Tool life model for abrasive wet micro-drilling of ceramic green bodies

Ceramic plates containing many micro-holes are used for MCPs (microchannel plates) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits. Several fabrication methods for MCP such as laser drilling and electron beam drilling of ceramic plates have been used. To increase the productivity, the micro-drilling of ceramic green body followed by sintering machined green body has been suggested. In this work, using the experimental results of alumina green body drilling with electro-deposited diamond grit WC micro-drills, a chip flow model on the worn-out micro-drill tip was constructed to estimate the tool life of micro-drills. The axial forces of abrasive grit micro-drills with respect to drilling time and drilling conditions were calculated from the model constructed. Finally, the tool life of micro-drills was estimated using the calculated axial forces under given drilling conditions.     

基于遗传算法的皮质骨钻削参数优化分析

骨外科手术钻孔要求对骨骼损伤较小以及术后快速恢复。基于ABAQUS建立皮质骨钻削模型,通过中心复合试验设计,研究钻削参数(进给速度、主轴转速和钻头直径)对轴向力的影响。使用MATLAB对试验数据进行多元线性回归分析,得到钻削力的数学模型,并结合遗传算法,找出皮质骨钻孔最小轴向力的最佳钻削参数组合。优化结果为骨科手术钻孔操作中钻削用量的选择提供参考。     

基于传递函数辨识的超声辅助微钻削轴向力动态模型

超声辅助微钻削过程中的动态钻削力严重影响刀具磨损以及微孔质量。通过建立动态钻削力模型,对超声辅助微钻削过程中的钻削力进行预测与控制,以达到提高刀具寿命以及微孔质量的目的。提出一种基于传递函数辨识的轴向力动态模型建立方法。在UAMD中,根据不同进给量时的钻削参数得到轴向力时间响应参数;通过系统辨识的方法对钻削系统进行建模,得到轴向力的原始传递函数模型;根据初步验证的结果和对传递函数频域的分析,采用多项式拟合的方法对模型的极点和增益进行修正;将优化后的数学模型转化为状态空间,得到超声辅助微钻削的轴向力动态响应模型。实验结果表明：优化后的动态模型与实验轴向力的时域响应吻合程度高。     

Response surface methodology-based approach to CNC drilling operations

Drilling operation is fundamental in the manufacturing industry to drill holes especially in sheet metal parts. This paper presents a mathematical model for correlating the interactions of some drilling control parameters such as speed, feed rate and drill diameter and their effects on some responses such as axial force and torque acting on the cutting tool during drilling by means of response surface methodology. For this exercise, a three-level full factorial design was chosen for experimentation using a PC-based computer numerically controlled drilling machine built in-house. The significance of the mathematical model developed was ascertained using Microsoft Excel^® regression analysis module. The results obtained show that the mathematical model is useful not only for predicting optimum process parameters for achieving the desired quality but for process optimization. Using the optimal combination of these parameters is useful in minimizing the axial force and torque of drilling operations; by extension, other drilling parameters such as cutting pressure, material removal rate, and power could be optimized since they depend on the combination of drilling parameters which affect the axial force and torque.     

Machining prediction of spindle–self-vibratory drilling head

The drilling of deep holes with small diameters remains an unsatisfactory technology, since its productivity is rather limited. The main limit to an increase in productivity is directly related to the poor chip evacuation, which induces frequent tool breakage and poor surface quality. Retreat cycles and lubrication are common industrial solutions, but they induce productivity and environmental drawbacks. An alternative response to the chip evacuation problem is the use of a vibratory drilling head, which enables the chips to be fragmented thanks to the axial self-excited vibration. Contrary to conventional machining processes, axial drilling instability is sought, thanks to an adjustment of head design parameters and appropriate conditions of use. A dynamic high-speed spindle/drilling head/tool system model is elaborated on the basis of rotor dynamics predictions. In this paper, self-vibratory cutting conditions are established through a specific stability lobes diagram. Investigations are focused on the drill's torsional–axial coupling role on instability predictions. A generic accurate drilling force model is developed by taking into account the drill geometry, cutting parameters and effect of torsion on the thrust force. The model-based tool tip FRF is coupled to the proposed drilling force model into an analytical stability approach. The stability lobes are compared to experimentally determined stability boundaries for validation purposes.     

