Optimal design of a frictional pair of a hub–plunger

Based on the model of a rough friction surface, the theoretical analysis of the displacement function for the external contour points of the hub of a frictional pair, providing the absence of the initial wear and tear, which takes place towards the end of the bedding period, is carried out. The obtained displacement function for the external contour points of the hub provides increased wear resistance of the frictional pair.     

Evaluation of a novel approach to a delamination factor after drilling composite laminates using a core–saw drill

Drilling is the most commonly applied method for hole making of fiber-reinforced materials owing to the need for structure joining. Delamination is the most common defect during drilling because of the heterogeneity of both the fibers and the matrix. The delamination, in general, is an irregular shape and size, containing long and fine breaks and cracks at the exit of the drilled hole, especially in the drilling of carbon-fiber-reinforced plastic (CFRP). On the other hand, a core–saw drill is designed to reduce the threat of chip removal in drilling composite materials. Since the thrust force of core–saw drill is distributed toward the periphery, the core–saw drill allows a larger critical thrust force than the twist drill at the onset of delamination when drilling composite materials. The aim of this paper is to present a novel approach of the equivalent delamination factor (F _ed) to characterize drilling-induced delamination using a core–saw drill and compare it with the adjusted delamination factor (F _da) and the conventional delamination factor (F _a). The experimental results indicated that the F _ed obtained is considered suitable for characterizing delamination at the exit of a hole after drilling CFRP.     

HFC 134a研究动向

本文给出HFC134a的热物性数据,介绍了它作为CFC12替代物用于冰箱和压缩机时对产冷量、功耗、排气温度、EER的影响和对润滑油的要求。     

原位叶绿素a精密测量方案设计

叶绿素a原位监测在海洋生态系统健康评估与碳循环过程研究中有重要价值。设计了一套原位叶绿素a的精密测量方案,以交流调制检测为基本方法,开发了交流模拟放大通路,使用开关检波系统完成最后的检波。噪声测试实验表明系统电流分辨力达到186.27 fA。通过仿真和对比实验证明了开关检波系统具有很强的频率选择特性,在系统噪声抑制方面起重要作用。标准叶绿素标定实验表明在0～30μg/L内系统线性度良好,用直线拟合R2=0.998 5,检测灵敏度S=0.008 1μg/L,满足使用需求。     

R152a与R134a混合制冷剂替代R22的可行性研究

制冷剂R407C和R410A是R22的主要替代物,它们的温室指数(GWP)值还较高,对环境仍然有一定的影响.本文对R152a和R134a组成的混合制冷剂进行了理论研究,通过分析该混和制冷剂的环境影响指数、温度滑移特性、热力学特性、安全特性和润滑油等问题,经理论循环计算并与R407C和R410A进行了对比,结果显示:由质量分数为50%的R152a和质量分数为50%的R134a组成的混和制冷剂对环境危害很小,具有合适的性能系数(COP)和排气温度,是一种润滑特性很好的优良近共沸制冷剂,在替代R22技术上完全具有可行性.     

Influence of friction during forming processes—a study using a numerical simulation technique

Friction has an important influence in metal forming operations, as it contributes to the success or otherwise of the process. In the present investigation, the effect of friction on metal forming was studied by simulating compression tests on cylindrical Al-Mg alloy using the finite element method (FEM) technique. Three kinds of compression tests were considered wherein a constant coefficient of friction was employed at the upper die–work-piece interface. However, the coefficient of friction between the lower die–work-piece interfaces was varied in the tests. The simulation results showed that a difference in metal flow occurs near the interfaces owing to the differences in the coefficient of friction. It was concluded that the variations in the coefficient of friction between the dies and the work-piece directly affect the stress distribution and shape of the work-piece, having implications on the microstructure of the material being processed.     

