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.     

Empirical mode decomposition approach for defect detection in non-stationary thermal wave imaging

This paper introduces a novel empirical mode decomposition based anomaly detection in Quadratic frequency modulated thermal wave imaging. Being suited for non-stationary signal analysis, its edge over other contemporary processing modalities in its anomaly detection capability has been verified using experimentation carried over a mild steel specimen with embedded flat bottom holes. It also addresses the effect of size and depth on anomaly detection using the proposed methodology in addition to considering the signal to noise ratio of defects for detection.     

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.     

Successful Hydrothermal Synthesis of α-Fe2O3 Hexagonal Micro-platelets and Its Application in Li-Ion Battery

介绍了一种界面接触热导的测试设备,为更好的实现测试过程中的轴向一维导热,该设备中增加了补偿加热装置.通过该设备,对高温合金GH4169和K417界面处,在温度160～280℃、载荷0～150 MPa条件下的接触热导进行了试验研究,验证了试验设备的适用性.对有、无补偿加热条件下的接触热导测试结果进行了对比分析.结果表明,同等条件下带补偿加热装置时的接触热导测试结果要比不带补偿加热装置时的大,且温度越高,补偿加热装置工作效果越好.     

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.     

WJ-3500×160型网架杆件专用自动焊设备及设计的研究

介绍了用于焊接多种规格的钢网架杆件CO2气体保护焊专用自动焊机的组成、技术参数及工作原理。与焊条电弧焊相比，该自动焊专机结构简单，可提高焊接质量，降低成本。     

温度对高温合金GH4169/K417间接触热导的影响

采用自主研制的带补偿加热的接触热导测试装置,测试了航空发动机用高温结构材料GH4169/K417间不同温度(160～280℃)和粗糙度下的接触热导,研究温度对其接触热导的影响行为,对比分析有无补偿加热条件下接触热导的测试结果。结果表明,带有补偿加热的接触热导测试装置能有效降低横向热流损失,且随着温度的升高效果逐渐明显。不同粗糙度的GH4169/K417材料组合,温度对其接触热导的影响不同,主要与其界面处材料的变形、氧化有关。     

载荷对高温合金GH4169/K417间接触热导影响

采用自主研制的带补偿加热的接触热导测试设备,对航空发动机用高温结构材料GH4169/K417间不同载荷(60~180MPa)和不同粗糙度下的接触热导进行试验研究。研究了载荷对其接触热导的影响行为,对比分析了有、无补偿加热条件下的接触热导测试结果。结果表明,带有补偿加热的接触热导测试装置能有效降低横向热流损失。不同粗糙度的GH4169/K417材料组合,接触热导随载荷变化规律一致,且粗糙度较大时接触热导值较大,两者的差值随载荷先增加后减小,主要与平行刀纹的界面啮合作用有关。     

High-temperature thermal stability of C/C-ZrC-SiC composites via region labeling method

To investigate the thermal stability of ceramic-matrix composites, three kinds of C/C-ZrC-SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration. Employing region labeling method, the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment. Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature, and a crystal transformation from β-SiC to α-SiC occurs in the composites. In the calibrated area, SiC phase experiences Ostwald ripening and volume change with location migration, while ZrC phase experiences a re-sintering process with diffusion. Moreover, it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time, which is mainly attributed to the faster diffusion rate of atoms.     

K24镍基合金钎焊接头热应力的有限元模拟

采用有限元方法,模拟计算了镍基合金粉末钎料在1270℃钎焊K24镍基合金时,接头在冷却过程中的热应力最大值和应力集中区.结果表明,在冷却过程中,K24合金接头的切应力主要集中在界面端点处,且切应力的最大值出现在镍基钎料/K24合金界面的右端点处,其随着温度的降低先减小后增大.同时,接头x方向拉应力最大值也出现在此处,且其随着温度的降低经历由负到正的变化过程.当承受外切切力时,接头并非在镍基钎料内部断裂,而镍基钎料,/K24合金界面易成为接头的主要断裂区.     

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。     

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.     

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。     

Er3Ni颗粒4-40 K温区表观热导率测量及其回热器漏热研究

磁性材料的应用对低温制冷机的发展有着重要的意义。目前磁性材料在液氮以下温区热物性参数的缺乏严重限制了制冷机回热器的设计与优化。研制了颗粒状磁性材料低温表观热导率测量装置,对Er3Ni在4-40 K及不同氦气压力下的表观热导率进行了测量并计算了Er3Ni热导率系数。在不同温区的测试结果表明,真空状态下,Er3Ni颗粒表观热导率为0.11-0.22 W/m·K,对应的热导率系数为0.31-0.53;当氦气压力增大至1.4-2.2 MPa后,表观热导率趋于稳定,稳定后的平均值为3 W/m·K,对应的热导率系数为7。进一步研究了Er3Ni型回热器不同工况下的漏热特性,提出了丝网与颗粒混合填充的方案以降低冷热两端的轴向漏热。结果表明,在Er3Ni回热器中混合填充尼龙网和316 L不锈钢丝网后制冷性能显著提高,在1.6 MPa压力下漏热降低幅度分别高达12%和8%。     

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.