GFRP低频轴向振动制孔的钻削力特性和套料钻磨损分析

GFRP的套孔钻削过程中极易产生分层、撕裂等加工损伤,其与轴向钻削力直接相关。为提高GFRP的制孔质量,采用新型金刚石薄壁套料钻,结合低频轴向振动加工技术,建立单颗磨粒的运动学模型和动力学模型,试验研究GFRP制孔中的轴向力变化规律,并对套料钻的烧焦概率、自动落料率进行分析。结果表明：对比常规钻削,低频振动钻削时的瞬时进给量和轴向力比常规钻削时的大,且随着振幅的增加,轴向力也随之增大;低频振动钻削和常规钻削时的轴向力皆随进给速度的增加而增大,随主轴转速的升高而降低。同时,低频振动钻削时磨粒间断性地参与钻削,大大降低了套料钻的烧焦概率,提高了其自动落料率,自动落料率高达88.24%,可实现GFRP的连续批量制孔。     

锥轴分布式球形柱塞泵润滑性能分析

圆锥轴配流是液压元件中的一种新型流量分配结构设计,它有圆柱轴配流和平面流配流的优点。本文研究了圆锥轴配流的稳态工况及其在变载荷作用下的动态响应。基于特殊的结构形式,建立了球面坐标系下的润滑模型。通过受力分析,建立了锥轴配流在轴向和径向自由度分布的动力学模型。采用数值方法对模型进行求解,得到了包括轴偏心率和分布间隙高度在内的静、动态润滑性能。结果表明,在冲击载荷作用下,轴的偏心距和分布间隙会剧烈振荡,并在短时间内恢复到平衡位置。这种无需外部调整的锥轴配流的润滑方式具有自适应性,对保证球柱塞泵工作的可靠性具有重要意义。     

深小孔超声振动钻削轴向力的仿真与实验研究

建立深小孔轴向振动钻削加工仿真分析模型,针对轴向力通过DEFORM-3D有限元软件进行了超声振动钻削与普通钻削仿真,对两组仿真结果进行分析比较,并在超声轴向振动钻削装置上对不锈钢板进行了深小孔振动钻削和普通钻削实验,利用压电传感器测量了振动钻削和普通钻削加工的轴向力。实验结果与仿真结果对比表明:仿真结果与实验结果偏差低于8%,超声振动钻削的平均轴向力小于普通钻削的平均轴向力,钻削过程平稳。     

Micro-drilling of alumina green bodies with diamond grit abrasive micro-drills

Since ceramic plates containing many micro-holes are used for MCPs (Micro-channel plates) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the efficient drilling of micro-holes in ceramic plates is important for productivity and cost. Since ceramics have poor machinability due to their low thermal conductivity, high hardness and high brittleness, in this work, alumina green bodies rather than sintered alumina were drilled to manufacture ceramic MCPs, followed by sintering the machined green bodies. Alumina green bodies were drilled with electro-deposited diamond grit WC micro-drills, and the cutting force with respect to drilling time was measured to determine a suitable micro-drilling condition. From the measurement of the micro-drill tip wear during micro-drilling of alumina green bodies, a model for the cutting force during micro-drilling was constructed.     

TC4钛合金深孔钻削方式和轴向力研究

针对钛合金钻削过程中的轴线偏斜问题,基于Abaqus对钛合金两种不同的钻削过程进行仿真,建立钻杆的有限元模型、数学模型,并将轴线的偏斜问题转化为两种不同钻削方式的轴向力大小问题。得出结论：在工件速度为180～900 r/min时,钻头与工件同时反向旋转时,轴向力随着工件速度的增大而减小。并对该方式进行工件转速为900 r/min的不同钻头转速、进给量的16组试验,结果表明：在钻头转速为900～1 800 r/min之间、进给量为0.02～0.08 mm/r时,平均轴向力减小了33.4%。因此,可以采用该钻削方式减小偏斜量。     

