铸造材料伸缩尾翼气动载荷下接触问题的分析与研究

采用有限元技术,应用MSC仿真软件分析铸造材料伸缩结构尾翼在弹道飞行过程中气动载荷矩阵作用下的接触应力问题.通过建立计算模型,施加边界条件及启动接触非线性求解器进行求解,得到尾翼三维结构下的位移和应力情况,该种MD Nastran隐式非线性求解器SOL600计算方法能够充分模拟实际三维结构的接触问题.     

胶印机印刷压力分布规律的理论及实验研究

为了确定胶印机印刷压力定量分布,应用ABAQUS有限元软件的CAE功能模拟真实的印刷条件,建立压印滚筒和橡皮滚筒之间相互挤压的模型,对平版印刷压力分布和滚筒挠曲变形进行计算。同时应用富士FPD9210压力测试系统在胶印机上进行压力分布测试。两种验证方法结果均表明:压印滚筒轴向压力分布类似于M形,依此可以更好地调节实际印刷压力和油墨的分布。     

滚动轴承接触的非线性有限元分析

利用MSC.Patran/Marc软件建立了滚动轴承的二维有限元分析模型,进行了接触非线性有限元分析,得到接触应力、应变随接触状态的变化情况.当不考虑摩擦接触时,压力与变形间呈现一定的非线性关系.当考虑摩擦接触时,下板面最大等效应力增加,应力分布形状发生改变,最大切向应力发生点向接触部位靠近,说明摩擦因素对接触表面切向应力大小与最大切向应力发生点产生影响.     

子午线轮胎静负荷实验的有限元模拟

建立了一种子午线轮胎的三维非线性有限元模型,来模拟子午线轮胎的静负荷试验。模型中考虑了橡胶材料的非线性和不可压缩性、帘线-橡胶复合材料的各向异性、轮胎大变形导致的几何非线性以及轮胎与轮辋、轮胎与路面的接触非线性边界条件。提出了一种单元重叠技术,通过重叠不可压缩橡胶单元和描述帘线的单元来模拟帘线-橡胶复合材料,这种单元重叠技术产生的轮胎模型比正交各向异性模型计算过程更稳定。通过有限元分析,得到了子午线轮胎在充气压力和静负荷作用下的变形和应力分布情况以及接地区的压力分布情况,并将计算结果与试验结果进行了比较,两者吻合得很好。     

销轴连接结构的接触应力分析

销轴连接结构是工程中最为常用的一种传力结构,对其进行细致的接触应力分析,研究各参数对接触应力大小和分布的影响,对此类传力结构的设计与应用显得尤为重要。该文以佛山东平大桥为例,在验证有限元模型接触参数设置的基础上,计算东平大桥在竖转脱架状态下销轴连接结构的接触应力,计算结果与实测结果相比,基本反应了接触应力的大小和分布,证明了有限元模型的可靠性。在此基础上,研究了提升力大小、材料本构关系等参数对销轴连接结构接触应力大小和分布的影响,得到以下结果:材料本构关系和提升力大小的选取是影响销轴连接结构接触应力大小和分布的关键因素;接触区域的摩擦因数对计算结果几乎无影响。     

舰船轴系用液压螺栓抗冲击性能的数值仿真

液压螺栓由于装拆方便,可承受大扭矩而在舰船轴系中得到广泛应用。基于非线性接触理论,建立某型液压螺栓接触有限元分析模型,获得最大扭矩工况下液压螺栓的接触应力。基于现代冲击基础理论,建立液压螺栓抗冲击仿真模型,分别采用频域法和时域法对其进行考虑接触应力时的抗冲击性能仿真。计算得到该液压螺栓冲击载荷作用下的应力分布,为其抗冲击设计与评估提供依据。研究结果表明该液压螺栓符合抗冲击要求。     

聚酯防尘罩静力学特性分析

通过试验和有限元计算的方法研究了聚酯防尘罩结构轴向压缩的刚度,并对其实际工况下的刚度和强度进行了计算分析.首先,根据橡胶产品的国家标准进行标准试样的拉伸试验,由此得到有限元模型中材料模型的参数;然后,建立相应的标准试样和聚酯防尘罩产品的有限元模型,并通过非线性有限元软件MSC Marc进行了计算,得到标准试样和聚酯防尘罩产品的刚度.计算结果与试验结果较为吻合,从而验证了有限元模型的正确性,在此基础上利用有限元软件分析了聚酯防尘罩在实际工况下的变形和应力分布.所采用的分析方法对企业进行防尘罩的设计和开发有着重要的指导意义.     

非线性接触状态下的盘式制动器制动噪声分析

针对盘式制动器的制动噪声问题,建立盘式制动器的动力学仿真模型。首先对盘式制动器制动时的瞬态结构进行分析,然后根据制动盘与摩擦片在制动过程中的接触状态,将制动盘与摩擦片之间的接触面划为4个具有各自特征的接触区域,每个接触区域对应不同的接触应力。仿真过程中,分别将各接触区域相应的接触应力作为输入载荷进行加载,通过复特征值法的有限元仿真分析,得到制动器不稳定模态的分布及其振型,进而得到可能产生制动噪声的频率。最后通过制动试验,验证仿真结果的正确性。结果表明,盘式制动器的制动过程是一种非线性的接触过程,过大的非均匀分布的接触应力及其非线性变化将导致制动噪声,噪声频率主要分布在1 500 Hz～2 100 Hz之间。     

法向接触刚度对装配体振动模态影响的研究

在对装配体进行模态分析时,装配体接触面间的法向接触刚度对计算结果具有很大影响,但在实际中由于处理困难却往往被省略。基于有限元建模方法分析了装配体接触面法向接触刚度对装配体振动模态的影响。首先,根据接触力学理论推导了法向接触刚度与接触表面粗糙度和接触应力之间的关系;然后,探讨了通过改变层单元弹性模量来模拟法向接触刚度的有限元建模方法;最后,通过算例分析了考虑与不考虑接触刚度时振动模态的差异。研究结果表明,考虑法向接触刚度的有限元等效模型计算结果与解析解非常接近,不考虑接触刚度的整体模型计算结果与解析解异较大,一般超过了10%以上,且频率越低差异越大,另外振型也有明显差异。本文建立的有限元建模方法可用于研究法向接触刚度对装配体振动模态的影响。     

套片式翅片管机械胀接接触热阻分析与模拟优化

本文采用有限元模拟方法,得到了套片式翅片管换热器机械胀接的翅片与基管间的胀后节点接触应力分布。提出模拟的总体接触应力并不是节点接触应力算术平均的观点和总体接触应力的计算式。通过对套片式换热器试件进行传热性能实验,获取了翅片与基管之间的接触热阻数值,由模拟计算的总体接触应力与实验接触热阻数值,计算两者的关联式。采用有限元模拟方法预测各种胀接量下的总体接触应力及最优的胀接尺寸,利用弹塑性理论计算对比模拟计算进行验证。结果发现,材料弹塑性理论计算结果与模拟计算结果的相对偏差为7. 3%,偏差较小,证明两者均具有效性。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.