Numerical simulation of tube profile growth during spray forming process

Spray forming is a new type of metal material forming process,which can produce metal blanks such as billet,tube,plate etc.A mathematical model has been developed to forecast the shape evolution of tube billets during the spray forming process.The atomizer mass flux as,radial distribution coefficient bs,draw velocity and diameter of mandrel were considered in this model and the influence of different parameters such as metal flowrate,draw velocity of mandrel,diameter of mandrel on the tube’s shape change were simulated and analyzed in this paper.The simulation results obtained from this model can be provided to engineers as reference.     

带烟气回流W型辐射管热过程数值模拟

基于商业软件FLUENT同时,采用RNG k-ε模型和非预混燃烧模型,建立了带烟气回流W型辐射管燃烧器的燃烧及传热的三维数学模型,对辐射管内湍流和燃烧状况进行了模拟,并得到了出口NOx排放的计算结果;通过与相应实验数据的对比,验证了模型的可靠性.分析了辐射管内流体流动,传热和燃烧的特征,研究了燃气流量及空气预热温度对辐射管使用性能的影响;结果表明:燃气流量的提高,会增大辐射管壁面温度的不均匀性,而提高预热温度则相反;两者与辐射管加热能力呈正相关,但都会使得出口烟气内的NOx含量增大.     

Energy-input-based finite-element process modeling of inertia welding

A coupled thermal and mechanical finite-element (FE) model has been developed to describe the inertia welding of RR1000 nickel-base superalloy tubes using the DEFORM 7.2 FE package. The energy input rate is derived from measurements of torque, angular rotation speed, and upset taken from actual inertia welding trials. The model predicts the thermal history of the joint as well as the deformation pattern and final residual stresses. The thermal variation has been validated by a microstructural study of the weld region of the trial joints. Thermal profile predictions have been made for three welds having the same initial kinetic rotational energy but different levels of flywheel inertia and rotational velocity. The concomitant residual stress predictions have been compared with nondestructive neutron diffraction residual stress measurements. The implications of the results for inertia welding are discussed.     

Theoretical and practical aspects of tube sinking by a rotary die

This paper is concerned with a method of analyzing the process of tube sinking by a rotary die, modifying the method of finite elements. The components of the state of strain tensor have been determined for the conventional tube sinking process as well as a rotary die. It has been proved that the adoption of a rotary die does not essentially change the scheme of the state of strain, but that it does, however, reduce the drawing force. The results of theoretical analysis have been compared with those of experimental tests effected by means of a special device ensuring die rotation.     

低翅片管换热过程的数值模拟及其结果分析

以用于冷凝器中的低翅片管为研究对象,利用ANSYS中的流体传热分析模块FLOTRAN CFD,建立管内通R22制冷剂,管外通空气的翅片管换热过程的二维模型,并对其进行流固耦合模拟分析.研究采用正交实验的方法,探究了换热过程中流场与温度场的分布状况,并结合传热学、流体学理论对结果进行了分析,研究表明:在等热流的情况下,翅片管的换热性能明显优于光管,在指定范围内,翅片管换热性能随翅片间距的增加而增强,随翅片厚度的增大而减弱,随翅片高度的增大而增强,但管外压降却随翅高的增大而显著变大,综合考虑换热性能与压降,对翅片管的结构参数进行了优化.      

Three-dimensional finite-element analysis of the quenching process of plain-carbon steel with phase transformation

In this study, three-dimensional finite-element (FE) analyses were carried out to predict the volume fractions of various phases generated during the quenching process of plain-carbon steel and the temperature history, considering the latent heat generated due to phase transformation. Diffusional phase transformation for a nonisothermal process was described by discretizing the cooling curve into various small isothermal steps and using a time-temperature-transformation (TTT) diagram for carbon steel. For this, Sheil’s additive rule was adopted to predict the incubation time which indicates the onset of phase nucleation, and, also, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation was used to model the phase growth. For handling diffusionless transformation, Koistinen and Marburger’s equation was employed to model the austenite-martensite transformation during the rapid quenching process. Finally, temperature variations obtained from the FE simulation were compared to the experimental data available in the literature to validate the reliability of the numerical solution, and its application was made to simulate the three-dimensional forming process of a bevel gear and cam lobe.     

NiTi合金线材无模拉拔加工过程热力耦合数值模拟

结合所研制的连续式无模拉拔加工设备的实际情况,利用DEFORM有限元软件建立了加工过程的热力耦合有限元分析模型,开展了NiTi合金线材无模拉拔加工过程的热力耦合模拟研究,获得了线材无模拉拔加工过程的温度场和应力场的分布规律,以及冷热源距离、冷却水流量及拉拔速度对成品线径的影响规律.通过实验验证了模拟结果的正确性.     

