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。     

Nomex蜂窝芯直刃尖刀超声切割表面微观形貌特征

Nomex蜂窝芯是典型的难加工材料,具有高比强度,比刚度及各向异性的特点。超声辅助切割是蜂窝芯复合材料的一种高效加工方法,可以得到比高速铣削更好的加工质量。但是在超声切割加工过程中依然会存在不同程度的纤维拔出,酚醛清漆层剥落等加工缺陷特征。为了研究其微观形貌特征,采用纵切,斜切,横切三种方式切割蜂窝芯,并对蜂窝芯的加工形貌进行观测。根据微观形貌在蜂窝芯壁上的位置,分别归纳为酚醛清漆层、热压芳纶纸层和蜂窝壁的形貌。研究超声刀具加工参数对材料破损形貌特征的影响。结果表明在10 μm到30 μm范围内提高超声刀具振幅,在500 mm/min到3 500 mm/min范围内降低进给时会降低蜂窝芯加工过程中的酚醛清漆层剥落的几率。     

涂层刀具高速铣削铁基高温合金的切削力及表面粗糙度研究

针对铁基高温合金GH2132高速加工时铣削力大、加工质量不稳定的特点,采用新型涂层硬质合金刀具进行高速干铣削试验,研究切削参数对铣削力及加工表面粗糙度的影响规律。运用极差分析法并根据泰勒公式、正交试验数据和回归分析得出拟合公式,结果表明:对铣削合力峰值影响较大的切削因素是轴向切削深度和径向切削深度;对加工表面粗糙度影响较大的因素是每齿进给量和轴向切削深度。当vc=50-100m/min、fz=0. 08-0. 10mm/z、ap=0. 2-0. 3mm、ae=3-4mm时,可以获得较小的铣削力和表面粗糙度,且拟合公式可以有效预测加工过程中铣削力和表面粗糙度值。本文对探究刀片磨损机理及提高表面加工质量提供了参考数据。     

C/SiC复合材料超声扭转振动铣削抑制损伤产生的机理

传统铣削加工碳纤维增强碳化硅(C/Si C)复合材料极易产生加工损伤,而超声振动加工技术是切削难加工材料的理想方法之一。为了分析超声扭转振动铣削C/Si C复合材料抑制损伤产生的机理,以传统铣削加工为参照,在分析超声扭转振动铣削刀具运动轨迹的基础上,利用两种刀具在超声扭转振动铣削与传统铣削状态下对C/Si C复合材料进行铣槽加工,并对试验中切削力、刀具磨损情况和铣槽质量进行检测与分析。结果表明,切削力是影响加工损伤产生的重要因素,而施加超声扭转振动后两种刀具的切削力均低于传统铣削切削力,两种刀具的切削状态也得到了改善,其中硬质合金铣刀底刃磨损面积降低了23.7%,有效避免了槽壁加工表面崩边及毛刺现象。     

PCBN刀具高速切削镍基高温合金切削力及刀具磨损试验研究

高速切削加工过程中切削参数的选择对刀具切削性能具有较大的影响。镍基高温合金因在高温条件下仍具有较高的抗疲劳强度、屈服强度、抗拉强度等特点,被广泛应用于航空航天、船舶、核电等行业。但是镍基高温合金的切削加工性能差,主要表现在切削力大、切削温度高、刀具磨损现象严重等方面。本文从切削速度、进给量、切削深度等切削参数对切削力的影响进行研究,同时对PCBN刀具磨损形貌进行分析。采用PCBN刀具进行高温合金车削试验,得到PCBN刀具切削高温合金GH4169时切削参数对切削力的影响规律,并探讨不同刀具磨损形貌产生的原因,为高温合金高速切削加工参数制定及工艺优化提供一定参考。     

高速铣削刀具磨损研究进展

介绍高速切削的特点、应用现状和加工时刀具遇到的问题,针对刀具磨损机理(刀具材料、切削参数、冷却方式、铣削方式)和刀具磨损监测等方面,综述了近几年高速铣削难加工材料时刀具磨损的研究进展,并对其发展趋势进行了讨论。     

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。     

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。     

吹气条件对石墨高速铣削过程的影响

在石墨高速铣削加工过程中采用合适的吹气及吸尘装置,可有效减小刀具磨损,提高加工质量.通过改变石墨高速铣削过程中的吹气条件,包括气流的喷射角度、距离和压力,对比了有无吹气条件时石墨切屑形式和吸附情况,精确测量切削后分布在工件和刀具表面的石墨粉屑质量,研究了切削速度、进给速度、轴向切削深度和径向切削深度等切削参数对石墨切屑吸附情况的影响,分析了石墨切屑的运动方式及吸附情况对石墨高速铣削加工过程的影响.     

