含内生硬质碳化物颗粒的金属堆焊层的抗磨性能及磨损机理

利用钛铁(Fe-Ti)、钒铁(Fe-V)、石墨和金红石等组分的电弧冶金反应合成了含TiC和VC硬质碳化物颗粒的金属堆焊层；采用MLD-10型动载荷摩擦磨损试验机考察了金属堆焊层的抗磨性能，探讨了其磨损机理．采用X射线衍射仪和扫描电子显微镜分析了堆焊层的相组成＼微结构及磨损表面形貌．结果表明：含硬质碳化物颗粒的金属堆焊层具有良好的耐磨粒磨损性能，其单位面积磨损质量损失仅为EDZCr-C-15焊条相应金属堆焊层的约1／9；所制备的金属堆焊层基体组织为低碳马氏体，内生硬质碳化物颗粒弥散分布于基体组织中；硬质碳化物颗粒同低碳马氏体基体表现出良好的韧性和硬度复合效果，从而有利于显著提高金属堆焊层的抗磨性能．     

含膦酸酯官能团离子液体对钢/铝摩擦副的润滑作用研究

合成了3种新型1-(O,O-二乙基膦酰丙基)-3-烷基咪唑六氟磷酸盐离子液体,采用SRV型摩擦磨损试验机评价了所制备的离子液体作为润滑剂对钢／铝摩擦副摩擦学性能的影响,并探讨了其润滑机理．结果表明,所合成的离子液体作为润滑剂对钢／铝摩擦副具有优良的润滑作用,摩擦系数低,抗磨性能优良．表面分析结果表明含膦酸酯官能团的离子液体在摩擦副接触表面形成化学吸附边界润滑膜,从而有效地起到抗磨和提高承载能力的作用．     

硼化含氮杂环衍生物的摩擦学性能研究

从分子设计的观点出发，设计并合成了硼化含氮杂环衍生物，考察了其作为润滑油添加剂的抗磨性能，并通过扫描电子显微镜和X射线光电子能谱仪分析探讨了其在基础油中的抗磨作用机理．结果表明：所合成的硼化杂环衍生物添加剂在摩擦表面生成了由非牺牲性B2O3沉积层、氧化物、酸性氧化产物和聚合物组成的润滑及防护薄膜，从而有效地起到抗磨作用．     

PG-2齿轮油复合剂的摩擦学性能研究

研制了同商用齿轮油添加剂Hitec343具有相似结构和组成的PG-2复合剂;通过热重分析考察了所研制的PG-2复合剂的热稳定性能;利用红外光谱分析考察了其化学结构特征;采用四球摩擦磨损试验机考察了其极压抗磨性能,并采用扫描电子显微镜分析了钢球磨损表面形貌.结果表明,所研制的PG-2复合剂具有优良的极压抗磨性能、防锈性能、防腐蚀性能及热稳定性,其总体性能同国外同类复合剂产品相当,而极压性能优于国外同类复合剂.     

钨钼铜贝氏体灰口铸铁的组织与耐冲蚀磨损性能之研究

利用等温淬火贝氏体球铁所制水泵的使用寿命是普通灰口铸铁水泵的３一５倍，但因这种材料的生产工艺复杂而使其推广应用受到了限制。为了既能提高水泵的使用寿命，又能简化材料的生产工艺，对在普通灰口铸铁中加入适量的钨、钼、铜所获钨钼铜贝氏体灰口铸铁的组织与耐冲蚀磨损性能进行了试验研究，扫描电子显微镜和透射电子显微镜观察发现，在钨和钼的加入量分别为１．５０％（ｗｔ）和０．６０％（ｗｔ）时，钨钼铜贝氏体灰口铸铁的组织为细小片状石墨、贝氏体基体和少量的白亮区。其中，贝氏体基体系由大量板条状无碳化物贝氏体和少量细针状贝氏体组成，其抗拉强度为４５０一５５０ＭＰａ，硬度为ＨＢ２８０一３５０。冲蚀磨损对比试验结果表明，钨钼铜贝氏体灰口铸铁的耐冲蚀磨损性能分别是普通灰口铸铁和硼铜合金铸铁的４．８３倍和１．６５倍，并与等温淬火贝氏体球铁的相当。     

