Calculation of Temperature Field During Laser Transformation Hardening of Cylindrical Bodies

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

Computer simulation of the continuous annealing recrystallization for cold-rolled strip in galvanizing line

The continuous heating transformation program is developed to investigate the influence of continuous annealing technological parameters on recrystalization for cold-rolled strip in galvanizing line. This program can be used for the calculation of the continuous annealing temperature field of strip steel, determination of the start and end time of recrystallization in continuous heating process, and procurement of the continuous heating transformation diagram. The temperature field for continuous annealing is simulated by means of finite difference method. Based on the Scheil superposition principle, the continuous heating transformation curve is obtained by using time temperature transformation (TTT) curve which is measured experimentally. The developed program has been used in practice, and the strip speed on production line increases by more than 10%.     

Integrated fluid-thermal-structural numerical analysis for the quenching of metallic components

The quenching of a metal component with a channel section in a water tank is numerically simulated. Computational fluid dynamics (CFD) is used to model the multiphase flow and the heat transfer in film boiling, nucleate boiling and convective cooling processes to calculate the difference in heat transfer rate around the component and then combining with the thermal simulation and structure analysis of the component to study the effect of heat transfer rate on the distortion of the U-channel component. A model is also established to calculate the residual stress produced by quenching. The coupling fluid-thermal-structural simulation provides an insight into the deformation of the component and can be used to perform parameter analysis to reduce the distortion of the component.     

钢桁斜拉桥板桁温差效应分析

以江津粉房湾大桥为依托工程,对钢桁斜拉桥所存在的板桁温差效应进行分析,在参考各国规范对温差效应规定的基础上,提出了钢桁斜拉桥板桁温差效应分析方法。通过比较不同温差作用下钢桁梁与桥面板连接部位的变形和受力情况,研究温差效应对结构的影响程度,并提出了有效解决温差效应的措施。     

供热系统的自动控制策略

在引进消化吸收北欧的先进的供热技术的基础上,考虑到我国的国情提出了一种能与我国目前供热现状相适应的自控模型。解决了北欧国家广泛采用的集散式供热系统自动控制在中国遇到的热源能力不足时失调的问题。同时解决了我国供热系统如何确定其最不利环路及计算最不利环路压差设定值的问题。     

基于能量变分原理的双层板层间温度应力计算

分析了双层板之间相互作用,以及层间约束对双层板变形的影响,在Goodman模型的基础上,用切向约束刚度和法向刚度模拟层间约束,运用能量变分原理导出了双层板平衡微分方程,提出了层间约束力计算双层板层间温度应力的计算方法。     

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

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

Thermal Transport in Nanoporous Yttria-Stabilized Zirconia by Molecular Dynamics Simulation

Yttria-stabilized zirconia (YSZ) is widely used as thermal barrier coatings (TBCs) to reduce heat transfer between hot gases and metallic components in gas-turbine engines. Porous structure can generally reduce the lattice thermal conductivity of bulk material, so porous YSZ can be potentially used as TBCs with better thermal performance. In this work, we investigate the thermal conductivity of nanoporous YSZ using the nonequilibrium molecular dynamics (NEMD) simulation, and comprehensively discuss the effects of cross-sectional area, pore size, structure length, porosity, Y₂O₃ concentration and temperature on the thermal conductivity. To compare with the results of the NEMD simulation, we solve the heat diffusion equation and the gray Boltzmann transport equation (BTE) to calculate the thermal conductivity of the same porous structure. From the results, we find that the thermal conductivity of YSZ has a weak dependence on the structure length at the length range from 10 to 26 nm, which indicates that the majority of heat carriers have very short mean free path (MFP) but there exists small percentage (about 3%) of phonons with longer MFP (larger than 10 nm) contributing to the thermal conductivity. The thermal conductivity predicted by NEMD simulation is smaller than that of solving heat diffusion equation (diffusive limit) with the same porous structure. It shows that the presence of pores affects phonon scattering and further affects the thermal conductivity of nanoporous YSZ. The results agree well with the solution of gray BTE with a average MFP of 0.6 nm. The thermal conductivity of nanoporous YSZ weakly depends on the Y₂O₃ concentration and temperature, which shows the phonons with very short MFP play the major contribution to the thermal conductivity. The results help to better understand the heat transfer in porous YSZ structure and develop better TBCs.     

