Application of embedded sensors in the thermal cycling of organic coatings

A standard Air Force polyurethane topcoat/epoxy chromate pigmented primer system was characterized using the thermal cycling method. This method is an accelerated test method for organic coatings that involves exposing the coating to alternating room temperature and elevated temperature cycles under constant immersion. Electrochemical properties were monitored using electrochemical impedance spectroscope for the total topcoat/primer system, the inner layer of primer, and the outer layer of the topcoat. The individual layers were monitored using platinum sensors embedded between the layers. Characterization of a system comprising of two layers of the epoxy chromate pigmented primer was also performed using EIS monitoring, and embedded sensors. The systems were cycled between room temperature, and set temperatures up to 80 °C. The barrier property of the topcoat and the bulk resistance of the primer were consistent with Arrehenius behavior. The results obtained were consistent with the intended design of the polyurethane topcoat and chromate primer with the former providing the significant barrier protection, whereas the primer providing the passivating chromate to the metal/coating interface. Analysis of the EIS data obtained from the sensor with an equivalent circuit decoupled the bulk primer properties from the metal/coating interface properties.     

Analytical thermal model of conduction mode double sided arc welding

Abstract

An analytical thermal model of conduction mode double sided arc welding (DSAW) has been derived and used to predict the weld pool dimensions and shapes and temperatures within 2˙5 and 1˙15 mm thick AA5182 Al alloy sheets as functions of the primary DSAW parameters. Separate Gaussian distributed arc heat sources from a plasma arc welding and gas tungsten arc welding torch were assumed to act on the top and bottom surfaces of the sheets. There was excellent correlation between observed and predicted DSAW weld pool dimensions and shapes provided that suitable values for arc efficiencies and distribution coefficients for the two separate arcs were used in the model. The model is capable of predicting weld pool dimensions and shapes of both full and partial penetration conduction mode DSAW welds made in Al alloy sheet, the welding speed at which there is a transition from full to partial penetration welding and the speed above which no melting occurs.     

Contact and thermal analysis of bronze and steel machined surfaces in sliding contact

Between engineering components in sliding contact there are usually small real contact areas inside the nominal contact area. The real contact pressure frequently is in the range of the plastic limit pressure.The effect of different machining processes (grinding, milling, spark-erosion and superfinising) on the contact parameters (real contact areas, contact pressure distribution and contact temperature) were analysed and compared between bronze and steel sliding surfaces.The developed contact algorithm can simulate the elastic and also the elastic-plastic sliding contact behaviour in the vicinity of the asperities in an approximate way.Assuming certain sliding speed and coefficient of friction the local contact temperature distribution is also calculated due to the heat generation over the real contact areas for'slow sliding' problems.     

3500mm炉卷轧机高压水除鳞系统射流参数设计

介绍了高压水除鳞机理,分析了各种参数对高压水除鳞效果的影响,提出了射流参数计算公式,并通过计算机软件进行模拟分析,验证了计算公式的正确性。在此基础上,确定了满足轧制工艺要求的3 500 mm炉卷轧机高压水除鳞系统的射流参数。     

Evaluation of thermal properties of UO2 and PuO2 by equilibrium molecular dynamics simulations from 300 to 2000 K

The thermal properties of UO₂ and PuO₂ have been investigated by the equilibrium molecular dynamics (EMD) simulations between 300 and 2000 K using the Born–Mayer–Huggins interatomic potential with the partially ionic model (PIM). The thermal expansion behaviors of UO₂ and PuO₂ are well reproduced by assuming that the effective ion valence is 67.5% for PIM. The constant-pressure heat capacities deduced only by the present EMD simulation are a little smaller than experimental data. This result explains that the electronic contribution, Schottky or small polaron contribution, is not small for the heat capacity of the actinide oxide including 5f-electrons. The thermal conductivity estimated by the Green–Kubo formula under the NVE ensemble is comparable with experimental data at temperatures greater than 500 K.     

