Timoshenko阻尼转轴的涡动不平衡响应

考虑系统的质量不平衡和材料的阻尼作用，应用Timoshenko梁理论和Hamilton原理，建立转轴的空间运动方程，它包含了剪切变形、旋转惯性、陀螺效应、动不平衡和内粘性阻尼与材料迟滞阻尼的影响。数值分析了系统的动力学响应和特性，由不平衡质量产生的强迫振动和材料阻尼引起的自激振动导致转轴产生复杂的涡动变形。     

混凝土泵车臂架振动响应的主动控制实验研究

考虑混凝土泵车臂架结构特点,采用独立模态空间控制方法对泵送混凝土激励下的臂架末臂节振动响应进行了主动控制试验研究。针对泵车臂架系统的动力学模型,采用模态滤波技术和最优控制理论设计主动控制策略,通过优选臂节油缸的作动控制以实现对臂架一阶模态振动响应的实时控制。实验结果表明,采用该主动减振控制后水平工况下臂架末端的减振精度可达80%,取得了显著的减振实验效果     

转子动力学研究的回顾与展望

回顾了转子动力学的发展历史，总结了在旋转机械转子系统的动力分析与计算方法，转子系统的不平衡强迫响应与平衡技术，支承转子的轴承动力学特性，转子系统的稳定性分析，转子系统的状态监测和故障诊断；转子系统的非线性振动，分叉与混沌和转子系统振动与稳定性的主动控制技术等方面的研究成果，建议了新的交叉学科研究方向，讨论了我国转子动力学研究的现状和存在的问题，展望了我国转子动力学的发展前景。     

动不平衡激励下光滑非线性车辆摆振系统建模分析

考虑前轮动不平衡为外激励,建立了车轮外激励作用下的三自由度车辆摆振系统动力学模型。应用数值分析方法,通过分岔特性等分析,讨论了考虑动不平衡激励的车辆摆振系统动力学响应,并对车辆摆振响应中的频率成分及其特征进行了系统的分析讨论。结果表明：动不平衡激励下的摆振形态和自激振动下的摆振形态有较大差别,随着动不平衡激励的增加,摆振会由系统自身结构引起的自激振动成分占主导逐步转变为由外激励引起的强迫振动占主导,摆振系统在摆振车速区间内由拟周期运动逐步变为单周期运动。相关理论可为转向系摆振的有效控制提供理论依据。     

多平行齿轮耦合转子系统的振动特性分析

通过建立系统各轴的振动方程，联立起来形成多平行齿轮耦合转子系统的振动方程，然后进行数值求解，获得系统固有模态和动态响应。分析了某三平行齿轮减速系统的固有频率及其振型和强迫振动响应特性。结果表明，由于齿轮的耦合作用，多平行齿轮转子系统的振动不同于单轴转子，突出表现为各轴间的弯扭耦合振动，派生出许多新的模态，各轴上的不平衡会引起整个系统的振动响应。     

结构振动的独立模态和耦合模态的组合控制

基于模态空间控制的基本原理，提出了一种将独立模态控制与耦合模态控制相结合应用于结构振动主动控制中，得以利用两者的优点而使控制更加有效和稳定的方法。利用该组合控制法，可实现在一个控制过程中实时跟踪主被控模态的变化从而对其实施独立模态控制以达到有效地抑制结构的主要振动。而对其它非主控模态则实行耦合模态控制。这样，可使控制系统的稳定性提高、减少作动器／传感器的数量、降低控制能耗，并能在不同的激励下达到最佳的控制效果。     

船舶推进轴系变结构控制

以船舶主推进轴系为研究对象,在变结构控制理论和设计方法的基础上,对主推进轴系的变结构控制方法进行研究。考虑到推进轴系在螺旋桨处的位移响应最大,在螺旋桨部位设置主动控制作动器,对推进轴系进行振动控制,并以主推进系统的弹性体动力学模型为基础,建立系统的变结构控制方法。采用单位向量控制形式的最终滑动模态控制器,并采用二次型最优控制理论设计最终滑动模态的切换函数。最后以一个带有六个弹性支撑的推进轴为例进行仿真计算。实例分析指出:变结构控制对于推进轴系的振动控制具有显著的效果。     

三峡大坝深孔弧形闸门流激振动水弹性模型试验研究

对深孔弧形闸门水弹性模型进行了模态测试和分析，其分析结果与数值模态分析结果进行对比，较准确地找出 了结构的模态参数，对模型设计的问题作了论述。对闸门在各种工况下的振动响应进行试验，获得了系统的动荷载与闸门的振动参数，结果表明：闸门在0．6－0．7开度时，出现了强迫振动。     

