【作者】 杨武雄；

【导师】 肖荣诗； 陈铠；

【作者基本信息】 北京工业大学 ， 光学工程， 2014， 博士

【摘要】 本文以我国大飞机为应用背景，以飞机结构中常见的壁板结构T型接头双光束激光焊接为主要研究对象，针对飞机壁板商用铝合金6056-T6511（桁条）/6156-T4（蒙皮）和第三代铝锂合金2099-T83（桁条）/2060-T8（蒙皮）材料，进行了包括以T型接头双光束激光焊接装置、铝合金表面处理、T型接头铝及铝锂合金的双光束激光焊接工艺在内的内容较为系统的研究。为进行铝合金T型接头双光束激光焊接技术的研究，首先自行设计集成了T型接头双光束激光焊接装置。该装置以两台高亮度固体激光器YLS-6000Fiber激光和DS040Disc激光作为能量源，以悬臂梁式三维数控机床为运动控制主体，以真空吸附平台为蒙皮定位基准，以多对相互垂直的压轮组作为桁条的定位方式，集成了包括外光路、送丝系统、保护气系统、光学元件保护、工装卡具等所必需的功能单元。该装置的研制成功为下一步进行双光束激光焊接技术研究奠定了良好的硬件基础。铝及铝锂合金T型接头的特殊结构和冷却条件使焊缝中的气孔率比其它接头高得多。为更彻底地解决T型接头的气孔问题，首先对焊缝中气孔的特征及分布规律进行了研究，发现多数气孔分布在沿上熔合线的U形区域中，且大气孔更为规律，这种分布规律的成因与气泡的生成、长大、浮出和受阻以及运动路径直接相关。解决焊缝中的气孔主要还以减小气孔的来源为出发点，同时配以优化的焊接工艺。为去除铝合金表面的氧化膜，通常都会采用化学或机械的方法进行处理，但传统的物理和化学处理方法存在污染环境、效率低下、工序衔接周期长等诸多不便因素。本文提出一种利用电弧阴极破碎原理的小电流摆动电弧阴极雾化法去除铝合金表面的氧化膜。这种方法克服了传统电弧反接存在的钨极烧损、清理厚度不均匀、对母材热影响大的缺陷。采用这种方法分别对6156-T4铝合金和2060-T8铝锂合金表面的氧化膜进行处理，并对处理后的铝合金表面进行了微观结构和氧、钨元素的分析。通过高速摄像对电弧的形态特征进行了观测和机理研究。为验证这种方法去除氧化膜的实际效果，对清理过的试样进行了双光束焊接实验，同时对焊缝进行了气孔的检测，结果表明：6156-T4经阴极雾化清理后焊缝的气孔率为0.01%，2060-T8铝锂合金焊缝的气孔率为0.05%，气孔最大直径约为100um，且气孔均匀分布在焊缝中。以自行设计集成的双光束激光焊接系统作为实验平台，采用本文提出的摆动电弧氧化膜清理方法，进行了航空商用铝合金6056-T6511/6156-T4T型接头的双光束激光焊接工艺研究。分别研究了激光功率、离焦量、送丝速度、送丝位置、激光入射高度、焊接速度等参数对焊缝成形的影响以及各工艺参数之间的合理匹配关系。T型接头焊缝对蒙皮性能的影响直接关系到壁板类工件的使用性能，因此本文还研究了焊缝不同的熔深对蒙皮拉伸性能的影响规律，总的趋势是焊缝熔深与蒙皮拉伸性能呈负线性相关的关系。2099-T83/2060-T8是新型的第三代铝锂合金，除气孔之外，热裂纹是铝锂合金双光束激光焊接时需解决的另外一个关键问题。为此首先对焊接热裂纹的分布规律和产生原因进行了研究，最后通过采用优化坡口形式增加填充材料含量比例的方式解决焊缝的裂纹敏感性问题。飞机壁板类结构的双光束激光焊接技术研究对我国正在重点研究的大飞机项目具有重要的参考价值，同时也为双光束激光焊接技术应用于飞机制造提供了技术支持和理论基础。更多还原