3500mm炉卷轧机支承辊断裂原因分析

采用低倍酸洗、金相检查、扫描电镜、能谱分析等手段,对使用初期断裂的3 500 mm炉卷轧机支承辊断口进行分析。结果表明,较大的残余应力与各类夹杂物及碳化物聚集分布是造成该件特大支承辊断裂的主要原因。     

YH40-200型2000kN精压成型液压机的研制

介绍一种用于飞机机翼精压成型设备的研制,简述了机器各部件结构设计特点和研制中的技术难点及解决措施等问题,产品达到了国外同类产品的先进水平.     

热爆法合成Al Ti C中间合金的工艺研究

采用热爆法来制备AlTiC中间合金,试验研究保温时间、配方及粉料粒度对制备中间合金的影响。通过X-ray衍射和SEM扫描电镜分析发现,随着保温时间的变化,TiC与TiAl3粒子的形态和分布会发生相应的变化。另外,在不同的配方和不同的粉料粒度下,TiC与TiAl3粒子的形态和分布也会发生相应的变化,而TiC与TiAl3粒子的形态和分布在很大程度上影响AlTiC中间合金的细化纯铝晶粒效果。研究结果表明,保温时间为10 min,Al∶Ti∶C(原子比)=5∶2∶1,碳粉料粒度为1 200目,钛粉500目时的细化晶粒的效果最好。     

自蔓延热爆合成MoSi2-WSi2复合粉末

以Mo、W和Si粉为原料,采用自蔓延热爆合成制备了不同组分的MoSi2-WSi2复合粉末,并利用X射线衍射仪和扫描电镜对合成产物进行了相组成和产物形貌分析.结果表明:热爆反应产物纯净,MoSi2-WSi2复合粉末中只有MoSi2和WSi2两相存在;颗粒的大小取决于体系的摩尔生成焓,摩尔生成焓越大,颗粒长大越显著;热爆合成反应以Si的熔化为先导,反应机制为熔化-溶解-析出-长大机制.     

区域集聚的产品供应链和多动态联盟体系--动态联盟的高效运行模式

提出了一种高效的动态联盟运行模式－－区域集聚的产品供应链和多动态联盟体系，并分析了该模式的运行机制和形成机理。文章还结合两个实例，分析了区域集聚的产品供应链和多动态联盟体系的形成过程和运行特点。     

The status of chemical sensors for hot-dip galvanization

Alloying elements are added to the zinc used in the hot-dip galvanization of sheet steel to control the properties and appearance of the resulting coating. For example, aluminum is added to improve the corrosion resistance and adherence of the coating. Other additions, such as antimony, are added to control the grain size and, thus, the appearance of the coating. The concentrations of these alloying elements may change during the process, either deliberately according to product specifications or due to factors such as preferential oxidation. These changes may require replenishment of a depleted alloying element or adjustments in other processing parameters to maintain optimal efficiency. Intelligent adjustments require knowledge of the alloy composition, which requires inline measurement of the concentrations of alloying elements. This article presents recent developments in chemical sensors for use in hot-dip galvanization. In particular, electrochemical sensors for measuring the concentrations of aluminum and antimony in molten zinc are reviewed.     

Real-time monitoring of transverse thermal strain of carbon fiber reinforced composites under long-term space environment using fiber optic sensors

