A comparative evaluation of K<Subscript>op</Subscript> determination and ΔK<Subscript>eff</Subscript> estimation methods

Methods for determination of the crack opening stress intensity factor (K_op) and for estimation of the effective stress intensity factor range (ΔK_eff) are evaluated for crack growth test data of aluminum alloys. Three methods of determining K_op, visual measurement, ASTM offset compliance method, and the neural network method proposed by Kang and Song, and three methods of estimating ΔK_eff, conventional, the 2/P10 and 2/PI methods proposed by Donald and Paris, are compared in a quantitative manner by using evaluation criteria. For all K_op determination methods discussed, the 2/PI method of estimating ΔK_eff provides good results. The neural network method of determining K_op provides good correlation of crack growth data. It is recommended to use 2/PI estimation with the neural K_op determination method. The ASTM offset method used in conjunction with 2/PI estimation shows a possibility of successful application. It is desired to improve the ASTM method.     

计算机大楼力博特300kV&#183;A UPS系统分析

以武钢计算机大楼力博特300kV·A UPS为例,分析了UPS不间断电源系统,包括整流器、逆变器、电池组以及静态开关的工作原理和由它们组成的不同工作模式。     

<Emphasis Type="Italic">CAD-Based Virtual Assembly Prototyping – A Case Study</Emphasis>

This paper presents the methodology for quantifying the blade assembly process with the future objective of fully automated assembly planning. The proposed method is aimed at eliminating the expensive and time-consuming physical prototyping needs by analysing and evaluating the feasibility of the blade assembly process using a CAD-based virtual prototype. The virtual prototype of the entire assembly operation is created for the blade assembly from a torque converter of an automobile transmission system. This model development is implemented using ProEngineer. Owing to the modelling requirements, the design intents, pertinent parameters, and their relationships in the entire blade assembly process must be captured and integrated into the model. The virtual assembly prototyping package developed is capable of computing and offering computer animated simulations of the interference of the blade tabs with the turbine and the pump shell during the assembly process. The work focuses on quantifying the blade assembly process by expertly defining some benchmarks and indices based on the kinematic behaviour of the assemblages. The benchmarks can also be used for documenting, evaluating, and comparing the blade assembly designs in various assemblages of torque converters to improve and transfer the experiences of the designers embedded in the model, for the torque converter industry. The model developed in this work has been tested and verified to be effective with a real torque converter model built at a local company. The results of the experiments are discussed. ID="A1"Correspondance and offprint requests to: Dr Y.-J. Lin, Department of Mechanical Engineering, The University of Akron, Akron, OH 44325–3903, USA. E-mail: yl@uakron.edu     

Microstructural and Tribological Properties of A356 Al–Si Alloy Reinforced with Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Particles

In the present study, the effect of the Al₂O₃ particles (average size of 12 μm, 3 and 10 wt.%) reinforcement on the microstructure and tribological properties of Al–Si alloy (A356) was investigated. Composites were produced by applying compocasting process. Tribological properties of unreinforced alloy and composites were studied, using pin-on-disc tribometer, under dry sliding conditions at different specific loads and sliding speed of 1 m/s. Microhardness measurements, optical microscope and scanning electron microscope were used for microstructural characterization and investigation of worn surfaces and wear debris. During compocasting of A356 alloy, a transformation from a typical dendritic primary α phase to a non-dendritic rosette-like structure occurred. Composites exhibited better wear resistance compared with unreinforced alloy. Presence of 3 wt.% Al₂O₃ particles in the composite material affected the wear resistance only at specific loads up to 1 MPa. The wear rate of composite with 10 wt.% Al₂O₃ particles was nearly two order of the magnitude lower than the wear rate of the matrix alloy. Dominant wear mechanism for all materials was adhesion, with others mechanisms: oxidation, abrasion and delamination as minor ones.     

A photo-thermally stimulated exoemission technique used to study the properties of HTSC ceramics based on YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−δ</Subscript>

The method of photo-thermally stimulated exoelectron emission (PTSE) is used to study the processes in the surface layers of HTSC ceramics based on YBa₂Cu₃O_7–. A correlation is observed between variations of the exoemission current and the transition to the superconducting state. The experimentally detected hysteresis in the PTSE intensity of YBa₂Cu₃O_7– ceramics, when thermally cycled in the range T=80–160 K, is limited by two processes. Below T=90 K, the chemisorption has a significant effect on the physical phenomena under study, thus impeding the search for new PTSE regularities in HTSC ceramics. At the same time, exoemission properties of the ceramics considerably change in the range 80–160 K. It is also shown that the superconducting transition and the thermal absorption phenomena for an YBa₂Cu₃O_6.8 specimen are split in the studied temperature range, which allows the PTSE technique to detect the superconducting state and to observe the transition dynamics.Translated from Defektoskopiya, Vol. 40, No. 12, 2004, pp. 54–59.Original Russian Text Copyright © 2004 by Syurdo, Kortov, Milman, Slesarev, Mikhailovich.This revised version was published online in April 2005 with a corrected cover date.     

