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31.
O.J Llegbusi 《Journal of Materials Engineering and Performance》1996,5(1):117-123
A mathematical model has been developed to describe the velocity field in an agitated Al- 5Cu alloy in which B4C particles
were suspended at different loading rates of up to 40 %. The material system was agitated by means of an electromagnetic rotary
stirrer. The non- Newtonian behavior of the melt/solid slurry was allowed for using two models: the steady- state model of
Joly and Flemings and the model of Brown, which takes account of time- dependent behavior. Calculations have shown that the
two models behave similarly at high shear rates. In addition, if agitation was discontinued, very little time was required
for the velocity (and hence the fluidity) of the slurry to decay. 相似文献
32.
33.
聚醚型聚氨酯的氢键、微相分离及性能 总被引:7,自引:0,他引:7
用本体一步法合成了5种不同硬段含量(11.0%~46.9%)的二苯甲烷-4,4′-二异氰酸酯/环氧乙烷封端型聚环氧丙烷聚醚/乙二醇的聚醚型聚氨酯,并借助于IR,DSC,DMS和材料试验机等手段对该聚氨酯的氢键、微相分离及力学性能进行了表征。结果表明:随着硬段含量的增加,其>NH与微区中的>C=O的氢键化程度逐渐提高,软段微区中—O—的氢键化程度逐渐降低;微相分离程度逐渐提高;拉伸强度及硬度随之增加,扯断伸长率在硬段含量40%左右出现极大值。 相似文献
34.
35.
36.
Deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation 总被引:1,自引:0,他引:1
The hot deformation behavior and microstructures of Al-7055 commercial alloy were investigated by axisymmetric hot compression at temperatures ranging from 300°C to 450°C and strain rates from 10-2 to 10 s-1,respectively.Microstructures of deformed 7055 alloy were investigated by transmission electron microscopy (TEM).The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation.The hot deformation activation energy of the alloy is 146 kJ/mol.... 相似文献
37.
Shape memory alloy ( SMA) torsion actuator is one of the key approaches realizing adaptive wings in airplanes. In this paper,the actuator is made up of SMA wires and a thin-walled tube,in which the SMA wires are twisted and affixed around the surface of the tube at an angle referenced to the center axis of the tube. A thermo-mechanical constitutive model is developed to predict the thermo-mechanical behaviors of the SMA torsion actuator based on the knowledge of solid mechanics. The relationship between the torsion-angle and tem- perature is numerically calculated by using the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. The numerical results are compared with the relative experimental results finished by Xiong and Shen. Influences of the twist-angle of SMA wires and geometrical factors on the primary actuation performances of the SMA torsion actuator are also numerically investigated based on the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. Results show that the thermo-mechanical constitutive model can well predict the thermo-mechanical behaviors of the SMA torsion actuator. 相似文献
38.
针对长句子引起句法分析性能下降的问题,本文提出了一种基于SVM的句子片段划分方法:先根据语法结构将句子划分为多个片段,识别出每个片段的类别;然后根据片段的类别将句子分割为几个部分,每个部分作为句法分析的基本单元;最后将句法分析之后的各个部分进行合并,形成完整的分析结果.该方法减小了句法分析的复杂度,提高了分析的准确率. 相似文献
39.
为了建立多维应力、应变空间的弹塑性本构关系,将一般加载规律一维全量理论的简单弹塑性模型推广到一般加载规律的多维增量理论,并且给出应力空间的加载函数和应变空间的加载函数以及它们之间的正确的变换关系.在此基础上,在应变空间中建立了推导一般加载规律的多维增量理论的本构关系的一种途径.应用这种途径,从应变空间的加载函数出发,推导了等向强化材料的一般加载规律的弹塑性本构关系.理论和实例表明,这种途径对等向强化材料、随动强化材料、理想弹塑性材料和热弹塑性问题都适用. 相似文献
40.
To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship,
a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone)
were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress—strain curves according
to the seepage variation were obtained. Based on the experimental results and by employing Hooke’s law, the formulation of
the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition,
the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that
can be respectively determined by using the experimental results were included. The calculated results show that the proposed
coupling model is capable of simulating the stress—strain relationship with considering the seepage-stress coupling in the
nonlinear elastic stage of two kinds of soft rock.
Foundation item: Projects(50378069, 50639090) supported by the National Natural Science Foundation of China; Project(50639090) supported by
the Joint Fund of Yalong River Hydropower Development, China 相似文献