FENG Meibin CHEN Xinzeng HE Jiawen 2nd Automobile Works
,
Shiyan
,
Hubei
,
China. Ningbo University
,
Ningbo
,
Zhenjiang
,
China. Xi'an Jiaotong University
,
Xi'an
,
China.
材料科学技术（英文）
The crack initiation behaviour under cyclic compression foy the notched specimen was investigated. It has been found that the cycles for crack initiation increase with the increase of compressive mean stress, and the decrease of stress amplitude. The stress amplitude plays a more important role than the mean stress does. Photoelastic coating and finite element methods were employed to measure and calculate the stress field in the notched part. The resul ts show that the crack initiation under compression is attributed to the tensile stress which may exist during unloadtng. If the true stress state in the notch is compressive, no crack initiates.
关键词:
crack initiation
,
null
,
null
尹君
,
岳古明
,
徐贲
量子电子学报
doi:10.3969/j.issn.1007-5461.2006.02.015
使用脉冲Nd:YAG四倍频激光抽运充有纯D2气体和D2/He混合气体的拉曼池.实验研究了受激拉曼散射的能量转换效率和能量稳定性与系统主要参量,包括抽运光能量、D2气体压强和加入惰性气体He的关系.实验表明,适量惰性气体He的加入在没有降低一阶斯托克斯散射光(S1,波长:289.04 nm)能量稳定性的前提下,有利于提高其能量转换效率,最大能量转换效率达到22.1%.通过实验分析,得到了受激拉曼散射一阶斯托克斯散射光的能量转化效率和能量稳定性的优化条件.
关键词:
非线性光学
,
受激拉曼散射
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四波混频
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能量转换效率
,
能量稳定性
冯文天
,
马新文
,
朱小龙
,
张少峰
,
刘惠萍
,
李斌
,
闫顺成
原子核物理评论
利用反应显微成像谱仪对70和100 keV He2+与He原子碰撞转移电离(TI)过程中不同出射角度的电子能谱进行了测量,观测到出射电子能谱具有如下分布特征:出射电子速度分布介于0和入射离子速度νp之间;在不同出射角度电子能谱分布均有一极大值存在,随着出射角度的增大,能谱分布极大值逐渐减小; 当电子出射角度等于45°时,多数电子集中在0 eV附近.上述特征可由低能离子-原子碰撞"准分子"模型进行定性解释.在100 keV He2+-He转移电离出射电子能谱中有靶电子被俘获至散射离子连续态(electron capture to continuum,简称ECC)电子的贡献,这可看做是动力学两步过程的作用.
关键词:
反应显微谱仪
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转移电离
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ECC电子
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"准分子"模型
Journal of Magnetism and Magnetic Materials
The magnetization process in a two-sublattice system is studied by a computer simulation program, without using the assumption that there exists a small canting angle between the magnetic moments of the two sublattices. A peak in the low-field range of the second derivative of the magnetization curve is reported, which depends on the competition between the comparatively weak exchange and the competing anisotropies.
关键词:
Wenbin SHENG
,
Dong LI
,
Rui YANG
,
Yuyin LIU
,
Jingjie GUO
,
Jun JIA
材料科学技术（英文）
Ti-48Al-2Cr-2Nb automobile exhaust valves were formed with permanent mold centrifugal cast method and their surface layer structure, microstructure, elements distribution and mechanical properties were analyzed by SEM, XRD and EMPA etc. Furthermore, the HIPped valves were tested on 483Q diesel engine. Results showed that the element distribution of TiAl based alloy exhaust valves was uniform and their microstructure was refined. The typical mechanical properties of HiPped exhaust valves were sigma (b)=670 MPa, sigma (0.2)=527.5 MPa and delta =3%. Engine test showed that the valves had excellent airtightness and wear resistance properties and satisfied the requirements of engine successfully.
关键词:
Physica Status Solidi a-Applied Research
The magnetization process in a two-sublattice system is studied by a computer simulation program established in Part I. Phase diagrams of the second derivatives with respect to different magnetization processes are determined for some ferromagnetic materials. Effects of both exchange and anisotropy on these phase diagrams are discussed.
关键词:
single-crystal;anisotropy
Science and Technology of Welding and Joining
The effect of the shielding gas concentration on the weld shape was studied for the moving bead on plate TIG welding of SUS304 stainless steel under He-O-2 mixed shielding. The small addition of oxygen to the helium base shielding gas can precisely control the oxygen content in a liquid pool and the weld shape. Oxygen is a surface active element for stainless steel. When the oxygen content in the liquid pool is above the critical value of similar to 70 ppm, the weld shape suddenly changes from a wide shallow type to a deep narrow one due to the change in the Marangoni convection from the outward to inward direction on the liquid pool surface. Weld shape variations influenced by the welding parameters including welding speed, welding current and electrode tip work distance under pure He and He-0.4%O-2 mixed gas shielding were systematically investigated. The investigation results showed that the final shape of the TIG weld depends to a large extent on the pattern and magnitude of the Marangoni convection on the pool surface, which is governed by the combined effect of the oxygen content in a liquid pool, temperature coefficient of the surface tension (d sigma/dT) and the temperature gradient on the pool surface (dT/dr, r is the radius of the weld pool surface). It is considered that the change in welding parameters alters the temperature distribution and gradient on the pool surface, and thus, affects the magnitude of the Marangoni convection and final weld shape.
关键词:
TIG welding (GTAW);weld shape;oxygen;helium;Marangoni convection;welding parameters;marangoni convection;oxide fluxes;tungsten arc;activating flux;stainless-steel
