Modeling of underwater wet welding seam forming based on support vector machines

Underwater welding is developing fast because of the exploration of marine resources, and underwater wet welding automation is urgently needed because of the rigorous environment. To control the welding process automatically, the model of the process should first be built to predict the current welding process status. In this paper, arc and visual sensors were used simultaneously to obtain the electrical and visual information of underwater wet welding, and support vector machines (SVM) were used to model the process, experiment results showed that the method could effectively use the information obtained and give precise prediction results.     

Ti-Al金属间化合物国内连接研究进展

本文综述了国内外Ti—Al金属间化合物的制备工艺与连接工艺研究现状。目前国内外主要采用铸造技术（包括精密铸造成型、定向凝固技术、高洁净度熔炼等）和粉末冶金制备等方法对Ti—Al金属间化合物进行制备研究,尚未形成成熟的制备工艺。国内针对Ti—Al金属间化合物的连接研究尚不深入,主要集中在钎焊、真空扩散焊、电子束焊、激光焊等连接技术上。部分研究者采用氩弧焊和自蔓延延烧合成（SHS）法针对Ti—Al金属间化合物进行了连接研究。     

钛及钛合金搅拌摩擦焊研究进展

搅拌摩擦焊技术已经成功应用于铝合金等低熔点材料的焊接,但针对钛及钛合金等高熔点材料的研究仍在进行之中。从焊具设计、接头显微组织与力学性能和焊接过程仿真等方面综述了钛及钛合金搅拌摩擦焊国内外研究进展,为搅拌摩擦焊技术应用于钛及钛合金提供参考。     

6N01铝合金MIG焊接头疲劳裂纹扩展性能研究

研究了6N01铝合金MIG焊接头不同区域的疲劳裂纹扩展速率,对接头的宏观形貌、显微组织、显微硬度和疲劳断口进行了分析。结果表明,焊缝区为等轴树枝晶,接头热影响区主要由淬火区和过时效软化区组成。疲劳裂纹在焊缝中的扩展速率最高;热影响区内,应力值范围较低时,疲劳裂纹扩展速率低于母材,随着应力值范围的增加,其扩展速率高于母材。疲劳断口分析表明,裂纹在焊缝中以不规则和粗糙的脆性疲劳条纹形式扩展,而在热影响区则以塑性的疲劳条纹扩展,扩展抗力较高。     

Formation mechanism of the porous zone at the bonded Si3 N4/Ni interface

Diffusion bonding of Si3N4 ceramic to itself was performed using Ni interlayer. A flat Si3N4/Ni interface was found at a lower temperature （ 1 273 K）. Whereas at a higher temperature （ 1 473 K）, a porous zone located at the Si3N4/Ni interface and some petal-like Ni3 Si compounds precipitated in the Ni interlayer were observed. The formation mechanism of the porous zone was investigated based on a fracture analysis. An additional stress （O＇add ） generated at the Si3NJNi interface played an important role in the formation of the porous zone, which was resulted from the aggregation of nitrogen during the bonding process. A calculation equation of the O＇aaj was derived to analyze its effects. The results indicated that %~ was directly in dependent with diffusion bonding temperature and dwell time.     

铜/钢异种金属焊接技术研究现状

重点介绍了国内外针对铜/钢异种金属连接的几种常用焊接方式，从不同焊接方法的特点入手，对其接头的成形机理、微观组织与力学性能进行了分析，并系统地总结了不同焊接方法的现存问题与解决办法。对于熔化焊，得到更为均匀的熔池以控制偏析是得到可靠接头的方式；传统电弧焊可通过控制填充材料以实现，而高能束焊可利用其控制精密的优势，利用束流偏析或周期运动以获得组织更为均匀的接头，是更可靠的熔化焊方法。对于钎焊及熔钎焊，选用合适的钎料则是实现可靠连接的关键，但其接头力学性能普遍较差，不适合应用于承载结构。而固相焊不涉及材料的熔化，相比于熔化焊，其接头具有更细小且均匀的微观组织，是具有巨大潜力的焊接方式。调控其界面反应层的形成是进一步提高接头强度的可行方式。在此基础上，进一步对未来铜/钢焊接的发展方向提出了展望，提出了关于上述焊接方法在未来可行的研究方向。