氧和水蒸气浓度及升温速率对生物质燃烧的影响

采用热重实验法,实验研究了升温速率、氧浓度和水分浓度对生物质燃烧的影响．研究结果表明,升温速率过大时会发生热滞后现象,着火倾向发生在颗粒表面,对燃烧特征温度、失重速率和剩余质量百分数均有影响;当氧浓度较大时,氧向固体层的质量传递作用加强,使得挥发分与固体层同时发生燃烧,燃烧速率明显增大而燃烬温度降低;水分浓度影响了生物质的燃烧,湿空气燃烧不稳定的原因是水分的凝结与蒸发,湿空气燃烧会造成炉膛热负荷波动．     

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…     

钢丝感应加热过程模拟及特性

在感应加热理论和热传导理论的基础上,建立了钢丝感应加热时的ANSYS模拟模型,对不同直径产品的加热频率、功率、最大线速度进行模拟计算,通过针对三种典型钢丝的加热时间,分析了其相应可达到的最大产品线速度,以及所需要的加热功率.还分析了工频频率的影响,选取合适的频率范围;通过实验验证了模型的准确性,为感应加热的计算和自动化控制提供了可靠的理论依据.     

隧道高地温的地质成因研究

为研究隧道高地温的地质成因，以云南某在建高速公路隧道——尼格隧道为研究对象，该隧道兼有高水温与高岩温，最高水温达63.4 ℃，最高岩温达88.8 ℃. 从区域地质构造及地震特征、水化学特征、地热储特征等对区域性的热因控制、水源、热源、导热通道等进行了分析，利用氢氧同位素分析法、锶同位素分析法、微量元素分析法、放射性元素分析法等对隧址区的热水来源及演变过程、热源成因进行了研究，并结合隧道工程地质、水文地质条件及开挖揭示状况，对隧道高水温段及高岩温段的地质成因过程进行了剖析. 研究结果表明:灰岩段高水温的成因过程与花岗岩段高岩温有所差异，隧道高水温的成因过程为热源（深部热异常体）—主要传热通道（深循环）—次级传热通道—浅表水体混合、水岩作用，其过程伴随着冷热水混合作用、离子交换作用等；隧道高岩温的成因过程为热源（深部热异常体、放射性元素衰变生热）—主要传热通道（深循环）—次级传热通道—热气沿裂隙传至隧道岩体，其过程伴随着S元素的富集，易形成H₂S或SO₂有毒有害气囊.      

Modeling on directional solidification of solar cell grade multicrystalline silicon ingot casting

Solar energy is considered as one of the best alternative energy in the future. Multicrystalline silicon ingot casting is the main production process for major supply of solar cell. However, the casting process cannot be understood clearly because of some difficulties, such as enclosed furnace, long cycle time of production and so on. In this paper, an integrated model, including casting process analysis, quality prediction and production parameters optimization, is proposed and the preliminary results are acquired. The framework of the proposed model is introduced and the numerical simulation results on the temperature field and grain growth process are also given out and discussed.     

起重机金属结构焊缝表面裂纹红外热波检测仿真研究

起重机金属结构焊缝检测主要采用通用的无损检测方法,检测效率低、检测长度严重不足。文中介绍了焊缝表面裂纹检测的一种新方法---红外热波检测法,利用ANSYS有限元仿真软件,分析了不同的加热和散热时间、不同裂纹尺寸、不同热流大小和加热面积、不同钢板厚度的焊缝表面裂纹的温度场异常分布情况,从而得到了红外热播法检测焊缝表面裂纹的各种影响因素。     

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。     

基于ANSYS的钢轨疲劳裂纹深度红外热波定量测量研究

钢轨疲劳裂纹深度定量测量是主动式红外热波技术缺陷检测研究的新方向.在分析钢轨伤损类型的基础上提出红外热波斜裂纹深度定量测定的方法.基于热传导的一维模型,分析了温度-时间二阶对数微分法的原理.利用ANSYS加载热流密度法模拟测量过程,采用温度-时间二阶对数微分峰值法计算裂纹深度.结果表明所建立ANSYS热波模型对于测量深度在6mm以内的裂纹具有较好的真实性,可作为实际检测裂纹深度的理论基础.     

