航空整体结构件高效高精度加工关键技术研究（下）

（2）薄壁结构件加工变形的预测与控制针对薄壁型结构件产生的局部加工变形问题，武凯等人采用有限元仿真技术研究了薄壁腹板、侧壁加工变形规律及其变形控制方案，指出大切深法以及分步环切法可以充分利用薄壁件自身刚性，减小加工变形，提高加工精度；王志刚等人基于材料始终处于弹性范围的假设，分析了薄壁零件的加工变形，数值模拟时考虑了切削力作用下侧壁的弹性变形，但没有考虑初始残余应力和切削热对变形影响；     

铝合金零件加工变形原因分析及工艺控制措施

在铝合金零件加工中,控制变形是面临的一项普遍又关键性的问题。就铝合金零件加工中变形的原因进行了分析,提出了控制变形的工艺措施,即控制切削过程中的切削力及切削温度,通过对薄壁腔体类零件多次切削加工实验,验证了不同切削参数及工艺措施对减小切削变形的显著影响,为解决铝合金零件加工变形问题提供参考。     

高精度薄壁开口筒件加工变形控制方案的研究

针对薄壁结构开口筒件切削加工中筒体变形问题进行了分析与研究.通过建立薄壁开口筒件切削加工力学模型、ANSYS有限元变形分析模型,结构切削试验,得到了薄壁开口筒件变形的基本规律,并提出了控制筒件变形相应的工艺措施.结果表明,薄壁开口筒件变形模式与工艺路线、工装、夹紧力位置、切削用量、刀具角度等因素的组合有关;采用合理的工艺路线、工装、夹紧位置可以减小加工变形,提高加工精度,是三种控制薄壁开口筒件加工变形的有效工艺措施.     

飞机铝合金薄壁件腹板数控加工质量改进措施

针对铝合金薄壁结构件腹板的加工表面质量进行阐述,分析了数控加工中腹板加工质量的主要影响因素,并论述了在数控加工过程中,从工艺方案、装夹定位方式、刀具轨迹、加工顺序等方面控制零件变形、提高零件加工过程中刚度的具体工艺改进措施,以提高薄壁零件腹板数控加工质量。     

薄壁铝合金件的高速切削工艺研究

分析了薄壁铝合金零件的结构特点及加工工艺方案；研究了高速切削中减小其加工变形的切削参数优化策略。采用该措施可以有效地减小薄壁零件的加工变形，保证加工质量；明显地提高生产效率，缩短飞机的制造周期。     

铝合金薄壁零件切削加工变形控制技术

基于对铝合金薄壁件切削加工的经验积累,归纳总结了汽车功能主模型中铝合金薄壁零件的切削加工变形的控制技术。有限元分析法被用于分析切削加工引起的弹性变形,以检验和优化加工工艺设计方案。同时,还系统分析了加工基准的设置、工艺桩位置的布置、铣刀材质的比较、冷却液的选用、CAM编程刀具轨迹的优化以及特殊形状的分型问题等方面对加工变形的控制技术。上述技术已在实际加工中获得成功应用,这些技术对其他领域的薄壁件加工变形控制也有很强的指导意义。     

薄壁零件的车削

针对薄壁零件的车削，设计了加工工艺、切削刀具和切削参数，选择合适的切削液，进行了试验研究。试验结果表明：优化切削工艺、切削参数，可以减少薄壁零件车削中的变形，加工出合格的薄壁零件。     

切削参数对弯曲薄壁件变形规律的有限元仿真

钛合金薄壁件在切削加工时易产生弹性变形,降低薄壁件的加工质量。针对钛合金弯曲薄壁零件加工易变形的问题,建立了薄壁零件的有限元模型,研究了刀具在加工零件时不同位置和不同切削参数下对薄壁零件铣削变形的影响,确定了零件的最大变形点,并运用多指标正交试验确立了最优的刀具切削参数。     

解决鼓轮类零件的变形问题

鼓轮类零件属于典型的薄壁套零件,极易变形。通过对原加工方式进行分析,提出了合理的改进方案,采用优化工艺路线、轴向压紧工装夹紧方式和优化刀具切削参数等措施,减少了加工过程中的各种变形,使加工的零件达到了图样的技术要求。     

