Stress Field Analysis of Carburized Specimen and Its Numerical Simulation

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

树脂基复合材料修补片固化过程中的温度场

为优化树脂基复合材料修补片固化工艺参数,采用有限元分析方法,建立了复合材料层合板修补片热固化过程的物理模型和数学模型,基于这些模型对复合材料预浸料修补片固化过程中温度和固化度的变化规律进行了数值模拟,分析了不同固化阶段预浸料修补片内部的温度分布,对比了修补片内部不同点的固化过程;研究了升温速率、补片厚度和补片形状等因素对补片固化过程中温度和固化度的影响.仿真计算结果表明:升温速率越快,固化完成时间越短,但修补片内温度梯度越大;补片越厚,固化完成时间越短,且补片内部温度梯度越小;非穿透性挖补修理的补片形状对补片固化过程中温度和固化度的影响可忽略.      

Application of Computer in the Design of Process Thermal Cycle of Steel

IntroductionSteelingot.steelslabbecomest6elproductsafterheatingandrollingorforging.Steelproductsofforgingneedtobeheattfeatedinheattreatingfumace,fOrexampleannealingnormalization.Heattreatinentcandecreasestress,reducehydrogenconcentrationandimprovetheorganizationandperformanceofsteel.Everyprocessofproductionthatsteelingotschangeilltosteelproductsisaprocessofthermalcycleofsteel.Thisprocesswillconsumealargeamountofeneasmaterialandequipment.Inthepast,inmetallurgicalenterpriseofourcountrythetimeo…     

基于Simufact的焊接应力的对比分析

焊接部位要经历不均匀的加热和冷却历程,最终在焊接结构中产生应力,焊接应力会导致焊接接头产生冷、热裂纹等缺陷,焊接结构破坏事故许多是由焊接应力和变形所引起。因此,为了提高焊接结构的质量和使用性能,简化焊条电弧焊焊接的实验过程,本文运用Simufact-Welding软件对Q345钢的T形接头进行平焊仿真,对比分析了焊件不完全约束和完全约束两种方法下在焊接过程中和冷却过程中熔合线处的应力。结果表明：该仿真过程中,其它参数相同的情况下,不同的焊件装夹方法得到不同结果的焊接应力,焊接过程中,两种方法下大部分熔合线处的等效应力的最大值大于Q345的屈服强度,焊件不完全约束方法下大部分熔合线处的残余应力大于Q345的屈服强度,焊件完全约束方法下大部分熔合线处的残余应力小于Q345的屈服强度。     

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

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

Microstructure Evolution of Different Forging Processes for 12％Cr Steel During Hot Deformation

Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.     

城市居民高峰时段出行方式选择

城市居民在高峰时段出行时,有多种出行方式可供选择,在选择的过程中会综合考虑多方面的因素。采用模糊综合评价法对居民出行所考虑的各种因素进行评价,可以预测居民在高峰时段出行方式的结构和比例,对合理设置交通结构、减轻城市高峰时段的交通拥挤有现实指导意义。     

钢结构桥梁中特厚钢板焊接应力动态数值模拟分析

钢结构中特厚钢板焊接应力的理论分析一直为人们所关注。基于有限元软件ANSYS,采用高斯热源模型加热,利用生死单元,动态模拟分析80 mm特厚钢板对接焊过程中,对多层、多道焊的温度场进行加热模拟,实现焊缝的动态生成,跟踪应力场的变化情况。分析结果与重庆观音岩长江大桥构件焊接试验结果基本一致,为特厚钢板构件的设计和制作提供有实用价值的参考依据。     

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.      

劲性骨架拱桥主拱圈混凝土四工作面浇筑法

为研究受力合理、施工方便、经济性好的劲性骨架拱桥主拱圈混凝土浇筑工作面设置方法, 以南盘江特大桥为对象, 分析了从两拱脚对称浇筑第1环混凝土在劲性拱骨架上产生的瞬时应力变化过程, 做出了劲性骨架主要控制截面的应力过程线, 提出了在全拱纵向对称设置4个工作面的主拱圈混凝土浇筑方法, 并将工作面分别设置在拱脚截面和控制性应力过程线峰值处, 使半跨内2个工作面上混凝土在劲性骨架中产生的应力增量异号, 以抵消部分应力; 通过分段拟合绝对控制应力过程线上升段和下降段的连续函数, 合理调整了混凝土的浇筑长度和顺序, 降低了劲性骨架的瞬时应力和变形; 讨论了四工作面浇筑法的施工操作性和经济性, 并采用该方法分析了南盘江特大桥主拱圈第1环混凝土浇筑过程中劲性骨架的应力和变形。研究结果表明: 拱脚管内混凝土应力过程线为控制性应力过程线且为单波曲线; 提出的先跨内、后拱脚, 并按拟合函数计算的长度进行南盘江特大桥混凝土浇筑的四工作面法是合理的, 该桥劲性骨架最大瞬时拉、压应力分别降至0.4和23.5 MPa, 被较好地控制在材料强度范围内, 拱顶无上挠, 最大瞬时下挠和环末下挠分别为192、82 mm, 拱轴线不发生反复变形; 四工作面浇筑法所需设备和人员较少, 具有良好的操作性和经济性, 适合于劲性骨架拱桥主拱圈混凝土浇筑, 可为同类桥梁采用。      

火灾下预应力型钢混凝土梁抗弯承载力计算

基于对常温下预应力型钢混凝土梁承载性能的研究,利用截面有限单元法建立了预应力型钢混凝土梁在火灾高温作用下的正截面抗弯承载力简化计算公式.并针对试验梁进行了计算分析,得到了基于标准升温情况下的正截面抗弯承载能力与升温时间的全过程关系曲线,揭示了预应力型钢混凝土梁随着升温时间的增加,其正截面抗弯承载力显著降低的劣化规律.将试验梁抗弯承载力的计算结果与试验实测结果进行了对比分析,相对误差为9.3%.      

