吴承伟
在先进材料试验、检测、分析与加工、工程力学、生物力学、燃料电池、大型工业装备结构试验与分析等学科交叉点上开展研究工作
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- 姓名:吴承伟
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学术头衔:
博士生导师
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学科领域:
水文学
- 研究兴趣:在先进材料试验、检测、分析与加工、工程力学、生物力学、燃料电池、大型工业装备结构试验与分析等学科交叉点上开展研究工作
吴承伟在先进材料试验、检测、分析与加工、工程力学、生物力学、燃料电池、大型工业装备结构试验与分析等学科交叉点上开展研究工作.这些交叉学科的研究以力学为主导,围绕新能源、新材料、新技术、新工艺,将应用基础研究与工程应用研究紧密结合,特别注意将先进的技术与工艺应用于工业生产。在国内外累计发表论文100余篇(其中英文论文40余篇),与国内外同行合著专著4部(其中中文两部,英文两部),获得国家专利2项。共主持和参加国家和省部级研究课题16项,获得过国家教委科技进步3等奖、辽宁省科技进步2等奖、中国青年科技奖、辽宁省青年技术拔尖人才、大连市劳动模范和大连市优秀专家等荣誉称号。发表的论文被SCI收录26篇、EI收录31篇,论文近五年在SCI上检索到被国际同行引用190余次。
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吴承伟
,-0001,():
-1年11月30日
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【期刊论文】Multi-coated spheres: recommended electrorheological particles
吴承伟, C W Wu† and H Conrad‡
J. Phys. D: Appl. Phys. 31(1998)3312-3315.,-0001,():
-1年11月30日
This paper considers the design of electrorheological (ER) particles. Multi-coated particles suspended in insulating (very weakly conducting) oil are recommended for obtaining high-performance ER suspensions. Only the outer two coatings determine the ER strength. The outermost coating should be a material with high dielectric constant, high electrical breakdown strength and a reasonable level of conductivity. The coating immediately below should be a highly conducting material. The inner coatings, including the core (which can be void), can be of any material having such a density that the composite particle has substantially the same density as the host liquid. Our analysis gives that multi-coated particles can have an ER shear strength as high as 29kPa when the volume fraction of particles is 0.4 and the applied field is 5kV mm-1. Results in the literature provide support for the concept and analysis.
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【期刊论文】Influence of mixed particle size on electrorheological response
吴承伟, C. W. Wu a) and H. Conrad
,-0001,():
-1年11月30日
Two sizes (6 and 100 μm average diameter) glass spheres suspended in silicone oil (volume fraction Ф=0.3) were used to investigate the influence of particle size on electrorheological response at a shear rate 2s-1. The larger particles gave a higher shear yield stress but a lower current density at zero shear than the smaller ones. When the two particle sizes were mixed together, the shear yield stress decreased, reaching a minimum when the volume fraction of the small particles equals that of the large particles. The minimum in the current density occurred when the ratio of the volume of small to large particles was ~1/3.
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【期刊论文】Influence of a surface film on the particles on the electrorheological response
吴承伟, C. W. Wu a) and H. Conrad
,-0001,():
-1年11月30日
A conduction model is developed for the dc electrorheological (ER) response of highly conducting particles (e.g., metal particles) suspended in a weakly conducting oil. The numerical analyses show that a surface film with some conductivity is desired, but not a completely insulating film as previously proposed. Increasing the film conductivity leads to an increase in the ER yield stress. However, too high a conductivity will give an unacceptable level of current density. The film should also have an intermediate thickness. A small thickness increases the possibility of electrical breakdown in the film; too large a thickness decreases the ER effect. Good agreement exists between the yield stress and the current density predicted by our model and those measured.
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吴承伟, C. W. Wu a) and H. Conrad
,-0001,():
-1年11月30日
A method was developed for the frequency dependence of the electrorheological (ER) response of suspensions of highly conducting particles with a low conducting surface film. At dc or low frequency ac field, the shear yield stress of the ER fluids considered is determined by the conductivity ratio σI/σf of the film to the host oil; at high frequency ac field it is determined by the permittivity ratio єI/єf. The critical frequency separating the conduction domain from the dielectric domain is proportional to σf/єf, the ratio of the conductivity to the permittivity of the host oil. To obtain a high shear yield stress at high frequency ac field, a high ratio of the permittivity of the surface film to the oil is desired and a reasonably thin surface film. Too thin a film increases the possibility of electrical breakdown in the film especially at a small ratio of єI/єf. An effective method for overcoming electrical breakdown in the surface film is to increase the permittivity of the film. Good agreement exists between the measured shear yield stress, current density, and the applied breakdown field for oxidized aluminum particles suspended in silicone oil and those predicted by the present model. Recommendations are given for the design of ER fluids with high yield strength and reasonable current density.