阿特拉斯&#183;科普柯GA系列压缩机赢得2008P＆A最佳节能产品奖

2009年3月23日,比利时安特卫普,阿特拉斯&#183;科普柯在由德国P＆A杂志举办的年度最佳产品评比中赢得了“泵与压缩机”组的第一名。阿特拉斯&#183;科普柯的最新GA90～160kW节能喷油压缩机最终征服了由6000名读者,以及主要的德国生产工艺工程师组成的评选小组。GA的卓越节能特点,使整机比功率（SER）低至350J／L。     

A small Raman laser based on a KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> : Nd<Superscript>3+</Superscript> Crystal (λ=1.538 µm) with passive resonator <Emphasis Type="Italic">Q</Emphasis> switching

Generation properties of a Raman laser based on a KGd(WO₄)₂ : Nd³⁺ crystal and operating in a mode of passive resonator Q switching by a YAG : V³⁺ crystal at a wavelength safe for human eyes is studied. A small laser with a mass of 35 g, operating over a wide temperature range at a wavelength of 1.54 µm and an output energy of >6 mJ, has been created on the basis of these studies.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 112–113.Original Russian Text Copyright © 2005 by Ustimenko, Zabotin.     

TH65100&#215;100／A型卧式镗铣加工中心回转工作台的电气控制

TH65100&#215;100／A型卧式镗铣加工中心除了具有X、Y、Z三个进行直线运动的坐标轴外,还有绕Y轴进行圆周运动的回转工作台（B轴）。回转工作台是镗铣床的重要附件之一,主要用来装夹工件,扩大主机的加工范围,机床在需要多轴联动加工曲线和曲面的场合,回转工作台必须进行连续圆周运动,本机床的回转工作台是由伺服电动机驱动的,可进行连续圆周进给运动。     

A two-channel two-frequency low-temperature photodetector at wavelengths of 119 and 220 μm of an H<Subscript>2</Subscript>O laser

The design and characteristics of a compact device consisting of four cooled photodetectors of radiations at two frequencies (2.53 and 1.36 THz) are presented. The photodetectors are based on two pairs of Ge:Sb and n-type InSb single crystals and equipped with preamplifiers. The photodetector is intended for operating jointly with an H₂O laser, which operates in a mode of generation of orthogonally polarized waves, and can be used in interferometers with insufficiently stable lengths of optical paths, e.g., during investigation of plasma in high-power pulsed facilities. The photodetector is manufactured in the form of an insert into a commercial portable helium Dewar flask with a 12-mm-diameter neck.     

工程机械的"补"与"不补"

工程机械是否应当进入＂农机补贴目录＂,一直是一个让人避讳莫深、难以回答的问题。近年来,各省农机补贴目录越来越多地出现了工程机械的身影,而且这些产品也已经不再仅仅是简易的农用工程机械。2011年,在国家的补贴目录中,也出现了斗容量≤0.4m~3的挖掘机的选项。     

&lt;机械制造业产品与市场预测&gt;出版

本刊讯为促使我国制造业特别是机械制造业广大企业能及时、全面了解本行业产品、技术的发展趋势及市场需求状况,机械科学研究院组织各方力量,对我国机械制造业18个产业产品与技术发展趋势进行了预测. 预测的主要内容包括: 1.各产业产品发展趋势和发展重点; 2.对重点发展产品的市场需求、发展方向、主要指标和技术特点、技术关键、实用化时间等进行分析和预测; 3.各产业需要解决的关键技术,并对每项关键技术进行论证.包括:技术概要、选择的依据、国内外现状与发展趋势、主要研究内容和目标. 18个产业分析与预测小组,经过充分分析论证,并咨询了数百名专家的意见,现已完成了课题研究工作.其成果已汇集成册,总计70万字.研究报告内容丰富、信息量大,具有权威性,可为制定这些行业的“十五”发展规划、计划提供依据,对制定企业发展战略和规划有导向作用.为满足各单位急需,现将其中的工程机械、农业机械、内燃机、冶金矿山机械、通用设备、石油机械、环境保护机械、发电及输变电设备、金属加工机械(机床)、通用仪器仪表、汽车、通用零部件、船舶、轻工机械、纺织机械等15个产业的预测结果做为资料予以发行. 价格:合订本每套300元,含邮寄费. 征订办法:通过邮局汇款.请将收件人姓名、详细地址、所在单位及部门、邮政编码用楷书写清,并在汇款单的留言中注明所需资料名称、数量.收款后即将资料和正式发票以挂号方式从邮局寄出, 联系人:王勇、郭壮电话:(010)68596023、68527633 详细地址:北京市月坛南街26号中国机电日报社邮政编码 100825 　　……     

Is “five-point” estimation better than “three-point” estimation?