蓖麻油聚氧乙烯醚水基润滑液摩擦学特性研究

本文以蓖麻油聚氧乙烯醚水基润滑液为研究对象,分别使用润滑膜厚度测量仪、微摩擦试验机和四球摩擦试验机对其成膜特性、摩擦磨损特性和抗磨极压特性进行了系统的研究,并用扫描电子显微镜和能量色散光谱仪对摩擦磨损机制进行了分析。结果表明：蓖麻油聚氧乙烯醚提高了纯水的成膜能力,能够在钢-铝摩擦副形成有效的润滑膜,起到良好的减摩抗磨效果。随着浓度的增大,对钢-铝摩擦副的减摩抗磨性能和四球摩擦试验的抗磨极压性能都得到了提高。     

一种新型S-N添加剂与磷酸三甲酚酯在500N加氢基础油中的摩擦学复合效应

合成了一种新型S-N无灰添加剂(DBTT)；利用四球摩擦磨损试验机考察了单剂DBTT、磷酸三甲酚酯(TCP)以及含不同质量比的DBTT和TCP的复合添加剂在500N加氢基础油中的摩擦学性能；用X射线光电子能谱仪和扫描电子显微镜分析了磨损表面形貌和元素化学状态．结果表明：合成的DBTT在500N加氢基础油中有良好的溶解性;所考察的添加剂都能有效提高基础油的承载能力；在一定条件下单剂DBTT和TCP能够有效提高基础油的减摩和抗磨性能；DBTT／TCP复合剂在基础油中表现出协同抗磨效应和增摩效应．含上述添加剂的500N加氢油在摩擦过程中发生摩擦化学反应，生成混合边界润滑膜，从而起减摩抗磨作用．     

两种含硫硼酸酯的合成及十二胺对其抗磨性能的影响

人们已对有机硼酸酯的减摩抗磨性能作了许多研究，但还很少见有含硫硼酸酯减摩抗磨性能之研究的文献报道．因此，合成了两种分子链烷基中含硫的有机硼酸酯，利用四球试验机和ＭＨＫ－５００型环－块试验机考察了它们添加到基础油（四球试验和环－块试验使用的基础油分别为液体石蜡和正十四烷）中的抗磨性能，以及十二胺对它们抗磨性能的影响，并用Ｘ射线光电子能谱仪对摩擦表面的元素组成和硼、硫元素的化学结合状态进行了分析，四球试验表明，含硫硼酸酯的承载能力比不含硫硼酸酯的更高；环－块试验表明，含硫硼酸酯的抗磨性能比不含硫硼酸酯的差．十二胺的加入能够明显提高含硫硼酸酯的承载能力和抗磨性能，Ｘ射线光电子能谱分析发现，在摩擦表面膜中硼是以降解的硼酸酯的形式存在，而硫则是以有机硫化物和ＦｅＳＯ４这两种形式存在；十二胺的加入降低了硫和硼在摩擦表面膜中的含量，其结果是提高了油品的抗磨性能和承载能力．     

室温离子液体介质中CdS纳米微粒的制备及其摩擦磨损行为研究

合成了1-甲基-3-己基咪唑四氟硼酸盐离子液体，并以此为反应介质通过有机金属化合物热分解法制备出CdS纳米微粒，采用X射线粉末衍射仪和透射电子显微镜对CdS纳米微粒的结构和形貌进行表征，在四球摩擦磨损试验机上考察了含CdS纳米微粒离子液体的摩擦磨损行为．结果表明：所制备的CdS纳米微粒具有六方相结构，粒径均一，约为15nm；含CdS纳米微粒离子液体的减摩抗磨性能明显优于纯离子液体；CdS纳米微粒以滚动／滑动方式起到了减摩抗磨作用，同时可以加速离子液体中阴离子的分解，促进FeF2和FeF3的形成，使复合体系的减摩抗磨性能有所提高．     