小型制冷装置HFC134a和HFC152a充注量的研究

针对制冷剂ＨＦＣ１５２ａ和ＨＦＣ１３４ａ的特性，对小型制冷系统充注量的计算方法及空泡系数关系式的影响进行了研究，并进行了实验验证，得到了这两种制冷剂充注量的计算方法。     

DD862a型单相电能表

该厂生产的DD862a型单相电能表,系原机械委等七个部委联合通知推荐生产的节能产品。它具有过载能力大,性能稳定,寿命长,装配调试方便、维修简单、造型新颖大方等优点。该厂于1989年1月由陕西省兵工局主持通过了产品的技术鉴定,投入批量生产。1989年5月通过了由电工仪表归口单位——哈尔滨电工     

Resonance of a flexible plate immersed in a von Kármán vortex street

Journal of Mechanical Science and Technology - This work presents a theoretical and experimental study of a flexible plate immersed in a von Kármán vortex street. The wake is generated in...     

Industrial culture and its implication for a development concept for a “culture of manufacturing”

A great challenge for mankind is to shape the dynamic tension and relationship between the emergence of global structures and regional structures, to encourage productive cooperation. The science of cognitive anthropology provides an interdisciplinary approach to this problem by a combination of cognitive science, cultural anthropology, occupational science and engineering science.Industrialised countries usually have a tradition of handicraft production which forms a basis for the acquisition of the skills of technological development and transfer. Technological development can be considered as a cyclic process in which the diverging elements of the regional industrial culture, and the converging elements of the global industrial society are dynamically related. In the initial stages of design and development, cultural elements tend to dominate, in the later stages socio-industrial forces become more effective, transforming the initial divergent phase into a convergent one. The traditional approach to product development is considered and its deficiencies in relation to the development of complex organizational structures are outlined. The paper concludes that the concept of culture of manufacture can only be developed by an interdisciplinary approach and if academic knowledge and the specific abilities and approach of appliers and users are integrated into the technology shaping process.     

Use of a higher order Heydemann–Welch model to characterize a controlled clearance piston gauge

We present a new method for characterizing a controlled-clearance piston gauge as a primary pressure standard. This method requires operating the piston gauge to jacket pressures of over 80% of the system pressure. We present measurements on a hydraulic piston gauge with a 290 MPa maximum pressure and a nominal piston diameter of 3.27 mm. Measurements showed that the cylinder becomes stiffer as the jacket pressure increases, and that non-linear models of the Heydemann–Welch parameters improve the determination of the effective area. The relative standard uncertainty in the effective area of the piston gauge ranges from 16.0 × 10⁻⁶ to 17.6 × 10⁻⁶, and the agreement to the present NIST pressure scale is within the standard uncertainty.     

Thermohydrodynamic Analysis of a Journal Bearing in a Turbulent Flow Regime—Part I: Theory

An attempt is made to formulate a thermohydrodynamic model of fluid-film lubrication that is valid in turbulent flow regimes. The model considers the flow to be a small perturbation of turbulent Couette flow. The modified Reynolds equation is obtained for the turbulent flow and the integro-differential energy equation makes the turbulence analysis easier by replacing the conductive terms in terms of the convective boundary conditions at two solid surfaces. Sample results applying the perturbation method agree well with available experimental data and theoretical methods.     

Reduction of sloshing effects in a rectangular tank through an air-trapping mechanism – a numerical study

A 2D rectangular tank subjected to horizontal excitations is used to analyze the effects of sloshing. The tank is fitted with horizontal baffles on two sides to suppress the impact pressure of sloshing by using an air-trapping mechanism. The volume of fluid method is adopted to create sloshing phenomena. Five cases with fixed baffle gaps and various baffle lengths are used to analyze the effects of suppressing the sloshing impact pressure in the tank. The peak pressure values of the cases with baffles are compared with those of the cases without baffles. Results show that the maximum suppression rate achieved is 63.6 % due to air trapping and baffle effects. Baffle ratio (Defined by G/L), a geometrical dimensionless factor, is considered to analyze the effects of baffle length and gap. A baffle ratio of 0.5 results in a 14.2 % reduction in the sloshing impact rate. An increasing amount of air is trapped within the baffle array as BR decreases.     

