虚拟水战略在西北干旱区的应用分析

在对虚拟水战略分析的基础上,估算了2006年西北干旱地区主要农产品虚拟水的含量,认为虚拟水战略在西北干旱区应用可行、也很有必要。提出了西北干旱地区应用虚拟水战略来协调区域经济、社会、生态发展的相关对策:巩固退耕还林还草成果、寻求区域发展最佳战略、加快区域生态区划工作、制定支持鼓励政策、推进产业结构调整等。     

Study on weld formation in a novel rotating arc horizontal GMAW

A novel rotating arc horizontal welding process was developed for solving the sagging of the molten pool which bottlenecks the application and the development of the horizontal welding. The principle of the effect of the rotating arc on the molten pool is that the rotating arc process not only can reduce the welding heat input by prolonging the welding path in the same welding distance caused by the arc rotation, but also disperse the arc force to affect the sidewall periodically to support the molten metal near the upper sidewall. The effects of the rotating speed and arc voltage on the weld formation were studied.The results indicate that there is an appropriate range of the rotating speed and the arc voltage to obtain the defect free horizontal welding.     

摆动电弧窄间隙焊接工艺参数对焊缝成形的影响

在优化设计摆动电弧窄间隙GMAW焊炬的基础上,研究了摆动角度、摆动速度和侧壁停留时间对焊缝截面尺寸的影响规律。结果表明,摆动电弧有利于改善窄间隙焊接过程中的侧壁未熔合问题;随着摆动角度的增大,焊缝熔深减小,而侧壁熔深增大,表面下凹量则随着摆动角度的增大而增大;摆动速度的增大有利于焊缝熔深的减小和下凹量的增大,但是其对于侧壁熔深的影响不显著;焊缝熔深随着停留时间的增大而显著增大,侧壁熔深则随侧壁停留时间的增大略有增加,表面下凹量随着侧壁停留时间的增大而增大。     

30CrMnSiA熔池谐振法熔透控制TIG焊工艺及其接头组织的研究

本文采用电弧传感熔池谐振法研究了30CrMnSiA钢熔透控制TIG焊工艺,同时选取普通连续TIG焊进行了对比讨论,并对其效果进行了分析。试验结果证明,该控制方法在适当的工艺条件下,对30CrMnSiA钢可实现高可靠性的熔透控制,不仅能单面焊双面成形,且熔宽均匀无下塌,不需焊前预热和焊后缓冷。在较大热输入量条件下,接头仍能保持较好的组织与性能。     

Formative mechanism of the undercut defect in horizontal variable polarity plasma arc welding

Abstract Horizontal welding is important for heavy or huge welding structures. Keyhole mode variable polarity plasma arc welding of aluminum alloy plates with medium thickness was carried out in horizontal position. The characteristic of welding defects was introduced. Preliminary experiments indicated that the undercut defect could not be eliminated easily. The relationship between welding parameters and the undercut defect showed that this deject could be lessened by using higher heat input. The fluid flow of weld pool was observed by a high speed camera. The fluid flow in weld pool was not symmetric and much of molten metal gathered in the lower part. The fluid flow velocity in the lower part was bigger than that in the upper part. To this end, the formative mechanism of the undercut defect was proposed. The flowability of the molten metal was an influential factor for the undercut defect. A preheating method was designed to verify the formative mechanism.     

Pulsed TIG welding-brazing butt joints of aluminum-stainless steel thin plates with different fillers

Aluminum and stainless steel plates with 1.5 mm thickness are joined by pulsed TIG welding-brazing process with ER1100, ER4043 and ER2319 fillers, separately. Good weld formation can be obtained by adjusting appropriate pulse parameters. The effects of the fillers on that the thickness of the intermetallic compound （ IMC ） and tensile strength of the joints are investigated. SEM results indicate layer with ER2319 filler is about 2 ~m, which is thinner than 2. 5 p~m of ER1100 filler and 3.5 txm of ER4043 filler. Moreover, the element distribution in both IMCs and welded seams with three fillers are different because of the different compositions of fillers. The results of mechanical property tests suggest that the joint strength with ER2319 filler is the highest, while the joint impact energy is the lowest. The joint with ERllOO filler exhibits the best comprehensive mechanical pet.formanee.     

特种钎剂辅助铝/钢异种合金TIG熔-钎焊

采用铝硅钎料进行了铝/钢异种合金TIG熔-钎焊试验,开发出了适用于TIG电弧热源下的特种钎剂,通过高速摄影观察了液态钎料的润湿铺展行为,并分析了接头特性.结果表明,特种钎剂能够显著促进钎料的润湿铺展,钎剂成分(质量分数,%)为:改性的Noclock钎剂(KAlF4:K3AlF6,65:35)55～78,Zn10～20,Sn10～20,K2SiF62～5.液态钎料的铺展包括两部分:一是通过成形槽,沿钢背面进行铺展,获得良好的背面成形;二是沿坡口表面进行"上坡"铺展,实现焊缝正面成形.铝/钢TIG熔-钎焊接头具有熔焊与钎焊的双重性质,接头抗拉强度可达115.5MPa,断裂于焊缝/不锈钢界面层.     

Experimental study on dissimilar TIG welding-brazing of 5A06 aluminum alloy to SUS321 stainless steel

Dissimilar metals TIG welding-brazing of 5A06 aluminum alloy to SUS321 stainless steel has been carried out with Al-Si12 eutectic filler metal and modified non-corrosive flux. The surface appearance and microstructures of the joint were analyzed and the average tensile strength of the joint was estimated. The results show that a sound dissimilar metals joint is obtained by TIG welding-brazing. Slag and residual flux on steel surface can be removed by sanding easily. The joint has dual characteristics: in aluminum alloy side, it is a welded joint, while in stainless steel side, it is a brazed joint. The whole interface layer, unequal in thickness at different position, ranges from 5μm to 25μm. The average tensile strength of the butt joint reaches 120MPa and the fracture occurs at the interface layer.     

2195铝锂合金超声TIG焊的组织与性能分析

采用了普通TIG焊和超声复合TIG焊对2 mm厚度的2195铝锂合金进行了平板对接焊,并对两种焊接接头的显微组织和力学性能进行了研究. 结果表明,由于超声的作用效果,超声TIG焊的焊缝具有更加致密的组织,熔合区附近的等轴细晶区区域较宽;拉伸性能测试表明,超声TIG焊接头具有较高的拉伸性能,接头强度系数比普通TIG焊提高6.7%,断后伸长率提高1.36%,拉伸接头均断裂在热影响区硬脆的晶界相内,显微硬度测试表明超声TIG焊接头受热影响软化区域较窄.     

微构件分子动力学集成仿真系统的研究

采用VC++集成环境和OpenGL技术开发了面向微构件特性评价的分子动力学模拟软件系统(MDIS).MDIS模拟系统可以实现微构件的纳米切削加工和微拉伸等参数化分子动力学仿真,同时可以实现特殊微构件-单壁碳纳米管的力学特性评价.软件利用了模块化设计思想,界面友好,易于操作,集成度高,适合微构件综合分子动力学分析.采用MDIS系统对金刚石刀具切削单晶铜材料以及单壁碳纳米管与单晶硅材料相互作用的分子动力学模拟进行了仿真模拟研究.