Calculation of Temperature Field During Laser Transformation Hardening of Cylindrical Bodies

IntroductionLaserTransformationhardeningtechniquehasbeensuccessfullyusedinindustryformanyyears.AlotsoftheoreticalworkshasbeendoneforheatflowduringthelasertfansformationhardeningofflatworkPieces["].Cyindricalbodiesarewidelyusedinindustrysuchaslocomotivecrankshaft,steelrollervalyeseat,enginecyinder.IftheschcesoftheseworkPiecesaretreatedbylasertheirwearresistancewiIIimProvealot.UptillnowmanyexPerimentalworkshasbeendoneforlasertransformationhardeningofcyindricalbodies,butfewtheoreticalworkshav…     

Finite Element Method Analysis of Stress Field Considering Thermal Coupled Force During Laser Process

IntroductionLaserphasetransformationhardeningisanewtechnologyduringwhichlaserheatresourceactsdirectlyonsurfaceofmaterialandcompositionscharacteristicofmaterialischanged.Thetechnologyproce8sesacharacterofrapidheatvelocity,highheattempelatureandquickcoolingspeed(l0'col0'aC/s).Thecompositionandcharacteristicofmaterialvariedwithvariousinnertemperaturewillleadtothermalresidualstress.Itiswellknownthattheresidualstressaffectssignificantlyoncharacteristicofmaterial,suchasimProvingstrengthoffatigUere…     

Computer Prediction on Stress Distribution During Laser Quenching

IntroductionInprocessofindustry,theproblemscoupIedwiththermaIandfOrceareusuaIIymet.LaserqueIlchinginvolvingphasetransformationisoneofthem.HowtosetupafitmatheInatica1modeltosimulatetl1elaserquenchingprocessandhowtocalculateandanalyzenumericallythestresgdistributionarefolIowedwithinterestbymanyresearchersIl'2'3J.Thoseeffol'tsareimportanttooPtilnizethetechnologyparametersandprovideareliablebasisforimprovingthesyntheticallymechanicspropertiesandtheuseagesofmaterials.Alongwithdevelopmentofcomp…     

采用间接耦合法分析斜拉桥索塔瞬态温度应力场

针对混凝土斜拉桥索塔,将以传热学原理为基础的温度场分析与采用有限元法的应力场分析间接耦合,准确分析了结构内瞬态温度场和应力场的分布。以实桥为例,求解了索塔上温度应力分布,表明：用有限元法求解瞬态温度场能准确模拟索塔的温度场分布;间接耦合法能准确、有效地处理温度-应力耦合问题,能将温度荷载与其他荷载作用应力场有效组合,从而得到结构上准确的应力分布;对比了瞬态温度场分布与采用温差分布经验公式的不同,证明采用温差分布经验公式计算索塔面板上温度产生的拉应力时误差不大。     

均匀火焰包围下液化气容器的瞬态应力场分析

针对均匀火焰包围下的球型液化气容器的热响应问题,运用传热学理论和有限元方法计算并分析了均匀火焰包围下的球型液化气容器的瞬态热应力、机械应力和总应力.结果表明对于均匀火焰包围下的球形液化气容器,容器的最大当量热应力远大于最大当量机械应力,最大当量应力位置出现在最高液面附近,液面的波动是产生较高应力的根本原因.应对与液面接触的壁面区域进行重点防护.     

X65管线厚板控制冷却时的相变效应

为明确相变效应对X65管线厚板控制冷却的影响,通过开发线性混合热膨胀模型、拓展Avrami相变动力学模型和应用Leblond模型建立了热力耦合有限元模型.用该模型研究了X65管线厚板在上下层流冷却系数分别为3和1 kW/(m2.K)的非对称控制冷却时,相变效应对温度、残余应力和应变的影响.结果表明:相变期间,潜热减缓心部和下表面的冷却速度达50%、25%;潜热和TRIP效应分别产生峰值为89、-89 MPa,并且130、-170 MPa的应力可减小整体残余应力;相变膨胀产生峰值为723、-479 MPa的组织应力决定了整体残余应力大小及分布.     

柴油机整体活塞温度场及热应力的三维有限元分析

本文以16V240ZJ 型柴油机整体薄壁球铁活塞为例,采用两段温度拟合法确定了其热边界条件,进而得到了活塞的三维稳态温度场,并以此温度场为热载荷,计算了其热变形和热应力,得出了一些有意义的结论.     