微铣削单晶高温合金刀具磨损实验研究

为研究微小刃径刀具切削难加工材料后刀具的磨损,针对单晶镍基高温合金材料的难加工特性,设计了单因素实验方案,采用直径为0.6 mm的硬质合金微小刃径刀具对单晶镍基高温合金DD98进行微铣削加工;通过磨损后的刀具直径和铣削槽底宽度尺寸的变化来定义微铣削刀具(微小刃径刀具)切削加工的磨损标准,建立了微铣削刀具磨损标准的数学模型;基于单因素实验方案,探讨了不同切削参数条件下,微铣削长度对刀具磨损量的影响.相关研究和实验数据对于探索难加工材料的切削机理具有理论指导意义.     

高温合金蜂窝芯冰固持低损伤加工技术研究

针对金属蜂窝芯存在的薄壁多孔、各向异性、面内弱刚性、径向强度小等加工难题,提出了高温合金蜂窝芯冰固持低损伤加工方法.分析了金属蜂窝芯冰固持装夹原理,验证了工艺系统的适应性和可靠性.开展了蜂窝芯冰固持超低温冷却加工的单因素试验,阐明了蜂窝芯加工缺陷形成规律.试验结果表明:在金属蜂窝芯加工中引入冰固持超低温冷却的装夹和加工...     

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.     

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.     

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.     

变截面涡旋盘高速铣削仿真加工与实验研究

为减小变截面涡旋盘涡旋齿的变形,提高加工精度,需确定合理的铣削参数。开展了变截面涡旋盘高速铣削仿真与实验研究以确定铣削参数的合理取值范围;选用HT250变截面涡旋盘为研究对象,研究了更接近实际的材料本构模型、刀-屑摩擦模型和热传导控制方程等关键技术;建立了变截面涡旋盘几何模型和简化后的二维铣削模型,利用ABAQUS软件仿真切屑成形过程及不同的铣削参数对铣削力、铣削热影响的变化曲线;通过多因素正交实验加工变截面涡旋盘。结果表明:当主轴转速为3500 r/min、每齿进给量为0.1 mm以及切削深度为2.5 mm时进行铣削更加合理。铣削变截面涡旋盘的研究为加工参数的选择提供了依据和参考;依据实验后所得的铣削参数进行铣削可减小铣削力、铣削温度及齿变形,提高了变截面涡旋盘的加工效率和质量。     

基于动力学不确定性的重型切削工艺参数优化

针对数控重型切削加工过程的切削稳定性具有不确定性的特点,提出了在切削稳定性和机床工作能力的约束下,获得最大材料去除率的工艺参数优化方法。根据重型切削加工的工艺特点建立三维动力学模型,以机床的固有频率、阻尼比、刚度和切削力系数作为不确定因素,结合排零定理和边理论对其进行不确定性分析,获得稳健的切削稳定性叶瓣图,结合切削深度、刀具直径和刀具齿数的关系,为加工过程选择能获得最大切削深度的刀具。在此基础上,建立工艺参数优化模型,选择最佳的轴向切削深度、径向切削深度和主轴转速的组合,最后以一台加工中心上某型号发动机缸体表面的粗加工过程为例进行了验证。     

A study on the effect of tool-edge radius on critical machining characteristics in ultra-precision milling of tungsten carbide