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【期刊论文】Electrorheology of a zeolite/silicone oil suspension with dc and ac fields
吴承伟, C W Wu, Y Chen and H Conrad
J. Phys. D: Appl. Phys. 31(1998)960-963.,-0001,():
-1年11月30日
The electrorheology of a zeolite/silicone oil suspension (
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【期刊论文】Dielectric and conduction effects in ohmic electrorheological fluids
吴承伟, C W Wu† and H Conrad
J. Phys. D: Appl. Phys. 30(1997)2634-2642.,-0001,():
-1年11月30日
Dielectric and conduction effects in electrorheological (ER) fluids with ohmic conductivity of the host liquids and with an applied AC electric field are considered. It is found that the conductivity ratio Γσ, the dielectric constant ratio Γε and the applied field frequency fare three important parameters which determine the ER effect. If Γσ>Γε, a stronger ER response is obtained with a low applied field frequency than with a high frequency. If Γσ<Γε, the opposite occurs. Empirical equations are given for the attractive force between the particles in an ER fluid and for the shear yield stress. The calculated current density is independent of the applied field frequency when the frequency is smaller than a critical value, but becomes a linear function of the frequency beyond the critical value. The predicted attractive force of two nearly touching polymer spheres inmineral oil is in good agreement with that measured; also the predicted shear yield stress of some common ER suspensions is in accord with measurements.
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【期刊论文】Dielectric and conduction effects in non-Ohmic electrorheological fluids
吴承伟, C. W. Wu* and H. Conrad
,-0001,():
-1年11月30日
Dielectric and conduction effects in electrorheological (ER) suspensions with non-Ohmic conductivity of the host liquid and with ac applied electric field are investigated. It is found that the conductivity ratio Гб, the non-Ohmic conductivity parameters A and Ec of the host oil, the dielectric constant ratio Гб, and the applied field frequency are important parameters that determine ER response. The effects of these parameters are more complex than in the case of host liquids with simple Ohmic conductivity. If the ac field frequency is high, the conductivity effect disappears; if the frequency is low the dielectric effect disappears. The current density is independent of the frequency below a critical value, but it increases with frequency beyond the critical value. The critical frequency is larger for ER suspensions having non-Ohmic conductivity of the host liquid than with Ohmic conductivity. Good agreement occurs between experimental measurements of the current density and attractive force between particles (including shear yield stress) and predictions by our model.
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【期刊论文】A new hydrodynamic lubrication theory for bilinear rheological fluids
吴承伟, C.W. Wu a.*, H.X. Sun b
J. Non-Ncwtonian Fluid Mech., 56(1995)253-266,-0001,():
-1年11月30日
Hydrodynamic lubrication of a bilinear rheological fluid plays an important role in the so-called electrorheological (ER) smart' bearings. There may not. however, be a reliable and efficient algorithm for the non-Newtonian lubrication problem of bilinear rheological fluids. In this paper, a finite element trethod (FEM), together with a mathematical programming solution technique, are proposed for solving such a non-Newtonian lubrication problem. This method was used to study the hydrodynamic lubrication of a journal bearing lubricated by a bilinear rheological lubricant. The computed results were compared with Tichy's work for the Bingham rhcological model. It was shown that the Bingham model should be regarded as a limiting case of the bilinear rhcological model.
Bilinear rheological model, Bingham model, Lubrication
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【期刊论文】A new algorithm of time stepping in the non-linear dynamic analysis
吴承伟, Yang Haitian*, Gao Qiang, Guo Xinglin and Wu Chengwei
Commun. Numer. Meth. Engng 2001; 17: 597-611,-0001,():
-1年11月30日
This paper presents a new scheme of time stepping for solving non-linear dynamic problems. By expanding variables in a discretized time interval, FEM-based recurrent formulae are derived leading to a self-adaptive algorithm for different sizes of time steps. There will be no requirement of iteration for the non-linear solutions. Numerical validation shows satisfactory results.
dynamic problem, time stepping, fnite element, viscoelasticity
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