振动辅助钻削对CFRP/钛合金叠层结构孔径阶差影响规律实验研究

在飞机部件装配过程中,CFRP/钛合金叠层结构的连接十分常见,而由于两种材料迥然不同的材料性能,导致制孔后存在孔径阶差,严重影响了CFRP/钛合金结构的疲劳强度。本文开展了低频轴向振动辅助钻削的正交实验,分析了低频振动辅助钻削工艺参数与切削力和切屑形态的关系以及工艺参数对CFRP/钛合金孔径阶差的影响。结果表明,由于低频振动辅助钻削刀具的周期性进给,钛合金切屑由连续长切屑变为扇形短屑,减少了对CFRP的扩孔效应,钻削区域切削热降低,平均轴向力降低;另外,振幅和进给量对孔径阶差的影响较为显著,而主轴转速的影响较小,且孔径阶差随着振幅的增大先减小后增大,随着进给量的增大而增大。通过试验验证和分析,确定面向孔径控制的最优工艺参数组合方案：主轴转速为600 r/min、进给量为0.02 mm/r、振幅为150μm。     

Machining of SiC ceramic matrix composites: A review

Continuous fiber reinforced SiC ceramic matrix composites (FRCMCs-SiC) are currently the preferred material for hot section components, safety–critical components and braking components (in the aerospace, energy, transportation) with high value, and have triggered the demand for machining. However, the high brittleness, anisotropy, and heterogeneity of materials bring great challenges to machining, due to high mechanical and thermal loads, severe tool wear, and poor machining quality. With the increasing demand of FRCMCs-SiC parts, high-quality and high-efficient machining has become a hot issue. This review paper provides a detailed literature survey on the machining of FRCMCs-SiC. The material removal mechanism, defect form, and interfacial mechanical properties of FRCMCs-SiC were summarized. The machining processes of FRCMCs-SiC were introduced, and their respective advantages and disadvantages were compared. Given the low machinability (high hardness, high brittleness, anisotropy, and heterogeneity) of FRCMCs-SiC, preliminary experiments have proved that ultrasonic-assisted machining and laser-assisted machining have shown unique advantages in reducing force and tool wear, improving machining quality and machining efficiency. The machined surface integrity was discussed, the influence of process parameters on the machined surface quality was analyzed, and the machining defects of FRCMCs-SiC were summarized. But for FRCMCs-SiC, the existing quantitative evaluation of the machined surface integrity was weak and unsystematic.     

基于动力学仿真技术的TC4整体叶轮铣削参数优化

针对某航空发动机TC4整体叶轮在数控加工过程中存在颤振、加工效率低及因加工变形而导致局部超差等问题,提出了相应的铣削参数优化解决方案。在进行切削力系数辨识试验获取TC4材料的切削力系数及锤击试验获取加工系统动力学特性参数的基础上,通过综合使用自行开发的铣削加工动力学仿真软件SimuCut和国外的CutPro软件进行动力学仿真与优化,获得了优化的切削参数。使用优化的切削参数进行加工,有效地消除了颤振和因加工变形引起的局部超差,提高了加工效率。     

Four-axis trochoidal toolpath planning for rough milling of aero-engine blisks

The Blade Integrated Disk (Blisk) is one of the key components in the aero-engine, it is generally manufactured by the multi-axis milling and almost 90% raw materials are removed. To avoid the full immersion of a cutter in the rough machining of a blisk channel, the trochoidal milling is a promising strategy since it can keep a small immersion angle in the rough milling process while maintaining the high machining efficiency. However, while toolpaths are being planned for the trochoidal milling process, the conventional methods are mainly for the planar machining area with fixed tool orientations, which cannot be used for complex channels where the multi-axis machining should be employed. To this end, this paper presents a four-axis trochoidal toolpath planning method with a ball-end cutter, and thus the blisk channel can be machined efficiently. For this to happen, the trochoidal paths are planned in the parametric domain and then mapped into the physical domain, with tool orientations controlled by the quaternion interpolation method to have smooth tool movement along the toolpaths. Both geometric simulation and physical milling experiments of the proposed method have convincingly demonstrated the validation of the proposed method.     

