医用球头铣刀铣削力模型与实验验证

在骨科手术中经常使用球头铣刀对骨材料进行加工,在此过程中铣削力大小的精准控制是改善手术质量的关键,但目前尚缺乏理论模型预测骨材料加工过程中的铣削力。本文将球头铣刀离散成沿切削刃分布的切削微元,并用球头铣刀的结构参数表达切削微元的位置。通过分析切削微元的铣削力模型最终积分得到整个球头铣刀的铣削力模型,并以人工骨为铣削材料设计了三个不同工艺参数的实验来验证模型预测值的准确性。结果表明,该模型能较准确地预测球头铣刀在不同工艺参数下的铣削力。     

球头铣刀高速铣削Cr12模具钢的振动特性分析

利用球头铣刀高速铣削Cr12模具钢,研究了切削速度、进给量和切削深度对主轴和刀具切削振动的影响变化规律,结果表明随着切削速度的增加,工件振动增加缓慢,而主轴的振动迅速增加,远超过工件的振动成为主振动,主轴进给方向的振动要小于非进给方向的振动。在小进给时,随着进给速度增加各向切削振动而迅速下降,在大进给速度时,各向振动随进给速度增加保持平稳;各通道的切削振动都随着切削深度的增大而增长,因此在高速铣削过程中,主轴振动为主振动,是影响加工表面质量的主要因素。     

一种螺旋刃球头铣刀的动态铣削力模型

针对高速铣削中广泛应用的螺旋刃球头铣刀建立刀具微元的铣削力模型,给出了瞬时切削厚度的计算方法,通过积分得出了一种新的整体铣削力模型。该模型考虑了动态铣削时刀杆振动对铣削力的影响,实验数据与仿真结果吻合较好,验证了该模型的正确性。     

6061铝合金球头铣刀铣削力模型的实验研究

根据4因素4水平法正交实验法设计实验方案,运用正交回归分析方法建立了球头铣刀切削力经验公式,对该回归方程和系数进行显著性检验,并通过铣削实验.验证所求公式的准确性.文中利用试验方法分析了铣削用量与铣削力的相互关系,为进一步优选铣削用量和薄壁件变形分析奠定了扎实的基础.     

一种新的螺旋刃球头铣刀铣削力模型

为提高铣削加工的安全性和生产效率，有必要在加工实际进行之前准确地预测切削过程的物理信息，如铣削力、刀具振动等。给出了球头铣刀丸线几何模型，采用理论削力分析与实验--系数识别相结合的方法建立了新的螺旋刃球头铣刀的铣削力模型。对不同切削条件下的铣削力进行了仿真，与实验测量数据吻合良好，证明离线仿真可以对铣削力做出较准确的预测。     

数控平行铣削中球头铣刀行距的确定

介绍了在曲面的数控铣削加工中采用平行铣削时。确定球头铣刀行距的一种计算方法，从而弥补了传统的凭经验确定行距的不足。     

基于傅立叶级数的球头刀铣削力模型

球头刀铣削广泛应用于复杂曲面零件的加工,精确的铣削力模型是加工过程控制优化的基础。本文分析了球头刀的铣削过程,将剪切系数拟为微元刀刃轴向高度的多项式,对考虑剪切与犁切双重效应的周期性铣削力进行傅立叶变换,建立了铣削力的傅立叶级数形式。加工实验表明,应用本文方法的预测结果与测量得到的铣削力吻合良好,铣削力模型的有效性得到了验证。     

一种螺旋刃球头铣刀的高速加工铣削力模型

研究了高速加工中球头铣刀的铣削力特性。通过综合运用理论建模法和经验系数法,并引入高速切削时引起切屑动量改变所需的作用力,建立了高速切削条件下球头铣刀的铣削力模型。实验验证结果表明,理论计算值与实验测量值吻合良好。     

