李海丽
,
赵九洲
,
李中原
,
何杰
金属学报
建立了偏晶合金液--液相变过程中的两相流动模型,
发展了偏晶合金凝固理论模型; 以Al-Pb合金为例,
模拟研究了偏晶合金凝固时的组织演变进程,
考察了流动对凝固组织形成的影响. 结果表明,
对流影响液--液相变的形核特性,
提高凝固界面前沿最高弥散相液滴数量密度、最大液滴半径和最高弥散相
体积分数, 促进宏观偏析组织的形成.
关键词:
液-液相变
,
two-phase fluid flow
,
monotectic alloy
,
modeling
朱鸣芳
,
陈
,
晋
,
孙国雄
,
洪俊杓
金属学报
对朱、洪已发展的一种微观尺度cellular automaton(CA)模型做了进一步改进.
在改进的模型中用二元合金的Gibbs-Thomson方程建立固/液界面的平衡关系.
考虑了动力学和表面能各向异性对枝晶择优生长方向的影响. 应用改进的模型
模拟了不同择优取向的单枝晶在过冷熔体中的自由生长、定向凝固过程中柱状
晶的竞争生长以及等轴晶的演变过程. 模拟结果表明, 改进后的模型成功地模
拟出各种不同择优取向的单枝晶和多枝晶的生长形貌.
关键词:
枝晶生长
,
modeling
D. Jin
,
E. D. Dominik
,
R. V. Kolarik II
,
J. E. Ives and E. B. Damm (The Timken Company
,
1835 Dueber Avenue
,
S.W.
,
Canton
,
Ohio 44706-0932
,
U.S.A.)
金属学报(英文版)
An integrated mathematical model to simulate seamless tube rolling processes has been developed at The Timken Company. The model is capable of simulating the thermal, deformation and microstructure evolution in the piercing, elongating and reducing/sizing and the austenite decomposition in the mill annealing and cooling operations. Finite difference schemes are employed to model cooling, reducing/sizing and stretch reducing, and finite-element schemes are employed to simulate piercing and elongating. The model predicts the thermal history, deformation, rolling load, torque, recrystallization and grain growth in hot tube rolling, austenite decomposition in cooling or annealing, and the final structure-properties. In this paper mathematical models which are employed to describe the thermal, deformation and microstructure evolution along with the modeling results are presented. The developed "tube rolling mill in the computer" provides a powerful tool for engineers for product and process development, process control, process optimization and quality control.
关键词:
modeling
,
null
,
null
,
null
,
null
J.C. Wang
,
Z.M. Zhang and G.C. Yang State Key Labortory of Solidification Processing
,
Northwestern Polytecnical University
,
Xi'an 710072
,
China
金属学报(英文版)
Taking three kinds of metal-matrix composites (MMCS) (laminated composites, fibers reinforced MMCs, and particle-reinforced MMCs)as examples, the recent develop ments in modeling the damping behaviors of MMCs are extensively reviewed. The damping mechanisms of different kinds of composites are quite different, and therefore, the analytical of numerical methods for different kinds of MMCs are also quite different. This will he shown in this extensive review. Furthermore, the directions of future developments in modeling the damping behavior of MMCs are also presented.
关键词:
modeling
,
null
,
null
刘旺中
,
陈照波
,
黄山云
,
焦映厚
功能材料
形状记忆合金（shape memory alloy,SMA）是一类新型功能材料,作为电热驱动器,广泛应用于工程领域。但由于材料内在的非线性性质和迟滞效应使其在控制系统的设计和热力学建模上较为困难,不利于简单控制系统和实时控制的实现。基于Preisach理论给出SMA驱动器系统的温度-位移迟滞模型,分析系统的热传导过程,将传统的比例-积分-微分PID（proportional-integral-differential,PID）策略应用于控制器的设计,并引入蚁群和粒子群两类智能算法优化控制器参数,讨论优化过程和控制效果;与传统PID参数整定方法相比,系统的阶跃响应和正弦信号跟踪性能取得比较理想的效果,且智能算法调节控制器参数的实时性更强,克服非线性和迟滞效应的影响。
关键词:
形状记忆合金
,
迟滞非线性
,
建模
,
PID控制
,
增益优化
,
智能算法
,
Preisach理论
,
热模型
H.D. Chen
,
Y.W. Wang
,
J. Xue
金属学报(英文版)
A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT). In this paper, one goal of the simulation is to compute ultrasoniceld radiated by arbitrary transducers into pieces under examination. The other simulates a testing experiment. The simulation approach is based on the model for the computation of the ultrasoniceld in isotropic media radiated from actual NDT transducers. After the eld is known, remaining to be modeled is the interaction between this eld and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchho's diffraction approximations theory applied to elastodynamics. We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous. The simulating results demonstrate that the model in ultrasonic NDT of welds is practical in further research and useful in optimizing testing congurations.
关键词:
ultrasonic testing
,
null
,
null
,
null
D. K. Zhang and J. T. Niu (National Key Laboratory of AdVanced Welding Production Technology of HIT
,
Harbin 150001
,
China)
金属学报(英文版)
By using alternating current plasma arc welding,the influences were studied of such parameters as welding curent,arc voltage,welding speed,wire feed rate,and magnitude of ion gas flow on front melting width,wdle reinforcement,and back melting width of LF6 aluminum alloy.Model of the formation of welding seam in alternating current plasma arc welding of aluminum was set up with the method of artificial neural neural network - BP algorithm. Qyakuty of formation was consequently predicted and evaluated.The experimental result shows that,compared with other modeling methods,artificial network model can be used to more accurately predict formation of weld,and to guide the production practice.
关键词:
alternating current plasma arc
,
null
,
null
,
null
