三维有限元分析在高速铣削温度研究中应用

高速切削过程中切削温度对刀具磨损、工件加工表面完整性及加工精度有极大的影响。应用有限元法对高速铣削铝合金薄壁件过程中工件与刀具接触面温度、工件内部的温度分布进行了仿真研究,仿真过程中考虑了切削速度、进给量对切削温度的影响。通过红外热像仪对不同主轴转速下工件表面温度的测量,验证了仿真结果与试验结果比较接近。得出在高速切削铝合金过程中,随着切削速度的增加,刀具与工件接触区的温度变化存在二次效应。该结论对铝合金薄壁件加工具有重要的实用价值。     

SiC_p/Al复合材料薄壁件钻削加工变形有限元仿真研究

基于ABAQUS有限元仿真软件建立体积分数为56%的SiC_p/Al复合材料钻削三维模型,研究分析了在两种不同工件约束方式下钻削加工薄壁件过程中工件的变形规律及特点,同时研究了切削参数对薄壁钻孔时工件变形量的影响规律。结果表明:随着钻削速度和进给量的增加,钻孔中心位置处(钻头横刃钻削至工件下表面)的最大变形量随之增加,进给量对钻孔件中心位置处最大变形量的影响较为显著;薄壁件残余变形量随着进给量的增大而增加,钻削速度对薄壁件残余变形量的影响较小。     

基于AdvantEdge FEM的薄壁外壳体零件仿真分析

导引头产品某较大型薄壁类零件在车削加工过程中,加工变形大,加工状态不稳定。考虑到影响加工变形的主要因素为切削三要素,现通过AdantEdge FEM及ANSYS-workbench有限元仿真法对薄壁外壳体零件的车削加工过程及模态、谐响应进行仿真分析,通过AdantEdge FEM后处理结果中温度场、应力场及变形的变化情况,对切削参数进行调整,优化切削加工过程,通过ANSYS-workbench对该薄壁模型进行模态分析及谐响应分析,得到工件的加工变形情况,从而采取最优切削加工方案控制薄壁外壳体零件的变形。     

铣削方式对残余应力影响的仿真及试验研究

机械加工过程中,薄壁件的残余应力控制是实现高性能精密制造的关键。目前,鲜有文献涉及铣削方式对工件表面残余应力影响的研究。以LY12铝合金工件为研究对象,运用Advant Edge有限元仿真软件构建三维铣削模型,提出工件表面残余应力的获取及分析计算方法。仿真与试验结果表明,逆铣加工产生的残余拉应力值小于顺铣加工,因此采用逆铣有利于控制框体类薄壁件的加工变形。此外,在顺铣过程中,相对于铣削宽度,提高切削深度更有利于控制表面残余拉应力;而在逆铣过程中,两者对残余应力的影响并不明显。     

薄壁件立铣切削力的有限元模拟与实验研究

薄壁件铣削加工中铣削力是导致加工变形的直接原因,是加工误差的主要影响因素.在考虑刀具变形、工件及刀具材料性能参数的基础上,建立了三维斜角切削力有限元模型,利用有限元分析软件ABAQUS对薄壁件斜角切削过程进行了仿真模拟.其次,针对铣削过程进行了切削力测试,结果表明本文提出的切削力有限元模拟方法具有较高的精度,对切削参数的优化提供了理论依据和便利工具.     

汽轮机叶片薄壁曲面加工变形分析及切削参数选择

汽轮机叶片是汽轮机的核心零部件,而薄壁曲面叶片的受力变形一直是加工难题。建立了叶片加工的刀具铣削力模型,采用ANSYS Workbench有限元软件将铣削力施加在数控程序所对应的工件各接触点处,对汽轮机薄壁叶片的加工变形进行分析研究并得到变形量最大的点。通过研究该点处切削宽度、切削速度、进给量和切削深度对叶片变形的影响规律,确定了实际加工薄壁叶片的切削参数,并通过仿真和实际加工验证了其可行性。     

自由曲面铣削误差预测

在航空航天工业等行业中,对于复杂薄壁曲面零件,极易产生由工件变形引起的加工误差,这直接影响了零件的加工精度及表面质量。本文研究了薄壁叶片型面精加工切削过程中工件变形对加工精度的影响:首先利用正交试验求出球头铣刀的铣削力公式,进而结合有限元方法,编写柔性切削变形迭代算法,计算出薄壁叶片的最终变形量,并分析了叶片的变形规律,这对提高叶片加工精度具有重要的实际应用价值。     

