Theoretical aspects of technological mechanics. 4. The plasticity condition, strengthening, and the stress-strain relationship

It is shown that preferences cannot be unambiguously assigned to different plasticity conditions. Strengthening is described, and relations between the stress and strain are established.     

SLS快速成形扫描动态轨迹误差的仿真

对SLS快速成形系统XY直线导轨高速扫描进给的动态轨迹误差进行研究 ,分析产生误差的原因 ,基于MATLAB的仿真计算方法 ,给出激光扫描运动在不同进给速度下的动态轨迹误差的仿真建模和计算方法。仿真结果表明 ,SLS快速成形XY直线导轨扫描的动态轨迹误差所引起的工件成形误差是不可忽略的因素     

Classical EHL Versus Quantitative EHL: A Perspective Part I—Real Viscosity-Pressure Dependence and the Viscosity-Pressure Coefficient for Predicting Film Thickness

That classical elastohydrodynamic lubrication (EHL) is not a quantitative field can be illustrated by its failure to provide a consistent and rigorous definition of the viscosity-pressure coefficient. Indeed, if the pressure dependence of viscosity cannot be accurately described, then the viscosity-pressure coefficient cannot be defined. Classical EHL has employed fictional narratives to justify the pressure dependences that have been utilized. In this context, the purpose of this perspective article is to review specific and real needs from EHL and to show that data and models describing the viscosity-pressure dependence are already available and how they can properly be used. The final aim is to encourage researchers to change their philosophy of classical EHL to a quantitative approach, in which every hypothesis and every result, whether experimental or numerical, would be justified on the basis of acceptable physics.     

SEM voltage contrast mechanism of passivated devices

The mechanism of voltage contrast of passivated devices is investigated. Previous works on the voltage contrast over the passivation are reviewed, and experimental results on glass cover slips with a carbon-coated surface are described. The voltage contrast is observed over the carbon-coated equipotential surface. This result cannot be explained by the surface potential model of voltage contrast. An interpretation of the result using a contrast model previously introduced by the authors is provided.     

Tribology in microforming

As the tribological conditions between tool and workpiece in metal working are of greatest importance for process feasibility and process quality this is even more true when the process is scaled from conventional down to micro dimensions. As can be shown by scaled friction tests the friction is increased by a factor of 20 and more which will have a distinct impact on all factors characterising the process. This cannot be described by the conventionally used friction laws but can be explained by the model of open and closed lubricant pockets characterising the surface topography. In the present paper, it will be shown that - starting from this model - the size effect in friction can be described by the general friction law developed by Wanheim/Bay.     

纳米碳化硅颗粒强化氧化铝基陶瓷材料机理的研究现状

综述和分析了纳米碳化硅颗粒强化氧化铝基陶瓷材料的强韧化机制,认为由沿晶断裂到穿晶断裂的断裂模式的改变不是使复相陶瓷材料强韧化的机制之一,而恰恰是其韧性得不到显著提高的重要原因,并由此提出了有关复相材料新的设计思路。     

Fiber-optical measurement of form deviations of rotation-symmetric parts

The quality inspection of products poses a challenge towards existing production metrology techniques in terms of accuracy and speed, especially when it comes to inline or in-process measurements. In this terms, optical metrology proves its capabilities, in particular for sensible and fragile work pieces. For the inspection inside small spaces and cavities or for complex geometries, many optical metrology system are to inflexible or cannot be miniaturized enough. Within this work a set-up for a fiber-optic low-coherence interferometer system is described. Due to the high degree of miniaturization of the sensing probe, the system can be used for demanding measuring tasks like roundness of small drilling holes or the run-out of shafts. Different evaluation measurement are presented, which underline the potential of the described system for highly accurate, non-contact inspection of rotational parts.     

Phase contrast without phase plates and phase rings—optical solutions for improved imaging of phase structures

Using the optical methods described, phase specimens can be observed with a modified light microscope in enhanced clarity, purified from typical artifacts which are apparent in standard phase contrast illumination. In particular, haloing and shade‐off are absent, lateral and vertical resolution are maximized and the image quality remains constant even in problematic preparations which cannot be well examined in normal phase contrast, such as specimens beyond a critical thickness or covered by obliquely situated cover slips. The background brightness and thus the range of contrast can be continuously modulated and specimens can be illuminated in concentric‐peripheral, axial or paraxial light. Additional contrast effects can be achieved by spectral color separation. Normal glass or mirror lenses can be used; they do not need to be fitted with a phase plate or a phase ring. The methods described should be of general interest for all disciplines using phase microscopy. Microsc. Res. Tech., 76:1050–1056, 2013. © 2013 Wiley Periodicals, Inc.     

高温蠕变疲劳试验机

简单的拉伸疲劳、压缩疲劳试验只是单一方向对试样施加动态载荷,不能反应出试件实际的工作状况。双向加载模式,可真实反映工件的疲劳失效形式。本文剖析蠕变疲劳试验机的结构原理、消隙方式、控制系统,并阐述了其应用和发展前景。     

串级控制在电容器真空干燥设备中的应用

电容器真空干燥过程中,对温度的控制要求较高,不能采用简单的单回路控制,采用PID串级控制并调节合适的PID参数能收到较满意的效果。介绍了PID串级控制在电容器真空干燥温控中的应用方法及系统的结构和PID参数整定的步骤及方法。     