二阶主共振下旋转叶片振动抑制器稳定性研究EI北大核心CSCD

旋转叶片作为燃气轮机的核心部件,在高温高压的环境中工作,通常由于振动过量而失效。主动控制有着附加质量小、控制频带宽等优点,适合旋转叶片的工作环境和结构。因此,近年来针对旋转叶片主动控制的研究逐渐受到国内外学者的重视。该研究探讨内共振条件下具有时间延迟的旋转叶片的振动控制器稳定性。压电纤维复合材料是一种新型的压电智能材料,在航天、航空等领域有着广泛的应用。利用压电纤维复合材料传感器和作动器,研究旋转叶片1∶2内共振时二阶主共振条件下的主动控制,建立了受控系统的运动微分方程,采用多尺度法推导出受控叶片的演化方程,推导出稳态时前两阶模态稳态响应的解析解。研究了参数变化对响应的影响规律和对系统稳定性的影响。随后对原系统进行数值积分对解析解进行了验证。结果为旋转叶片动力学行为的研究提供了理论基础。     

不对称转子系统的参激强迫振动

研究不对称转子系统的参激强迫振动,先用Hamilton原理导出运动微分方程,这是刚度系数周期性变化的参数激励和强迫激励振动方程,再用多尺度法研究1／2亚谐共振－主共振,求得平均方程,分叉响应方程和定常解,讨论了刚度不对称性,质量偏心以及外阻尼对幅频响应的影响,刚度不对称性,质量偏心都能增大不稳定区,而外阻尼能使共振振幅减小,最后用稳定性理论分析分叉响应方程和定常解的稳定性。     

An integrated machine-process-controller model to predict milling surface topography considering vibration suppression

Surface topography is an important factor in evaluating the surface integrity and service performance of milling parts. The dynamic characteristics of the manufacturing system and machining process parameters significantly influence the machining precision and surface quality of the parts, and the vibration control method is applied in high-precision milling to improve the machine quality. In this study, a novel surface topography model based on the dynamic characteristics of the process system, properties of the cutting process, and active vibration control system is theoretically developed and experimentally verified. The dynamic characteristics of the process system consist of the vibration of the machine tool and piezoelectric ceramic clamping system. The dynamic path trajectory influenced by the processing parameters and workpiece-tool parameters belongs to the property of the cutting process, while different algorithms of active vibration control are considered as controller factors. The milling surface topography can be predicted by considering all these factors. A series of experiments were conducted to verify the effectiveness and accuracy of the prediction model, and the results showed a good correlation between the theoretical analysis and the actual milled surfaces.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00386-7     

Exploration of Shaping Conductive Ceramic by Ultrasonic Aided Wire Electrical Discharge Machining

An investigation has been made into the shaping of conductive ceramics by means of ultrasonic-aided electrical discharge machining. A vibrating device has been designed to undertake the work, and the theory to describe the vibration modes of the wire under ultrasonic action has been established. Experimental results show that there is a peak current limit on the cutting rate when the conductive ceramic is processed by the wire cut machine. Once the current exceeds the limitation, cutting rate drops rapidly. After the ultrasonic vibration is introduced, the cutting rate increases, and machining can be carried out under the greater peak current, hence the maximum cutting rate can increase by 50% or more. In addition, the surface integrity of the workpiece machined can be improved by the combined technology.     

基于主动空气轴承作动器的模糊主动振动控制研究

提出基于主动空气轴承作动器的溜板模糊主动振动控制。在溜板的空气静压支承基础上,以主动空气轴承为作动器,采用模糊控制方法,实现运动中的溜板振动主动控制。在自制的空气静压导轨上用电磁激振器模拟干扰力进行控制实验,取得良好效果。     

微磨削与超声振动复合加工技术研究现状与展望

微细切削技术是传统加工工艺向微观尺度的延伸,在微加工领域具有重要的作用,尤其适用于三维零件及微结构的加工。与其他微细切削技术相比,微细磨削技术具有加工零件棱边精度高、适于硬脆性材料加工等优势,但其存在加工效率低、磨削热量大、微砂轮易磨损等缺陷。已有研究表明,于机械加工辅加超声振动的复合加工技术可有效降低切削力、切削温度,增大脆性材料脆-塑转变临界切削深度,改善加工表面质量等。因而超声振动辅助微磨削技术被认为是一种可有效解决微磨削加工现存缺陷的技术。主要从微磨削技术研究现状、尺寸效应机理研究、脆性材料塑性域去除机理研究、超声振动切削实验研究、超声振动切削断续切削机理研究及微磨削动态有效磨刃密度建模研究六个方面,对微磨削技术及超声振动辅助切削技术相关领域研究进行综述,并探讨超声振动辅助微细磨削技术加工机理研究及未来发展需注重解决的问题。     

