钛金属焊接技术研究

针对ASME标准对珠海PTA钛金属管道焊接质量的验收要求,制定钛金属管45°对接固定焊的焊接工艺评定,填补和掌握钛金属管道的焊接技术。     

快速凝固耐热铝合金AA8009的TIG焊接

喷射沉积耐热铝合金AA8009的焊接技术是该合金实用化中必须解决的关键问题之一.试验采用ER5356、ER4043和母材作为焊丝对合金成分(质量分数,%)为Al-8.52Fe-1.23V-1.6Si、板厚为2 mm的耐热铝合金AA8009进行钨极氩弧焊焊接.结果表明,采用三种不同焊丝对耐热铝合金AA8009进行钨极氩弧焊焊接,断裂发生在熔化区边界,采用ER5356作为焊丝时焊接系数最高,为52.6%.焊缝冷却速度约为20℃/s,焊缝凝固组织为平衡或近平衡组织,在熔化区边界有针状析出相,热影响区及熔化区均发生了不同程度的软化.     

TIG焊弧光传感弧长控制的研究

通过对ＴＩＧ焊接光辉光强σ弧长之间关系的研究，建立了微机控制的弧长调节系统。实现结果表明，该系统的控制精度为±０．１ｍｍ而且该系统具有自动适应工件表面的变化而无需发迹硬件结构的特点。     

旋风除尘器弧形导向板技术实验研究

利用实验方法研究了可以降低旋风除尘器阻力损失的弧形导向板技术，并对实验结果进行了 分析，找到了弧形导向板的最佳尺寸。     

Influence of zirconium on microstructure and toughness of low-alloy steel weld metals

The influence of zirconium on microstructure and toughness of low-alloy steel weld metal was studied. Weld metals with different zirconium contents were obtained adding iron-zirconium alloy in the welding flux formulation. Weld metal chemical composition proved that zirconium was able to be transferred from the flux to the weld metal. The addition of zirconium refined the weld metal microstructure, increasing the acicular ferrite content. Weld metal toughness, determined by means of impact Charpy-V tests, showed that the zirconium addition is beneficial up to a content of 0.005 wt.%. Above this level, zirconium was not able to produce further microstructure refinement, although the toughness was reduced, possibly due to the formation of microconstituent such as the martensite-austenite constituent (M-A), which is considered to be deleterious to the weld metal toughness.     

Plasma transferred arc deposition of beryllium

The exceptional properties of beryllium (Be), including low density and high elastic modulus, make it the material of choice in many defense and aerospace applications. However, health hazards associated with Be material handling limit the applications that are suited for its use. Innovative solutions that enable continued use of Be in critical applications while addressing worker health concerns are highly desirable. Plasma transferred arc solid free-form fabrication is being evaluated as a Be fabrication technique for civilian and military space-based components. Initial experiments producing Be deposits are reported here. Deposit shape, microstructure, and mechanical properties are reported. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

折流板开孔孔径对换热器壳程性能的影响

试验测试和研究表明 ,对于管壳式换热器 ,在其单弓形折流板的管桥处开11mm孔时 ,与未开孔折流板相比 ,壳程进出口压降下降 2 4 5 %～ 2 6 4 % ,α/Δp升高 33 3%～ 36 4 % ,Δtm 增加 2 5 %～ 3 2 % ,总传热系数K升高 0 4 %～ 4 5 %。由此可见 ,对折流板管桥开适当孔径 ,可使换热器的各项性能均获得一定程度提高 ,具有较好的节能降耗效果。     

Value Constraints in the CLP Scheme

We define value constraints, a method for incorporating constraint propagation into logic programming. It is a subscheme of the CLP scheme and is applicable wherever one has an efficient method for representing sets of possible values. As examples we present: small finite sets, sets of ground instances of a term, and intervals of reals with floating-point numbers as bounds. Value constraints are defined by distinguishing two storage management strategies in the CLP scheme. In value constraints the infer step of the CLP scheme is implemented by Waltz filtering. We give a semantics for value constraints in terms of set algebra that gives algebraic characterizations of local and global consistency. The existing extremal fixpoint characterization of chaotic iteration is shown to be applicable to prove convergence of Waltz filtering.     

Effects of current waveform parameters during droplet transfer on spatter in high speed waveform controlled Short-circuiting GMAW

0IntroductionThe spatter in GMAW-S process is mainly caused byrapid heating of the melted liquid bridge between the weldpool and the electrode during droplet transfer phase or byfailure of arc reignition.To reduce spatter,the early effortwas to control th…     

Neural network methods for the modeling and control of welding processes

While welding processes are of great importance in manufacturing, their modeling and control is still subject of research. The highly nonlinear, strongly coupled, and multivariable nature of these processes renders the use of analytical tools practically impossible. In this article a novel approach is presented which employs networks of simple nonlinear units: a neural network. A widely used welding process, the Gas Tungsten Arc Welding is presented and the problem of its modeling and control is exhibited. A very brief introduction to neural networks is followed by presenting the experimental results for modeling the static and dynamic behavior of the process, as well as some practical recommendations regarding the use of the neural network techniques for controlling these processes.