Z.M. Zhang
,
T. Lu
,
C.J. Xu
,
X.F. Guo
金属学报(英文版)
Directionally solidified binary Mg-Al eutectic
alloy wires of approximately 5mm in diameter were produced by the
Ohno continuous casting (OCC) process and the microstructure was
examined. It was found that the wires possess obvious unidirectional
growth characteristic along its axial direction. The microstructure
consists of parallel columnar grains that resulted from the
competitive growth of equiaxed grains solidified on the head of
dummy bar. Each columnar grain comprises regular eutectic
α-Mg and β-Mg17Al2 phases, which grew along the axial direction of the wires. The morphology of the eutectic ismainly lamellar, meanwhile rod eutectic exists. The formation of rod eutectic was attributed to the ``bridging effect" caused by
incidental elements in the alloy.
关键词:
Mg-Al alloy
,
null
,
null
,
null
魏洪亮
,
杨晓光
,
于慧臣
材料工程
doi:10.3969/j.issn.1001-4381.2005.04.011
针对涡轮盘用GH4169合金开展了高温下单调拉伸、对称循环及非对称循环的实验工作,结果表明,该材料具有比较明显的循环软化和平均应力松弛特性.采用带Ohno/Wang修正的Chaboche粘塑性理论本构方程,对其表现出的复杂力学现象进行本构建模,介绍了Levenberg-Marquadt非线性优化算法,结合材料实验数据并通过该算法识别了本构方程参数,将本构方程通过用户子程序嵌入到有限元软件ABAQUS中,对GH4169合金的上述实验现象进行了数值模拟,计算曲线与实验曲线取得了较好的一致性.
关键词:
循环软化
,
平均应力松弛
,
本构方程
,
参数识别
Author M. AbdelKarim
,
M. Mizuno and N. Ohno\= Department of Mechanical Engineering
,
Nagoya University Chikusaku
,
Nagoya 4648603
,
Japan Manuscript received 18 October 1998
金属学报(英文版)
In the previous paper, in order to express steadystate ratchetting, the present authors extended the cyclic plasticity model proposed by Ohno and Wang (1993), and the validity of the extended model was discussed on the basis of uniaxial ratchetting experiments of 316FR steel at room temperature. In the present paper, the validity of the extended model is discussed further on the basis of nonproportional experiments of IN738LC at 850 such as multiaxial ratchetting, multiaxial cyclic stress relaxation, circular cyclic straining with strain hold, and so on. Predictions based on the OhnoWang model as well as the ArmstrongFrederick model are also given for the sake of comparison. It is shown that the extended model is capable of simulating the nonproportional experiments accurately, and especially that the extended model can predict much less steadystate ratchetting than the ArmstrongFrederick model. It is also shown that the extended model provides almost the same predictions as the OhnoWang and th
关键词:
dynamic recovery
,
null
,
null
,
null
,
null
倪永中
,
徐鸿
材料科学与工程学报
本文提出了一种基于粒子群算法和有限元方法的弹塑性本构方程参数的确定方法,并在此基础上开发了参数自动优化系统CMPI(Constitutive Material Parameter Identification).通过使最小二乘形式的目标函数达到极小值,实现参数的动态寻优;模型参数作为粒子群优化模块的输入,采用应变(应力)控制方法,调用材料非线性有限元模块计算特定参数时的应力(应变)响应,并计算与实验数据的误差,从而实现优化过程.CMPI目前适用于A-F类模型(Chaboehe、Ohno-Wang、Jiang-Sehitoglu)的参数优化,以此为基础,不难扩展到其他材料模型.
关键词:
粒子群
,
材料非线性
,
有限元
,
Ohno-Wang 模型