开颅手术中面向低损伤制孔的钻头结构优化设计

为降低颅骨钻孔过程中的钻削温度与轴向力,通过有限元仿真软件ABAQUS建立颅骨钻削模型,探究麻花钻主要几何参数（顶角、螺旋角、腹板厚度与横刃斜角）对机械损伤与热损伤的影响规律。制备可减小机械损伤与热损伤的优化钻头,进行试验。结果表明：麻花钻最优几何参数为顶角96°、螺旋角38.802°、腹板厚度0.8 mm、横刃斜角131.018°;与优化前的钻头相比,优化后的钻头具有更低的轴向力与钻削温度。     

Time domain simulation of torsional–axial vibrations in drilling

A time domain model of the torsional–axial chatter vibrations in drilling is presented. The model considers the exact kinematics of rigid body, and coupled torsional and axial vibrations of the drill. The tool is modeled as a pretwisted beam that exhibits axial and torsional deflections due to torque and thrust loading. A mechanistic cutting force model is used to accurately predict the cutting torque and thrust as a function of feedrate, radial depth of cut, and drill geometry. The drill rotates and feeds axially into the workpiece while the structural vibrations are excited by the cutting torque and thrust. The location of the drill edge is predicted using the kinematics model, and the generated surface is digitized at discrete time intervals. The distribution of chip thickness, which is affected by both rigid body motion and structural vibrations, is evaluated by subtracting the presently generated surface from the previous one. The model considers nonlinearities in cutting coefficients, tool jumping out of cut and overlapping of multiple regeneration waves. Force, torque, power and dimensional form errors left on the surface are predicted using the dynamic chip thickness obtained from the exact kinematics model. The stability of the drilling process is also evaluated using the time domain simulation model, and compared with extensive experiments. This paper provides details of the mathematical model, experimental verification and simulation capabilities. Although the surface finish from unstable cutting can be predicted realistically, the actual drilling stability cannot be determined without including process damping.     

螺杆式连续油管水力振荡器轴向力及其影响因素分析

随着长水平段油气井的增多，外径小、柔性大的连续油管在井下越来越易发生螺旋屈曲锁死以至无法继续下入。连续油管水力振荡器能够有效降摩减阻，延迟螺旋屈曲锁死，增加连续油管的下入深度，因而得到广泛应用。根据螺杆式连续油管水力振荡器工作过程中的运动和受力分析，得出其轴向力计算公式。采用灰色关联度法分析各影响因素对连续油管水力振荡器轴向力的影响程度，得出流量、流体密度以及转子偏心距对其轴向力影响最大。实例计算表明：连续油管水力振荡器最大轴向力随流量、流体密度以及转子偏心距的增加而变大；连续油管水力振荡器轴向力变化频率与流体密度无关，随流量增加而变大，随转子偏心距增加而减小。     

进给量对超声振动钻削力的影响研究

在振动钻削加工原理的基础上建立了振动钻削过程中平均钻削力的数学模型,在超声轴向振动钻削试验装置上进行了0Cr17Ni4Cu4Nb不锈钢的普通钻削和振动钻削的钻削力测量试验,通过试验分析了进给量对钻削力和钻头磨损的影响规律。试验结果表明,振动钻削过程中的钻削力明显减小,钻削力曲线更加平缓;振动钻削过程中,随着钻头进给量的增大钻削力逐渐增大,钻头磨损加剧。     

大直径深孔凿岩钻孔偏斜的机理及其控制方案

通过对钻孔偏斜的影响因素及力学特征的分析,建立了钻头偏载的力学模型,从而揭示了凿岩过程钻孔偏斜的机理,提出了控制钻孔偏斜的推进力控制方案,试验结果表明,该控制方案能够随钻孔过程中孔内钻杆质量的变化及孔内因素的变化,自动改变推进器的推进力,从而有效地控制钻孔偏斜。     

航空喷嘴9Cr18Mo小孔钻削刀具结构与工艺参数优化

针对9Cr18Mo马氏体不锈钢航空喷嘴小孔的钻削加工,基于DEFORM-3D有限元软件,开展硬质合金钻头几何结构和加工工艺参数优化仿真与试验研究.基于钻削刀具的螺旋槽和后刀面数学模型,采用UG三维建模软件建立钻头三维模型,利用DEFORM-3D软件建立钻削有限元仿真分析模型,综合分析不同刀具几何结构和工艺参数对排屑、钻...     

