【作者】 王志坚；

【导师】 夏伟； 徐滨士；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 再制造技术在资源节约型和环境友好型和谐社会建设中显示出越来越重要的作用,各种再制造成形技术也正得到大力发展。其中,激光再制造成形技术克服了传统修复技术的不足,在机械零部件的再制造中得到日益广泛的应用,对于装备零件的维修保障工程发展具有重要军事意义和应用价值。本文侧重于激光再制造成形的工艺过程控制原理及应用研究。基于模块化思想,提出装备零件激光再制造成形模块化分类成形修复研究的方法,研究激光再制造成形结构几何特征并控制成形结构的形状,以提高修复结构的几何精度。针对损伤零件几何形状恢复技术进行研究,以实现多种损伤装备零件缺损部位预期形状修复结构的快速、高精度和自动化激光再制造成形为研究目的,构建了装备零件战场快速再制造成形软硬件系统,研究了基于激光再制造成形的结构几何形状的形成和变化机理,解决装备零件的激光再制造成形中修复结构局部几何特征不均匀的问题,建立工艺参数局部调整和成形结构几何特征变化的定量关系,并对表面、薄壁结构和三维立体结构三种类型损伤零件进行了激光再制造成形实际应用。本文的主要研究结论如下:以高机动性灵活性、装备现场保障、快速高精度成形修复为特点,构建了激光再制造成形软硬件系统,为激光再制造成形技术应用奠定坚实的硬件基础。系统主要由DLA60100型全固态激光器、AX-V6型机器人和AX-ST离线编程软件组成,该系统解决了复杂曲面上激光表面熔覆的位置精度问题,提高了激光扫描路径的位置精确性和编程灵活性;设计了环形送粉通道与光束同轴和四管环绕光束同轴两套方案的同轴送粉喷嘴,以解决侧向送粉在粉末利用率、成形效率和复杂路径的各向异性方面的不足。提出对多种损伤装备零件进行激光再制造模块化分类成形修复的研究思路,系统研究了线、表面、薄壁成形结构和三维立体成形结构四种类型的激光再制造成形结构的几何特征,为损伤零件几何形状恢复技术应用建立理论基础。从激光熔池的能量输入、粉末材料输入和熔池基面形状三个方面说明成形结构局部几何特征不均匀现象的形成原因,发现在激光再制造成形中,实际工艺参数和设定参数之间的差异导致熔池的形状变化是成形结构变形的主要原因;提出通过定量改变成形结构局部的工艺参数来改善成形结构的局部几何特征不均匀的控形方法。系统研究了通过控制结构局部工艺参数的方法来实现预期形状结构的成形和改善成形结构的局部几何特征不均匀的方法,提高了修复结构的形状精度。建立了激光再制造成形主要工艺参数包括激光输出功率、送粉量和激光扫描速度与成形结构几何特征之间的定量关系,建立了激光成形结构形状预测模型;通过与试验结果对比,验证了该模型的预测精度较高,预测误差在5%以内;提出了激光成形结构形状的具体方法和实际应用情况,主要控形方法为控制激光扫描速度、送粉量、熔池基面形状变化。基于控形方法对复杂表面磨损、薄壁结构局部缺口和局部立体结构缺损三种损伤类型的典型装备零件进行了快速、高精度和自动化激光再制造成形应用研究。复杂表面损伤修复的典型零件为某型坦克发动机凸轮轴,解决了其凸轮桃尖磨损造成升程超差的问题;典型薄壁结构激光再制造成形应用为圆筒缺口修复;而零件立体结构缺损的激光再制造成形典型零件为齿牙断裂的低载直齿轮,肋板有深裂纹的结构支撑件;上述应用实践中均实现了预期形状尺寸的结构激光高精度成形,且提出了实现高形状精度成形的关键工艺措施,对类似结构和损伤零件的激光再制造成形修复具有重要参考意义。更多还原

【Abstract】 The remanufacturing engineering technologies have been widely used with great success for the development of resource conservation and environmental protection society. A lot of remanufacturing forming technologies has improved too. Mechanical parts remanufacturing technology with high-energy beam such as laser was widely used and it overcome the shortcoming of other traditional repair technologies.The quick repairing of local damaged equipment parts by laser remanufacturing forming technology has important military significance and applied value to repair and supply engineering of equipment parts. A classify research method about modularization of laser remanufacturing forming equipment parts was introduced. The typical technological process of laser remanufacturing forming was established, and its key elements were been analyzed too. The paper aimed at restoring of geometrical form of damaged parts, represented the laser forming technique of local structure formed at part damage region with expectant shape. As a result, a software and hardware system of laser remanufacturing forming was build, and the forming and deforming mechanics of laser remanufacturing forming structure were been expounded. In addition, the problem of non-uniform geometric character of formed structure in laser remanufacturing forming process was been solved. The practical applications of laser remanufacturing forming damaged surface, thin-wall structure, and local broken three-dimensional structure were been introduced too.The main research conclusions are as follows:With the features such as high flexibility, part repair on site and rapid forming with high dimensional accuracy, the laser remanufacturing forming software and hardware system was been built. The system was the base of application of laser remanufacturing forming technology. The system mainly composed with DLA60100 solid-state laser, AX-V6 robot, and AX-ST off-line programming software. The location accuracy of laser scan path and adaptability of forming path programming were been increased by using this system. Two designs of coaxial powder feeding nozzle with ring-shaped powder deliver passage and four pipes surround laser beam were represented, and the shortages of lateral powder feeding nozzle such as poor powder usage, low formed efficiency and aeolotropism at laser scanning path were overcame.The theoretical basis of applications of damaged parts geometrical shape restores technology was system researched, which composed with geometry research of laser remanufacturing forming line, surface, thin-wall structure and 3D structure. A nonuniform phenomenon of geometrical characters of laser formed local structure was discovered, and its formative reasons were explained by analyzing molten-pool laser energy input, powder particles input and the shape of molten-pool bounded surface shape. The results show that the difference between actual processing parameters and ideal processing parameters was the main reason that leads to nonuniform phenomenon of geometrical characters. A technologic method to avoid this nonuniform phenomenon by quantitative accurate control of processing parameters was been presented.The geometric shape control methods of laser formed structure were been investigated systematically. The dimensional accuracy of laser formed structure was notable increased by using these methods. The function between mainly processing parameters, such as laser power, laser scanning speed and powder feeding rate, and laser formed structure geometry was been built. A dimensional prediction model was been built based on energy conservation principle and equation of mass conservation of laser molten-pool. The model forecast accuracy was satisfied and with maximal 5% error by experimental verification. According to the model, the geometric shape control objects were follows: laser-scanning speed, powder feeding rate and molten-pool bondage surface shape.Using laser remanufacturing forming technology, a wear part surface with complex shape, a thin-wall structure with top notch and a part with local structure cracked were been repaired creatively. The successful repairing result of these equipment parts indicated that we have expanded the application range of laser remanufacturing forming technology. The typical part of surface damaged with complex shape was a camshaft of tank engine, and its worn cam face was shape restored. The typical laser remanufacturing forming thin-wall part was a thin-wall cylinder with a top notch, and typical local 3D structure cracked parts were a low-load spur gear with broken gear tooth and a strutting piece of airplane undercarriage with cracking ribbed panel. The reparative structures with prospective shape and high dimensional accuracy were laser formed, and the key technological operation of shape control of laser formed structure was been presented too. The researches of laser remanufacturing forming typical parts have important reference significance to remanufacturing other parts with similar shape or similar damage.更多还原