Prediction of undeformed chip thickness distribution and surface roughness in ultrasonic vibration grinding of inner hole of bearings

Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of workpiece.However,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational efficiency.In this study,a symbolic difference method is proposed to calculate the UCT.The UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding process.Meanwhile,the UCT distribution characteristics under different machining parameters are analyzed.Then,a surface roughness prediction model is established based on the UCT distribution.Finally,the correctness of the model is verified by experiments.This study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.

Analysis of the Cut-thickness in the Process of Gear Shaping

For helping find out the cause of the extrusion wound of gear and the abnormal abrasion wear in the process of gear shaping, this disquisition studies the varying law of the cut-thickness of chips in gear shaping and deduces a set of formulas for it.

塔形组合式金刚石圆盘锯能耗建模及参数优化

为准确预测塔形组合式金刚石圆盘锯在荒料锯切过程中的功率,以组合锯切系统中单锯片的单磨粒平均未变形切屑厚度为媒介,建立了锯切功率的参数模型,并对其进行修正,提出一种少样本快速预测模型,通过锯切实验测量不同参数组合下的锯切功率,采用多元线性回归方法拟合数据以获取可靠的模型系数。最后以锯切参数为优化变量,以锯切比能和锯切时间最小为优化目标建立优化模型,并采用改进粒子群算法对模型进行优化求解。试验结果表明,参数模型充分解释了各锯切参数对锯切功率的影响,能够准确预测不同锯片组合方式下的锯切功率,改进的粒子群算法有较高的优化性能,使用优化后的参数能够显著降低锯切功率。

基于刀齿轨迹模型的五轴侧铣加工铣削力预测

在五轴侧铣加工过程中刀具的刀轴姿态变化复杂,导致瞬时切屑厚度计算困难。为提高切削力的预测精度,首先通过五轴侧铣几何模型描述了圆柱铣刀的刀齿运动轨迹,在建立微元切削力模型后,提出了一种瞬时切屑厚度的计算方法,计算当前切削刃上切削点到前几个刀齿回转圆柱面的映射距离,并在齐次坐标变换下,将空间中的线面求交计算转换成二维平面的线与圆弧的求交运算,在考虑刀具跳动对圆弧轨迹的影响后,求解方程组获得瞬时切屑厚度值。最后在五轴机床上进行了切削力试验,对比测量的力数据发现,仿真结果无论趋势还是大小都和实测值较好地吻合,验证了所建立的切削力预测模型的有效性。

混合集成电路的自动上芯吸嘴开发

芯片贴装是微电子元器件封装工艺流程中的关键环节,贴装后芯片的可靠性对电路整体性能及质量具有重要影响。介绍了1种适用于厚膜混合集成电路的自动上芯吸嘴,该吸嘴基于IP-500型自动上芯机,针对厚膜混合集成电路和国产裸芯片的特点进行研发。从自动上芯吸嘴的结构和材料入手,利用有限元仿真软件计算压力并对吸嘴和芯片的应力分布情况进行重点分析。结果表明,优化后的橡胶吸嘴能有效解决国产裸芯片在自动上芯过程中发生损伤的问题。

Chip Formation in Micro-cutting

The miniaturisation context leads to the rise of micro-machining processes. Micro-milling is one of the most flexible and fast of them. Although it is based on the same principles as macro-cutting, it is not a simple scaling-down of it. This down-sizing involves new phenomena in the chip formation, such as the minimum chip thickness below which no chip is formed. This paper presents a review of the current state of the art in this field from an experimental and a numerical point of view. A 2D finite element model is then developed to study the influence of the depth of cut on the chip formation. After the model validation in macro-cutting, it highlights the phenomena reported in literature and allows to perform a minimum chip thickness estimation.

