变螺距内螺旋线分立式阴极齿设计及仿生减阻研究

发布时间：2018-03-11 01:23

本文选题：螺旋线　切入点：螺旋角　出处：《西安工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：在等螺距螺旋线电解加工中传统阴极的工作齿与阴极体是一体的,沿用传统阴极加工变螺距螺旋线,线槽必然被加宽,造成阳线“塌壁”,特别是从0°起变的大螺旋角变螺距螺旋线几乎不能加工,这是因为刚性工作齿不能按螺旋线方程改变角度。本文提出一种新的分立式阴极,沿阴极的轴向并垂直于轴将工作齿切成若干某种厚度的片,每片均含阴极体整圈的工作齿,称为轮盘。当阴极按螺旋线方程运动时,受内嵌于阴极体的微电机驱动的每个轮盘各自按加工的螺旋线位置取向,实现工作齿的包络线与被加工螺旋线螺旋角方向一致。但是工作齿相邻齿节间台阶临近流场易出现空穴、分离、涡流等缺陷,影响成型精度。为解决得到均匀的流场,本文提出了圆弧等齿厚工作齿和圆弧变齿厚工作齿两种齿牙形状的分立式阴极设计,先后采用八种修形方案,基于COMSOL Multiphysics模拟各方案工作齿与被加工工件之间的加工间隙流场分布,比较各方案的流线场、流速场以及压力场,结合时均阻力系数的计算结果进行分析,结果表明,方案八中将每片厚轮齿一侧切去一半,同时将旋出的台阶全部倒成0.3mm的圆角,并将薄齿的另一侧旋出台阶的右下角全部倒成0.4 mm的圆角,流场效果显著改善。这种根据工作齿错位形成的位置设计的圆弧变齿厚工作齿,有效地降低了轮盘旋转形成工作齿节间的台阶对流场的影响。为进一步对齿牙形状优化,基于脊状表面减阻机理,在上述最佳方案的基础上,设计了侧表面具有不同尺寸分布的脊状结构的工作齿,利用COMSOL Multiphysics对工作齿与被加工工件之间的加工间隙流场进行分析,研究脊状结构的形状参数与电解液流速、湍流参数和剪切速率之间的关系,结果证明,工作齿表面脊状尺寸为s=0.2mm、h=0.05mm的脊状结构不仅可以减小摩擦阻力,而且有效地稳定了间隙流场。
[Abstract]:The working teeth of the traditional cathode and the cathode body are integrated in the equal pitch helix ECM. If the traditional cathode is used to process the variable pitch helix, the slot will be widened. This causes the "wall collapse" of the positive line, especially the helical spiral line with large helical angle from 0 掳, which can hardly be machined, because the rigid working teeth can not change the angle according to the helix equation. A new discrete cathode is proposed in this paper. Along the axis of the cathode and perpendicular to the axis, the working teeth are cut into a number of plates of some thickness, each of which contains the working teeth of the cathode body in a whole circle, called a wheel. When the cathode moves according to the helix equation, Each wheel driven by a micromotor embedded in the cathode is oriented separately according to the helical position of the machining, The envelope of the working tooth is consistent with the spiral angle of the spiral line being machined. However, the defects such as cavity, separation, eddy current and so on are easy to appear near the flow field between the adjacent teeth of the working tooth. In order to solve the problem of obtaining a uniform flow field, the forming accuracy is affected by the defects such as cavity, separation, eddy current and so on. In this paper, a discrete cathode design for the shape of two kinds of tooth teeth with circular arc equal thickness working teeth and circular arc variable tooth thickness working teeth is presented. Eight modification schemes have been adopted one after another. Based on COMSOL Multiphysics, the flow field distribution between the working teeth and the machined workpiece is simulated, the streamline field, velocity field and pressure field of each scheme are compared, and the calculated results of the average resistance coefficient are analyzed. In the eighth scheme, each thick gear tooth is cut off in half, at the same time, the spinning steps are all turned into a round angle of 0.3 mm, and the other side of the thin tooth is rotated out of the lower right corner of the step into a 0.4 mm corner. The effect of flow field is greatly improved. The circular arc variable tooth thickness working tooth is designed according to the position of the working tooth dislocation, which effectively reduces the influence of rotating disk on the step flow field between the working teeth. In order to further optimize the tooth shape, Based on the drag reduction mechanism of the ridge surface, the working teeth with different size distribution on the side surface are designed on the basis of the above optimum scheme. The flow field between the working teeth and the machined workpiece is analyzed by COMSOL Multiphysics. The relationship between the shape parameters of the ridge structure and the electrolyte flow rate, turbulence parameter and shear rate is studied. The results show that the ridge structure with a ridge size of 0.2 mm / h on the surface of the working tooth can not only reduce the friction resistance, but also reduce the friction resistance. Moreover, the gap flow field is effectively stabilized.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG662

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