成分和组织对衬板钢在腐蚀料浆环境下的冲击磨损性能与机理的影响

利用改造后的MLD-10型冲击磨损试验机研究了3种冶金矿山湿磨衬板钢在铁矿石酸性矿浆中的冲击腐蚀磨损行为;采用扫描电子显微镜观察了试样磨损表面形貌,用光学显微镜分析了垂直于试样磨损表面的亚表层金相组织.结果表明:低碳高合金钢的耐冲击腐蚀磨损性能优于高锰钢及中碳合金钢;低碳高合金钢的冲击腐蚀磨损机制主要为挤出硬化棱剥落、轻微的腐蚀磨损及浅层疲劳剥落,高锰钢的主要冲击腐蚀磨损机制为较深层的累积变形疲劳剥落和严重的腐蚀磨损,而中碳合金钢的主要冲击腐蚀磨损机制为深层脆性剥落和严重的腐蚀磨损.     

STICTION AND ANTI—STICTION IN MEMS AND NEMS

Stiction in microelectromechanical systems (MEMS) has been a major failure mode ever since the advent of surface micromachining in the 80s of the last century due to large surfacearea-to-volume ratio. Even now when solutions to this problem are emerging, such as self-assembled monolayer (SAM) and other measures, stiction remains one of the most catastrophic failure modes in MEMS. A review is presented in this paper on stiction and anti-stiction in MEMS and nanoelectromechanical systems (NEMS). First, some new experimental observations of stiction in radio frequency (RF) MEMS switch and micromachined accelerometers are presented. Second, some criteria for stiction of microstructures in MEMS and NEMS due to surface forces (such as capillary, electrostatic, van der Waals, Casimir forces, etc.) are reviewed. The influence of surface roughness and environmental conditions (relative humidity and temperature) on stiction are also discussed. As hydrophobic films, the self-assembled monolayers (SAMs) turn out able to prevent release-related stiction effectively. The anti-stiction of SAMs in MEMS is reviewed in the last part. The project supported by the Distinguished Young Scholar Fund of NSFC (10225209), key project from the Chinese Academy of Sciences (KJCX2-SW-L2) and National “973” Project (G1999033103)     

水和水蒸汽热力学物性参数及导数的计算与应用

本文针对现代换热设备设计、两相流动与传热研究的需要,介绍了可供科研使用的水和水蒸汽物性计算方法,完善了计算程序。根据超临界锅炉设计中的超临界水的物性计算,两相流研究和换热设备动态特性研究中对物性导数计算的需要,提供了两个算例,并进行了定性分析。     

Flows around two airfoils performing fling and subsequent translation and translation and subsequent clap

The aerodynamic forces and flow structures of two airfoils performing “fling and subsequent translation“ and “translation and subsequent clap“ are studied by numerically solving the Navier-Stokes equations in moving overset grids. These motions are relevant to the flight of very small insects. The Reynolds number, based on the airfoil chord length c and the translation velocity U, is 17. It is shown that: (1) For two airfoils performing fling and subsequent translation, a large lift is generated both in the fling phase and in the early part of the translation phase. During the fling phase,a pair of leading edge vortices of large strength is generated; the generation of the vortex pair in a short period results in a large time rate of change of fluid impulse, which explains the large lift in this period. During the early part of the translation, the two leading edge vortices move with the airfoils;the relative movement of the vortices also results in a large time rate of change of fluid impulse, which explains the large lift in this part of motion. (In the later part of the translation, the vorticity in the vortices is diffused and convected into the wake.) The time averaged lift coefficient is approximately 2.4 times as large as that of a single airfoil performing a similar motion. (2) For two airfoils performing translation and subsequent clap, a large lift is generated in the clap phase. During the clap, a pair of trailing edge vortices of large strength are generated; again, the generation of the vortex pair in a short period (which results in a large time rate of change of fluid impulse) is responsible for the large lift in this period. The time averaged lift coefficient is approximately 1.6 times as large as that of a single airfoil performing a similar motion. (3) When the initial distance between the airfoils (in the case of clap, the final distance between the airfoils) varies from 0.1 to 0.2c, the lift on an airfoil decreases only slightly but the torque decreases greatly. When the distance is about lc， the interference effects between the two airfoils become very small.     

Fracture and stability of materials and structural members with cracks: approaches and results

A new alternative approach to fracture problems for materials and structural elements with cracks is set out. It is based on the mechanism of local instability near defects. The approach is used to study the fracture of materials compressed along interacting cracks and the fracture of thin structural members with cracks under tension with allowance for local buckling.__________Translated from Prikladnaya Mekhanika, Vol. 40, No. 12, pp. 18–64, December 2004.     