基于动力学响应的球头刀五轴铣削表面形貌仿真

针对自由曲面球头刀五轴铣削中刀具与工件复杂的位姿关系,利用球头铣削刃的三维次摆线轨迹,提出一种在工件表面等距离间隔缓存残留高度、在刀具端等时间间隔缓存振动响应的双缓存离散机制,分别实现五轴铣削中的名义加工表面形貌建模与系统动态响应轨迹仿真。在此基础上,以切削刃经过工件表面残留区域的时间信息为纽带,利用系统瞬时动态位移响应的插值信息对已加工表面法向残留高度进行修正,建立考虑铣削系统动力学响应的已加工表面形貌预测模型。以变切深、变转速、恒定的刀具倾角与每齿进给量所进行的验证试验表明,提出的球头刀五轴铣削表面形貌建模方法可有效预测颤振工况与稳定铣削工况的加工表面形貌与纹理特征。     

基于球头微铣刀的铣削力建模与试验研究

以光学玻璃材料为加工对象,基于铣削力微元分析方法,建立了微铣削力理论模型,并通过试验研究对理论分析进行了验证,结果表明,理论计算模型与实验实测的结果较为吻合,球头铣刀动态铣削力模型与实测铣削力曲线总体趋势基本吻合,其误差范围在20％以内.     

球面铣刀制造中的数学模型研究

介绍了球面铣刀成形原理、刃口曲线求解模型、刃口曲线相关参数的优化模型、磨制后刀面的机构和相应数学模型，并用实例验证上述模型的可靠性，最后还讨论了砂轮磨损对刃口曲线的影响。为球面铣刀的国产化提供了参考。     

MODELING OF 5-AXIS MILLING PROCESSES

5-axis milling operations are common in several industries such as aerospace, automotive and die/mold for machining of sculptured surfaces. In these operations, productivity, dimensional tolerance integrity and surface quality are of utmost importance. Part and tool deflections under high cutting forces may result in unacceptable part quality whereas using conservative cutting parameters results in decreased material removal rate. Process models can be used to determine the proper or optimal milling parameters for required quality with higher productivity. The majority of the existing milling models are for 3-axis operations, even the ones for ball-end mills. In this article, a complete geometry and force model are presented for 5-axis milling operations using ball-end mills. The effect of lead and tilt angles on the process geometry, cutter and workpiece engagement limits, scallop height, and milling forces are analyzed in detail. In addition, tool deflections and form errors are also formulated for 5-axis ball-end milling. The use of the model for selection of the process parameters such as lead and tilt angles that result in minimum cutting forces are also demonstrated. The model predictions for cutting forces and tool deflections are compared and verified by experimental results.     

MODELING OF 5-AXIS MILLING PROCESSES

5-axis milling operations are common in several industries such as aerospace, automotive and die/mold for machining of sculptured surfaces. In these operations, productivity, dimensional tolerance integrity and surface quality are of utmost importance. Part and tool deflections under high cutting forces may result in unacceptable part quality whereas using conservative cutting parameters results in decreased material removal rate. Process models can be used to determine the proper or optimal milling parameters for required quality with higher productivity. The majority of the existing milling models are for 3-axis operations, even the ones for ball-end mills. In this article, a complete geometry and force model are presented for 5-axis milling operations using ball-end mills. The effect of lead and tilt angles on the process geometry, cutter and workpiece engagement limits, scallop height, and milling forces are analyzed in detail. In addition, tool deflections and form errors are also formulated for 5-axis ball-end milling. The use of the model for selection of the process parameters such as lead and tilt angles that result in minimum cutting forces are also demonstrated. The model predictions for cutting forces and tool deflections are compared and verified by experimental results.     

AN ANALYTICAL MODEL OF OBLIQUE CUTTING WITH APPLICATION TO END MILLING

A new analytical cutting force model is presented for oblique cutting. Orthogonal cutting theory based on unequal division shear zone is extended to oblique cutting using equivalent plane approach. The equivalent plane angle is defined to determine the orientation of the equivalent plane. The governing equations of chip flow through the primary shear zone are established by introducing a piecewise power law distribution assumption of shear strain rate. The flow stress is calculated from Johnson-cook material constitutive equation. The predictions were compared with test data from the available literature and showed good correlation. The proposed model of oblique cutting was applied to predict the cutting forces in end milling. The helical flutes are decomposed into a set of differential oblique cutting edges. To every engaged tooth element, the differential cutting forces are obtained from oblique cutting process. Experiments on machining AISI 1045 steel under different cutting conditions were conducted to validate the proposed model. It shows that the predicted cutting forces agree with the measurements both in trends and values.     

