubeNCbendingprocesshavebeenstudiedandimprovedmethodsandalgorithmshavebeen.proposed:Theinstabilitypredictingmodelhasbeenimprovedwhichmakepredictionresultsmoreprecise.Shellelementwithabsolute-relativedegreeoffreedomandcorrespondingsetingmethodofvelocityboundaryc

6、onditionsmakethesimulationresultsmoreefficientlyandmoreaccurately.Frictionsonfourareasintheformingprocessandsidepushingvelocityhavebeenaddedintothefiniteelementequations,whichmakesFEMmodelmorecorrespondthereality.BasedonOOP(Object-OrientedProgramming)theory,onenumericalwrinklingpredictionsystemTB

7、WS-3DforvisualNCTubeBendinghavebeenreconstructedsuccessfullywithVC++.Thevalidityofsystemhasbeenverifiedbyexperimentationandcomparisonwithdataintheliterature.(2)ByusingimprovedwrinklingsystemTBWS-3D,asystematicalandthor