检索结果-南通市图书馆

Discussion forthe Semiinfinite Medium Approximation and the Thermal Diffusion Velocity in Laser Heat Treatment

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 1999年第4期8卷 90-96页

作者： LI Junchang LI Xingyi CHEN Jingbo FAN Zebin CHEN Qinghua (Kunming University of Science and Technology, Kunming, 650093, China) received Dec. 14, 1998 revised manuscript received Apr. 12, 1999 昆明理工大学云南昆明 650093 昆明理工大学云南昆明

It is a conventional method to regard laser iradiated object as a semi infinite medium with invariable thermal physical property parameters for approximate analyses of thermal acting of laser heat treatment. So far, 2αt and α/t have been taken as the thermal diffusion distance and the thermal diffusion velocity respectively, at the time t after heat fluctuation in materials with a thermal diffusion coefficient α, and as a result, the feasibility of the approximately estimating method about semi infinite medium is judged. This paper indicates that, due to quantitative investigation of heat energy diffusion, the thermal diffusion distance of 3αt and the thermal diffusion velocity of 1.5α/t can more accurately describe the physical process of heat conduction. Finally, an applied example of approximately estimating the temperature field of laser heat treatment is presented.

关键词： laser heat treatment temperature field estimate thermal diffusion velocity

Investigation of Sintering Technology for Composite of Stainless Steel and Partially Stabilized Zirconia

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2002年第1期18卷 10-12页

作者： Wenquan ZHANG, Jianxin XIE, Changjing ZHANG and Zhiguo YANGSchool of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China [ manuscript received September 4, 2000, in revised form April 13, 2001] Sch. of Mat. Sci. and Eng. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The sintering technology for mixed powdered extrusion rods of different proportions of stainless steel to magnesia partially stabilized zirconia (PSZ) was investigated. The effects of some sintering parameters including holding time, atmosphere and protective gas pressure on shrinkage, relative density, microstructure, micro-Vickers hardness and compression strength of sintered samples were mainly researched. The experimental results are as follows: (1) The shrinkage and the relative density of the sintered samples decrease as increasing stainless steel content in the composite, except for the case containing 90 percent of stainless steel; (2) The porosity in PSZ matrix rises as increasing the stainless steel content in the composite; (3) Longer sintering holding time, higher sintering vacuum and gas-pressure sintering process not only enhance the relative density, but also improve microstructure of composite; (4) Micro-Vickers hardness of PSZ matrix decreases as increasing stainless steel content, while that of stainless steel particles in sintered samples varies unnoticeably.

关键词： PSZ Stainless steel Composite Sintering technology

Processing TiAl-Based Alloy by Elemental Powder Metallurgy

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2000年第6期16卷 605-610页

作者： Yong LIU, Baiyun HUANG, Yuehui HE and Kechao ZHOU (National Key Laboratory for Powder Metallurgy, Central South University of Technology, Changsha 410083, China) [manuscript received July 31, 1999, in revised form November 19, 1999] Natl. Key Lab. for Powder Metallurgy Central South Univ. of Technol. Changsha 410083 China

TiAI-based alloys with various compositions (including Ti-48Al, Ti-47Al-2Cr-2Nb, Ti-47Al-2Cr-2Nb-0.2B and Ti-47Al-3Cr, in mole fraction) had been prepared by elemental powder metallurgy (EPM). The results have shown that the density of the prepared Ti-48AI alloy increases with increasing hot pressing temperature up to 1300℃. The Ti-48AI alloy microstructure mainly consisted of island-like Ti3Al phase and TiAl matrix at hot pressing temperature below 1300℃, however, coarse α2/γ lamellar colonies and γ grains appeared at 1400℃. It has also indicated that the additions of elemental Cr and B can refine the alloy microstructure. The main microstructural inhomogeneity in EPM TiAI-based alloys was the island-like α2 phase or the aggregate of α2/γ lamellar colony, and such island-like structure will be inherited during subsequent heat treatment in (α＋γ) field. Only after heat treatment in a field would this structure be eliminated. The mechanical properties of EPM TiAl-based alloys with various compositions were tested, and the effect of alloy elements on the mechanical properties was closely related to that of alloy elements on the alloy microstructures. Based on the above results, TiAI-based alloy exhaust valves were fabricated by elemental powder metallurgy and diffusion joining. The automobile engine test had demonstrated that the performance of the manufactured valves was very promising for engine service.