MAGNETIC BEARING SPINDLES FOR ENHANCING TOOL PATH ACCURACY

Thin rib machining of electronic components or airframe structures can benefit from high speed machining for burr free cutting, improved surface quality and increased metal removal rate. It is suggested that the use of a magnetic bearing spindle can not only successfully provide the benefits of high speed machining but, more importantly, minimize tool path errors. In this paper the various sources of tool path error are discussed as functions of machine tool positioning errors and cutting force errors which are characterized as static, dynamic and stochastic. The operation of high speed magnetic bearing spindles is described and a control scheme whereby the spindle may be translated and tilted for minimizing tool path errors is discussed. This overall research activity is a cooperative effort between the University of Maryland, Cincinnati Milacron, Magnetic Bearings, Inc., The Uestinghouse Corporation, and The National Bureau of Standards.     

Milling operations in continuous flow production lines

Within the Collaborative Research Center CRC 666 at the TU Darmstadt bifurcated structures in integral style are produced out of steel sheet band. In this context, the cutting technology is used to prepare the semi‐finished product for subsequent forming and machining operations as well as to even manufacturing induced shape and dimensional inaccuracies. In contrast to conventional cutting processes, the workpiece is constantly moved because of the continuous flow production. Thus, high dynamics of the machining process are required. To meet this demand, special built machine tools and the high speed cutting (HSC) technology are applied. This article shows the achieved results in sheet metal and edge milling.     

多孔金属纤维烧结板制造技术及应用研究进展

多孔金属纤维烧结板是随着新型化材料制备以及机械加工复合技术的飞速发展而出现的一类新颖的多孔金属材料。近年来由于其特殊孔隙结构的开发和多学科领域的强大应用需求,多孔金属纤维烧结板的制造技术取得快速进步,其相关应用领域正从传统的应用领域不断地向高新技术应用领域拓展。根据其制造工艺过程综述了金属纤维制造技术(熔抽法、拉拔法和切削法)和多孔金属纤维烧结板制造技术(固相烧结和液相烧结技术)的最新研究进展,并详细分析了其已有或潜在的应用领域,最后展望了多孔金属纤维烧结板的应用前景。     

螺旋瓦楞横切机振动分析

目的分析螺旋瓦楞横切机剪裁瓦楞纸板产生的机械振动,并通过减振减小上、下刀轴振动响应,使其达到生产所需剪裁精度要求。方法对螺旋瓦楞横切机进行了动力学建模,通过数学解析和Ansys仿真软件分别进行振动分析。结果将解析结果与Ansys仿真结果进行对比,分析得到所建立的振动模型是正确的,通过分析横切机系统振动特性参数,提出降低振动响应方法,即采用碳纤维材料使上、下刀轴振动响应控制在0.07 mm范围内,使其达到横切机剪裁精度要求。结论建立的动力学数学解析模型和Ansys仿真对研究横切机振动特性,降低振动响应,改善横切机剪裁质量是有效的。     

Optimal selection of machining rate variables by geometric programming

The selection of economically optimal machining rate variables, i.e. cutting speed and feed rate, is of major importance in the field of metal cutting.

In this paper, apart from the conventional methods used for optimization in machining economics, geometric programming, a relatively new non-linear programming technique, is employed to optimize the constrained unit cost problem in turning. The cutting power available from the machine tool and the permissible CLA value of surface roughness are used as the forced constraints in the primal programme.

Initially, the primal and dual programmes are formulated. Furthermore, a numerical example is presented to illustrate the application of geometric programming which has been proved successful.

It is pointed out that geometric programming may be also used for optimization of unit cost in machining processes other than turning under the assumption that the imposed restrictions, discussed in this paper, are valid.     

Machining Parameter Optimization with Lot Size Considerations

The research literature on metal cutting contains numerous papers on optimizing machining parameters for maximum production rate or minimum production cost. Analyses presented in the literature, however, have been limited to conditions of “steady-state” manufacture (i.e., a large number of parts were to be produced). In today's metal cutting industry, over ninety percent of all parts are produced in lots of thirty or less. This implies that steady-state manufacturing may never be reached. This paper introduces lot size information into the selection of machine operating rates. A solution procedure is presented for the single decision variable (machine speed) case. An example problem is also presented to illustrate the gains that can be attained using lot size information.