氧化锆陶瓷微孔钻削加工工艺试验研究

针对氧化锆陶瓷钻削微孔过程中出现的轴向力大和出口崩边严重的问题，使用直径为0.2 mm的金刚石涂层钻头钻削完全烧结的氧化锆陶瓷微孔，通过单因素试验方法，研究主轴转速、进给速度和步进距离对轴向力的影响，在此基础上开展啄钻工艺对比试验，探索变进给啄钻工艺对出口崩边尺寸的影响。结果表明：轴向力大小随着进给速度和步进距离的增加而增大，随着主轴转速的增加先降低后增大；采用变进给啄钻可以有效提高孔出口加工质量。     

大厚径碳纤维复合材料三维钻削有限元仿真及试验研究

针对CR929远程宽体客机承力构件制孔出口分层缺陷预测难、制孔载荷预测试验成本高等问题,开展大孔径碳纤维增强树脂基复合材料(CFRP)三维钻削仿真及试验研究。首先基于ABAQUS用户自定义子程序接口,利用Fortran语言编写CFRP宏观力学本构模型;随后建立大孔径CFRP三维钻削仿真过程有限元模型,并验证其正确性;最后利用有限元模型预测不同加工参数下的制孔轴向力、扭矩及出口分层损伤。研究结果表明:基于三维实体单元建模的复合材料,三维钻削有限元仿真模型可以可靠地预测制孔过程中的轴向力、扭矩。在CFRP出口处嵌入黏结单元可以预测制孔出口分层的形状。在相同工艺参数条件下, 制孔的轴向力、扭矩、出口分层的仿真预测与试验结果最大相对误差分别为15.0%、19.0%、12.4%。      

Generalized modeling of drilling vibrations. Part I: Time domain model of drilling kinematics, dynamics and hole formation

This two part paper presents a comprehensive exercise in modeling dynamics, kinematics and stability in drilling operations. While Part II focuses on the chatter stability of drilling in frequency domain, Part I presents a three-dimensional (3D) dynamic model of drilling which considers rigid body motion, and torsional–axial and lateral vibrations in drilling, and resulting hole formation. The model is used to investigate: (a) the mechanism of whirling vibrations, which occur due to lateral drill deflections; (b) lateral chatter vibrations; and (c) combined lateral and torsional–axial vibrations. Mechanistic cutting force models are used to accurately predict lateral forces, torque and thrust as functions of feedrate, radial depth of cut, drill geometry and vibrations. Grinding errors reflected on the drill geometry are considered in the model. A 3D workpiece, consisting of a cylindrical hole wall and a hole bottom surface, is fed to the rotating drill while the structural vibrations are excited by the cutting forces. The mechanism of whirling vibrations is explained, and the hole wall formation during whirling vibrations is investigated by imposing commonly observed whirling motion on the drill. The time domain model is used to predict the cutting forces and frequency content as well as the shape of the hole wall, and how it depends on the amplitude and frequency of the whirling vibration. The model is also used to predict regenerative, lateral chatter vibrations. The influence of pilot hole size, spindle speed and torsional–axial chatter on lateral vibrations is observed from experimental cutting forces, frequency spectra and shows good similarity with simulation results. The effect of the drill–hole surface contact during drilling is discussed by observing the discrepancies between the numerical model of the drilling process and experimental measurements.     

钻孔法中的残余应力场Ⅰ.理论分析

钻孔法测量残余应力时,由于切削力的作用,会在孔口附近产生加工硬化层。硬化层内材料的特性会发生明显变化,从而影响残余应力的释放。通过增大孔口附近区域材料的弹性模量的方式,将硬化层简化为一个异质圆环,利用弹性力学方法求得了无限大板在双向均布载荷作用下钻孔后的释放应力的解析解。应用有限元软件MSC／Patran ＆ Nastran,对304不锈钢板在二向应力状态下的释放应力进行了数值计算,并与文中的解析解进行了比较。结果表明,将硬化层简化为异质圆环的分析模型是有效的,文中推导的解析解是正确的,钻孔法测量残余应力时考虑硬化层的影响会有助于提高测量精度。