基于切削参数和刀具状态的车削功率模型

动态切削功率建模是切削功率信号用于切削过程监控的关键。本文首次建立了基于切削参数 (主轴转速、进给量、切削深度 (即背吃刀量 )、工件材料及刀具材料 )与刀具状态 (主要考虑后刀面磨损量 )的车削功率模型。试验证明 ,该模型基本能正确反映车削功率信号与刀具状态及各种切削参数之间的关系     

机械功在热能与动力工程中的应用与优化

探讨了工程热力学中的体积功、流动功、技术功、轴功等几种机械功的物理意义和相互之间的关系,分析了其在热能与动力工程领域中的实际应用,提出了优化几种机械功的应用方案。通过调整混合气余气系数、调整滑油温度、废气利用等方式可提高航空活塞发动机曲轴功,提高发动机热效率;提高压气机增压比可提高燃气涡轮发动机热效率,增大发动机推力;采用定温压缩和级间冷却可降低空调、制冷装置压缩机的压缩功,节约电能;充分冷却热力发电装置中冲击汽轮机做功后的水蒸气可以减少水泵加压所消耗的轴功,减少水泵的功率和数目。     

MEMS尺寸效应的分析模型及应用

论述了尺寸效应的内涵及其对微电子机械系统(MEMS)基础理论研究的重要影响；提出了广义尺寸效应、狭义尺寸效应，正效应、负效应及其判据；建立了狭义尺寸效应的分析模型，从尺寸泛函的绝对值、相对值和对尺寸的灵敏度三个方面进行泛函分析。将该模型应用到两端固支多晶硅微梁的弯曲测试，分析结果与实验相符。     

Unique regenerative chatter in wiper-turning operation with burnishing process Part 2: Experimental verification of predicted generation mechanism,critical stability,and characteristics

In this paper, the predicted generation mechanism, chatter stability, and characteristics of the unique regenerative chatter with the burnishing process in wiper-turning operations are verified experimentally. It was found in the first part of the paper that the vibration regenerates in the burnishing process by the wiper part of the insert causing a novel type of chatter. In this second part, this chatter phenomenon is investigated in an experimental manner to verify its mechanism. The specific burnishing force, which is a gain factor characterizing the burnishing process, is determined by the Hertzian contact law. In addition, the specific cutting force is measured by a cutting test, the compliance of the flexible structure is measured by a hammering test, and the residual compliance is measured by a static indentation test. Then, experiments are conducted where the tilt angle and the feed rate are varied to find the critical stability. The conducted chatter experiments prove that the predicted generation mechanism, critical stability, and characteristics are true.     

Development of Empirical Models for Surface Roughness Prediction in Finish Turning

Surface roughness plays an important role in product quality. This paper focuses on developing an empirical model for the prediction of surface roughness in finish turning. The model considers the following working parameters: workpiece hardness (material); feed; cutting tool point angle; depth of cut; spindle speed; and cutting time. One of the most important data mining techniques, nonlinear regression analysis with logarithmic data transformation, is applied in developing the empirical model. The values of surface roughness predicted by this model are then verified with extra experiments and compared with those from some of the representative models in the literature. Metal cutting experiments and statistical tests demonstrate that the model developed in this work produces smaller errors than those from some of the existing models and have a satisfactory goodness in both model construction and verification. Finally, further research directions are presented.     

干式高速车铣时金属陶瓷刀具磨损机理研究

研究了干式高速车铣D60钢时金属陶恣刀具的磨损机理和磨损特性。与水溶性冷却液浇注冷却的湿式高速车铣相比,干式高速车铣D60钢时,金属陶瓷刀具有更高的耐磨性。硬质相颗粒的脱落是干式高速车铣D60钢时金属陶瓷刀具磨损的主要原因。     