Prediction of Welding Residual Stress in 2. 25Cr-1Mo Steel Pipe

Introduction2.25Cr-1Mo-steel is widely used in thepetroleum industry and in steam power generatingof both nuclear and conventional power plants be-cause of its excellent high-temperature strength,corrosion resistibility,and resistance to high-tem-perature hydrogen attack.Because several alloy el-ements are added into2.25Cr-1Mo-steel,marten-site is prone to form after welding.It has been rec-ognized that phase transformation can radically af-fect the development of residual stresses[1-2].Inor…     

考虑瞬态温度场的水平井水力冲砂临界排量

针对目前油气田水平井水力冲砂施工难度大、难以辨识合理的冲砂排量的问题.基于水平井地层-井筒瞬时温度场模型,提出水平井环空临界流速计算模型,考虑瞬时温度场对冲砂液黏度的影响.通过有限体积法求解瞬时温度场,结合冲砂液温度-黏度方程,求取了水平井全井段全过程环空临界流速,在此基础上建立了临界排量计算新方法.通过对4种常用冲砂液进行实例分析表明:与不考虑温度情况相比,考虑温度时全过程最大环空临界流速分别增大了9.20%、17.26%、9.85%和7.64%,临界排量分别增大了8.33%、18.18%、10.00%和11.11%,说明了水平井水力冲砂排量计算考虑温度影响的必要性.      

Stress Field Analysis of Carburized Specimen and Its Numerical Simulation

IntroductionCarburiZingiswidelyaPPiedheattre8boellttechnologyinindustry.Duringcarburizing,acasewithcarboncontellthigherthanthatofthecoreisformd;andaftethecarburzedmachinepwtbeingquenched,sdsehardenedlayeconsistedmainlyofmartensite,aswellasresidualstfOssfieldappearinit.Theresidua1stressfieldofcarburizedsteelanditsinfluenceonfatiguestrengthhavebeenstudiedexPerimenally["'],whilefewrePortscanbefoundaboatnumericalsimulationofresidualstressfieldincarburizedsPecmenaswellasitsinstataneousstressdist…     

Computer Predictions and Experimental Verification of Residual Stresses and Distortion in Carburizing-Quenching of Steel

IntroductionInordertoobtainimprovedmechanicalpropertiesandfatiguestrengthofmachinecomponents,stlchasgears,shaftsandsoon,carburizing-quenchingprocessasamethodofstirfacehardeningisoftenusedinindustry.Howevef,carbtirizing-quenchingisusuallyaccompaniedwithcarbonconcentrationandleadtodistortion,residualstressesandhardnessofsteelparts.Theeffectofcarboncontentisspeciallysignificantonphasetransformationbel1aviorThispaPerwillpresentthesimulationresultsoftheresidualstressfieldanddistortionofasteelcylin…     

非均匀变温场中主缆初始位形的迭代计算

利用解析法推导了变温度场中悬索桥空缆线形的悬链线线形公式;建立了两种已知设计条件时悬索桥空缆线形的迭代方法;根据主缆的温度变化方程导出了温度变化时无应力索长计算公式。计算结果表明:在非设计温度下,主缆的位形及其内力值均与设计理论值有较大误差,因此在悬索桥的结构分析中必须考虑温度变化的影响。     

磨削淬火技术的温度场仿真研究

目前对磨削淬火的研究,多采用实验的方法,通过大量的实验来制定合适的工艺参数,但由于磨削加工的复杂性,常使得实验研究带有一定的偶然性和盲目性.文中对影响磨削淬火工艺的关键因素——温度场,利用有限元方法进行了仿真研究,得到了磨削温度场的等温线图和工件各处的温度变化历程,预测了工件表层是否发生马氏体相变及相变层厚度,并进行了实验验证.研究表明,磨削淬火技术可以替代常规表面淬火工艺,利用磨削温度场仿真技术可以减少实验量、节省实验费用.     

送粉激光熔覆温度场数值分析

在ANSYS平台上,建立了瞬态三维送粉激光熔覆熔池温度场的物理模型,对在特种钢材34CrNiMo为基材上进行Ni基粉末激光熔覆的过程进行了数值模拟.使用生死单元法来模拟熔覆粉末在熔池形成前后与熔池的交互作用,计算出了激光熔覆熔池的自由表面形状、熔池温度场.计算所得熔池截面形状与试验熔池截面形状基本吻合,证明所建立的瞬态三维激光熔覆熔池温度场的物理模型是正确合理的.     

