【作者】 金柏冬；

【导师】 赵万生； 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 在微纳米加工领域,目前人们已经普遍认可了两种材料加工方式,即“自上而下”的减材加工方式和“自下而上”的增材加工方式。如果能在同一加工系统中,通过简单地改变控制策略即可实现减材与增材可逆加工,则无疑对丰富材料加工技术的内涵和提供新的加工手段具有十分重要的意义。没有宏观作用力、具有以柔克刚特性的电火花加工技术是解决复杂零部件和难加工材料制造难题的有效方法之一。而本文提出的微细电火花沉积技术不仅可以对有缺陷的零件进行生长或修正加工,还可以加工出具有凹面特征和凸面特征的三维微细结构。微细电火花沉积技术是在电火花常规加工基本原理之上发展起来的。因此本文先对微细电火花沉积的基本原理进行分析,预测了其实现条件,然后通过选取合适的热源模型、热边界条件和放电通道半径等,建立了气中微细电火花沉积的热传导模型。利用Ansys有限元分析方法,对单脉冲条件下的工具电极和工件的瞬态温度场进行数值模拟,并预测了适合气中微细电火花沉积的工艺参数的选择范围。在普通电火花成形加工机床DP30上,采用45钢、钨和黄铜作为工具电极,在空气介质中可以实现微细电火花沉积加工,再通过仅仅改变电极和工件的极性就可以对生成的沉积材料进行有选择性的去除加工,进而实现材料的可逆加工。通过大量实验对此进行了系统研究,得出各工艺参数的影响规律。另外,为了探索微细电火花沉积的内在本质,还在克服重力、氩气介质和磁场中进行了沉积实验研究。为了进一步构造二维和三维的微细结构,本文提出了两种沉积策略:单圆柱连续沉积策略和分层扫描式沉积策略。通过对电极的路径规划,实现了HIT字符型阵列、往复直线、圆弧、四边形等形状的沉积。并发现在特定参数下用黄铜电极可以沉积出微三维螺旋结构,这种微三维结构是在没有使用X、Y轴和数控功能,而仅仅是Z轴进给的条件下得到的。通过实验总结了微螺旋沉积的工艺规律,发现在克服重力、电极和工件呈任意角度下均可以稳定沉积。对微细电火花沉积得到的材料进行了性能检测,检测表明沉积材料的成分取决于工具电极材料,并呈明显的分层结构,与基体结合紧密。电火花沉积之后45钢和钨的硬度有大幅提高,并且微三维螺旋具有较强的耐腐蚀性。另外,在氩气中沉积可以避免被氧化,在磁场中沉积可以使组织更致密。气中微细电火花加工方法具有设备简单、可操作性强、材料适应范围广、能量易于控制和面向车间的特点,因此具有广泛的应用前景。更多还原

【Abstract】 In micro and nanometer machining field, two material machining modes are popularly taken. One is reducing material top down, the other is increasing material bottom up. If the reversible machining of reducing and increasing material can be easily achieved by changing control strategy in the same machining system, it is significant to rich material machining technologies and to provide new machining methods. Because electrical discharge machining (EDM) has no macro resistance, and removes hard material using soft material, it is one of effective ways to solve manufacturing questions of complex parts and hard-to-cut material. The new micro electrical discharge deposition (EDD) technology proposed in this paper is able to not only grow or modify material on defective parts, but also obtain micro three-dimensional structures with concave and convex characters.Micro EDD is based on the basic principles of ordinary EDM. So the basic principles of micro EDD are analyzed, and the realized conditions are predicted. Then a heat conduction model of micro EDD machining in the air is built through selecting a proper heat-source model, thermal boundary conditions and discharge channel diameters etc. With the finite element analysis method of Ansys, the transient thermal field of the tool electrode and workpiece is analyzed under single pulse, and the processing parameters range of micro EDD in the air is predicted.Then with an ordinary EDM shaping machine DP30, and 45# steel, tungsten and brass as electrodes, micro EDD machining can be realized in the air. By only exchanging the polarities of electrode and workpiece, the deposited material can be removed selectively, thus the reversible material machining is realized. A large number of experiments are carried out to obtain the effects of different processing parameters on micro EDD. In order to search the intrinsic essence of micro EDD, the deposition experiments are also carried out against the gravity, in argon and in magnetic field.To fabricate further two and three-dimensional structure, two deposition strategies are brought forward in this paper, which are the continuous deposition strategy of single cylinder and the delamination scanning deposition strategy. Through planning electrodes’path, the shapes of HIT character type array, reciprocating straight, arc and quadrilateral are deposited. In addition, only using the feed in Z axis without X, Y axis or NC function, a micro three-dimensional spiral structure can be obtained with brass electrode using special parameters. The process rules of micro spiral deposition are generalized experimentally. It is found that micro spirals can be deposited stably against the gravity and under the random angle between the electrode and workpiece.The materials by micro EDD are detected performance. The measurements show that the components of the deposited material depend on those of the tool electrode material. The deposited material features obvious delaminating structures, and the combining of the deposited material and the base is compact. The hardness of 45# steel and tungsten both increase obviously after EDD. The micro spiral is corrosion resistant. In addition, the deposition in argon can avoid oxidation, that in magnetic field can make structure more compact.The micro EDD method in the air has some features, such as more simple facilities, better operability, wider material adaptability, easily controlling energy and facing on workshops. Therefore, is has wide application foreground.更多还原