高温合金蜂窝芯加工振动分析与试验研究

高温合金蜂窝芯具有薄壁、多孔、面内弱刚性等特点,加工过程中易出现毛刺、撕裂、塌边等缺陷,采用冰固持加工后改善了加工质量,但仍然存在振动幅值较大的问题。针对高温合金蜂窝芯冰固持加工的振动问题,分析并确定冰固持条件下的高温合金蜂窝芯加工振动的主要形式是非谐波非周期性激励下的强迫振动,求解切入角变化导致的强迫振动激励间隔时间的变化规律。通过试验获得切削用量对高温合金蜂窝芯冰固持加工振动的影响规律,试验结果表明,当主轴转速为7000r/min、进给速度为4000mm/min、切削深度为0.5～1.5mm、切削宽度为0.5mm时,振动幅值较小,加工状态稳定,加工质量较好。     

高速铣削铝蜂窝芯壁变形研究

铣削铝蜂窝芯的过程中,由于材料在垂直于芯格轴向的方向上刚性很低,刀具在初始接触蜂窝壁时材料很难直接被完全切除,蜂窝壁会发生让刀变形,进而导致蜂窝壁发生翻转和弯曲。另外,刀具对蜂窝壁的挤压、摩擦会影响金属在切削加工表面的塑性流动,从而影响蜂窝壁的变形,因此控制铝蜂窝芯壁的变形对于研究铝蜂窝芯缺陷的形成有非常重要的意义。本文通过ABAQUS软件进行有限元模拟和铣削实验,探究了铣削深度和冰固持高度对槽铣过程中蜂窝壁变形的影响规律。研究证明,铣削深度和冰固持高度对蜂窝壁变形过程有显著影响。     

蜂窝材料冰结加工技术试验研究

蜂窝材料属于难加工材料,其加工方法和固持方法对加工质量有着重要影响。本文介绍了蜂窝芯的结构性能特点,阐述了装夹蜂窝芯的方法。试验采用硬质合金圆刀片组合铣刀对冰结夹持条件下的铝基蜂窝材料进行高速铣削,分析了切削参数对切削力和切削温度的影响规律以及加工缺陷的形成原因,验证了冰结法对蜂窝材料的固持效果。试验结果表明:蜂窝芯表面质量有较大提高,有效抑制了加工缺陷;获得了切削参数对切削力和切削温度的影响规律。该方法提高了蜂窝芯强度,改善了断屑方式,并为低温加工为面内强度小、刚度弱的薄壁金属基蜂窝芯高效加工提供了新方法。     

气凝胶填充金属蜂窝夹层结构隔热性能试验与模拟

在1300℃温度和30 min保温时间的条件下,使用Nb基钎料对铌合金进行钎焊来成形铌合金蜂窝。对铌合金蜂窝与气凝胶填充铌合金蜂窝进行加热试验,测定了热面与冷面的瞬态温度。在与实际试验条件基本保持一致的情况下,建立了金属蜂窝与气凝胶填充金属蜂窝的有限元模型,并对不同几何参数的蜂窝进行传热模拟,分析了蜂窝芯格壁厚、芯体高度、芯格内径对隔热性能的影响,并以此总结出蜂窝的隔热机理。研究结果表明：气凝胶可有效地提高蜂窝隔热性能;芯格壁厚越小,芯体高度越大,蜂窝隔热性能越好;填充气凝胶时,芯格内径越大隔热性能越好,蜂窝芯空腔时,芯格内径越大,隔热性能越差。     

基于超声波机床的蜂窝芯数控加工技术研究

以蜂窝芯的结构及力学性能为基础,介绍了当前芳纶纸蜂窝芯的加工现状,并分析了其存在的主要问题.阐述了超声波机床加工蜂窝芯的基本原理及切削方式,在此基础上对超声波机床加工芳纶纸蜂窝芯的数控加工技术进行了研究,取得了一定的成果.     