A SIMPLIFIED SOLUTION FOR THE DEPTH OF CUT IN MULTI-PATH BALL END MILLING

Abstract

The axial depth of cut is an important factor in the dynamic cutting force analysis of milling. In multi-path ball end milling, it varies with the cutting edge position angle. General equations are derived from which the instant depth of cut in ball end milling can be calculated. Examples are given for four path increment modes. The cutting condition in each mode is discussed with respect to the depth of cut. The conditions needed to disengage the tip of the ball end mill from the cut are determined. The "step-up" increment mode has the most favorable cutting condition for cutter tip relief and high cutting velocity. In order to obtain an instant evaluation of the cutting stability, the equations of maximum depth of cut in ball end milling are derived. The exact solutions are obtained from the general equations for the instant depth of cut. More conservative estimates are obtained from the simplified solutions. The results in this paper can be used as a guide in NC part programming to select an optimal cutting strategy and to ensure a stable cutting process in ball end milling.     

A SIMPLIFIED SOLUTION FOR THE DEPTH OF CUT IN MULTI-PATH BALL END MILLING

The axial depth of cut is an important factor in the dynamic cutting force analysis of milling. In multi-path ball end milling, it varies with the cutting edge position angle. General equations are derived from which the instant depth of cut in ball end milling can be calculated. Examples are given for four path increment modes. The cutting condition in each mode is discussed with respect to the depth of cut. The conditions needed to disengage the tip of the ball end mill from the cut are determined. The "step-up" increment mode has the most favorable cutting condition for cutter tip relief and high cutting velocity. In order to obtain an instant evaluation of the cutting stability, the equations of maximum depth of cut in ball end milling are derived. The exact solutions are obtained from the general equations for the instant depth of cut. More conservative estimates are obtained from the simplified solutions. The results in this paper can be used as a guide in NC part programming to select an optimal cutting strategy and to ensure a stable cutting process in ball end milling.     

小直径铣刀铣削淬硬钢切入过程的动力学仿真研究

小直径铣刀是硬铣方式加工复杂型面淬硬模具必不町少的刀具之一，但其切人过程的崩刃、断刀现象非常突出。文中采用动力学仿真软件ADAMS，对小直径铣刀在不同切削参数条件下的切人过程进行仿真分析，以确定小直径铣刀切人过程的载荷、运动形式；然后根据仿真分析的载荷结果，用有限元分析软件ANSYS确定不同切削参数下，铣刀切人过程对刀刃的应力、变形影响，为寻求合理的切人条件、减少刀具破损和提高加工效率提供参考。     

难加工材料型腔圆角数控铣削的切削力预测

在难加工材料型腔的数控铣削过程中,圆角区域的加工阶段,径向切削深度和真实进给量的变化很大程度上影响切削力,造成扎刀、撞刀、振动等很多的问题, 影响工件的加工准确度和刀具的寿命,甚至使得加工无法顺利进行.文中建立端铣刀和圆角轮廓几何关系的数学模型,提出普遍适用于矩形与梯形型腔圆角的切削力预测方法.最后,对型腔圆角切削力的变化规律预测方法进行验证.     

MODELING OF OCCUPANT DYNAMIC RESPONSE TO CAR-BARRIERS CRASH ON HIGHWAY

The dynamic response involved in car-roadside barrier impacts is studied. The risk of oc-cupant injures in such accidents is investigated. An approach based on accident analysis and mathe-matical modeling is developed and described in three steps. Firstly a Study of car-roadside barrier im-pact accidents is carried out with available data to define a system including car,road, roadside barrier,and occupant. Secondly a mathematical model to simulate car-to-barrier impact is developed by usingmulti-body program MADYMO. Finally, dynamic responses of the occupant during impact are simu-lated using a car compartment model with a HYBRID Ⅲ occupant model and an input load pulsecalculated in the second step. The dynamic responses of the car are analyzed by changing impact con-ditions such as impact angle and impact velocity The injury risks of the occupants are discussed interms of the occupant kinematics and calculated parameters: accelerations of the head, chest, and pelvis,as well as HIC value. Verification