Comparison of Biomechanical Properties and Hemodynamics of Three Different Vena Cava Filters

The interaction mechanism of three types of vena cava filters (VCFs) with blood vessels and their influence on the bloodstream during the process of implantation are investigated by finite element method and computational fluid dynamics. The VCF models are set up with Solidworks software. Using ABAQUS software, we simulate the working conditions of the VCFs in the vessel to analyze the stress distribution and radial support stiffness of the vessel wall and the filter surface. Using FLUENT software, we simulate and analyze the velocity, pressure and shear stress distributions of blood flow when the VCFs are at their working conditions. For the retrievable VCF (R-VCF), the peak stress at the working conditions of the VCF is the highest, the peak stress toward the vessel wall is the lowest, and the support stiffness is the lowest. For the permanent VCF (P-VCF), the peak stress at the working conditions of the VCF is the highest, the peak stress toward the vessel wall is the lowest, and the support stiffness is the highest. Because of the structure of scaffolding support units and the tendency to form intimal hyperplasia on their support units, both the convertible VCF (C-VCF) and the P-VCF can embed their support units in the hyperplasia skin. This effectively prevents them from harming blood veins through filter damage at the pulse load conditions. As the biomechanical property of the C-VCF is between those of the R-VCF and the P-VCF, it has smaller obstacle to blood flow after conversion and has some fragmentation effects on the thrombus. The results show that different types of VCFs differ in their biomechanical and hemodynamic properties after implantation. Therefore, the simulative analysis can provide a reference basis for filter design and clinical decision making.     

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.     

铁道货车车轮CL60钢在450℃时的低循环疲劳行为

铁道货车车轮产生损伤失效的主要原因是承受了复杂的热载荷和机械载荷的联合作用,而高温低循环疲劳是车轮踏面区域产生损伤的重要机理之一.针对铁道货车车轮CL60钢进行了450℃时的高温低循环疲劳实验.研究发现：在整个循环过程中,应力-应变关系曲线的变化趋势基本一致;随着循环周次的进行,拉压应力峰值呈现出连续的降低态势,压应力峰值减幅略大于拉应力峰值减幅,表现了低循环疲劳的典型特性;试样断口上出现了较为严重的氧化现象,断口裂纹扩展以穿晶为主.     

履带板加热器消除焊接残余应力的试验研究

测试了履带板加热过程中温度沿钢板厚度方向的分布，并用小孔释放法测试了补焊试板在焊态、经履带板加热以及炉内加热后残余应力的分布．结果表明，履带板加热时所需加热时间较长，但温度沿试板厚度方向梯度小，截面温度分布均匀；履带板加热器消除焊接残余应力效果与炉内加热相当．     

加热温度和时间对沥青混合料老化的影响

通过提高短期老化温度,模拟高温生产工艺对沥青混合料老化性能的影响,以研究沥青混合料在拌和、运输、摊铺、碾压过程中抗老化性能的变化;根据不同老化时间(2 h,4 h)、不同老化温度(135℃,155℃)沥青混合料间接拉伸破坏试验结果的变化,证明了加热温度和时间对沥青混合料老化有明显的影响。试验结果表明:高温生产对抗车辙剂沥青混合料的抗老化性能有所削弱。     

带裂缝沥青小梁弯曲破坏的数值模拟

应用真实破裂过程分析系统(RFPA 2D),数值模拟与分析了带裂缝沥青混凝土小梁在三分点加载条件下的应力分布状态及其变化规律,讨论了沥青混合料的均质度、裂缝深度、裂缝与加载中心距离对含有竖向裂缝试样的裂纹扩展规律及断裂破坏的影响.模拟过程表明,试件本身的非均匀特性对破坏峰值强度,声发射次数分布规律及其裂纹的扩展有很大的影响.同时,梁的裂缝越深,与加载中心距离越小,则它的破坏峰值强度越小.     

三向应力下典型岩石破坏预警及峰后特性

为探讨岩石在三向应力下的变形、破坏规律及其峰后本构模型,对不同围压下石灰岩和砂岩进行了三 轴压缩全过程试验,分析了2种典型岩石的变形、破坏规律和峰前、峰后承载能力与变形之间的关系,在此基础 上建立了岩石的本构模型.研究结果表明:石灰岩在低围压下易于发生失稳破坏,在高围压下较难发生失稳破 坏,围压的增大对岩爆有一定抑制作用;同种岩石峰值应力时对应的环向应变不随围压的改变而改变,近似为一 定值,可以将其作为岩石破坏的一个预警指标;石灰岩的剪胀效应发生在破坏后,而砂岩在轴向应力达到其峰值 的70%左右时就开始出现剪胀;岩石峰后应力与其承载能力相等,由侧向变形控制,随侧向变形增大逐渐衰减 至残余强度;基于本构模型的计算结果与三轴压缩试验结果吻合较好.      

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%.     

Calculation of Transient Stress Field During Laser Transformation Hardening Process

IntroductionHighpowerCOzlaserssdsetransformationhardeningtechniquehasbeensuccessfullyusedinindusnyforWYears.BecausethetemPeratUrefleldislocalizedinmaterialdurllglasertransfonnationhMngProcess,highthermstrCsswillgenerateinmatgrialduringlasertfansformationhardeningProcess.Therisalsohighresidualstressinmaterial,bothintCnsionandcomPression['-'].ComPressresidualstressishelptoincreasethefatigueldrimeofthelasertreatedmaterial,butthetensilestresswillshortenthefatiguelifetmeofthelasertreatedmator…