微小孔加工试验及刀具磨损机理

由于钛合金和印刷电路板的难加工性使得微小孔的加工精度和表面质量难以保证,刀具技术成为提高加工效率的主要障碍。本文应用3种不同涂层钻头对钛合金和印刷电路板进行微小孔钻削对比试验,研究了进给速度与切削力和扭矩的关系,分析了刀具的磨损特征以及孔的表面质量和孔入口处的毛刺情况。结果表明:钻削印刷电路板的临界进给速度为1 591.2 mm/m in,涂层对钻削力和扭矩的影响不明显;类金钢石(DLC)涂层硬质合金钻头比普通硬质合金钻头和T iC涂层硬质合金钻头更适合加工钛合金材料微小孔。     

加工钛合金大口径深盲孔的研究

钛合金属难加工材料,其深孔加工的难度更为突出,加工质量不易保证。本文通过实验对比,对加工钛合金大口径深盲孔中出现的偏孔、切屑堵塞、切削振动、刀具破损等主要问题进行了分析,提出了解决办法,得出了切削用量的优化参数。由于钛合金的化学亲和作用,深孔加工刀具的导向条表面易于粘附,结果拉伤已加工表面,造成表面粗糙度上升。加大导向条与孔壁的间隙虽可减少导向条表面的粘附,但同时会引起切削振动的加剧。针对这一矛盾,本文着重对加工刀具的导向条分布、导向条与孔壁的间隙以及导向条的选材方面进行了探讨,提出了以非金属导向条代替硬质合金导向条进行钛合金深孔精加工的方法,使得已加工表面的粗糙度大大降低。这些研究结果对实际加工具有一定的指导作用。     

(TiB+TiC)/TC4复合材料电解钻孔试验研究

钛基复合材料是一种典型的难加工材料,采用传统机械加工方法存在加工效率低和加工质量差等问题。利用电解加工技术,采用直径为10mm的管状阴极,对(TiB+TiC)/TC4复合材料进行电解钻孔加工试验研究。进行了(TiB+TiC)/TC4复合材料的电化学特性研究,测量了(TiB+TiC)/TC4复合材料在10%NaNO₃溶液中的极化曲线和电流效率。探究了加工电压、电解液压力对加工精度的影响。结果表明,当加工电压为30V,电解液压力为0.6MPa时,电解钻孔可以在1mm/min的进给速度下稳定加工。当加工的盲孔深径比为3.06时,孔的圆度误差为41.1μm,锥度为0.4°,具有较高的加工精度。     

Vibration suppression of thin-walled workpiece machining considering external damping properties based on magnetorheological fluids flexible fixture

Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological(MR) fluids is designed to investigate the regenerative chatter suppression during the machining.Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular cantilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler–Bernoulli beam assumptions. Then,the displacement response function of the bending vibration of the beam is represented by the product of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equation of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests.     

螺旋槽数控立铣刀圆周刃前角的测量及计算方法

前角是影响刀具切削性能的最主要因素,尤其是螺旋槽数控立铣刀的圆周刃前角将直接影响到其切削性能.应用先进的测量技术与计算机技术,对螺旋槽数控立铣刀圆周刃前角测量方法及其实际作用角度计算方法进行研究,实现了精确的螺旋槽数控立铣刀圆周刃前角测量及其实际作用角度计算,为提高螺旋槽数控立铣刀的质量及其切削加工效率提供了重要的方法和工具.     

纤维增强陶瓷基复合材料加工技研究展

纤维增强陶瓷基复合材料具有高熔点、低密度、耐腐蚀、抗烧蚀以及抗氧化等一系列优点,被列为新一代高温热结构材料的发展重点,在航空、航天、能源等领域具有极大的应用前景.但纤维增强陶瓷基复合材料具有硬度大的特点,其加工是一个难点,主要对纤维增强陶瓷基复合材料的传统加工工艺和特种加工工艺及其研究进展进行了介绍,并对纤维增强陶瓷基复合材料的加工工艺的发展趋势作了展望.