球头铣刀铣削斜面的三维有限元仿真研究

在能源动力、汽车、航空航天、模具制造等关键零部件的加工过程中,球头铣刀因其特有的刀具几何结构,常作为零件加工的最终成型刀具。考虑到在球头铣刀立铣加工中不同的刀具与工件相对姿态会对切削过程产生不同的影响,本文研究切屑形成和不同走刀方式下切削过程中各物理量(切削力、切削温度等)的变化情况,结合有限元仿真技术在切削加工中的应用,建立硬质合金球头铣刀铣削斜面的有限元模型,模拟相同切削参数下,八种不同走刀方式的球头铣削过程,分析刀具切入切出工件时切屑的形成过程,探究切削力和切削温度的变化规律。仿真结果表明:不同的走刀方式,平均切削合力各不相同,同时切屑和工件的最大切削温度也出现较大差异,而斜坡上坡逆铣的走刀方式所对应的平均切削合力和最大切削温度均最优。     

0Crl8Ni9不锈钢的铣削力系数辨识研究

分析了铣削加工的力学模型,针对典型的难切削加工材料0Crl8Ni9不锈钢,进行了油雾冷却、干切削和切削液冷却三种方式下的立铣加工试验,测定了各种冷却条件下的切削力系数,并将切削力计算结果和实际测量结果进行了比较,对切削力模型的实际建立以及切削机理研究等具有重要的理论和应用价值.     

圆片刀超声切削蜂窝芯材料试验研究

为提高加工Nomex蜂窝芯材料的质量和效率,采用试验方法对超声切割时的切削力进行测量,研究其影响因素和变化规律,并对切削后蜂窝芯的表面进行观察。使用回归分析法分析不同振幅和切削深度下的切削力,推导切削力的经验公式。结果显示:切削力F_y,F_z与切削深度a_p,圆片刀底部边缘处振幅A呈指数关系。通过对比切削力拟合结果和试验数据,发现误差在10%内。切削后蜂窝芯表面平整、毛刺更少。      

超精密车削加工有限元仿真研究

为研究不同的切削加工参数对超精密车削加工的切削力、切削温度、切削应力等的影响,用有限元法对金刚石车削过程进行三维仿真,得到在不同切削参数下车削铝合金时的切削力、切削温度、切削应力的变化,以及切削区的微观应力的分布状态。仿真结果表明:刀具所受到的主切削力明显大于其余两个方向的力;当切屑和母体发生分离的时候,切削力会突然降低;工件上应力最大的部分是和前刀面相对的部分;切削温度较低,最高为30℃。根据仿真结果可对切削参数进行优化。     

圆盘锯齿刀超声切削Nomex蜂窝芯力热分析

为探究Nomex蜂窝芯圆盘锯齿刀超声切削过程中切削参数与切削力热的映射关系,开展圆盘锯齿刀超声切削Nomex蜂窝芯复合材料仿真及试验研究,分析主轴转速、进给速度、切削宽度和切削深度对切削过程中切削力热的影响,建立了切削温度随进给速度、主轴转速的一次回归模型。结果表明:所建立仿真模型最大误差为11.2%,可有效预测切削力与切削温度;三向切削力随着切削宽度,切削深度,进给速度的增大而增大,随着主轴转速的增大而减小;进给速度与主轴转速对切削温度影响显著;实际加工中,应采用大切削深度与切削宽度增加切削效率,采用小进给速度和主轴转速以降低切削温度,减少刀具磨损。     

切削用量对切削力和切削振动的影响

为探究车削时切削用量对切削力和切削振动的影响,设定半精加工的切削用量范围,采用正交试验设计方法制定试验流程,在数控机床上使用硬质合金外圆车刀对45#圆钢进行切削试验,切削过程不加冷却液,并分别使用Kistler切削力测量系统和Vib Pilot M+P切削振动测量系统同时采集3个方向的切削力信号和切削振动信号,对试验数据使用方差分析(ANOVA)、贡献率计算和相关分析的方法进行处理。结果表明:背吃刀量对主切削力和进给力的影响最大,进给量对背向力和3个方向切削振动的影响最大,而切削速度对各方向切削力和切削振动的影响都最小;切削力信号的误差要远小于切削振动信号的误差。试验分析结果可以为合理设计切削用量参数,有效选择切削状态监控信号提供参考。     

单晶锗纳米切削温度场分布及各向异性对切削温度的影响研究（英文）

为深入理解单晶锗纳米切削特性,提高纳米锗器件光学表面质量,首次采用三维分子动力学(MD)的方法研究了单晶锗纳米切削过程中工件原子的温度分布情况,研究了晶体的各向异性(100),(110),(111)晶面对切削温度的影响及切削温度对切削力的影响。结果表明,在切削过程中最高切削温度分布在切屑当中,达到了460 K。刀具的后刀面与已加工表面之间的区域也有较高的温度,在400 K以上。在3个不同的晶面中,(111)晶面的切削温度最高,(111)晶面的原子密度最大,即为单晶锗的密排面,释放出的能量最多。切削温度对切削力也有影响,切削温度越高,工件中原子受到的切削力越小。     