旋转超声钻削的切削力数学模型及试验研究

通过分析硬脆材料脆性断裂去除机理和旋转超声加工特点,确定旋转超声加工时单颗磨粒的切削时间、切削深度、切削速度及切削轨迹长度,建立旋转超声恒进给率钻削硬脆材料的切削力数学预测模型。光学玻璃加工试验研究表明,切削力随进给速度的增大而增大,随主轴转速的提高而减小;在高进给速度条件下,切削力对主轴转速的变化更为敏感,在低主轴转速条件下,切削力对进给速度的变化更为敏感;从而很好地验证了已建立的切削力数学预测模型。旋转超声加工和普通加工的对比试验表明,旋转超声钻削加工可以有效降低切削力,一定程度上减小出孔崩边尺寸,从而提高加工效率、降低加工成本。根据旋转超声加工的表面粗糙度值略高于普通加工,提出硬脆材料脆性断裂去除时磨粒实际切削深度决定加工表面粗糙度的判断。     

ARX Modelling and Compensation of Roundness Errors in Taper Turning

The forecasting compensatory control (FCC) strategy is successfully applied to the taper turning process to improve the roundness accuracy of the workpiece during cutting. This strategy, which is based on active error sensing, stochastic modelling and forecasting control, is capable of compensating both repeatable and non-repeatable errors. In the stochastic modelling, the effect of cutting force is considered, thus yielding an autoregressive model with exogeneous input (ARX). The resultant force is obtained from the outputs of the piezoelectric force sensor while the relative motion error between the tool and the workpiece is determined by means of a master taper and a capacitive sensor. The forecast error is sent to a piezoelectric actuator that moves the cutter to compensate for the error motion. Practical tests were performed on an experimental lathe with the FCC system using models with different orders and forgetting factors. A maximum improvement of 33% can be achieved by this FCC strategy using ARX (3,3) and forgetting factor of 0.997.     

基于热力耦合模型的切削加工残余应力的模拟及试验研究

航空精密薄壁零件具有复杂的型腔结构,切削加工残余应力是薄壁零件精度稳定性的重要影响因素,因此必须对切削加工残余应力进行研究。根据热—弹塑性有限元理论,建立切削加工三维有限元模型,对航空铝合金材料Al2A12进行切削加工非线性弹塑性有限元模拟分析,对切削加工表面残余应力进行预测和计算。通过有限元分析,得到不同切削参数、刀具参数条件下的已加工表面残余应力的模拟结果,并对结果进行比较分析,得到各个因素对工件已加工表面残余应力的基本影响规律;进行不同加工工序条件下的切削加工残余应力的有限元模拟,在加工表面已有一次切削加工残余应力分布的情况下,进行二次切削加工有限元模拟,得到二次切削加工对工件已加工表面残余应力的影响规律;并且进行不同切削参数对残余应力影响的试验研究,验证有限元模型的正确性。     

Defining the effects of cutting parameters on burr formation and minimization in ultra-precision grooving of amorphous alloy

Amorphous nickel phosphorus (Ni-P) alloy is a suitable mold material for fabricating micropatterns on optical elements for enhancing their performances. Ultra-precision cutting is preferred to be used to machine the mold material for high precision in a large workpiece. However, burrs and chippings always form and are detrimental especially when fabricating micropatterns. The formation mechanisms of burrs and chippings have not yet been revealed precisely in the cutting processes of amorphous alloys, because their cutting behavior is more complex and less discussed in existing researches than that of crystalline metals. In the present study, the burr formation process of amorphous Ni-P is defined and a three-dimensional cutting model using energy method is proposed to predict and minimize burrs and chippings. Microgrooving experiments were conducted with different undeformed chip geometries using three types of cutting tools to observe burr formation processes. Large burrs and chippings were formed when cutting with a tapered square tool and a tilted triangle tool. These large burrs and chippings were found to be induced by large slippages that are unique to amorphous alloys. It was revealed that burrs and chippings appear when the angle between the chip flow direction and the groove edge is less than a critical value. Energy method was used to predict the chip flow directions and the calculated results agree with the experimental ones, which proved that the energy method is valid for designing an appropriate undeformed chip geometry to reduce burrs and chippings in ultra-precision grooving.     