薄壁铸造铝合金壳体加工变形控制研究

根据薄壁壳体整体结构特征,对其加工工艺进行分析,确定加工工艺方案;基于整体工艺方案,充分考虑零件加工过程中装夹定位,以最大程度减少零件加工过程中的变形问题;通过选取合适的加工刀具及加工参数,减少零件加工过程中因切削而导致的变形问题;其他控制措施还包括采用增加辅助支撑等方式,减少零件加工过程中的震颤问题,从而控制零件变形。     

薄板类零件加工精度可靠性分析及工艺参数优化

针对薄板类零件加工过程中加工变形导致加工精度低的问题,利用有限元法和高斯过程回归算法建立了加工变形预测模型,综合考虑机床运动误差与工件加工变形,对薄板件加工精度可靠性进行分析,建立了以加工效率和平均加工变形为目标、加工精度可靠度为约束的铣削加工工艺参数优化设计模型,并利用多目标优化算法进行求解,确定了协调加工效率和加工变形最优的工艺参数组合。案例研究结果表明,经优化设计后最低加工精度可靠度达到98.21%,平均加工变形减小21.14%,加工效率提高了4.18%,为薄板类零件铣削加工工艺参数选择提供了一种可行的方法。     

虚拟加工中的加工误差分析与预测

分析了影响虚拟环境下复杂曲面产品数字化端铣加工误差产生的主要因素,综合考虑刀具和工件的柔度,同时考虑加工表面的变形敏感度,讨论面向虚拟制造的加工尺寸误差预测模型总体框架,提出了一个端铣加工过程表面加工尺寸误差预测模型。所给出的表面误差预测模型较全面地考虑了端铣加工过程,适于多种加工条件,能够反映端铣加工过程由切削力导致的系统变形对加工误差所造成的影响。最后给出了一个仿真实例。     

Machining deformation prediction for frame components considering multifactor coupling effects

The machining deformation prediction model was developed considering multifactor coupling effects including original residual stresses, clamping loads, milling mechanical loads, milling thermal loads, and machining-induced residual stresses. The machining deformation of a true frame monolithic component was predicted by this model. To validate the accuracy of prediction model, deformations also were measured on a coordinate measuring machine. The deformations predicted by the model show a good agreement with the experiment’s results. The deformation prediction model can provide an effective way to study further control strategies of machining deformations for monolithic component.     

木材用高速螺旋式玉米铣刀的变形分析与优化

刀具在加工过程中的变形和振动直接关系到加工精度,是衡量刀具的重要性能指标。本文针对木材用高速螺旋式玉米铣刀,采用有限元分析的方法,对其进行了切削过程的变形分析和振动变形分析,根据分析结果所发现的不足,提出了将刀具体内壁加厚后成台阶状和将配重拉杆截断后加粗的优化方案。研究结果表明:优化后的刀具在加工中的变形由原来的2.2-3.7μm降低到1.8-2.5μm,降低了因刀具设计而导致的加工精度误差;刀具共振频率由262Hz左右增加到1000Hz以上,避免了低频激振;刀具拉杆的共振变形由原来的1.5-2.0m降低到0.22-0.24m,提高了刀具整体刚性。本文的分析与优化工作为木材用玉米铣刀的设计与样板试验提供了重要的技术数据。     

END MILLING SYSTEM COMPLIANCE AND MACHINING ERROR

Tool deflection resulting from cutting forces places a constraint on the achievable precision and productivity in machining. This paper presents an analytical model of machining error, in terms of part form deviation in end milling due to the elastic compliance of cutting tool. Based on the relationship of local cutting forces and chip thickness, the shear loading and bending moment on the tool cross section are presented in terms of cutter angular position. The tool deflection resulting from the bending moment is then established from the principle of virtual work. The resulting deflection of workpiece and machine tool structure is also considered through shear loading analysis. The expression for machining error is derived as a closed-form function of the machining parameters, cutting configuration, material characteristics, and machine receptance. End milling experiments were conducted to verify the analytical model under various cutting conditions. Error maps are presented to illustrate the effects of process conditions on the achievable part accuracy.     