纵扭超声辅助磨削氮化硅亚表面损伤及其试验研究

目的探究纵扭超声辅助磨削工艺参数对氮化硅陶瓷亚表面损伤的影响规律。方法首先,建立纵扭超声振动下单颗磨粒的切削轨迹及其切削弧长模型,分析纵扭超声辅助磨削独特的加工机理。其次,考虑砂轮表面磨粒的随机分布特性,并基于硬脆材料脆塑转变特性及其临界转角界定,给出纵扭超声辅助磨削单颗磨粒未变形切屑厚度的概率学模型,进而建立纵扭超声辅助磨削过程中单颗磨粒的平均法向磨削力模型。最后,建立纵扭超声辅助磨削氮化硅亚表面损伤深度模型,并进行试验验证。结果纵扭超声振动的引入增大了纵扭超声辅助磨削过程中单颗磨粒的切削弧长,减小了单颗磨粒平均未变形切屑厚度,降低了单颗磨粒的法向磨削力,最终降低了氮化硅陶瓷亚表面损伤的深度,获得了较好的氮化硅陶瓷表面加工质量。氮化硅亚表面损伤深度随着超声振幅的增大而降低,当超声振幅为6μm时,亚表面损伤深度为5.65μm,相较于普通磨削亚表面损伤深度降低了33.6%。理论模型预测结果与试验结果趋势一致,预测结果与试验结果的最大误差为13.38%,平均误差为8.34%,因此该模型能够为氮化硅实际加工中亚表面损伤深度的预测提供一定参考。结论纵扭超声辅助磨削能够有效降低氮化硅陶瓷加工表面的亚表面损伤深度,进而提高氮化硅陶瓷工件的使用性能。

Reconfigurable Digital Circuits Based on Chip Expander with Integrated Temperature Regulation

This article is dealing with a development of custom chip expander platform with the possibility of accurate temperature control and integration of additional silicon-based features. Such platform may serve as a useful tool which facilitates the burdens connected with measurement and analysis tasks of experimental semiconductor structures. The devised solution provides the functionality of carrier substrate (Al2O3 compound) with CTE compatibility to the experimental silicon chip and is fully customizable with respect to a particular chip. It also allows achieving an easy fan-out of small-diameter chip terminals into a larger, more convenient area and placement of chip specimens conveniently into space-constrained chamber of the AFM microscopes, probe stations, etc. Real application of the developed chip expander platform is demonstrated in context of digital reconfigurable circuits based on polymorphic electronics. In this case the chip expander with attached polymorphic chip REPOMO is thermally stabilized at an ambient temperature level up to approximately 135。C and its sensitivity to this phenomenon is demonstrated.

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。

基于切削力的燃气轮机用高温合金铣削进刀方式

以燃气轮机用典型高温合金难加工材料作为研究对象,借助铣削过程中切削力测试,分析不同进刀方式下对应的切削力和切屑厚度变化。对比总结两种不同铣削加工方法特征,提出有利于燃气轮机常用高温合金铣削加工工艺方法。

Material Removal Mechanism and Force Modeling in Ultrasonic Vibration-Assisted Micro-Grinding Biological Bone

Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottleneck of mechanical stress-induced crack damage. In response to this challenge, the ultrasound-assisted biological bone micro-grinding novel process with a spherical grinding head has been proposed by researchers. Force modeling is a prerequisite for process parameter determination in orthopedic surgery, and the difculty in establishing and accurately predicting bone micro-grinding force prediction models is due to the geometric distribution of abrasive grains and the dynamic changes in geometry and kinematics during the cutting process. In addressing these critical needs and technical problems, the shape and protrusion heights of the wear particle of the spherical grinding head were frst studied, and the gradual rule of the contact arc length under the action of high-speed rotating ultrasonic vibration was proposed. Second, the mathematical model of the maximum thickness of undeformed chips under ultrasonic vibration of the spherical grinding head was established. Results showed that ultrasonic vibration can reduce the maximum thickness of undeformed chips and increase the range of ductile and bone meal removals, revealing the mechanism of reducing grinding force. Further, the dynamic grinding behavior of diferent layers of abrasive particles under diferent instantaneous interaction states was studied. Finally, a prediction model of micro-grinding force was established in accordance with the relationship between grinding force and cutting depth, revealing the mechanism of micro-grinding force transfer under ultrasonic vibration. The theoretical model’s average deviations are 10.37% in x-axis direction, 6.85% in y-axis direction, and 7.81% in z-axis direction compared with the experimental results. This study provides theoretical guidance and technical support for clinical bone micro-grinding.