An Improved Method for the Determination of 3D Cutting Force Coefficients and Runout Parameters in End Milling

A simple improved method is suggested for determining constant cutting force coefficients, irrespective of the cutting condition and cutter rotation angle. This can be achieved through the combination of experimentally deternimed cutting forces with those from simulation, performed by a mechanistic cutting force model and a geometric uncut chip thickness model. Additionally, this study presents an approach that estimates runout-related parameters, and the runout offset and its location angle, using only one measurement of cutting force. This method of estimating 3D end milling force coefficients was experimentally verified for a wide range of cutting conditions, and gave significantly better predictions of cutting forces than any other methods. The estimated value of the runout offset also agreed well with the measured value.     

The Computer Simulation of Tribological Influence on Strain Path and Forming Limit in Punch Stretching of Sheet Metal

The purpose of this paper is to describe the principles and results of some numerical simulations of strain path and forming limit analysis in punch stretching operations which include the tribological influence by using a realistic friction model. Three tribological variables (i.e. the mean lubricant film thickness, tooling roughness, and workpiece roughness) are required for the simulation. The calculation of these variables using lubrication theory and related semi-empirical equations are described. The active lubrication regime and suitable friction model can be determined from the current local values of these tribological variables. Friction stress can then be computed from these variables combined with more traditional parameters such as pressure and sliding speed. The limiting dome height and variation of strain path are then predicted by using the coupled FEM and lubrication/friction model. The comparison between the calculated and measured results shows that the present scheme is efficient in computation and will provide a useful tool for industrial applications.     

电力设备招标采购中层次分析法的优势与应用

在最近几年,我国大规模的进行了电力工程的改造和建设,这样以来,就需要大量的资金去采购电力设备,招标采购以本身的优势成为现在最受欢迎的采购形式。在招标投标一些列工作中,对评标结果起最重要的作用就是评价指标的权重值分配。对于电力设备招标采购需要很多的指标评审,对于权重值的指标分配很难达到合理的程度,采用层次分析法来衡量各指标的权重值,再配合专家打分法即定量综合评议法用实例来证明该方法的可实性。     

动力学相似理论及在结构振动分析中的应用研究评述与展望

相似试验模型在大型结构振动与冲击试验研究中起到重要作用。综述动力学相似理论在结构动力学相似试验模型设计中的应用研究进展与发展趋势,并引述大量文献。总结动力学相似理论在多个领域的结构振动与冲击问题分析中的主要成果,包括动力学相似理论在海洋结构、土建结构及大型动力装备动力学相似试验模型设计中的应用,复合材料结构的动力学相似设计方法,以及转子系统的动力学相似试验模型设计方法。介绍动力学相似理论的重要研究进展情况,如畸变试验模型的设计及修正方法、动力学相似模型的试验验证。讨论动力学相似理论在结构振动与冲击研究中存在的主要问题并做出展望。     

变可信度近似模型及其在复杂装备优化设计中的应用研究进展

变可信度近似模型通过融合不同精度分析模型的数据,可有效平衡近似模型预测性能和建模成本之间的矛盾,在复杂装备优化设计中受到广泛的关注。综述变可信度近似模型及其在复杂装备优化设计中的应用研究进展。概述三类常用变可信度近似建模方法的基本思想,并介绍变可信度近似建模方法研究的最新进展。回顾面向变可信度近似模型试验设计方法的发展现状,包括一次性试验设计方法和序贯试验设计方法。综述直接影响变可信度近似模型优化设计求解精度和效率的两类近似模型管理策略,探讨基于变可信度近似模型的智能优化和可靠性/稳健性优化这两个领域前沿问题。归纳总结变可信度近似模型应用于复杂装备优化设计的现状。针对变可信度近似建模及其优化设计给出了一些应用建议,并指出未来值得深入研究的方向。     

载流磨损的最佳法向载荷三维关系模型研究

以地铁第三轨受流为研究对象,试验了法向载荷对第三轨与受电靴之间载流摩擦磨损特性的影响。结果表明:载流磨损体积损失随着法向载荷的增大均呈现出现先快速减小而后缓慢增大的U形变化趋势,发现存在最佳法向压力,此压力下的磨损体积损失最小,且随着速度的增大最佳法向压力相应增大。建立了W-F-V模型(磨损量-法向压力-速度三维关系模型)能与实际的试验结果较好的吻合,研究对于载流摩擦磨损状态的预测,及最优磨损条件的选择等都具有积极的意义。