新型装配式倒T形空心板桥受力性能

为解决现有装配式空心板桥的铰缝病害, 提出了一种新型装配式倒T形空心板桥; 进行了跨径8 m的倒T形空心板桥足尺模型试验和非线性有限元分析, 研究了车辆荷载作用下倒T形空心板桥各组成构件的应力、挠度和裂缝分布等, 得到了倒T形空心板桥的受力机理与破坏模式; 对比了倒T形空心板桥与带门式钢筋空心板桥的受力性能, 验证了倒T形空心板解决铰缝开裂问题的有效性。研究结果表明: 倒T形空心板桥的破坏过程分为弹性阶段、空心板开裂阶段、现浇结构层混凝土开裂阶段和受拉钢筋与钢板屈服阶段, 其整体受力性能良好, 极限荷载是带门式钢筋空心板桥的1.4倍; Ω形钢板上方受拉区混凝土首先达到拉应力限值3.17 MPa, 是受力薄弱部位; 由于Ω形和L形钢板的设置, 现浇结构层混凝土开裂时, 与结构层等高度的各结合面处的法向和切向黏结应力均不会超过限值2.30和0.29 MPa, 避免了结合面的黏结失效; 与带门式钢筋的空心板桥相比, 倒T形空心板构造不会减小空心板的开裂荷载, 且新旧混凝土结合面开裂在空心板开裂之后, 可从根本上解决传统空心板桥在车辆荷载作用下铰缝先于空心板开裂的问题。      

钢渣沥青混合料应用现状

总结了钢渣的物理性质、化学成分及矿物相组成; 分析了影响钢渣体积安定性的因素及其改善措施; 探讨了钢渣沥青混合料的配合比设计方法; 分析了钢渣沥青混合料的路用性能(高温稳定性、低温抗裂性、水稳定性、抗疲劳性、体积安定性、抗滑性)及其功能特性(导电性与微波加热); 研究了钢渣沥青混合料的生态、社会及经济效益; 介绍了国内外的工程应用。研究结果表明: 钢渣可用于沥青混合料, 且应为陈化半年以上的转炉钢渣或电炉钢渣; 钢渣的物理力学性能优良, 而化学成分及矿物相组成受炼钢工艺影响有所区别; 钢渣体积安定性的不足可通过预处理或陈化处理得到较好的改善; 钢渣沥青混合料的配合比设计要点包括钢渣替代传统集料的方式和比例、沥青混合料级配修正、有效相对密度测定以及最佳油石比的确定; 钢渣沥青混合料的路用性能及功能特性优于天然集料沥青混合料, 具有较好的环境影响性且综合经济效益更高; 关于钢渣沥青混合料路用性能的研究较多, 而作用机理方面相对缺乏, 关键性的限制因素如密度较高、体积安定性不良、混合料沥青用量增加等仍未得到根本性解决; 未来应重点研究钢渣沥青路面的长期性能及质量控制体系, 并开展全寿命周期研究, 以加快钢渣沥青路面的应用与推广。      

高强贝氏体钢与钢轨钢焊接热模拟过热区组织与性能

采用焊接热模拟的方法,模拟了高强贝氏体钢的Ｕ７４钢轨钢过热区在正火和回火状态下的组织,结果表明：高强贝氏体钢过热区在两种热处理状态下的组织均为粒状贝氏体,而钢轨钢过热区为珠光体加少量铁素体。拉伸试验结果表明,贝氏体钢过热区在正火和回火状态下,其强度与贝氏体钢母材相当,延伸率大于１２％,与母材匹配,钢轨钢过热区的强度与钢轨相当,但延伸率低。断口分析表明,贝氏体钢过热区断口呈韧窝状,为延性断裂,而钢轨     

浸管式加热装置的数值模拟及应用

针对浸管式加热装置设计中普遍存在的热平衡计算复杂、致使设计的加热装置耗能大、热效率低或加热功率达不到生产要求等问题。利用相关的物性参数和经典的燃烧学、传热学公式,编写了用于浸管式加热装置设计的计算机模拟程序。实践表明：程序模拟的结果与实测结果较为吻合。模拟程序的使用可以方便准确的进行设计方案的比选,为浸管式加热装置的设计提供了非常有效的工具。