铣削淬硬模具钢SKD11铣削表面质量试验研究

为了对高效铣削淬硬模具钢SKD11的新型铣刀进行优选,对不同几何结构的铣刀加工得到的表面质量进行了分析.综合考虑了加工表面粗糙度、切屑微观形态、硬度及硬化层深度、残余应力分布和晶相组织结构变化等多方面因素,研究了不同铣刀的几何特性及其磨损特性对表面质量的影响.实验结果表明,前角5°,后角10°,刀尖圆弧半径为1 mm,铣刀螺旋角为45°的几何结构铣刀完成了表面完整性试验中.此外,在淬硬钢铣削加工中合理地选择加工参数可以获得0.4μm的表面粗糙度;采用合理的正前角可以抑制锯齿形切屑的产生.铣削淬硬模具钢能在加工表面产生残余压应力,通过增加铣刀后角和抑制后刀面磨损可以推迟加工表面软化现象的发生.     

Elliptical model for surface topography prediction in five-axis flank milling

In five-axis flank milling operations, the intersecting surfaces of different cutting edges create roughness on the milled surfaces that cannot be ignored in situations with strict requirements, especially in aeronautical manufacturing. To focus on motion problems in milling operations, this paper presents a new model that utilizes elliptical paths as cutting edge trajectories on 3D surface topography machined by peripheral milling. First, the cutter parallel axis offset and location angle are considered, which change the location of the ellipse center and intersection point of the cutting edges. Then, through the proposed model, the predicted surface topography is obtained, and the factors that affect the development tendency of roughness are analyzed. Next, the effects of the cutter location position (CLP) geometric parameters, cutter parallel axis offset and curvature on the roughness are evaluated by a numerical simulation. Finally, machining tests are carried out to validate the model predictions, and the results show that the surface topography predictions correspond well with the experimental results.     

带螺旋内筋薄壁筒形件旋压变形特征

采用有限元模拟和实验结合的方法,研究了带螺旋内筋薄壁筒形件旋压变形特征。首先建立带螺旋内筋薄壁筒形件旋压有限元模型,并通过实验验证模型的可靠性。然后基于有限元模拟结果,分析旋轮作用下不同区域的应力特征及成形工件不同区域的应变特征。结果表明:筒壁区材料在旋轮作用下受三向压应力,内筋处外层材料受三向压应力,内层材料径向受压应力,切向和轴向受拉应力;成形后工件具有明显的不均匀变形特征,外层材料应变大于内层材料应变,筒壁区材料应变大于内筋处材料应变;筒壁区材料的应变特征为径向压缩应变,切向和轴向为拉伸应变,而内筋区的应变特征主要为外层材料的径向压缩应变和内层材料的径向拉伸应变。     

基于极坐标的数控铣削手工编程零件加工

通过数控编程中直角坐标系与极坐标系的比较,分别介绍了在我国广泛使用的FANUC系统、SIEMENS系统以及国产华中数控系统的极坐标编程规定,针对用角度和长度尺寸给定的工件手工编程较难解决的问题,应用实例说明了基于极坐标进行手工编程加工零件的方法,从而简化了编程.     

Vibrations characterization in milling of low stiffness parts with a rubber-based vacuum fixture

Fixtures are a critical element in machining operations as they are the interface between the part and the machine. These components are responsible for the precise part location on the machine table and for the proper dynamic stability maintenance during the manufacturing operations. Although these two features are deeply related, they are usually studied separately. On the one hand, diverse adaptable solutions have been developed for the clamping of different variable geometries. Parallelly, the stability of the part has been long studied to reduce the forced vibration and the chatter effects, especially on thin parts machining operations typically performed in the aeronautic field, such as the skin panels milling. The present work proposes a commitment between both features by the presentation of an innovative vacuum fixture based on the use of a vulcanized rubber layer. This solution presents high flexibility as it can be adapted to different geometries while providing a proper damping capacity due to the viscoelastic and elastoplastic behaviour of these compounds. Moreover, the sealing properties of these elastomers provide the perfect combination to transform a rubber layer into a flexible vacuum table. Therefore, in order to validate the suitability of this fixture, a test bench is manufactured and tested under uniaxial compression loads and under real finish milling conditions over AA2024 part samples. Finally, a roughness model is proposed and analysed in order to characterize the part vibration sources.     

