分离型超声波振动车削抑制颤振的实验规律研究

采用功率谱分析技术证实了由Janet Devine现发的分离型超声波振动切削对颤振的抑制作用，并由正交实验设计确定各主要参数对其抑振效果的影响程度。实验给出了切削速度υ0，刀具超声波振动振幅A及其搭配(交互作用)对抑振因子r的影响规律，这一结果与作者在文献中提出的分离型超声波振动切削消减颤振的理论相吻合。     

分离型超声波振动切削消减颤振的机理

分析了分离型超声波振动切削动态切削力特征,提出了分离型超声波振动切削消减颤振的机理,并用实验验证了消减颤振的物理根源和切削动力学解析。     

柔性制造系统切削稳定性在线监测技术的研究

主要讨论柔性制造系统(FMS)切削稳定性的在线监测方法,在研究FMS切削过程中振动信号变化规律的基础上^[1],提出了用μ_a=E(a)/F(a)作为FMS切削稳定性的监测参数,并进行了理论分析和试验验证.     

变速切削抑振技术的研究现状

介绍了目前最常见的两种变速切削抑制切削颤振机理,讨论了变速切削抑振研究国内外的最新成果及其存在的问题,提出了变速切削未来的发展方向可能是利用振动的在线监测技术实现自动控制的变速切削.     

外圆切入磨削颤振的预报及时变进给控制

根据磨削由稳定阶段向颤振向颤振阶段过渡时，振动信号在幅值域上概率密度曲线的变化趋热，建立了颤振预报函数；对时变进给抑振机理进行了分析，并设计了在线抑振方法。在线监控实验取得了较好的效果。     

变速切削抑制颤振的控制系统及实验研究

为解决切削颤振给加工过程带来的不利影响,设计了基于DSP的适用于变速切削的电动机控制系统,编制了控制程序,并应用改造后的铣床进行了变速切削抑振试验。根据检测所得的加速度信号和声音信号,分析了变速幅值和变速频率对切削振动的抑制效果,对变速铣削进行了较为深入的分析和研究。     

超声振动干式车削尺寸精度实验研究

采用超声振动干式车削方法对钨基合金材料进行了车削加工实验,研究了切削参数、振动参数对零件加工尺寸精度的影响。结果表明,在切削深度一定的前提下,对于加工圆度影响的主次关系为:进给量>振动振幅>切削速度;而对锥度影响的主次关系为:振动振幅>切削速度>进给量。在低速低进给加工方式下,振动车削的抑振效果不明显,但随着切削速度、进给量的增大,振动切削抑振效果显著。本实验条件下,当振动振幅为3μm时,对工艺系统具有较佳的抑振效果。     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

变速切削抑制颤振的控制系统及实验研究

为解决切削颤振给加工过程带来的不利影响,设计了基于DSP的适用于变速切削的电动机控制系统,编制了控制程序,并应用改造后的铣床进行了变速切削抑振试验.根据检测所得的加速度信号和声音信号,分析了变速幅值和变速频率对切刘振动的抑制效果,对变速铣削进行了较为深入的分析和研究.     

全光谱配色的匀色空间权重因子方法

在CIE 1976(L^*a^*b^*)匀色颜色空间中,本文为全光谱匹配方法提供一种权重因子。这种权重因子使∑_j[ΔE(λ_j)]²→min.实验结果表明,使用这种色差型权重因子进行计算机配色比Schmid和Strockash设计的两种权重因子效果好。     

基于颤振预报和预测的稳定性控制理论及方法研究

针对由颤振预测控制策略指导的稳定切削控制方法实时动态调整能力差的缺点,综合颤振预报、预测理论,进行了稳定性在线寻优控制理论及方法的研究。基于刀具—工件系统铣削再生颤振动力学模型,研究了考虑系统结构参数(刀具、工件装夹刚度)和加工参数(切削加工参数优化选择)的切削稳定性评价方法,提出了以扩大稳定性区域和稳定最大材料切除率为控制目标的机床稳定性控制方法。形成了以"预报—控制—效果评估—再控制"为步骤的在线监测、智能诊断和实时控制的集成一体化策略。设计并实施了稳定性控制理论验证实验,获得了与理论分析一致的结论。     

Mg(PO3)2-BaF2-AlF3系统玻璃的振动谱研究

应用红外及拉曼光谱研究了Mg(PO₃)₂-BaF₂-AlF₃系统氟磷玻璃的结构特征.证实了双键氧(P=O)及由Al(O.F)₄四面体和P(O.F)₄四面体所混合构成的网络结构存在于玻璃之中.在拉曼光谱中,V_Ba-F、V_Mg-F和V_Al-F振动吸收峰分别出现在480-510cm^-1、530-550cm^-1和580cm^-1处.根据红外及拉曼光谱的结果得出:随系统中氟化物含量的增加,玻璃结构逐渐由聚磷酸盐转变为焦磷酸盐和一氟正磷酸盐混合物,同时双键氧(P=O)消失.     

Image processing for chatter identification in machining processes

Identifying chatter or intensive self-excited relative tool–workpiece vibration is one of the main challenges in the realization of automatic machining processes. Chatter is undesirable because it causes poor surface finish and machining accuracy, as well as reducing tool life. The identification of chatter is performed by evaluating the surface roughness of a turned workpiece undergoing chatter and chatter-free processes. In this paper, an image-processing approach for the identification of chatter vibration in a turning process was investigated. Chatter is identified by first establishing the correlation between the surface roughness and the level of vibration or chatter in the turning process. Images from chatter-free and chatter-rich turning processes are analyzed. Several quantification parameters are utilized to differentiate between chatter and chatter-free processes. The arithmetic average of gray level G _a is computed. Intensity histograms are constructed and then the variance, mean, and optical roughness parameter of the intensity distributions are calculated. The surface texture analysis is carried out on the images using a second-order histogram or co-occurrence matrix of the images. Analysis is performed to investigate the ability of each technique to differentiate between a chatter-rich and a chatter-free process. Finally, a machine vision system is proposed to identify the presence of chatter vibration in a turning process.     