汽车主模型薄壁件加工防变形夹具设计与研究

针对汽车检测工具主模型薄壁部分切削加工过程中工件容易变形的问题,设计了薄壁件加工防变形夹具,利用浮动的辅助支撑杆对工件进行支撑,可以在磁流变液浮力的作用下与工件表面自适应贴合。设计了真空吸盘和定位装置对工件夹紧与定位,滑动定位装置可实现夹具在空间区域进行定位,采用真空吸盘装置的夹紧方案可以快速更换加工工件,不影响表面加工质量且方便稳定。柔性体现在夹具能够自适应调整以适用于不同类型主模型薄壁件的切削加工,从而节省夹具的制造成本。利用计算机辅助软件算出夹紧点的合理位置,能保证工件在加工中不产生位移和变形;利用磁流变液锁紧装置可快速改变辅助支撑杆的松紧状态;提高了工件的装夹效率,节省工时,实现加工要求。     

铝合金薄壁件数控铣削加工变形试验与分析

薄壁工件刚度差,在数控加工过程中在切削力的作用下极易产生加工变形,影响工件加工精度和成本。在THA5656立式加工中心上对铝合金材料LY12CZ方形直侧壁工件变形进行了试验研究,并进行误差分析。通过正交试验,研究薄壁件在铣削精加工过程中各个切削用量情况下工件的变形情况,为提高生产率和进一步控制加工变形和验证加工过程计算机仿真模型提供依据。     

航空薄壁结构件铣削加工变形数值模拟分析

针对广泛应用于航空航天制造业中的整体薄壁结构件刚性差、易产生加工变形,从而难以保证其加工品质的问题,基于金属切削原理的物理仿真,采用Production Module 3D仿真软件对工件的加工变形进行数值模拟,并与相同条件下的试验数据进行了对比验证,仿真结果与试验数据基本相符.在验证了仿真模型的有效性前提下,研究了走刀路径、切削用量和刀具结构参数对薄壁零件加工变形的影响,获得了其加工变形的规律.所做研究为通过改善加工工艺、优化切削参数和优选刀具来控制加工变形提供了理论依据.     

Improvement of flatness error in milling plate-shaped workpiece by application of side-clamping force

To improve flatness error of plate-shaped workpieces in milling under side clamp holding mechanisms, appropriate magnitudes of clamping forces and method of application are studied in this paper. The effect of side-clamping force on workpiece deformation is investigated by experimental and computational analyses for the case where the workpiece is clamped at a position higher than the neutral plane of bending of the plate-shaped workpiece. It is found that the thermal deformation and elastic deformation caused by clamping force are in two opposite directions. Then, an appropriate method is proposed to compensate for the workpiece thermal deformation caused by cutting heat with the opposite elastic deformation caused by the side-clamping force, so as to keep the machined top surface of the workpiece flat as much as possible. The proposed method has been confirmed through computational analyses and experiments. © 2000 Elsevier Science Inc. All rights reserved.     

曲轴复合车削的工件变形分析

复合车削曲轴连杆颈时,曲轴在切削力的作用下会产生弹性变形,这会使切削加工后的曲轴连杆颈相位产生误差,如果误差过大,将会使工件报废.因此必须首先分析相位误差的特点,而后在此基础上进行补偿.为研究曲轴在复合车削加工时的变形,在受力分析的基础上.研究了切削力产生的加工误差变化规律,并用ANSYS计算了曲轴在加工过程中不同工况...     

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。     

Fundamental modeling for oblique cutting by thermo-elastic-plastic FEM

In this paper, the finite deformation theory and updated Lagrangian formulation were used to describe the oblique cutting process. Either the tool geometrical location condition or the strain energy density constant was combined with the twin node processing method to act as the chip separation criterion. An equation of three-dimensional tool face geometrical limitation was first established to inspect and correct the relation between the chip node and the tool face. And, a three-dimensional finite-difference heat transfer equation was derived. Based on this approach, tool advancement was achieved in displacement increment step by step from the initial tool contact with the workpiece till the formation of steady cutting force. In this case, a large deformation thermo-elastic–plastic finite element model for oblique cutting was established. The mild steel was used as the workpiece, the tool was P20 and the cutting speed was 274.8 mm/s in this article. The chip deformation process and temperature effect on the strain energy density, chip flow angle, cutting force and specific cutting energy were studied first. Finally, the integrity on machined workpiece surface was explored from the variation of residual stresses and temperature distribution on it after cutting. During the chip deformation process, the chip flow angle obtained by this simulation result was approximately equal to the tool inclination angle, which confirmed with the geometrical requirement of Stabler’s criterion. Besides, the simulated specific cutting energy was compared with the experimental specific cutting energy value, the result of which was within acceptable range. It is obvious from the above findings that the model presented in this paper is consistent with the geometrical and mechanical requirements, which verifies the proposed model is acceptable.     