Theoretical considerations are presented to show that, regarding [1], for a sinusoidal signal, “five-point” estimation is a better estimation than “three-point” estimation.     

Tribological Properties of Organic Functionalized ZrB<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Epoxy Composites

The tribological behaviors of epoxy composites filled with organic functionalized ZrB₂–Al₂O₃ were environmentally investigated and compared with those with as-received fillers under both dry and oil sliding conditions in this work. The worn surfaces and the transfer films on the counterparts were characterized by scanning electronic microscope (SEM), and the frictional temperature rising was investigated by infrared thermometer. The results demonstrated that the coefficient of friction (CoF), the wear rate, as well as the frictional temperature rise of the epoxy composites were all decreased due to the introduction of ZrB₂–Al₂O₃ fillers. And with the increase in filler content, similar variation tendencies of CoF and wear rate of epoxy composites were observed under the different sliding conditions. Besides, the organic functionalization of ZrB₂–Al₂O₃ fillers, which made the epoxy composites exhibit lower CoF and wear rate than those with as-received fillers, lowered the frictional temperature as well. In comparison, the epoxy composites filled with 5 vol% modified fillers presented better tribological properties, suggesting a stronger interfacial bonding between modified fillers and epoxy matrix. The dominant wear mechanisms of filled composites under dry and oil sliding conditions could be inferred as the combination of adhesive wear and abrasive wear and the fatigue wear, respectively, on the basis of SEM images of worn surfaces.     

In Situ Studies of TiC<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Hard Coating Tribology

TiC_1−x N _x hard coatings present time-dependent tribological behavior with an initial running-in period (500–2000 cycles) marked by an elevated friction coefficient, followed by >10000 cycles with low-friction and wear at room temperature (RT) in ambient air. The mechanisms behind this behavior are not completely understood. Tribological tests performed at RT and at different relative humidity (RH) levels revealed that a minimum value between 15 and 25% RH is needed to trigger the low-friction regime at a sliding speed of 100 mm s⁻¹. By in situ observations of transfer film growth, it could be observed that third body material is formed during this running-in period by plowing of the coating and shearing of the removed material. The appearance and thickening of the transfer film marks the beginning of the steady-state low-friction regime where the velocity is accommodated by interfacial sliding. At this stage in the tribological test, the recorded Raman spectra indicated the presence of C–H bonds in the wear track. Use of in situ analytical tools during wear tests provided insights with respect to tribological phenomena that were not available by conventional, post-mortem analysis methods.     

A shaper of multiply repeated picosecond high-voltage pulses in a range of 10<Superscript>−10</Superscript> s

A pulse-shaping device is described that reproduces multiply repeated picosecond high-voltage pulses with a duration of 10^?10 s, an amplitude of >100 kV, and a repetition rate of up to 10³ Hz. The principle of switching the circuit using a single spark gap filled with a compressed gas instead of conventional spark peakers and a chopping gap, connected in series, is applied. The use of compressed hydrogen at a pressure of 30 atm as the working gas favors stability of the discharge voltage and a virtually unlimited lifetime of the shaping device.     

Dynamics of Growth of the Native Oxide of Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te

The growth of the native oxide of the Cd_xHg_1?xTe (MCT) compound is studied by methods of laser and spectral ellipsometry. It is found that a non-absorbing oxide film is formed from the very beginning in the case of MCT oxidation with hydrogen peroxide vapors, whereas oxidation with atmospheric oxygen leads to the formation of absorbing layers on the surface at the first stages of the process. When the oxide film thickness reaches 1–2 nm, the oxidation rate drastically decreases. If MCT samples that were stored for a long time (for years) in air at room temperature are heated at T = 200 °C, the optical thickness of the oxide film decreases.     

Environmental Effects on the Tribology and Microstructure of MoS<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>3</Subscript>–C Films

The tribology of molybdenum disulfide (MoS₂)–Sb₂O₃–C films was tested under a variety of environmental conditions (ambient 50% RH, 10⁻⁷ Torr vacuum, 150 Torr oxygen, and 8 Torr water) and correlated with the composition of the surface composition expressed while sliding. High friction and low friction modes of behavior were detected. The lowest coefficient of friction, 0.06, was achieved under vacuum, while sliding in 8 Torr water and ambient conditions both yielded the highest value of 0.15. Water vapor was determined to be the environmental species responsible for high friction performance. XPS evaluations revealed a preferential expression of MoS₂ at the surface of wear tracks produced under vacuum and an increase in Sb₂O₃ concentration in wear tracks produced in ambient air (50% RH). In addition, wear tracks produced by sliding in vacuum exhibited the lowest surface roughness as compared to those produced in other environments, consistent with the picture of low friction originating from well-ordered MoS₂ layers produced through sliding in vacuum.