【Abstract】 The background of this research is the national aircraft manufacture. The mainresearch object is the dual beam laser welding technology of aluminum fuselage. Thedual beam laser welding technology has been presented on aircraft commercialaluminum alloys (6056-T6511stringer/6156-T4skin) and the third generation of Al-Lialloys (2099-T83stringer/2060-T8skin).The systemic study of this paper mainlyincludes three aspects as follows. The first is about dual beam laser welding devicesof T type joints. The second is about surface treatment of aluminum alloy. And thethird is about dual beam laser welding technology of T type joints on aluminum andaluminum lithium alloy.In order to conduct the research of dual beam laser welding technology of T jointof aluminum alloy, T type dual beam laser welding device has been designed andintegrated. Two high brightness laser YLS-6000fiber laser and DC040Disc laserhave been used as the T type joint of dual beam welding power source. The cantilever3D NC machine tool designed by ourselves has been used as motion control subject.Vacuum adsorption platform have been adopted as the locating datum of skin. Thewelding device integrates all necessary functional units, which comprises the outerlight path, the wire feeding system, the protective gas system, the protection of anoptical element and the fixture. The successful development of the equipment has laida good hardware foundation for the next step research of dual beam laser weldingtechnology.The special structure and cooling condition of T type joint of aluminum andaluminum lithium makes porosity rate of the laser welds much higher than the otherjoints. In order to solve porosity problems of the T type joint, the features anddistribution of the pores in the weld have been studied. The study shows that themajority of stomata distributed along V shaped region of the fusion line, and thedistribution of large pore is more rules. The reason about the distribution of bubble isdirectly related to those factors, such as bubble formation, growth, hindered andmoving path. To solve the pore in weld, the ways mainly rely on the decreasing sourceand welding process optimization.To remove the oxide film on the surface of aluminum alloy, chemical or mechanical methods have usually adopted as pre-welding treatment. But the filmprocessing method has low efficiency, environmental pollution and long perioddocking process. Referred to the principle of crushing effect of arc on film, thisresearch puts forward a method of using small value of reverse current combined withthe swing arc cleaning of oxide film on aluminum alloy surface. This methodovercomes the problem of traditional arc reversal of tungsten electrode, unevensurface cleaning, not enough width of cleaning and the large heat impact on parentmetal. This pre-treatment method has been presented on6156-T4aluminum alloy and2060-T8aluminum lithium alloy. The surface microstructure of aluminum alloy hasbeen observed after surface treatment. The composition of oxygen and tungstenelement has been analyzed. And the arc shape characteristics of cleaning process areobserved and analyzed by high speed camera. To test the effect of oxide film dislodge,dual beam welding experiment has been presented in this paper. And the porosity inweld is also detected. The results show that weld porosity in6156-T4aluminum is0.01%when the metal cleaned by cathode atomization. And the weld porosity in2060-T8aluminum lithium alloy is about0.05%. Pores are uniformly distributed inthe weld and their size is very small.The dual beam laser system has been used as experimental platform. The methodof swing arc has been adopted to clean the oxidation film. Dual laser weldingexperiment has been presented on6056-T6511/6156-T4aviation commercialaluminum alloys. Influence of process parameters included laser power, defocus, wirespeed, wire position, laser incident angle and welding speed on weld forming of the Ttype joint and the relationship of mutual matching of each parameters have beenstudied in this paper. Because of the influence of T type weld on skin performance isdirectly related to the performance of fuselage parts, this paper also studies the law ofdifferent depth affect the weld tensile properties of skin. The general trend is that theweld penetration was negative linear correlation with the skin stretch performance.2099-T83/2060-T8is a new third generation of high strength aluminum lithiumalloy. Thermal crack is another important problem encountered in laser welding ofhigh strength aluminum lithium alloy. The reason and the distribution of hot crackhave been studied in this paper. The results show that the sensitivity of crack in weldcan be decreased by optimizing the groove size and increasing the volume ratio offiller material. The research on dual beam laser welding of airplane fuselage panelhas animportant reference value to the large aircraft project, which is the major concern ofour country now. At the same time, this study also provides technical and theoreticalbasis for dual beam laser welding used in aircraft manufacturing.更多还原