电弧盘铣加工设计与实验分析

电弧加工因其高放电能量和非接触式加工的特点而在难加工材料去除方面得到了广泛的应用。为研究电弧盘铣加工的加工特性,提出一种基于正交实验的多目标参数优化方法。综合考虑了低转速、低电压条件下,电极转速、工件进给速度、电流、气压和进刀深度等因素对加工材料去除率和电极损耗率的影响,得出了在低转速、低电压条件下电弧盘铣加工多目标优化的最优加工参数组合,提高了电弧盘铣加工的应用性。研究结果为电弧盘铣加工参数的合理制定与加工工艺的优化提供了参考依据。     

小尺寸工件的配合特性

小尺寸工件的公差与配合有其自身特性,从加工误差、测量、公差配合、装配使用等方面分析了小尺寸工件的特点,并说明了与常规工件的不同之处。     

LNG储罐工程用低温钢筋机械连接接头研发初探

综合考虑LNG储罐工程的特点以及耐-165℃的低温钢筋的力学性能,根据钢材的低温性能规律和钢筋机械连接的传力机理,设计低温钢筋镦粗直螺纹接头。按照相关标准进行了一系列低温钢筋和低温钢筋接头的常温和-165℃低温加载试验,接头试件各项试验结果均满足要求。最后根据实际情况对低温钢筋接头提出了更高的要求,并给出了实现方案。研究成果可为LNG储罐工程低温钢筋机械接头的研发和国内相关标准的制定提供参考。     

低温氢泄漏及射流火传播特性研究现状

阐述了低温氢的应用前景及泄漏危险性,从气体扩散特性和射流火点火、传播行为两方面介绍了低温氢泄漏的研究现状,对低温氢泄漏气体扩散及射流火传播特性的研究方法、手段及结论进行了总结分析。目前,低温氢泄漏研究方法包括实验研究和数值模拟,多数研究集中在气体扩散特性,对射流火的点火、传播行为的产生条件及影响因素尚不明确。未来应完善低温氢泄漏气体扩散预测模型,以建立有效的低温氢泄漏气体扩散过程及射流火点火、传播预测模型。     

Development of a directly-driven thread whirling unit with advanced tool materials for mass-production of implantable medical parts

Medical screws are a common mass-produced implantable medical component made of Titanium. To machine the threads of these types of components, thread whirling with carbide tools is typically used. However, tool wear and low cutting speed limit the productivity and increase the manufacturing cost of such medical parts. In this study, a direct motor driven thread whirling unit for an advanced Swiss-type CNC lathe was developed and it was used with advanced tool materials such as low binder content Cubic boron nitride (CBN) and Polycrystalline diamond (PCD) to find a cost-effective and more productive alternative to carbide tools.     

Efficient and damage-free ultrashort pulsed laser cutting of polymer intraocular lens implants

Ophthalmic intraocular lenses are conventionally machined by diamond tools. A promising alternative approach is contour cutting by ultrashort pulsed laser micromachining. To improve process knowledge, a parametric study of picosecond and femtosecond laser machining of medical grade hydrophilic copolymers and PMMA is carried out. Material removal rates and machining quality with respect to main process parameters are determined. Reasons for chipping and formation of heat affected zones are identified and an optimized process strategy is derived. By choosing a defined pulse overlap, heat accumulation is kept minimal while increasing absorptivity through incubation avoids chipping.     

Sub-zero cooling: A novel strategy for high performance cutting

In this paper, a novel cooling strategy for high performance cutting is presented. A metalworking fluid, composed of water and polyhydric alcohols is applied at temperatures below 0 °C, but above the temperatures used for cryogenic cutting. This cooling strategy is applied when rough turning Ti-6Al-4V. An analysis of temperatures, forces, tool wear and chip formation is carried out. The results are compared with those obtained using emulsion, CO₂, LN₂, and dry turning. It can be shown that when tempering the sub-zero metalworking fluid down to ?30° C, tool temperatures as well as tool wear are reduced, and favourable chips are produced.     

Anomalous influence of polarity in sink EDM of titanium alloys

An anodic tool polarity is generally adopted in sink electrical discharge machining (EDM) to maximize material removal relative to tool wear. Sink EDM of Ti and Ti6Al4V is however atypical in that these materials necessitate a cathodic tool polarity. Adding to the intrigue is γ-TiAl, which machines better under the conventional anodic polarity. This research focused on clarifying the phenomena behind this interesting behavior by investigating removal mechanisms over a range of relevant process conditions. The anomaly is demonstrated to arise from the polarity-dependent nature and extent of TiC formation on the work surface, which significantly affects material removal.     

激光织构工艺对铜表面红外激光吸收率的影响

目的高功率红外激光进行铜构件加工时,激光吸收率低是阻碍其工业加工、影响加工质量的重要因素,因此拟通过皮秒激光织构预处理工艺,将铜表面红外激光吸收率从低于10%提高至70%以上。方法从改变铜表面特性着手,利用精密微细加工系统进行凹槽织构处理,通过共聚焦显微镜和扫描电镜对20%～50%激光功率、20～90次扫描次数下的织构特征进行分析,通过反射率检测仪对不同织构下铜表面的红外激光吸收率进行测试。结果相比原始铜板,织构后铜表面红外激光吸收率有了大幅提高,且十字凹槽织构工艺下的吸收率高于同参数下的平行凹槽织构。在30%激光功率、60次扫描次数的工艺下,形成深度44mm、间距50mm、表面粗糙度12.15mm、倾角75°的十字凹槽织构,铜表面红外激光吸收率达86.75%。结论织构深度、表面粗糙度、氧化物是影响吸收率的重要因素,经过"周期性微米级织构-相爆炸喷溅颗粒物-形成黑色CuO层"三个过程,对应"光自陷织构-表面喷溅颗粒物-CuO层"三步吸收,织构工艺能够将铜表面红外激光吸收率提高近9倍。     

非正交五轴数控机床后置处理的研究与应用

近年来,五轴数控机床运动轴的方式呈现出多样化发展趋势,出现了一些带倾斜摆头的非正交五轴数控机床,亟需开发这类特殊运动轴方式的后置处理器。针对德国DECKEL MAHO公司生产的DMU60P型非正交五轴数控机床的后置处理器进行研究和开发,发挥此类先进非正交五轴数控机床的功能,具有一定的参考价值和工程应用价值。