Electrogas- and electrohydrodynamic control of gas and liquid jets and flows

The physical and mathematical principles of the method of electrogas-and electrohydrodynamic conversion of electrical signals to pneumatic (hydraulic) signals and vice versa for control of gas and liquid jets and flows in electropneumohydraulic systems are considered. St. Petersburg State Technical University, St. Petersburg 195251. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 25–31, March–April, 2000.     

Sound and vorticity interactions: transmission and scattering

We review several aspects of the propagation of sound in vortical flows. We restrict ourselves to isothermal, humidity-free flows at low Mach number M. Since vorticity plays a major role in vortex-flow interactions we focus on vortical flows. We consider two main canonical situations. The first concerns the transmission of sound. We analyze the evolution of acoustic wavefronts as they propagate across a single vortex. The second situation addresses the scattering of sound waves by nonstationary vortices. We study the evolution of the acoustic pressure emitted in the far field, at an angle with the initial direction of propagation. In this geometry one performs direct spectroscopy of the flow vorticity field. In each case, we review theoretical results and compare with experimental measurements and numerical simulations when available. We also briefly report how the following new acoustic techniques have recently been used to study complex or turbulent flows: time-resolved acoustic spectroscopy, speckle interferometry and Lagrangian particle tracking. PACS 43.25, 43.28, 47.32, 67.40     

Data-driven modeling and learning in science and engineering

In the past, data in which science and engineering is based, was scarce and frequently obtained by experiments proposed to verify a given hypothesis. Each experiment was able to yield only very limited data. Today, data is abundant and abundantly collected in each single experiment at a very small cost. Data-driven modeling and scientific discovery is a change of paradigm on how many problems, both in science and engineering, are addressed. Some scientific fields have been using artificial intelligence for some time due to the inherent difficulty in obtaining laws and equations to describe some phenomena. However, today data-driven approaches are also flooding fields like mechanics and materials science, where the traditional approach seemed to be highly satisfactory. In this paper we review the application of data-driven modeling and model learning procedures to different fields in science and engineering.     

Reordering and incomplete preconditioning in serial and parallel adaptive mesh refinement and coarsening flow solutions

The effects of reordering the unknowns on the convergence of incomplete factorization preconditioned Krylov subspace methods are investigated. Of particular interest is the resulting preconditioned iterative solver behavior when adaptive mesh refinement and coarsening (AMR/C) are utilized for serial or distributed parallel simulations. As representative schemes, we consider the familiar reverse Cuthill–McKee and quotient minimum degree algorithms applied with incomplete factorization preconditioners to CG and GMRES solvers. In the parallel distributed case, reordering is applied to local subdomains for block ILU preconditioning, and subdomains are repartitioned dynamically as mesh adaptation proceeds. Numerical studies for representative applications are conducted using the object‐oriented AMR/C software system libMesh linked to the PETSc solver library. Serial tests demonstrate that global unknown reordering and incomplete factorization preconditioning can reduce the number of iterations and improve serial CPU time in AMR/C computations. Parallel experiments indicate that local reordering for subdomain block preconditioning associated with dynamic repartitioning because of AMR/C leads to an overall reduction in processing time. Copyright © 2011 John Wiley & Sons, Ltd.     

Phase transitions and hysteresis in nonlocal and order-parameter models

The paper describes two types of regularization to the basic quasistatic double-well potential problem in one space dimension. One model features a spatially nonlocal term while the other incorporates the use of an order parameter. Some basic existence and regularity results for these modified models are derived and some numerical calculations that show hysteresis and motion of phase boundaries are presented.

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Sommario Il lavoro descrive due tipi di regolarizzazione del problema quasistatico per un potenziale con due minimi in una dimensione. Un modello evidenzia caratteri di non località spaziale, mentre l'altro conduce ad una teoria con parametro d'ordine. Si derivano alcuni risultati di esistenza e regolarità e si presentano alcuni studi numerici che mostrano l'isteresi e il moto delle frontiere tra le fasi.