铝蜂窝芯铝芯材成形过程仿真与实验研究

针对规整度要求高的铝蜂窝芯的需要,研究了采用滚压成形法制备半蜂窝波形条的工艺,加工中采用两个齿形轮做模具。结果表明:铝蜂窝芯铝芯材成形与齿形轮模具的齿数、边长、分度圆半径及齿顶角相关;通过数据分析与仿真,计算得出它们之间的函数关系式。运用金属塑性成形有限元分析软件DEFORM-3D对半蜂窝波形条的成形过程进行数值模拟,并对仿真结果进行分析,得到了与试验相吻合的结果,为成形法制备半蜂窝铝芯芯材的成形工艺及设备的设计有参考意义。     

基于TRIZ理论的飞机蜂窝芯零件数控加工固持方法研究

针对蜂窝芯零件数控加工装夹固持出现的效率低、稳定性差、成本高等问题,应用TRIZ理论及相应工具,对其工艺流程进行了系统功能分析,运用矛盾矩阵及创新原理,提出了一种新型的、更为经济的真空吸附装夹方式,并得到了成功的应用。     

蜂窝夹层玻璃钢复合材料的铣削加工

开展了蜂窝夹层玻璃钢复合材料的铣削加工工艺试验,对比了不同装夹方式和工艺参数的加工效果,得出了表面质量良好的蜂窝夹层玻璃钢复合材料铣削加工方案。试验表明,采用硬质合金刀具,较小的转速和进给量,较大的切削深度,干式切削,就能铣削出表面质量良好的蜂窝板工件。     

基于凸台搭接的蜂窝芯零件数控加工工艺技术研究

为了实现蜂窝芯零件高质高效、低成本加工,提出了一种凸台搭接的蜂窝芯零件固持方法,基于该固持方法,建立了一套蜂窝芯零件加工工艺方案,详细阐述了蜂窝芯零件毛坯尺寸选择方法、型面刀轨生成以及刀具倾角获取方法,实现了蜂窝芯零件无专用工装的数控加工,并在实际生产中得到应用验证。结果表明:该技术提高了蜂窝芯零件的加工质量和效率,降低了制造成本,改善了生产环境。     

NOMEX薄壁蜂窝芯型面加工技术

NOMEX蜂窝芯薄壁、铺层的复杂结构使其切削性能差和易撕裂,而现有顺铣方法不能解决切割后纸基蜂窝芯的边缘分层、起毛、薄边铣缺等问题。本文分析了纸蜂窝的破坏模式、纸蜂窝芯的压缩破坏过程及破坏机理,提出了非常规的逆向旋转加工薄壁纸基蜂窝芯型面的方法,并通过试验验证了该方法的可行性。     

Milling of Ti alloy honeycomb treated by ice fixation in cryogenic

ABSTRACT

This article presents the first comprehensive investigation on ice fixation milling method for titanium (Ti) alloy honeycomb with cryogenic cooling. Milling simulation model of ice fixation was established, the material was treated by ice fixation process, and a series of cryogenic experiments was conducted by CNC milling machine. The honeycomb properties and reasons of machining defects were analyzed in details, whilst cryogenic milling mechanism with ice fixation was deduced. The analysis indicated that compared to the conventional processing way, the ice fixation milling surfaces have great improvement, and the processing defects such as burr, collapse edge are effectively suppressed, as well as ice fixation cryogenic method can improve the strength of honeycomb. Meanwhile, the cutting depth has greater influence on surface quality. Furthermore, the influence order of cutting parameters on the milling force: cut deep is the largest and more than three times can be improved, followed by feed speed, and the spindle speed has minimal impact. Conclusion: for efficient processing of Ti alloy honeycomb material with small in-plane radial equivalent strength and low rigidity thin-wall, the ice fixation provides a new processing method with cryogenic cooling.     

