王刚
,
马兵善
,
范宗良
,
杨蓉霞
,
李绍勇
工程热物理学报
对方腔一侧壁面温度随时间按正弦规律变化、充满CuO-水纳米流体的二维方腔内的非稳态自然对流换热进行了数值研究.在相关参数一定的条件下,研究了Ra数、纳米颗粒体积份额φ和纳米颗粒布朗运动对自然对流换热特性的影响.数值模拟结果表明:考虑布朗运动时壁面时均Nu数均大于不考虑布朗运动时的相应值;不考虑布朗运动时,时均Nu数均随φ的增大而增大;而考虑布朗运动时,当Ra数较小时,时均Nu数均随φ的增大而增大,而Ra数较大时,存在有最佳的φ值,可使时均Nu数达到最大值.
关键词:
自然对流
,
纳米流体
,
方腔
,
布朗运动
,
周期性变化热边界条件
F.R. Cao and J.Z. Cui(Department of Metalforming
,
P.O.B 317
,
Northeastern University
,
Shenyang 110006
,
China)
金属学报(英文版)
The maximum elongation-to-failure of 960% has been achieved in the Mg-8wt%Li alloy. It is shown by measurement of true stress-strain curve and microstructure observation that dynamic recrystallization takes place during superplastic deformation, which turns the banded grains into equiaxed grains. It is postulated by theoretical analysis that during superplastic deformation,continuous introduction of lattice dislocations into the phase interfaces contributes to the superplasticity in this alloy.During superplastic deformation,grain growth and cavity nucleation at α phase grain boundaries have also been observed.
关键词:
superplasticity
,
null
,
null
,
null
,
null
N. Tada
,
T. Kitamura
,
R. Ohtani and E. Nakayama (Department of Engineering Physics and Mechanics
,
Graduate School of Engineering
,
Kyoto University
,
Yoshida-hommachi
,
Sakyo-ku
,
Kyoto
,
606-8501
,
Japan)
金属学报(英文版)
Creep-fatigue test was carried out using smooth round bar specimens of Type 304 stainless steel. Cavities and small cracks on the cross-section of the specimen were carefully observed by a scanning laser microscope. Moreover, direct current electrical potential method (DC-EPM) was applied in order to evaluate non-destructively the distribution of internal cracks. The distribution evaluated by DC-EPM agreed well with the actual one.
关键词:
creep-fatigue
,
null
,
null
,
null
,
null