A crack-free surface can be finished on brittle materials by a specialized but traditional machining technique known as ductile-mode machining. In ductile-mode machining of brittle material, crack propagation is suppressed by selecting a suitable combination of tool and machining parameters leading to the removal of material through plastic deformation enabled by dislocation motion. In ductile-mode machining, the tool–workpiece interaction is of critical significance for the capability of the cutting process to finish a crack-free surface on a brittle material. This interaction is largely dictated by the cutting-edge radius of the tool when the undeformed chip thickness is comparable to the edge radius as is the case of ductile-mode machining. This paper presents the experimental results of ductile-mode milling of tungsten carbide to investigate the effect of cutting-edge radius on certain critical machining characteristics associated with the ductile–brittle transition specific to milling process of brittle material. The experimental results have established that an increase in the cutting-edge radius within a certain range increases the critical feed per edge leading to the improvement of material removal rate in ductile-mode milling. An increasingly negative effective rake angle is desired during milling with larger edge-radiused tool to suppress the crack propagation in the cutting zone to achieve ductile-mode machining. The results also identify the effect of the edge radius on certain other parameters such as critical specific cutting energy, plowing effect and subsurface damage depth to comprehend the ductile–brittle transition phenomenon in ductile-mode milling.     

An experimental investigation on micro machining of fine-grained graphite

Industrial applications of the micro milling process require sufficient experimental data from various micro tools. Research has been carried out on micro milling of various engineering materials in the past two decades. However, there is no report in the literature on micro milling of graphite. This paper presents an experimental investigation on micro machinability of micro milling of moulded fine-grained graphite. Full immersion slot milling was conducted using diamond-coated, TiAlN-coated and uncoated tungsten carbide micro end mills with a uniform tool diameter of 0.5 mm. The experiments were carried out on a standard industrial precision machining centre with a high-speed micro machining spindle. Design of experiments (DoE) techniques were applied to design and analysis of the machining process. Surface roughness, surface topography and burrs formation under varying machining conditions were characterized using white light interferometry, SEM and a precision surface profiler. Influence of variation of cutting parameters including cutting speeds, feedrate and axial depth of cut on surface roughness and surface damage was analysed using ANOVA method. The experimental results show that feedrate has the most significant influence on surface roughness for all types of tools, and diamond tools are not sensitive to cutting speed and depth of cut. Surface damage and burrs analysis show that the primary material removal mode is still brittle fracture or partial ductile in the experimental cutting conditions. 3D intricate micro EDM electrodes were fabricated with good dimensional accuracy and surface finishes using optimized machining conditions to demonstrate that micro milling is an ideal process for graphite machining.     

High-speed milling of CFRP composites: a progressive damage model of cutting force

Three-dimensional Hashin failure criterion and material stiffness degradation model were compiled by VUMAT subroutine. The Abaqus/Explicit solver was performed to establish progressive damage model of cutting force for CFRP high-speed milling, and high-speed milling experiments with different cutting parameters were carried out. Further, the impact mechanism of fiber cutting angle and cutting parameters on cutting force, stress, and material failure during milling was explored, and the material removal mechanism in high-speed milling of CFRP was revealed. The results show that the error between the experimental and simulated of cutting forces is less than 5%, which indicates that the progressive damage model is feasible. The fiber cutting angle has significant influence on cutting force and stress in cutting process, and the cutting direction has a significant influence on cutting force. In addition, cutting parameters play a critical role in cutting force, and the feed per tooth is the most significant factor affecting the cutting force. Simultaneously, the progressive damage model predicts that the shear failure of materials mainly concentrates in the cutting area and extends along the feed direction. Finally, the material removal mechanism of CFRP in high-speed milling was revealed combining cutting force experiment.     

螺旋铣孔工艺的切削稳定性及工艺参数规划

以螺旋铣孔工艺时域解析切削力建模、时域与频域切削过程动力学建模、切削颤振及切削稳定性建模为基础,研究了螺旋铣孔的切削参数工艺规划模型和方法。切削力模型同时考虑了刀具周向进给和轴向进给,沿刀具螺旋进给方向综合了侧刃和底刃的瞬时受力特性;动力学模型中同时包含了主轴自转和螺旋进给两种周期对系统动力学特性的影响,并分别建立了轴向切削稳定域和径向切削稳定域的预测模型,求解了相关工艺条件下的切削稳定域叶瓣图。在切削力和动力学模型基础之上,研究了包括轴向切削深度、径向切削深度、主轴转速、周向进给率、轴向进给率等切削工艺参数的多目标工艺参数规划方法。最后通过试验对所规划的工艺参数进行了验证,试验过程中未出现颤振现象,表面粗糙度、圆度、圆柱度可以达到镗孔工艺的加工精度。