感光鼓用铝管挤压温度场数值模拟与研究

本文使用基于有限体积法的MSC.Superforge软件对感光鼓用铝管挤压过程进行了数值模拟,使用欧拉法表征了挤压过程中金属的温度场。研究了在不同预热温度下坯料的挤压温度分布情况;研究了坯料温度从非稳态到稳态的转变过程,得出了金属在挤压筒与分流组合模焊合室内部的温度变化规律。研究表明在铝管挤压时,由于存在大量变形热和摩擦热而使坯料温度升高;同一预热温度的坯料各部位的温升不相同;不同预热温度的坯料温升也不相同;在其它条件不变的情况下,预热温度越高则坯料温升幅度越小。     

钛基非晶合金电子束焊接热力耦合模拟及非晶化

根据电子束焊接焊缝形貌特征及其深宽比大等特点,选用复合热源作为热源模型.通过线性插值等方式估计材料热力学参数随温度变化,模拟Ti基非晶合金电子束焊接温度场.模拟结果与实际焊缝取得良好的吻合,验证了热源模型的准确性.获得一定变量参数下电子束焊接钛基非晶合金温度场及热循环曲线.在温度场的基础上再进行焊接应力场的模拟,获得残余应力分布曲线.实验验证整个焊件没有晶化相析出,验证了该焊接工艺的可行性.      

Ti,Nb复合添加IF钢热模拟过程中的析出行为

对Ｔｉ，Ｎｂ复合添加的ＩＦ钢进行再加热、热轧及卷取等过程的热模拟实验，用透射电镜和定量金相分别进行样品中Ｔｉ，Ｎｂ析出物的观察和粒度分析。结果表明，Ｔｉ的碳、氮化物先天Ｎｂ的碳、氮化物析出，析出过程主要在热轧时进行；在卷取及冷却过程中析出物长大，但在此过程中并不能清楚地看出有新的析出物产生。     

1650板坯压下过程热/力学行为及压下工艺优化

为了控制梅钢1 650板坯连铸包晶钢过程铸坯内裂纹发生,基于梅钢1 650板坯连铸机生产实际,建立了1 560mm×230mm断面包晶钢铸坯凝固过程三维热/力耦合有限元模型,揭示了铸坯凝固过程各冷却区内的温度场分布规律和铸坯压下过程应力与变形行为演变规律。结果表明,铸坯在结晶器及零段内冷却强度大,沿拉坯及其垂直方向的温度分布梯度大;在实施铸坯凝固末端压下过程中,铸坯宽面中心与宽向1/4处的表面变形及应力变化较为同步,且靠近铸坯内弧侧凝固前沿的塑性应变最大,铸坯应力最大值集中在角部区域;目前梅钢包晶钢连铸压下区间设置不当,易引发铸坯产生内部裂纹。     

利用湿法炼锌赤铁矿法沉铁渣制备铁红工艺

针对赤铁矿渣中存在杂质,影响其综合回收利用的问题,开展赤铁矿渣高温水热法脱杂,制备铁红的研究。研究了不同酸度、温度、时间和液固比条件,对铁红产品中铁、锌、硫含量以及锌、硫脱除率和铁溶出率的影响。实验结果表明:pH值为1,温度220 ℃,保温时间3 h,液固比6∶1,转速400 r·min?1条件下,铁红产品中铁质量分数由58.66%上升为66.83%;赤褐铁类矿物含铁由占总铁质量分数94.05%,上升为97.79%;硫质量分数由2.96%下降至0.82%;锌质量分数由1.03%下降至0.18%。经X射线衍射检测,与赤铁矿渣相比,铁红产品中氧化铁信号峰值提高,杂峰减少。通过扫描电镜/能量散射X射线分析,铁红产品表面附着的硫酸盐等杂质经高温水热法处理后明显减少;实验前后,赤铁矿渣与铁红产品颗粒形貌与大小没有发生变化。实验处理后的铁红产品经检测,满足国家标准氧化铁红含铁量C级,水溶物和水溶性氯化物及硫酸盐含量III型,筛余物2型,105 ℃挥发物V₂型,来源a型标准。      

钢管斜轧穿孔工艺的FEM分析

通过FEM模拟法将无缝管生产中的孔腔形成与扩展机理模型化，并将其结果与实验结论进行比较。     

Laval喷管内流动特征的数值模拟

借助商业软件CFX4．4，对laval喷管内的流场进行数值模拟，从理论上分析了不同滞止压力下管内的流动状态以及激波的产生情况，并验证了k-ε湍流模型的适用性。     

A thermal elastic-plastic finite-element analysis to roll-life prediction on the twin roll strip continuous casting process