Numerical Simulation on Thermal Stress of Large-scale Bearing Roller during Heating Process of Final Heat Treatment

IntroductionThetemPeratUredifferencebforeentheinsideandoutsideofthelnye-scaleforgingworkPieceislmpewhenheatedbecauseofitsbigcross-seCtion.ThelereetCmPerforedffeencewillgeneratethermalstrCss.IfthethemalstressislargeenOugh,theforsingworkPiecewil1crack.Howtodesigntheheatingtechnology,controltheheatingProcess,avoidtheoverlargethemalstresscausingcrackisanimPortatPToblemfortheheattreWntofthelarge-scalefOrgingworkPiecel'].InthispaPeqthethermalstressevolvingProcessofthe70Cr3Mobearingrollerdur…     

Computer simulation of microscopic stress distribution in complex microstructure using a phase field model

Microscopic stress distribution in a metallic material which has complex microstructure is simulated using a phase field model. The fundamental equations which take into account the coupling effects among phase transformation, temperature and stress/strain are used, while thermal effects are neglected to focus on the volumetric change due to phase transformation in this paper. A two-dimensional square region is considered, and the evolution of microscopic stress and the resultant residual stress distribution are calculated using the finite element method. As the phase transformation progresses and grains grow larger, stress is generated around the growing interface. When a grain collides with another one, specifically large stress is observed. Residual stress is finally distributed in the microstructure formed, and apparently large stresses are retained along the grain boundaries. Subsequently, dependency of the stress distribution on microstructure pattern is investigated. First, variously sized square grains are tested, and it reveals that the maximum stress tends to decrease as the grain size becomes smaller. Next, the shapes of the grains are varied. As a result, the stress distribution is remarkably affected, while the maximum stress value does not change so much. More complicated grain arrangement is finally tested with eight or nine grain models. Then, it is revealed as a common feature that large stress is generated along the grain boundaries and that the stress distribution is dependent on the grain arrangement.     

Analysis of stress and strain fields of laser cladding process on ring circular orbit

The cracking of coatings and the deformation of base frustrate the application of laser cladding technology especially on surface of the ring circular orbit. In order to solve the two problems above, the stress and strain fields of the laser cladding process on the ring circular orbit were analyzed through the finite-element method, based on the temperature field. The wedge module of the ring circular ring was the subject investigated. The calculating results show that during the cladding process the crank point tends to generate the transversal crack; the centre point on the coating/base interface tends to generate longitudinal crack; the intersecting edge of the coating and base tends to generate toe crack. Moreover, the cracking tendency of the outer marginal point is obviously greater than that of the inner marginal point. The rather high stress appears at the border position where the constraint exists, and the stress on the point in front of molten pool under the range of laser irradiation is large as well. And the displacement becomes larger as the cladding process proceeds.     

Computer modeling and validations of steel gear heat treatment processes using commercial software DANTE

The heat treatment process of a gear made of AISI 9310 carburized steel is modeled using the commercial heat treatment simulation software DANTE. Both carburization and quenching processes affect the residual stress distribution and distortion of heat-treated parts, which are important to service quality and fatigue life. DANTE/VCARB is used to design the boost/diffuse schedule of a vacuum carburization process. Oil quenching is modeled following the vacuum carburization process. Thermal gradient and phase transformation are two main sources of distortion and residual stresses in quenched parts. The relation of the carbon distribution, thermal gradient, and phase transformations during quenching is studied through the gear modeling example. Because of geometry, the residual stress distribution after quenching is non-uniform along the gear surface. In general, the root fillet has higher residual compression than either the root or tooth face locations after traditional oil quenching of carburized gears. The predicted residual stresses from the oil quenching model are imported into a single tooth fatigue bending model. The gear stresses under bending load indicate the possible cracking locations during the bending fatigue test. The importance of heat treatment residual stresses during gear design is pointed out, and it is commonly ignored in the gear design and manufacturing industry.     

FEM-BEM Coupling for the Modelling of Induction Heating Processes Including Moving Parts

IntroductiollAnyelectricalconductorplacedinatime-varyingmagneticfieldistheseatofeddycurrentsthatdissipatepowerthroughJouleeffect.ThispowerisconcentratedinthesurfaceofthecomPonent,inaverysmallthicknesswhichdependsontheelectricalconductivityandmagneticpermeabilityofthematerial,butalsoonthefrequencyofthecurrents.Inductionhardeningprocessestakeadvantageofthiseffectbecauseitthereforepossibletocontrolthethicknessofthetreatedlayer.InductionhardeningofsteelcomPonentsisrealisedintwosteps.First,anindu…     

钢箱梁面板与U肋焊接残余应力的分布特性

为研究残余应力场对钢箱梁疲劳性能影响效应,以港珠澳大桥正交异性钢桥面板为例,采用数值模拟的方法,研究了正交异性钢桥面板焊接全过程及残余应力分布特性,分析了板件参数对残余应力的影响效应,得到钢箱梁确定正交异性钢桥面板焊接残余应力分布的经验公式.研究结果表明:采用ANSYS热-结构弱耦合数值模拟方法可反映实际焊接过程中残余应力场的分布;焊缝区域残余应力峰值受板件参数影响较小,横向最大残余应力约为300 MPa;沿板厚方向焊接残余应力符合正弦分布,表明采用正弦函数作为其经验分布模型是可行的.