于海岐朱苗勇
金属学报
建立了描述圆坯连铸结晶器电磁搅拌过程的三维数学模型. 采用有限元和有限体积结合的方法求解Maxwell方程组和湍流Navier-Stokes方程, 分析了结晶器电磁搅拌过程的磁场、流场、温度场和夹杂物轨迹特征, 并考虑了励磁电磁强度和频率的影响. 研究表明, 磁场模拟结果与现场实测数据一致, 电磁力在圆坯水平截面上呈周向分布. 钢液在结晶器纵截面内形成两对回流区, 且在水平截面内旋转流动; 过热钢液滞留在结晶器上部区域, 铸坯芯部温度迅速降低, 凝固前沿温度梯度提高; 大部分夹杂物积聚到结晶器上部区域旋转运动. 励磁电流强度和频率对结晶器内钢液的流动、温度分布及夹杂物运动均有明显影响.
关键词:
圆坯结晶器
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electromagnetic stirring (EMS)
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electromagnetic field
,
flow field
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Temperature field
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Inclusion
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numerical simulation
高士友
,
石力开
,
席明哲
,
纪宏志
,
张永忠
,
杜宝亮
金属学报
建立了模拟直薄壁件逐点沉积过程中温度场的有限元模型,用等价导热系数和焓值法处理了固-液耦合热传导问题和固液混合区的焓. 模拟结果真实地反映了沉积316L不锈钢直薄壁件的温度场特征. 通过对模拟结果的分析得出, 在高温阶段(700℃以上)熔池的平均冷却速率达到1000 ℃/s数量级, 在240℃以下的冷却速率仅为10 ℃/s数量级. 基板的温度变化经历温度上升、温度平稳、温度下降3个阶段；在温度下降阶段, 基板中的热传导对熔池冷却速率影响很小. 有限元模拟结果与已有文献的实验测量数据吻合很好.
关键词:
激光直接沉积
,
Metallic Vertical thin wall samples
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Temperature field
何亚章
,
王东坡
,
王颖
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2014.Z1.007
以5 m直径大型运载火箭贮箱筒段为研究对象,对该筒段进行了环缝焊接过程的有限元模拟,得到了焊接过程的温度场分布情况以及简化工装约束条件下焊接后和约束卸载后的应力变形情况.结果表明,筒段的整体变形以径向变形为主;焊后最大应力出现在焊缝,最大应力429 MPa,由于应变强化而高于屈服强度;焊缝处的应力除外表面轴向应力为压应力,其他皆为拉应力.
关键词:
贮箱
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筒段
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环缝焊接
,
有限元
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温度场
,
应力变形
Fengli SUI
,
Liqing CHEN
,
Xianghua LIU
,
Lintao WANG
,
Wei LI
金属学报(英文版)
doi:10.1016/S1006-7191(08)60074-5
A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continuous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method (FEM). The temperature of characteristic analysis points in the intermediate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 ℃ and initial velocity in range of 0.15-0.55 m．s-1. Based on finite element analysis and microstructural observation in cylindrical hot compression experiments, the appropriate hot continuous rolling technologies have been designed for rod products with different diameters. For a real rolling practice, the simulated surface temperature was examined and is in good agreement with the measured one.
关键词:
Hot continuous rolling
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null
,
null
,
null
,
null
Aiying WANG
,
Chao SUN
,
Rongfang HUANG
,
Lishi WEN
材料科学技术（英）
A three-dimensional model was developed to investigate the influence of various hot filaments parameters on substrate temperature fields that significantly affect the nucleation and growth of diamond films over large area by hot-filament chemical vapor deposition (HFCVD). Numerical simulated results indicated that substrate temperature varies as a function of hot filaments number, radius, temperature, emissivity, the distance between filaments, and the distance between substrate and filaments arrangement plane. When these filaments parameters were maintained at the optimal values, the homogeneous substrate temperature region of 76mm×76mm with the temperature fluctuation no more than 5% could be obtained by a 80mm×80mm hot filaments arrangement plane. Furthermore, the homogeneous region could be enlarged to 100mm×100mm under the condition of supplementary hot filaments with appropriate parameters. All of these calculations provided the basis for specially optimizing the hot filaments parameters to deposit uniform diamond film over large area by HFCVD.
关键词:
HFCVD
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null
,
null
,
null
Zhao ZHANG
,
Jun BIE
材料科学技术（英）
A fully coupled thermo-mechanical model was developed to study the temperature fields and the plastic deformations of alloy AL6061-T6 under different process parameters during the friction stir welding (FSW) process. Three-dimensional results under different process parameters were presented. Results indicate that the maximum temperature is lower than the melting point of the welding material. The higher temperature gradient occurs in the leading side of the workpiece. The calculated temperature field can be fitted well with the one from the experimental test. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface, which is formed by the specific material flow patterns in FSW. The maximum temperature can be increased with increasing the welding speed and the angular velocity in the current numerical modelling.
关键词:
Fully coupled thermo-mechanical model
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null
,
null
,
null
Xiaohua ZHANG
金属学报(英文版)
The temperature field of AZ91D magnesium alloy extruded by equal channel angular extrusion (ECAE) has been simulated using finite element method (FEM). A series of tests were designed to obtain the simulation parameters: flow stress of AZ91D, friction factor and heat transfer coefficient. The simulated temperature agrees well with the measured one. The evolution of temperature and influencing factor was discussed in details. Furthermore, the extrusion pressure of ECAE was analyzed.
关键词:
Simulation
,
温度场
,
等通道角挤压
,
AZ91D；镁合金
Shunhong LIU
,
Xiong FANG
,
Pengteng WAN
,
Jing YAN
材料科学技术（英）
Laser bending of sheet metal is a flexible forming technique by using laser scanning. Based of temperature grads mechanism, the temperature field of sheet metal bending process by using single laser scanning is studied with the ANSYS soft. A finite element model of temperature field is built. The dynamic variation process and distribution of temperature field of laser bending at given parameters are analyzed. Furthermore, the influence parameter on the peak temperature and temperature grads are also studied.
关键词:
Laser bending
,
null
,
null
Kaijin HUANG
,
Dawen ZENG
,
Changsheng XIE
,
Desheng XU
材料科学技术（英）
A 3D unsteady state numerical model of heat transfer in the circumferential laser oxygen cutting of pipes was developed. In order to minimize the computing time required for solving the finite difference equations as much as possible, the alternating direction implicit (ADI) method was adopted. Based on the characteristics of the pipe cutting process, the periodic boundary condition was applied to calculate the temperature distribution in the θ direction and the self-adaptive grid technology was also used. The mathematical model takes account of the temperature-dependent thermal properties of the pipe. The calculated kerfs width and the heat-affected zone (HAZ) were compared with the experimental results.
关键词:
Laser cutting
,
null
,
null