低温冷风MQL切削镍基高温合金的仿真与实验研究

为探究低温冷风微润滑这种绿色加工技术应用于难加工材料时的效果,对难加工材料GH4269在干式、浇注式和低温冷风微量润滑条件下进行仿真模拟与切削试验。用ABAQUS对GH4169在3种方式下切削力和切削温度进行仿真;设计多因素正交实验对仿真结果进行验证。通过比较不同润滑方式对切削力及切削温度的影响,得出影响曲线图,从而揭示难加工材料GH4169在车削过程中切削力的变化情况,为实际的生产加工积累和提供基础数据。     

航空薄壁件切削加工变形控制与实时监测研究

由于航空薄壁件刚度较低,工艺性差,容易发生切削变形,是机械加工中的难题。以减小航空薄壁件的变形为目标,采用有限元分析方法,分析工件在切削力作用下的变形;通过预先考虑薄壁件在切削力作用下的加工变形及其对应的变形回弹量,采用变形主动补偿的方法,在局部刀位点修正补偿刀具的切削深度。经有限元计算比较,补偿后刀位点的最大切削加工误差相对于补偿前降低95%以上,同时航空薄壁件的切削加工误差的分布更加均匀,误差值的变化波动范围更小;最后设计了一个切削力实时监测系统,对切削加工过程进行监测,形成了一种提高航空薄壁件切削加工精度的系统性方法。     

碳纤维复合材料T型铣刀的切槽试验研究

针对碳纤维复合材料(CFRP)的齿槽加工,提出采用T型铣刀切制齿槽。以平纹CFRP为研究对象,通过齿槽的切削试验,分析切削力和残余因子。试验表明:切削力随着切削速度vc的增大而减小,但切削速度vc大于245 m/min时,进给方向切削力Fx将逐渐增大;与切削速度vc相比,进给速度vf对残余因子Fb的影响更大,随着它的增大,残余因子Fb平均减小46.63%;顺铣时的切削力和残余因子比逆铣时的明显要小。研究结果为CFRP的齿槽铣削加工提供了技术指导。     

Prediction of cutting forces in milling of circular corner profiles

This paper proposes an approach to predict the cutting forces in peripheral milling of circular corner profiles in which varying radial depth of cut is encountered. The geometric relationship between an end mill and the corner profile is investigated and a mathematical model is presented to describe the different phases of the cutter/workpiece contact. The milling process for circular corner is discretized into a series of steady-state cutting processes, each with different radial depth of cut determined by the instantaneous position of the end mill relative to the workpiece. A time domain analytical model of cutting forces for the steady-state machining conditions is introduced to each segmented process for the cutting force prediction. The predicted cutting forces can be calculated in terms of tool/workpiece geometry, cutting parameters and workpirece material property, as well as the relative position of the tool to workpiece. Experiments are conducted and the measured forces are compared to the predictions for the verification of the proposed method.     

Modelling the cutting edge radius size effect for force prediction in micro milling

This paper presents a theoretical model for cutting force prediction in micro milling, taking into account the cutting edge radius size effect, the tool run out and the deviation of the chip flow angle from the inclination angle. A parameterization according to the uncut chip thickness to cutting edge radius ratio is used for the parameters involved in the force calculation. The model was verified by means of cutting force measurements in micro milling. The results show good agreement between predicted and measured forces. It is also demonstrated that the use of the Stabler's rule is a reasonable approximation and that micro end mill run out is effectively compensated by the deflections induced by the cutting forces.     

In-process prediction of cutting depths in end milling

In geometric adaptive control systems for the end milling process, the surface error is usually predicted from the cutting force owing to the close relationship between them, and the easiness of its measurement. Knowledge of the cutting depth improves the effectiveness of this approach, since different cutting depths result in different surface errors even if the measured cutting forces are the same. This work suggests an algorithm for estimating the cutting depth based on the pattern of cutting force. The cutting force pattern, rather than its magnitude, better reflects the change of the cutting depth, because while the magnitude is influenced by several cutting parameters, the pattern is affected mainly by the cutting depth. The proposed algorithm can be applied to extensive cutting circumstances, such as presence of tool wear, change of work material hardness, etc.     

Influence of tool inclination on brittle fracture in glass cutting with ball end mills

Glass milling is discussed with influences of tool inclination on brittle fracture. Cutting tests are performed to observe surfaces in the up-cut and the down-cut processes with a ball end mill inclined in the feed direction of the cutter. Brittle fracture occurs in the down-cut process at high feed rates. Then the machined surfaces in cutting with the ball end mills tilted in the vertical plane with respect to the feed direction are associated with those of the up-cut and the down-cut processes. The cutting forces are also measured to discuss brittle fracture with the change of the undeformed chip thickness. The scratches on the surface finished with the tilted ball end mill are shown in an analytical model with a notched edge shape. The maximum feed rates at which brittle fracture does not occur are shown with the tool inclination in the cutting tests.     