10.6μm高能激光高反镜的研制

本文从膜系设计、材料选择、制备工艺及测量,较全面地论述了10.6μm高能激光高反膜的研制过程。研制成一种性能良好的三元混合氟化物（BaF₂,SrF₂,CeF₃）低折射率材料,并对由此材料蒸镀的膜层进行了晶体结构分析。已研制出反射率分别达99.0%、99.3%和99.5%的保护银膜、增强银膜和高增强银膜等三种高能激光高反膜,反射率是用自行研制的测量装置测定的。     

冗余自由度仿人机械臂自适应迭代学习控制研究

在深入研究自适应迭代学习控制理论、七自由度乒乓球机械臂动力学模型及轨迹规划的基础上,提出将改进后的自适应迭代学习控制算法运用到带有重复时变干扰的冗余自由度机械臂上。该控制系统旨在实现两大目标：一是使乒乓球机械臂准确快速地跟踪参考轨迹并在末点达到指定的击球速度;二是引入饱和函数减小输入转矩的抖振。Lyapunov理论分析及MATLAB仿真验证了整个控制系统的有效性：当迭代次数增加时,跟踪误差关于有限时间区间内一致收敛到零;加快迭代学习的收敛速度,并消除抖振。     

Chatter reliability prediction of side milling aero-engine blisk

Reliability analysis of a dynamic structural system is applied to predict chatter of side milling system for machining blisk. Chatter reliability is defined as the probability of stability for processing. A reliability model of chatter was developed to forecast chatter vibration of side milling, where structure parameters and spindle speed are regarded as random variables and chatter frequency is considered as intermediate variable. The first-order second-moment method was used to work out the side milling system reliability model. Reliability lobe diagram (RLD) was applied to distinguish reliable regions of chatter instead of stability lobe diagram (SLD). One example is used to validate the effectiveness of the proposed method and compare with the Monte Carlo method. The results of the two approaches were consistent. Chatter reliability and RLD could be used to determine the probability of stability of side milling.

     

稀土掺杂钙钛矿型氟化物晶体生长及其光谱

用Bridgman-Stockbarger法长出了Eu²⁺:KMgF₃和LiBaF₃单晶。用区熔法长出Re:LiBaF₃(Re=Ce³⁺,Tb³⁺,Eu²⁺)晶体。X光衍射分析表明由相图得到的原料比BaF₂:LiF=40:60(mol%)时生长的是多晶,因为,最开始析出的是BaF₂。对掺杂晶体进行了光谱研究。氮分子激光器泵浦的Eu²⁺:KMgF₃荧光光谱显示了多中心结构。     

Stability of high frequency machining vibration by extended chatter model

An extended chatter model was proposed in a previous paper [1], which explains the onset of machining chatter at frequencies as high as 10,000 Hz in fine boring operation. The model consists of an equation of energy equilibrium, including two sources of energy supply and other two sources of energy dissipation. The sources of energy supply are by the regeneration and X–Y looping of the tool tip, and the sources of energy dissipation are by the structural damping and the cutting process damping.The present study applies the energy equilibrium equation for predicting the stability borderline in terms of cutting condition. At the cutting condition above the stability borderline where the chatter should occur, some parameters are further predicted by computation to characterize the vibration of the tool tip. The transition from the borderline to the condition above the borderline has been evaluated by the predictive calculation of the time phase between X and Y vibration displacements, the inner to outer modulation phase lag, and the percentage share by mechanisms of the energy supply and dissipation.Validity of the prediction in terms of borderline width of cut, and X to Y amplitude ratio are confirmed by comparison with experimental measurements obtained in cutting tests.     

Measuring error and sampling variation in stereology: comparison of the efficiency of various methods for planar image analysis

An evaluation is made of the relative efficiency (precision of the final estimate per unit time of measurement on a given set of sections) of different methods for planar analysis aimed at estimating aggregate, overall stereological parameters (such as V_v, S_v). The methods tested are point-counting with different densities of test points (4 ≤ P_T ≤ 900 per picture), semiautomatic computer image analysis with MOP and automatic image analysis with Quantimet, for obtaining V_v and S_v estimates. One biological sample as well as three synthetic model structures with known coefficients of variation between sections are used. The standard error of an estimate is mainly determined by the coefficient of variation between sampling units (= sections in the present paper) so that measuring each sample unit with a very high precision is not necessary. Automatic image analysis and point-counting with a 100-point grid were the most efficient methods for reducing the relative standard errors of the V_v and S_v estimates to equivalent levels in the synthetic models. Using a 64-point grid was as precise, and about 11 times faster than using a tracing device for obtaining the estimate of V_v in the biological sample.     

基于有限元分析的滚齿SLD构建

针对稳定性耳垂线图(SLD)应用于滚齿颤振预测时存在动力学参数获取困难、切削深度难以确定等问题,建立了考虑滚刀刀杆柔性的三维滚齿系统动力学模型,通过滚刀极限切屑厚度与轴向进给量的关系计算滚齿系统动力学参数,并在此基础上绘制出滚齿SLD。设计了滚齿颤振实验方案,通过采集的实验数据分析平稳切削与颤振切削振动的特征量,确定颤振频率及颤振主体,证实了所建立的动力学模型及SLD的有效性。所提方法为滚齿工艺颤振预测、切削参数选取提供了一种新手段。