叶片型面曲率属性对数控铣削加工过程的影响

提出了一种基于曲面曲率属性分析数控铣削加工过程的方法.该方法通过在构建的自由曲面上规划走刀轨迹,建立刀位轨迹等参数曲线,来分析等参数曲线曲率属性对加工干涉和加工带宽度的影响.同时,通过对刀位轨迹和残留高度与曲面曲率属性之间关系的研究,获得了影响数控铣削加工效率、加工精度及发生干涉的一些规律.此外,研究表明通过对刀具半径、残留高度与加工表面曲率之间的吻合关系曲线合理优化,可有效提高加工带宽度.试验结果证明该曲面曲率属性分析数控铣削加工过程的方法是有效的,加工效率可提高5%~8%.      

空间对接机构螺旋电缆设计

对一种用于空间对接机构的螺旋电缆设计进行了研究。介绍了电缆的材料选择、结构设计和生产制造工艺。给出了材料蠕变、伸缩性能和空间环境等试验结果,均符合设计要求,并成功地用于神舟八、九、十号飞船与天宫一号目标飞行器的空间交会对接。应用情况表明:该电缆的结构紧凑,伸缩性能良好,满足低轨空间环境使用要求。     

高温合金螺纹铣削力优化研究

针对高温合金材料的螺纹铣削加工,分析了切削厚度的表达方法,建立了相邻两次走刀形成的截面积的表达方法。在此基础上,研究了高温合金螺纹铣削过程中的铣削力和扭矩,结果表明:螺纹铣削时,铣削力及扭矩与截面积呈正相关。提出了通过使螺纹粗精加工过程中每次走刀的截面积相等,进而优化高温合金螺纹铣削径向切深的加工策略。该策略可有效控制切削力值和扭矩值,这不仅有利于提高刀具寿命和加工精度,亦为制定难加工材料螺纹铣削工艺提供了依据。     

通道曲面的柱面逼近方法及其在叶轮插铣中的应用

为了使叶轮粗加工后的通道表面与其设计曲面尽可能接近,将整体叶轮的定轴插铣理论模型概括为通道曲面的最大内接柱面优化问题。同时,为简化该问题的计算难度,将最大内接柱面的优化问题转化为柱面直母线方向和柱面准线的确定两个步骤。提出了确定内接柱面直母线方向的最小二乘模型与解算方法,在此基础上,将通道曲面沿柱面的直母线方向进行投影,通过相关曲线间的裁剪操作,获得了最大内接柱面的准线。以最大内接柱面的准线作为插铣加工时的边界曲线,以柱面直母线方向作为插铣加工时平头刀的轴线方向,给出了计算刀心位置和安全高度的迭代算法。最后通过数值算例验证了所提方法的正确性。该方法将有助于叶轮粗加工效率的提高,同时为叶轮的精加工预留较均匀的加工余量。     

基于Z-map模型的球头铣刀铣削力建模与仿真

对球头铣刀铣削力建模进行了研究。在Z-map仿真模型的基础上,提出了识别加工中参与切削的切削刃单元的方法,通过考虑刀具偏心和刀具变形对瞬时切削厚度的影响,推导出了瞬时切削厚度的表达式,由铣削力和切削负载之间的关系,建立了球头铣刀三轴铣削力仿真模型。铣削力仿真计算与铣削实验的对比表明在考虑刀具偏心和刀具变形后所建立的铣削力模型能够对铣削力进行准确的预测。