Contact Fatigue Analysis of a Dented Surface in a Dry Elastic–Plastic Circular Point Contact

The present article proposes a methodology for the computational analysis of damage induced in the vicinity of dents in a dry circular point contact under repeated rolling. The failure risk is evaluated through the use of the Dang Van multiaxial fatigue criterion. The dent is a typical surface defect encountered in rolling element bearings when operating in contaminated environments. It is usually created by a solid particle not removed by seals or filters when passing through an EHL conjunction. Since local plasticity occurs when the debris is first entrapped between the contacting surfaces, and later when the resulting dents are subjected to moving contact load, the elastic–plastic behavior of the material should be captured by the model. First, the dent shape and the subsurface stress and strain fields produced by the presence of a spherical particle are obtained by the finite element method. Second, the rolling of the load over the surface defect is simulated using a semi-analytical elastic–plastic code. The simulations are carried out for two different debris materials, both ductile but one significantly softer than the contacting surfaces, i.e., made of stainless steel 316L, the other one being made of bearing steel AISI 52100 similar to the contacting surfaces. The dent shape and initial stress and strain states are first presented. Subsequent stress and strain states after a few rolling cycles are then presented. Finally the effects of the coefficient of friction, presence of residual stress, and contact load magnitude are highlighted.     

原位海水叶绿素a传感器的电路设计

为提取LED激发海水叶绿素a产生的痕量荧光信号,实现海水叶绿素a原位检测,基于荧光诱导检测原理结合正交同步检波电路,设计了荧光叶绿素a传感器。通过对激发光源的调制,输入电流信号的转换与放大,荧光信号的正交同步解调以及数字混合低通滤波算法实现海水叶绿素a浓度的原位检测。实验证明该海水叶绿素a传感器具有精度高、抗环境光干扰能力强、小型化、功耗低等优点,分辨率可达到0. 01μg/L。     

R134a、R417a和R22用于空气源热泵热水器的性能研究

在焓差法空调器性能测试平台上,对空气源热泵热水器分别用R134 a、R417 a和R22进行各种典型工况下的试验,对3种制冷工质的吸排气压力、吸排气温度、压缩机输入功率、制热量、性能系数进行对比分析,分析验证了各参数随环境工况变化的关系,得出了在不同工况下的各特性参数的变化规律,为热泵热水器的设计及工质选用提供了参考。     

HFC—134a状态方程的比较

本文论述了ＨＦＣ－１３４ａ状态方程的发展，对几个重要的方程式与实验数据进行了比较，发现Ｐｉａｏ方程式是工况范围内最佳关系式。     

原位叶绿素a和浊度传感器设计

主要研究了叶绿素a和浊度传感器技术及其设计实现.该传感器技术基于荧光诱导的叶绿素a检测原理和基于散射的浊度检测技术原理进行设计,实现后可以实时测量海水的相关参数.该设计经过仿真验证,能够实现设计所要求的微弱光信号检测功能,为后续系统联调做好了准备.     

FuncDesigner—a functional design software system

Engineering design focuses on the development of products and artefacts to satisfy the specified function. Although considerable advances have been made over the last two decades in functional modelling, there is not very much progress on commercial Computer-Aided Design (CAD) systems that really aid the designer in converting functional specifications to concept variants. Based on our previous work on Behaviour-driven Function-Environment-Structure (B-FES) modelling framework, this paper presents a functional design software system, called "FuncDesigner", to support the functional design of mechanical products through functional reasoning steps, including causal behavioural reasoning and functional decomposition. A function object library and a behaviour object library have been developed as well to serve as the knowledge base for the computerised functional modelling environment. The proposed functional design software system has been evaluated with a design example of a terminal insertion unit in an automatic assembly system for manufacturing electronic connectors.