Optimization of cryogenic milling parameters for aluminum honeycomb treated by ice fixation method

This paper presents the first comprehensive investigation that aluminum honeycomb has inevitable machining defect in milling process, such as deformation, burr, and collapse. Ice fixation method was used to clamp workpieces, and inner-injection liquid nitrogen was employed for a series of cryogenic milling machining. In the machining process, the main machining parameters including in honeycomb orientation, milling width, cutting depth, cutting speed, and feed were executed experimental research. Meanwhile, the machining parameter optimization, range, and significant analysis were adopted to analyze the influence of machining parameters on the machining surface quality, as well as the optimal parameter combination and milling machining surface quality were predicted and verified. The results show that the ice fixation aluminum honeycomb method with cryogenic milling is much advanced than that of conventional ones, and many machining defects are effectively restrained. At the same time, the influence of machining parameters on machining qualities in descending order is cutting depth, cutting speed, honeycomb orientation, feed, and milling width. The minimum roughness value (Ra?=?0.356 μm) of the predicted machining surface is similar to the actual machining result (Ra?=?0.362 μm). It verifies the feasibility of the optimization method. Furthermore, it is proved that the ice fixation + liquid nitrogen cooling method has a positive effect on the high milling quality and implement efficiency for aluminum honeycomb and other difficult-to-machine materials.     

Investigate on milling force of cryogenic cooling processing aluminum honeycomb treated by ice fixation

Aerospace metal honeycomb materials with low stiffness had often the deformation, burr, collapse, and other defects in the mechanical processing. They were attributed to poor fixation method and inapposite cutting force. This paper presented the improvement of fixation way. The hexagonal aluminum honeycomb core material was treated by ice fixation, and the NC milling machine was used for a series of cryogenic machining. Considering the similar structure of fiber-reinforced composite materials, the milling force prediction model of ice fixation aluminum honeycomb was established, considering tool geometry parameters and cutting parameters. Meanwhile, the influence rule on milling force was deduced. The results show that compared with the conventional fixation milling method, the honeycomb processing effect is improved greatly. The machining parameters affect order on milling forces: the cutting depth is the most important, followed by the cutting width, then the spindle speed and the feed. Moreover, too small cutting depth (a_p?=?0.5 mm) will cause insufficient cutting force, while a_p?>?2 mm with higher force will reduce the processing quality of honeycomb. Simultaneously, the honeycomb orientation (θ) has a great influence on processing quality. Using the model, the predicted and measured error values of the feed and main cutting force are all small in θ?<?90°. But, the rate is 33 and 26% for the main cutting force and feed force error in θ?>?90°, respectively, while they all exhibit the smallest error in θ?=?60°. This bigger error mainly is due to unstable cutting force with obtuse angle. In addition, the tool rake angle has little influence on cutting quality in θ?<?90°, but bigger on that in θ?>?90°. Furthermore, the calculation model successfully conforms to the main deformation mechanism and influences parameters of the cutting force in the milling process, and it can accurately predict the cutting force in θ?<?90° and guide the milling process.     

高温合金蜂窝芯高速铣削材料去除机理与损伤行为

高温合金蜂窝芯材料具有高比刚度、轻质和能量吸收特性好等优异性能,被视为下一代高超声速飞行器热防护结构极具潜力的材料。高速铣削是高温合金蜂窝芯零件成型过程中重要的减材制造工艺,在蜂窝芯材料高速铣削时,蜂窝芯材料面内刚度低且高温合金塑性好,较小的切削力就会使蜂窝壁产生较大的塑性变形,导致蜂窝芯加工精度较低、加工损伤难以控制,对后续焊接、装配等工序产生不利影响。基于有限元仿真对蜂窝壁切削材料去除机理进行了深入研究,探索了铣削参数、刀具类型和铣削方式对铣削过程中铣削力和加工损伤的影响。研究结果表明,蜂窝壁切入角是影响蜂窝芯材料切削加工过程中瞬时应力分布和成屑机理的关键性因素。得到了铣削参数、刀具类型和铣削方式对高温合金蜂窝芯加工过程中加工损伤的影响规律。对于铣削参数,过大的进给量会导致芯格变形等加工损伤,降低切削速度会提高微小毛刺等加工损伤发生的频率;本文采用的三种刀具的对比结果表明,立式铣刀加工质量最好。插铣方式会产生明显的轴向冲击,而侧铣方式可以有效避免轴向冲击。研究成果为高温合金蜂窝芯低损伤高性能加工提供了理论依据和工艺技术储备。     

