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。     

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.     

<机械制造业产品与市场预测>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 　　……     

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.     

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.     

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.     

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.     

Dependences of the optical characteristics of Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>N films on the substrate composition and polarity

Optical properties of Ga- and N-polar triple nitrides Al _x Ga_1−x N with molar fractions of aluminum from 0 to 0.6 are studied by a nondestructive contactless method of spectroscopic ellipsometry. Correlation dependences of the shift of the fundamental absorption edge and the behavior of the real and imaginary parts of the pseudodielectric function on the composition x and polarity of the Al _x Ga_1−x N layers are revealed. It is verified that the polarity of the layers grown by molecular beam epitaxy is defined by the formation of the AlN nucleating layer.     

泵&#183;阀

林德厦门叉车有限公司HPV-02闭式回路用变量泵HPV-02的设计特点为高压斜盘式轴向柱塞泵,左旋或右旋均可,该产品具有精确而可靠的变量控制机构（手动、液压先导或电比例）,集成带补油功能的高压溢流阀用于保护补油、控制和冷却回路,可更换滤油器。该产品还有SAE高压油口、     

液压&#183;气动元件

意大利阿托斯有限公司中国技术服务中心数字伺服执行器 ATOS为用户提供的数字伺服执行器可根据不同应用场合为用户定制电液轴。在有经验的工程师的帮助下,用户可以选择正确的装置并设定参数,获得高的动态特性/速度,采用低摩擦密封动态比例阀,频响可达50 Hz,响应时间为2m/s;     

轴承&#183;齿轮

舍弗勒（中国）有限公司双列角接触滚子轴承该创新轴承的研发建立在带有创新滚动体、O形排列和双列角接触推力滚珠轴承基础上。传统的不承担载荷的滚动＂球＂体被拆除,这就意味着15%的球直径将从球体两侧切除。这就形成了球辊,它比一个真正的球窄30%,而且重量更轻。     

Effect of Grain Boundary on the Wear Behaviour of NiTi Shape Memory Alloys When <Emphasis Type="Italic">M</Emphasis><Subscript>f</Subscript> &lt; <Emphasis Type="Italic">T</Emphasis> &lt; <Emphasis Type="Italic">A</Emphasis><Subscript>f</Subscript>

Wear behaviour of NiTi SMA is closely corresponds to deformation mechanisms associated with different plastic strain accumulation process. Plastic strain accumulation is achieved by dislocation motion; however, grain boundary acts as a strong barrier. In this work, wear behaviour of single-crystalline and polycrystalline NiTi SMAs was studied to understand the effect of grain boundary on the plastic strain accumulation in the wear process. Wear tests were conducted at M_f < T < A_f, where phase boundary exists between martensitic and austenitic phases. Tests were conducted under ball-on-disc sliding wear mode, and alumina (Al₂O₃) counter-body was used. For single-crystalline NiTi SMA, transition wear occurred even when the applied load was relatively low (i.e., 100 mN). For polycrystalline NiTi SMA, with increasing applied load and wear cycles, the wear has shifted from near-zero wear stage to severe wear stage; no transition behaviour was observed. Significant differences in the wear process were discussed with respect to deformation mechanisms associated with dislocation motion in the single-crystalline and polycrystalline NiTi SMAs.     

Fabrication In Situ TiB<Subscript>2</Subscript>–TiC–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Multiple Ceramic Particles Reinforced Fe-Based Composite Coatings by Gas Tungsten Arc Welding

A Fe-based composite coating reinforced by multiple TiB₂–TiC–Al₂O₃ ceramic particles was developed by gas tungsten arc welding (GTAW) melting process. Mixture of aluminum (Al), boron carbide (B₄C), and titanium dioxide (TiO₂) powders was used as precursors, and as a consequence TiB₂–TiC–Al₂O₃ multiple ceramic particles were in situ synthesized during GTAW melting process. Microstructural investigations showed that TiB₂ particles exhibit a blocky morphology, TiC particles are of flower-like shape, and the Al₂O₃ particles exist as small black dots and located in the core of reinforced particles. The hardness and wear resistance of the coatings increased drastically in comparison with that of the substrate.     

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.     

Manufacturing and mechanical characterization of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/β-TCP/TiO<Subscript>2</Subscript> biocomposite as a potential bone substitute

This paper focuses on the mechanical characterization of a bioceramic based on commercial alumina (Al₂O₃) mixed with synthesized tricalcium phosphate (β-TCP) and commercial titania powder (TiO₂). The effect of β-TCP and TiO₂ addition on the mechanical performance was investigated. After a sintering process at 1600 °C for 1 h, various mechanical properties of the samples have been studied, such as compressive strength, flexural strength, tensile strength, elastic modulus, and fracture toughness. The measurements of the elastic modulus (E) and the tensile strength (σ _t ) were conducted using the modified Brazilian test while the compressive strength (σ _c ) was determined through a compression test. Also, semi-circular bending (SCB) specimens were used to evaluate the flexural strength (σ _f ) and the opening mode fracture toughness (K _IC). From the main results, it was found that the best mechanical performance is obtained with the addition of 10 wt.% TCP and 5 wt.% TiO₂. Alumina/10 wt.% tricalcium phosphate/5 wt.% titania composites displayed the highest values of mechanical properties and a good combination of compressive strength (σ _c ?≈?352 MPa), flexural strength (σ _f ?≈?98 MPa), tensile strength (σ _t ?≈?86.65 MPa), and fracture toughness (K _IC?≈?13 MPa m^1/2).