Prediction of Grinding Force by an Electroplated Grinding Wheel with Orderly-Micro-Grooves

The ability to predict a grinding force is important to control,monitor,and optimize the grinding process.Few theoretical models were developed to predict grinding forces when a structured wheel was used in a grinding process.This paper aimed to establish a single-grit cutting force model to predict the ploughing,friction and cutting forces in a grinding process.It took into the consideration of actual topography of the grinding wheel,and a theoretical grinding force model for grinding hardened AISI 52100 by the wheel with orderly-micro-grooves was proposed.The model was innovative in the sense that it represented the random thickness of undeformed chips by a probabilistic expression,and it reflected the microstructure characteristics of the structured wheel explicitly.Note that the microstructure depended on the randomness of the protruding heights and distribution density of the grits over the wheel.The proposed force prediction model was validated by surface grinding experiments,and the results showed(1)a good agreement of the predicted and measured forces and(2)a good agreement of the changes of the grinding forces along with the changes of grinding parameters in the prediction model and experiments.This research proposed a theoretical grinding force model of an electroplated grinding wheel with orderly-micro-grooves which is accurate,reliable and effective in predicting grinding forces.

基于未变形切屑厚度的砂带磨削表面粗糙度预测模型

表面粗糙度作为衡量表面质量常用的评价标准,直接影响着产品的使用性能与寿命。由于工件与砂带之间存在的弹性接触变形及砂带表面磨粒的随机分布特征,因此对砂带磨削表面粗糙度进行准确预测具有较高难度。综合利用机理分析与智能算法的优势,该文建立基于未变形切屑厚度(UCT)的砂带磨削表面粗糙度神经网络预测模型。首先,考虑砂带磨削柔性特征,给出未变形切屑厚度参数计算方法;然后,在未变形切屑厚度参数特征分析的基础上,依据参数可确定性进行参数分类,并给出不确定参数的影响因素;最后,以未变形切屑厚度、磨粒平均粒径和法向磨削力作为输入参数,采用广义回归神经网络(GRNN)建立砂带磨削表面粗糙度预测模型。多模型试验结果对比表明,该模型具有较高的预测精度,并且适用于不同工况下的粗糙度预测。

基于厚薄膜混合封装基板的射频系统级封装设计

采用芯片倒装的形式可以有效解决高功率微波芯片系统级封装(SIP)的散热问题,但基于厚膜工艺的LTCC/HTCC封装基板与倒装芯片存在尺寸失配、无法直接互联的问题.为此设计了一种基于厚薄膜混合技术的封装基板.首先通过内部采用传统厚膜工艺、表面采用薄膜布线工艺的厚薄膜混合技术解决了芯片与封装基板尺寸失配的问题;然后对与芯片匹配的带地共面波导(CPWG)尺寸进行设计,采用梯形过渡结构使之与封装基板垂直过孔尺寸匹配;最后通过热仿真验证了该结构的系统散热性能.仿真结果表明,在射频性能良好情况下,本文封装结构散热性能优于传统形式封装.