关键词： TiAl Processing TiAl-Based Alloy by Elemental Powder Metallurgy

Study of a Waveguide CO2 Laser with Two Parallel Tubes

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 1998年第1期 12-17页

作者： HUANG Yuangqing(Dept. of Sci. Instr. and Precision Mech. of Xiamen Univ.,Xiamen, 361005, China)received Dec. 23 1996 revised manuscript received Apr. 22 1997

ＳｔｕｄｙｏｆａＷａｖｅｇｕｉｄｅＣＯ２ＬａｓｅｒｗｉｔｈＴｗｏＰａｒａｌｅｌＴｕｂｅｓＨＵＡＮＧＹｕａｎｇｑｉｎｇ（Ｄｅｐｔ．ｏｆＳｃｉ．Ｉｎｓｔｒ．ａｎｄＰｒｅｃｉｓｉｏｎＭｅｃｈ．ｏｆＸｉａｍｅｎＵｎｉｖ．，Ｘ... 详细信息

ＳｔｕｄｙｏｆａＷａｖｅｇｕｉｄｅＣＯ２ＬａｓｅｒｗｉｔｈＴｗｏＰａｒａｌｅｌＴｕｂｅｓＨＵＡＮＧＹｕａｎｇｑｉｎｇ（Ｄｅｐｔ．ｏｆＳｃｉ．Ｉｎｓｔｒ．ａｎｄＰｒｅｃｉｓｉｏｎＭｅｃｈ．ｏｆＸｉａｍｅｎＵｎｉｖ．，Ｘｉａｍｅｎ，３６１００５，Ｃｈｉｎ...

关键词： two parallel tubes waveguide CO2 laser single cathode double anode

Magnetism of Metals, Alloys and of Clusters of Transition Metal Atoms

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2001年第6期17卷 581-589页

作者： N.H.March Oxford University, Oxford, England Department of Physics, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium [manuscript received March 28, 2001, in revised form July 6, 2001] Univ Oxford Oxford England Univ Antwerp Dept Phys RUCA B-2020 Antwerp Belgium

A condition for local moment formation in metals derived by Stoddart and March (Ann. Phys. NY 1972 64, 174) is first used to discuss the ferromagnetism of body-centred-cubic Fe. A less detailed discussion is also added on Ni and Co. This leads into a treatment of the non- linear response of such 3d ferromagnets to dilute substitutional impurities. Antiferromagnets responding to local changes in the exchange field caused by such impurities are also studied, Mn in Cr being one such system discussed. The paper concludes with a brief summary of clusters of transition metal atoms, with most attention devoted to Cr and to Mn.

关键词： NiCr Alloys and of Clusters of Transition Metal Atoms Magnetism of Metals

在线全文

学校读者我要写书评

暂无评论

高、低强度钢疲劳短裂纹扩展特性

金属学报 1987年第3期23卷 211-216页

作者：杨正瑞茅新伟李锋钢上海交通大学

本文研究了5C钢和两种不同强度的40CrNiMo钢长、短裂纹近门槛区域的疲劳裂纹扩展性能。并测定了它们的闭合效应和断面粗糙度,结果表明:长、短裂纹的扩展速率和门槛值差别与钢强度有关,5C钢短裂纹的门槛值只是长裂纹的一半。长、短裂纹... 详细信息

本文研究了5C钢和两种不同强度的40CrNiMo钢长、短裂纹近门槛区域的疲劳裂纹扩展性能。并测定了它们的闭合效应和断面粗糙度,结果表明:长、短裂纹的扩展速率和门槛值差别与钢强度有关,5C钢短裂纹的门槛值只是长裂纹的一半。长、短裂纹疲劳特性的差别可用闭合效应来解释。

关键词：裂纹扩展速率闭合效应高倍缺陷(金属) 疲劳裂纹扩展扩展特性门槛值阈值

单面约束Birkhoff系统的Noether理论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

物理学报 2001年第10期50卷 1837-1841页

作者：张宏彬巢湖师专物理系巢湖238000

应用变换群Gr 的无限小群变换的准对称性 ,给出了受单面约束的Brikhoff系统的Noether理论 ,并举例说明结果的应用 .

关键词：单面约束Birkhoff系统 Noether理论分析力学守恒量对称性变换群

Distortion Invariant Binary Image Recognition Based on Central Projection Correlation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 2001年第4期 42-48页

作者： WU Yaming XIAO Yanping SUN Fanghong  FANG Nian (School of Communication and Information Engineering, Shanghai University, Shanghai 200072, China) received Aug. 9, 2000 revised manuscript received Dec. 20, 2000

A method of central projection correlation which is invariant to distortion of shift, scale and rotation of the binary target image is proposed. A 2 D binary image is transformed into an 1 D central projection referring to the centroid of the binary image. The distortion invariant central projection correlation is successfully performed by computer simulations and its optical implementation is presented.

关键词： central projection distortion invariant image recognition optical matched filter correlation

Spectroscopic Properties of Yb3+ doped Borate Glasses

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 1999年第4期B8卷 79-84页

作者： JIANG Chun ZHANG Junzhou HUANG Guosong GAN Fuxi (Shanghai Institute of Optics and Fine Mechanics, The Chinese Academy of Sciences, Shanghai 201800, China)received Sep. 7, 1998 revised manuscript received Jan. 15, 1999 Shanghai Institute of Optics and Fine Mechanics The Chinese Academy of Sciences Shanghai 201800 China

The spectroscopic properties of Yb 3+ doped some borate glasses have been determined from absorption and emission measurements at room temperature. The emission cross sections range from approximately 1.0 to 1.7 pm 2. Systematic variations of the spectroscopic properties with glass composition and activator concentration can be used to optimize emission cross sections and fluorescence lifetimes.

关键词： Yb 3+ borate glasses spectroscopic property