Cf/SiC复合材料低温铣削工艺优化研究

对超硬金刚石刀具低温铣削Cf/SiC复合材料进行工艺优化研究,主要研究聚晶金刚石刀具低温铣削Cf/SiC复合材料过程中,低温冷却介质(干冰、液氮)和冷却工艺参数(阀体出口压力和喷嘴喷射角度)对切削力、加工表面完整性和切屑的影响规律。研究表明:在干冰、液氮低温介质的冷却作用下,工件的加工表面质量得到了较大提高,主切削力显著降低。     

薄壁叶片精密加工装夹方案设计与优化

针对航空发动机薄壁叶片刚性弱、加工工艺性差、加工过程中易发生弹性变形等问题,提出了无预载荷、有轴向拉压载荷的装夹方案,分析了3种装夹方案中的弯曲和扭转变形,建立了叶片的弯扭组合变形数学模型。通过对叶片弯扭组合变形数学模型的分析,得出了3种装夹方案下叶片几何尺寸与叶片加工变形位置的关系,以及拉压载荷对叶片加工变形的影响规律。     

NOMEX蜂窝芯高速铣削加工工艺的优化

为了解决NOMEX蜂窝芯高速铣削加工过程中固持可靠性差和加工效率低以及加工表面质量差的问题，提出一种新的基于强磁场和摩擦学原理的蜂窝芯高速加工固持方法。该方法利用灌入蜂窝孔中的铁粉自重以及强磁场平台对铁粉产生的吸引力，在铁粉与蜂窝孔侧壁之间以及蜂窝、铁粉与固持平台之间产生摩擦力，实现对蜂窝底部的全约束和固定。建立了NOMEX蜂窝芯高速铣削加工的铣削力模型，进行了以铣削力最小为目标的铣削参数的优化。通过铣削参数的优化，保证了加工过程中蜂窝的固持稳定性，同时保证了蜂窝加工效率和加工质量。     

Cryogenic minimum quantity lubrication machining: from mechanism to application

Cutting fluid plays a cooling–lubrication role in the cutting of metal materials. However, the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers. Environmental machining technologies, such as dry cutting, minimum quantity lubrication (MQL), and cryogenic cooling technology, have been used as substitute for flood machining. However, the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application. The technical bottleneck of mechanical–thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL. The latest progress of cryogenic minimum quantity lubrication (CMQL) technology is reviewed in this paper, and the key scientific issues in the research achievements of CMQL are clarified. First, the application forms and process characteristics of CMQL devices in turning, milling, and grinding are systematically summarized from traditional settings to innovative design. Second, the cooling–lubrication mechanism of CMQL and its influence mechanism on material hardness, cutting force, tool wear, and workpiece surface quality in cutting are extensively revealed. The effects of CMQL are systematically analyzed based on its mechanism and application form. Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone. Finally, the prospect, which provides basis and support for engineering application and development of CMQL technology, is introduced considering the limitations of CMQL.     

Evaluation of machining performance in cryogenic machining of Inconel 718 and comparison with dry and MQL machining

There has been significant work on establishing relationships between machining performance and the cutting parameters for various work materials. Recent trends in machining research show that major efforts are being made to understand the impact of various cooling/lubrication methods on machining performance and surface integrity characteristics, all aimed at improving process and product performance. This study presents the experimental results of cryogenic machining of Inconel 718, a high-temperature aerospace alloy, and comparison of its performance in dry and minimum quantity lubrication machining. Experimental data on force components, progressive tool wear parameters such as flank wear, notch wear, crater wear, cutting temperature, chip morphology, and surface roughness/topography of machined samples are presented. New findings show that cryogenic machining is a promising research direction for machining of high-temperature aerospace alloy, Inconel 718, as it offers improved machining performance in terms of reduced tool wear, temperature, and improved surface quality. It was also found that the number of nozzles in cryogenic machining plays a vital role in controlling cutting forces and power consumption in cryogenic machining of Inconel 718.     

车床加工薄壁零件内孔的方法和技巧

在使用车床加工薄壁零件时,由于薄壁零件刚性差,加工内孔时容易引起变形,影响零件的加工精度,是车削加工中的难题.结合多年工作经验,总结出通过掌握薄壁零件的安装和夹紧,从而减少加工中的变形;选择合理的切削用量、刀具的切削角度和几何参数以及选用适合的切削液,大大提高了薄壁零件加工的质量.