硬脆材料微磨削表面形成机理试验研究

微磨削作为微尺度硬脆材料元器件的一种重要加工方法越来越受到重视,分析硬脆材料微磨削材料去除机理、提出其应为脆性去除与延性去除的综合作用,并就硬脆材料微磨削中材料去除过程与传统磨削方式的不同建立微磨削表面形成模型。为揭示硬脆材料微磨削过程的表面形成机理,验证所提出的微磨削未变形切屑厚度hm与微磨削表面粗糙度Ra计算模型的科学性和准确性,针对钠钙玻璃这一典型硬脆材料设计了正交微磨削试验,就试验结果进行硬脆材料微磨削表面形貌分析,讨论硬脆材料微磨削表面影响因素以及影响规律。基于试验数据结果对所建立微磨削模型的科学性进行了验证,并通过试验获得了微磨削后表面粗糙度Ra从78 nm至0.98μm的一系列表面,为硬脆材料微磨削表面形成机理研究提供了理论参考与试验依据。

球头铣刀三维曲面加工的铣削力预报

针对球头铣刀三维曲面加工,提出一种考虑进给方向和刀具切触界面任意变化的铣削力预报方法。基于微分的思想,将曲面加工中单个齿频周期内的切削过程看成是切削条件恒定的微小稳态加工,进而将整个三维曲面加工视为一系列微小稳态加工的组合。根据各微小稳态加工的始、末刀位点坐标,建立进给转向角和进给倾斜角模型,刀具切触界面应用基于逻辑数组的Zmap方法确定,并修改了未变形切屑厚度模型的参数,使其适应三维曲面加工中刀具切触界面和进给方向的任意变化。分别进行凸圆弧曲面、凹圆弧曲面和自由曲面三个铣削加工试验,数值计算及试验测量结果表明,提出的方法能够很好地描述曲面加工中进给方向及刀具切触界面的变化,预报的铣削力和试验测量结果在幅值和变化趋势上都吻合良好,从而验证了该铣削力预报方法的有效性。

切削速度和切削厚度对纤维板切削力和表面粗糙度的影响

研究了纤维板铣削过程中切削速度和平均切削厚度对切削力和表面粗糙度的影响。结果表明:平行进给方向的切削分力Fx和垂直进给方向的切削分力Fy都会随着切削刃在工件中位置的变化而变化;切削分力Fx的最大值、切削分力Fy正值的最大值与负值的最小值的绝对值,以及表面粗糙度均随着平均切削厚度的增加而增大;高速铣削时的切削分力Fx的最大值、切削分力Fy正值的最大值和负值的最小值的绝对值,以及表面粗糙度均小于低速铣削时;当加工表面粗糙度要求相同时,高速铣削时的平均切削厚度可大于低速铣削时。因此,高速铣削不仅可以提高加工效率,还可以改善表面的加工质量。

电磁超声测厚原理及其应用——一种新型超声测厚法

介绍了电磁超声产生的机理及其测厚原理 ,并提出了用于铁磁材料测厚且简单方便的电磁超声激发和接受的方法 ,同时很好的解决了实际应用中存在的关键技术 :磁场与线圈匝数之间的关系、高压窄脉冲、高速采样等 .采集并分析了电磁超声在钢板内的回波信号 ,给出基于 MCS- 5 1单片机的电磁超声测厚系统的设计框图 .在此基础上 ,成功地研制了适用于钢板、管材的电磁超声测厚仪 .通过对标准试块的实测结果表明 ,电磁超声测厚精度达到 0 .5 % .

55钢平面磨削中未变形磨屑厚度及单位磨削力的研究

从简化磨粒形状入手,用解析法对未变形磨屑平均厚度模型进行了修正;通过日本某公司生产的超景深三维显微系统VHX-600测量了磨粒间距,并根据55钢的平面磨削实验,采用非线性回归法推导出了基于未变形磨屑平均厚度的单位磨削力和切向磨削力的经验公式。

一种新型便携式超声波测厚仪的设计

设计了一种便携式新型超声波测厚仪,系统采用ATMEGA128单片机作为主控芯片,并包含超声波发射接收电路、LCD液晶显示电路、电源电路、键盘电路、232通信电路、实时和计数器电路。实现了精确测量、丰富的信息量实时的显示、电池和USB切换供电功能,并把测量的数据通过串口传输到PC中进行了分析与比较,给出了测量误差产生的原因。