Chatter stability of micro end milling by considering process nonlinearities and process damping

The micro end milling uses the miniature tools to fabricate complexity microstructures at high rotational speeds. The regenerative chatter, which causes tool wear and poor machining quality, is one of the challenges needed to be solved in the micro end milling process. In order to predict the chatter stability of micro end milling, this paper proposes a cutting forces model taking into account the process nonlinearities caused by tool run-out, trajectory of tool tip and intermittency of chip formation, and the process damping effect in the ploughing-dominant and shearing-dominant regimes. Since the elasto-plastic deformation of micro end milling leads to large process damping which will affect the process stability, the process damping is also included in the cutting forces model. The micro end milling process is modeled as a two degrees of freedom system with the dynamic parameters of tool-machine system obtained by the receptance coupling method. According to the calculated cutting forces, the time-domain simulation method is extended to predict the chatter stability lobes diagrams. Finally, the micro end milling experiments of cutting forces and machined surface quality have been investigated to validate the accuracy of the proposed model.     

Wall thickness error prediction and compensation in end milling of thin-plate parts

End milling has been widely adopted to machine the thin-plate parts that play increasingly important role in the aerospace industry, due to the advantages of high machining accuracy and fine machined surface quality. In this paper, a systematic method is proposed to predict and compensate the wall thickness errors in end milling of thin-plate parts. The errors are caused by the static deflections induced by the varying cutting force imposed on the weakly rigid part. To improve the efficiency of computing the part deformation, a novel FE model is firstly developed by combing the methods of substructure analysis, special mesh generation and structural static stiffness modification. Then, the time- and position-dependent deformations of the part are calculated based on the proposed FE model to predict the wall thickness errors left on the finished part. It reveals for the first time that the surface topography of the finished thin-plate part is formed by the repeated cutting with the bottom edge of the cutter (BEC) in end milling. Owing to the coupling between the axial cutting depth (ACD) and the force-induced deflection, the modified ACDs for compensation of the static wall thickness errors are finally determined by an iterative adjustment method. The proposed method is verified by three-axis end milling experiments. The experiment results show that the predicted wall thickness errors match well with the really measured ones, and the errors are reduced by 77.18% with the help of the proposed compensation method. Moreover, the proposed FE model reduces the computational time elapsed for error prediction by 67.44% as compared with the benchmark FE model.     

基于Rayleigh-Ritz法的钛合金薄壁件非均匀余量加工变形控制研究

为减小钛合金薄壁件切削加工过程中的变形，提出了一种新型的非均匀余量设计策略。建立了基于Rayleigh-Ritz法的薄壁件铣削加工变形预测数学模型，提出了离散化的余量体积单元设计思路并完成了工件的非均匀余量设计，最后对比分析了不同余量设计策略对薄壁悬臂结构件加工变形的影响。研究结果表明：所提出的基于Rayleigh-Ritz法的离散余量体积单元非均匀余量设计策略对工件自身刚度利用率高，表面加工误差分布一致性好，且对控制最大表面加工误差具有更优的效果。     

END MILLING SYSTEM COMPLIANCE AND MACHINING ERROR

Abstract

Tool deflection resulting from cutting forces places a constraint on the achievable precision and productivity in machining. This paper presents an analytical model of machining error, in terms of part form deviation in end milling due to the elastic compliance of cutting tool. Based on the relationship of local cutting forces and chip thickness, the shear loading and bending moment on the tool cross section are presented in terms of cutter angular position. The tool deflection resulting from the bending moment is then established from the principle of virtual work. The resulting deflection of workpiece and machine tool structure is also considered through shear loading analysis. The expression for machining error is derived as a closed-form function of the machining parameters, cutting configuration, material characteristics, and machine receptance. End milling experiments were conducted to verify the analytical model under various cutting conditions. Error maps are presented to illustrate the effects of process conditions on the achievable part accuracy.