Composites are promising alternatives for space structures because of their versatile characteristics such as high specific stiffness and strength. When composite structures are exposed to the space environments (low Earth orbit, LEO), however, they are known to undergo considerable temperature change induced by the direct sunlight and the Earth's shadow in addition to ultraviolet, high vacuum, atomic oxygen and so forth. Therefore, for the successful completion of their missions, it is important for the structures to maintain the consistent dimensional stability in such a thermal cycling condition. The coefficient of thermal expansion (CTE) of the structures is suitable to express the dimensional stability, and it is needed to be monitored throughout the mission. For this purpose, fiber optic sensors, which have many advantages, were investigated to check their suitability in this paper.Two fiber Bragg grating (FBG) sensors have been adopted for the simultaneous measurement of thermal strain and temperature to get the CTE change of a carbon/epoxy composite laminate. LEO conditions with high vacuum, ultraviolet and thermal cycling environments were simulated in a thermal vacuum chamber. As a pre-test, a FBG temperature sensor was calibrated and a FBG strain sensor was evaluated through the comparison with the electric strain gauge (ESG) attached on an aluminum specimen in the same temperature range as the thermal cycling. The change of the transverse CTE in a composite laminate exposed to the space environment was measured for intervals of aging cycles in real time. As a whole, there was no abrupt change of the CTE after 1000 aging cycles. After aging, however, the CTE decreased a little all over the test temperature range. These changes are thought to have been caused by outgassing, moisture desorption, matrix cracking, etc. In this paper, embedding application of FBG sensors to composites operated under space environment and their successful real-time monitoring of thermal deformations over a long time was shown.     

3500轧机辊端联轴器结构与强度分析

采用三维CAD建模装配体有限元分析方法对改造后的3500轧机辊端十字轴式万向联轴器进行结构和强度方面分析。十字轴最大应力发生在圆弧过渡处,因此,应提高该处的表面加工质量。     

Amorphous magnetoelastic sensors for the detection of biological agents

Freestanding amorphous magnetoelastic (ME) biosensors were fabricated by two ways. One type with larger size, 2000 × 400 × 15 μm, 1000 × 200 × 15 μm and 500 × 100 × 15 μm, was made from an ME Fe40Ni38Mo4B18 ribbon, the other with smaller size 200 × 40 × 4 μm was manufactured by dual beam sputtering and non-traditional microelectronic fabrication techniques. Both platforms were immobilized with JRB7 phage and were developed for the real-time in vitro detection of Bacillus anthracis spores. The experimental results show that the measured sensitivity of the ME sensors agrees with theoretical predictions and the specificity of ME sensors coated with JRB7 phage for B. anthracis spore species is excellent. The 200 × 40 × 4 μm biosensor was found to have a detection limit of 10² cfu/ml and sensitivity of 13.1 kHz/decade.     

南京钢厂3500mm 轧机大型机架的冶炼浇注

简要介绍了多包精炼在南京钢厂 3 5 0 0mm轧机机架生产上的应用。利用三包冶炼 ,成功地冶炼浇注了两片 3 5 0 0mm轧机的两片机架 ,是我公司迄今为止生产过的最大的铸件。     

Cu-Cr合金触头材料制备技术的研究进展

Cu-Cr合金是新一代中压大功率真空开关触头材料之一,有着广泛的应用前景。本文综合述评了Cu-Cr合金的几种传统制备方法,粉末烧结法、熔渗法和电弧熔炼法,以及制备新技术真空感应熔炼法、自蔓延熔铸法、机械合金化法等工艺方法,分析了它们的优缺点及研究现状,并指出了Cu-Cr合金发展趋势。     

Laser treatment of aluminum surface: Analysis of thermal stress field in the irradiated region

Laser surface treatment of aluminum is considered and the temperature as well as the stress fields developed in the laser irradiated region are predicted using the finite element method (FEM). The predictions are obtained for two laser pulses with different pulse lengths. In the simulations, the variable thermal properties of the substrate material are used. The experiment is conducted to treat the aluminum specimen surface with the laser beam. The laser output pulse intensity consists of repetitive pulses, which are used in the model study to examine the metallurgical changes in the irradiated region. SEM and XRD are carried out in this regard. It is found that the von-Mises stress reaches the maximum in the surface vicinity, particularly at the onset of cooling cycle starts. The von-Mises stress attains values less than the critical values for the crack formation, which is particularly true after the end of the cooling cycle. The residual stress formed in the surface region is in the order of a few MPa.