A stability analysis of regenerative chatter in turning process without using tailstock

A new approach to analyze the stability of cutting processes when considering the deformation of the workpiece is proposed in this article. In past studies, the workpiece was assumed to be rigid and no deformation was considered. In those studies, the stability of the cutting process was analyzed by merely the dynamic equation of tools. However, the workpiece does have deformation when there is external force exerting on it. Such deformation will change the chip thickness and have an effect on the critical chip thickness of stability. To describe the cutting in turning process, partial differential equations are used and a set of dynamic equations will be considered based on the interaction between the tool and the workpiece. After performing the Laplace transformation, stability can be analyzed based on the length, radius, natural frequency, deflection, aspect ratio and material stiffness of the workpieces. The effect of the critical chip width under different spindle speed will also be discussed in this article. By considering the deformation of the workpiece under different conditions, the results show that the critical chip width of the deformed case is always larger than the rigid body case.     

大型铝合金薄壁回转体零件切削力分析研究

根据大型薄壁回转体零件切削力测试试验要求,研制了外圆专用压电式测力仪和内孔专用压电式测力仪。通过单因素试验分析,得出切削力的变化规律曲线,并采用有限元分析方法对切削力和工件变形影响进行了分析研究。最终得出在切削过程中主切削力Fz数值最大且对工件的加工精度影响最大。     

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel,workpiece characteristics,and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.     

An improved cutting force model for micro milling considering machining dynamics

Micro milling, as a versatile micro machining process, is kinematically similar to conventional milling; however, it is significantly different from conventional milling with respect to chip formation mechanisms and uncut chip thickness modelling, due to the comparable size of the edge radius to the chip thickness, and the small per-tooth feeding. Considering tool runout and dynamic displacement between the tool and the workpiece, the contour of the workpiece left by previous tool paths is typically in a wavy form, and the wavy surface provides a feedback mechanism to cutting force generation because the instantaneous uncut chip thickness changes with both the vibration during the current tool path and the surface left by the previous tool paths. In this study, a more accurate uncut chip thickness model was established including the precise trochoidal trajectory of the cutting edge, tool runout and dynamic modulation caused by the machine tool system vibration. The dynamic regenerative effect is taken into account by considering the influence of all the previous cutting trajectories using numerical iteration; thus, the multiple time delays (MTD) are considered in this model. It is found that transient separation of the tool-workpiece occurring at a low feed per tooth, caused by MTD and the existing cutting force models, is no longer applicable when transient tool-workpiece separation occurs. Based on the proposed uncut chip thickness model, an improved cutting force model of micro milling is developed by full consideration of the ploughing effect and elastic recovery of the workpiece material. The proposed cutting force model is verified by micro end milling experiments, and the results show that the proposed model is capable of producing more accurate cutting force prediction than other existing models, particularly at small feed per tooth.     

Numerical study the flow stress in the machining process

In the machining process, the workpiece is under severe plastic deformation with large strain, high strain rate, and temperature. It is necessary to know the flow stress of workpiece material in such condition to better understand the mechanism of chip formation, tool wear and damage, etc. In this study, a Split Hopkinson Pressure Bar (SHPB) with synchronically assembled heating system was employed to study the flow stress similar to the deformation condition in the machining process. A phenomenological constitutive model was proposed by the regression analysis of the experimental results. Furthermore, orthogonal metal cutting processes were carried out by the finite element method (FEM). The cutting force predicted by the FEM showed good agreement with the experimental results, which confirmed that the proposed constitutive model can give an accurate estimate of the flow stress in the machining process.     

Milling Force Model for Aviation Aluminum Alloy:Academic Insight and Perspective Analysis

Aluminum alloy is the main structural material of aircraft,launch vehicle,spaceship,and space station and is pro-cessed by milling.However,tool wear and vibration are the bottlenecks in the milling process of aviation aluminum alloy.The machining accuracy and surface quality of aluminum alloy milling depend on the cutting parameters,material mechanical properties,machine tools,and other parameters.In particular,milling force is the crucial factor to determine material removal and workpiece surface integrity.However,establishing the prediction model of milling force is important and difficult because milling force is the result of multiparameter coupling of process system.The research progress of cutting force model is reviewed from three modeling methods:empirical model,finite element simulation,and instantaneous milling force model.The problems of cutting force modeling are also determined.In view of these problems,the future work direction is proposed in the following four aspects:(1)high-speed milling is adopted for the thin-walled structure of large aviation with large cutting depth,which easily produces high residual stress.The residual stress should be analyzed under this particular condition.(2)Multiple factors(e.g.,eccentric swing milling parameters,lubrication conditions,tools,tool and workpiece deformation,and size effect)should be consid-ered comprehensively when modeling instantaneous milling forces,especially for micro milling and complex surface machining.(3)The database of milling force model,including the corresponding workpiece materials,working condi-tion,cutting tools(geometric figures and coatings),and other parameters,should be established.(4)The effect of chatter on the prediction accuracy of milling force cannot be ignored in thin-walled workpiece milling.(5)The cutting force of aviation aluminum alloy milling under the condition of minimum quantity lubrication(mql)and nanofluid mql should be predicted.