A new method of cutting force measurement based on command voltages of active electro-magnetic bearings

In this paper, a new indirect method of measuring dynamic cutting forces is proposed. Milling tests have been performed on a five-axis machine, Gambin 120CR, fitted out with an electro-spindle with magnetic bearings developed by the company S2M, and named SMB30. These bearings are not affected by friction and wear. An experimental approach has been developed to determine the cutting forces as a function of the measured command voltages of the milling spindle’s magnetic bearings. The spindle is treated as a “black box”, where the transfer functions linking the unknown cutting force with command voltages are established experimentally. The cutting forces calculated from the command voltages of magnetic bearings are in good agreement with the ones measured with a Kistler four-component dynamometer. This indirect method of cutting force determination provides a useful way to estimate tool wear and monitor product quality in high-speed milling on-line.     

通用立铣刀真实切削轨迹下五轴铣削力计算

针对五轴铣削中刀具位姿变化和刀具类型差异所导致的铣削力预测难的问题，提出通用立铣刀五轴铣削力计算方法。基于通用立铣刀结构形式，建立通用立铣刀几何模型；综合考虑刀齿真实运动轨迹和刀具姿态变化，构建刀具瞬时切屑厚度模型；将刀具沿轴线方向等分成若干切削刃微元，并根据线性切削力假设建立刀具微元铣削力；将微元铣削力从刀具坐标系转换至工件坐标系下，并沿刀具轴向铣削深度进行积分，获得通用立铣刀的五轴铣削力模型；最后，在混联五轴数控加工实验平台上开展了铣削力测试。实测结果表明:所提铣削力计算方法正确有效，可作为后续五轴铣削工艺参数优选的理论依据。     

Mechanics and dynamics of general milling cutters.: Part I: helical end mills

A variety of helical end mill geometry is used in the industry. Helical cylindrical, helical ball, taper helical ball, bull nosed and special purpose end mills are widely used in aerospace, automotive and die machining industry. While the geometry of each cutter may be different, the mechanics and dynamics of the milling process at each cutting edge point are common. This paper presents a generalized mathematical model of most helical end mills used in the industry. The end mill geometry is modeled by helical flutes wrapped around a parametric envelope. The coordinates of a cutting edge point along the parametric helical flute are mathematically expressed. The chip thickness at each cutting point is evaluated by using the true kinematics of milling including the structural vibrations of both cutter and workpiece. By integrating the process along each cutting edge, which is in contact with the workpiece, the cutting forces, vibrations, dimensional surface finish and chatter stability lobes for an arbitrary end mill can be predicted. The predicted and measured cutting forces, surface roughness and stability lobes for ball, helical tapered ball, and bull nosed end mills are provided to illustrate the viability of the proposed generalized end mill analysis.     

Cutting force estimation in sculptured surface milling

Cutting force milling models developed up to now are mostly used for planar milling using end-mills. Only a reduced number of models applying ball-end mills have been developed. Furthermore these models usually only consider horizontal surface machining, even though the main application of ball-end mills is sculptured surface machining. This article proposes a model that is able to estimate the cutting forces in inclined surfaces machined both up-milling and down-milling. For this purpose a semi-mechanistic model has been developed that calculates the cutting forces based on a set of coefficients which depend on the material, the tool, the cutting conditions, the machining direction and the slope of the surface.A coordinate transformation has been included in order to consider the slope milling case with different cutting directions.The model has been tested on two materials, an aluminum alloy Al7075-T6 and a 52 HRC tool steel AISI H13. Validation tests have been carried out on inclined planes using different slopes and different machining directions.The results provide errors below 10% in most of the cases and both the value and shape of the predicted forces adjust the measured cutting force.     

基于改进瞬时刚性力模型的机床铣削加工监测

针对用于切削力预测的瞬时刚性力模型所需参数较多且依赖初步切削实验的问题,提出一种不需要切削实验的新型切削力预测方法,实现在实际工厂中监测机床铣削加工过程。在斜角切削模型和正交切削理论的基础上,对传统的瞬时刚性力模型进行改进,减少切削力预测所需的切削参数。改进后的模型仅需在铣削操作开始时从测量的主轴电机扭矩得到的剪切角参数,无需任何额外的传感器就可以实现铣削力预测。在所提模型中,刀具跳动的影响可通过每个切削刃处的旋转半径偏差表示,以精确预测切削力。为验证该模型的有效性,进行切削实验。结果表明：切削力的预测值与实测值吻合较好,在实际加工过程中,无需任何实验铣削或任何额外的力传感器就可以准确了解机床加工状态。