IRIS/AP型电感耦合等离子体光谱仪激发光源常见故障分析

本文介绍IRIS/AP型ICP的激发光源(炬管),并较为全面地阐述和分析其不能正常激发点燃的常见故障及其原因。     

振动加工时金属材料的本构关系的人工神经网络建立方法

在对金属材料进行振动拉伸时 ,材料的本构关系与静态拉伸明显不同 ,因而不能直接引用现有的弹塑性模型来描述。本文以常规频率下振动拉伸时实测的材料应力应变值为样本 ,利用 BP人工神经网络(BPANN)建立了振动加工过程中材料的应力应变关系。这种 BPANN本构模型可以方便地用于振动加工的理论分析和工程应用     

A fast spatial representation method (applied to fixture design)

A type of cellular-decomposition, solid-model representation based on variable orthorhombic cells and using a threedimensional matrix data structure is presented. It was developed to do two things that other representation methods cannot do easily or quickly. This method directly provides information concerning intersecting components, and it is fast enough to allow checks for intersection to be made in iterative routines. The method has application to layout design where interference checking is important. The method and the essential algorithms are described. An application to fixture design is presented.     

Application of a fast tool servo for diamond turning of nonrotationally symmetric surfaces

The fabrication of nonrotationally symmetric surfaces by diamond turning requires tool actuation at a bandwidth significantly higher than the rotational frequency of the surfaces. This requirement cannot be met by standard slide drives due to their large mass and consequent low natural frequency. This articles describes the development of a laboratory-scale diamond-turning machine with piezoelectric-driven fast tool servo. The capability of this apparatus will be demonstrated for high-speed features such as sine wave, square wave, and ramp-shaped surfaces. Also described is the implementation of this fast tool servo on a commercial diamond-turning machine. Several nonrotationally symmetric surfaces have been machined, and their images are included.     

A cooperative robotic system based on multiple sensors to construct metallic structures

This paper describes a multisensorial robotic system to automatically construct metallic structures. Two robots must work cooperatively in the same workspace to perform the task. The robots are automatically guided using visual and force sensor information. A new time-independent visual force control system which guarantees the adequate robot behaviour during the construction of the structure is described. During the construction of the structure, a human operator works cooperatively with the robots in order to perform some tasks which cannot be automatically developed by the robots. To do so, a new human–robot cooperation approach is described in order to guarantee the human safety. The correct behaviour of the different subsystems proposed in the paper is demonstrated in Section 6 by the construction of a real structure composed of several metallic tubes and different types of pieces to join them.     

Evaluation of kinematic coupling stability via centroid tracking of a lighted pinhole

Kinematic couplings are simple devices that provide rigid, repeatable connections between objects. The stability of these couplings cannot be measured using interferometry due to the repeated separation and engagement nature of the components. In this work, a measurement technique that is based on centroid tracking of a lighted pinhole is described. It is essentially based on a miniature target attached on an object surface that is recorded and tracked using a microscope. The technique has the advantage of being invariant to object rotation. An analysis of the performance limits as well as a simple experimental demonstration of the technique is presented.     

Practical inspection system of drill point geometry by using simple measurement jig and image processing

The proper simple inspection system for drill point geometry will support the skillful drill regrinding operation. In this paper, a newly developed system for practical use in machine shops has been described. The measurement method is based on silhouette image processing described in the author’s previous papers. But, for easy and robust inspection, a simple measurement jig was designed and the identification method of the five geometrical parameters describing its complete geometry was modified. Then, the error motion of the jig was tested and a compensation strategy of its error was proposed. The results show that the drill angles such as the outer clearance angle measured by this system are more precise than those measured by a microscope. Moreover, this system can measure the five geometrical parameters of the drill, which cannot be measured by using the microscope.     

Modeling of a blending and marine transportation planning problem with fuzzy mixed-integer programming

Transportation management is an area that remains critical to overall logistics and supply chain success. The problem of multi-commodity, multi-period blending and marine transportation planning in a wheat supply chain is addressed in this paper. In real world problems, practical situations are often not well-defined and thus cannot be described precisely. Therefore fuzzy mathematical programming becomes a valuable extension of traditional crisp optimization models. This research resolves the blending and marine transportation planning problem using fuzzy mixed-integer programming (FMIP) method. Two types of fuzzy mathematical programming models are used. A real-life example is used to illustrate the potential savings which can be attained by using fuzzy models. Results obtained in this study clearly demonstrate that FMIP provides a better and more flexible way of representing the problem.     

基于小波包参数模型的滚动轴承智能故障诊断

针对平稳自回归模型无法准确描述滚动轴承振动信号的非平稳性,提出一种结合小波包分解与自回归模型的故障特征提取方法,以提取能准确反映轴承运行状态的特征向量。首先,通过小波包变换对滚动轴承运行时产生的非平稳振动信号进行分解,得到一系列刻画原始信号特征的系数;然后,利用自相关算法对各系数建立自回归模型,并将自回归模型的参数作为特征向量;最后,采用支持向量机分类器对提取的特征向量进行故障分类,从而实现滚动轴承的智能故障诊断。仿真结果表明该方法的有效性。     

基于Client/Server模式下实现大数据量文件的传输

数字X光影像仪(CR)图像数据每幅高达21MB,需在两套计算机之间进行如此大数据量的传输,以往多使用并口进行传送,数据率仅为500KB/s,不能满足快速传输的要求,为此,将图像采集系统作为客户机,图像处理工作站作为服务器,构成Client/Server(C/S)模式,讨论了分布式结构、Winsock通信机制核心技术,利用VC++编写了通信程序。实验结果表明,采用C/S模式,实现高达21MB的大数据量文件无差错快速传输,仅需2s。