The rolling force and roll deformation behavior in the twin-roll-type strip continuous casting process have been computed to estimate the thermal characteristics of a caster roll. To calculate the rolling force, the relationship between the flow stress and strain for a roll material and a casting alloy are assumed as a function of the strain rate and temperature, because the mechanical properties of casting materials depend on temperature. The three-dimensional (3-D) thermal elastic-plastic analysis of a cooling roll has also been carried out, to obtain roll stress and plastic strain distributions, with the commercial finite-element analysis package of ANSYS. Temperature field data for a caster roll, provided by the authors, were used to estimate the roll deformation. Therfore, numerical models considering the thermal and rolling forces have been developed to estimate the roll life. Roll life considering the thermal cycle is calculated using thermal elastic-plastic analysis results. The roll life is proposed in terms of roll revolution in the caster roll models with and without the fine crack failure on the roll surface. To obtain plastic strain distributions of the caster roll, thermomechanical properties of a roll sleeve with a copper alloy are obtained by a uniaxial tensile test for variation of temperature. The proposed analysis techniques have improved in caster roll design.     

Investigation of striation formation in thin stainless steel tube during pulsed Nd:YAG laser cutting process by numerical simulation

The formation of a striation pattern in a thin stainless steel tube was investigated by numerical simulation during a pulsed Nd:YAG laser cutting process. The simulated results were compared with the experimental results, which were performed under the same conditions for simulation. The simulated results showed good agreement with the experimental results. Although the formation of the striation pattern was influenced by various laser parameters, the laser power density had become the most important factor in the formation of striation patterns, since the laser power density is the most influential in the heating of metal, and the striation formation is caused by the ejection of molten metal and evaporation during laser cutting process. Although a high power density resulted in clear regular striation patterns, relatively low power density caused the formation of a hot spot, which hindered the formation of regular striation patterns and caused less striation. The numerical simulation calculations can be used to predict the shape of striation patterns and to offer a way to provide a smooth cut wall.     

不同工艺参数下电渣重熔过程的数值模拟

为研究工艺参数对电渣重熔过程的影响,建立了能够考虑电磁现象并耦合动量和热量传输的三维瞬态数学模型,运用商业软件Fluent进行了模拟研究,计算值与测量值吻合较好。模拟结果表明:在极间距相同的2种工况下,监测点的电流密度值基本相同,说明当渣池深度变化时,可以通过调节电极浸入深度,以符合设定的操作制度。电势降主要发生在渣池区域,渣金界面处的电压仅为0.1V;焦耳热最大值出现在电极端角与渣池接触区域,最小值出现在渣金界面;电磁力最大值出现在电极边角附近,随着纵向深度增加,轴向分量越来越小。极间距为20mm时,电极端角与渣池接触区域的速度和温度均出现最大值,金属熔池深度也最大,其大小分别为0.045m/s,2 250K,41.5mm。     

料层减荷烧结支撑板数值模拟

在烧结台车上安装支撑板,可以支撑起上部烧结饼,减轻下部料层荷重,从而改善下部料层透气性,提高垂直烧结速度,进而提高烧结生产率.应用ANSYS软件对烧结过程中料层内支撑板的热应力进行模拟.结果表明:烧结过程中,支撑面中间部位和支撑板窄面中上部是最容易损坏的部位;排矿时,支撑板支脚部位产生应力集中,当支脚厚度大于40mm时可以满足要求.料层减荷烧结工业试验验证了模拟结果的正确性.     

管坯钢夹杂物成因分析及工艺控制

针对管坯钢非金属夹杂物的形态、组成及形成原因进行了分析,据此采取了相应的工艺控制措施,使管坯钢的冶金纯净度得到了很大提高。     

挤压工艺参数对挤压过程影响规律的仿真模拟研究

研究对象是某6063工业铝型材,将建立好的三维模型导入到有限元Altair Hyperxtrude分析软件进行仿真模拟,通过改变型材挤压工艺参数（挤压比、棒料预热温度、模具预热温度、挤压筒预热温度、挤压速度）,研究其对金属流动的规律,基于直交表Taguchi方法分析各挤压工艺参数对型材截面速度分布和挤压力的影响规律.结果表明:对于型材截面流动均匀程度指标参数,最佳挤压参数为挤压棒料外径205 mm、挤压垫速度3.2 mm/s、棒料预先加热温度480 ℃、挤压模具预先加热温度470 ℃、挤压筒预先加热温度440 ℃;对于挤压力指标参数,棒料外径200 mm、挤压垫速度1.4 mm/s、棒料预先加热温度490 ℃,挤压模具预先加热温度480 ℃、挤压筒预先加热温度460 ℃.