角接触球轴承热力学耦合模型与分析方法

接触球轴承运行时,其力学性能与热态特性之间存在高度耦合与交互,轴承热预紧力在这一过程中起着桥梁连接作用。在研究角接触球轴承非线性力学性能与热效应耦合机制的过程中,分析了结合面接触热阻、油气润滑及周边组件换热等边界条件对轴承热态特性的影响,提出了一种角接触球轴承热力学耦合分析方法,并基于多软件协同计算平台建立了轴承热力学耦合模型。在轴承实验平台上,借助热巡检仪,利用轴承套表面开设的测温工艺孔实施了温度实验,对轴承热力学耦合模型的仿真计算结果进行了验证。该模型可用于预测角接触球轴承在不同转速下热预紧力的变化规律,分析比较热预紧力对轴承运行刚度的影响。     

Optimization-based cosmetic formulation: Integration of mechanistic model,surrogate model,and heuristics

Multiple functional and hard-to-quantify sensorial product attributes that can be satisfied by a large number of cosmetic ingredients are required in the design of cosmetics. To overcome this problem, a new optimization-based approach for expediting cosmetic formulation is presented. It exploits the use of a hierarchy of models in an iterative manner to refine the search for creating the highest-quality cosmetic product. First, a systematic procedure is proposed for optimization problem formulation, where the cosmetic formulation problem is defined, design variables are specified, and a set of models for sensorial perception and desired product properties are identified. Then, a solution strategy that involves iterative model adoption and two numerical techniques (i.e., generalized disjunctive programming reformulation and model substitution) is applied to improve the efficiency of solving the optimization problem and to find better solutions. The applicability of the proposed procedure and solution strategy is illustrated with a perfume formulation example.     

Structure,crystallization, and performances of alkaline-earth boroaluminosilicate sealing glasses for SOFCs

We study the structure, crystallization, and performances of the sealing glasses with the composition (mol.%) of 12Al₂O₃·8B₂O₃·40SiO₂·40RO (R = Mg, Ca, Sr) for solid oxide fuel cells (SOFCs) before and after isothermal treatment at 700°C, which is within the operation temperature range (600-800°C) of SOFCs. The crystallization behavior has been investigated by differential scanning calorimetry and X-ray diffraction under both dynamic and isothermal conditions. The structural evolution is probed using the Raman and nuclear magnetic resonance spectroscopies. The performances of the sealing glasses are characterized in terms of the coefficient of thermal expansion, the crystallization-induced stress at glass–steel interface. We find that strong crystallization occurs at the operation temperature (700°C) far below the crystallization onset temperature measured by DSC. The structure origin of this anomalous crystallization is discussed in terms of structural heterogeneity of the three studied glasses. We determine the residual stress at the interface between the Ca-containing glass and the steel after isothermal treatment at 700°C for 48 h, but this stress does not lead to falling off the glass layer from the steel. This indicates that this glass is a good candidate to be applied in SOFCs.     

Engineering all-aromatic polyamide surface from hydrophilic to superhydrophobic and the accelerated strategy

Being a new kind of nanomaterials, aromatic polyamide nanofibers (ANF) have been much highlighted in recent studies. We here demonstrate an isopropyl alcohol (IPA) accelerated chemical cleavage on poly (p-phenylene terephthalamide) chopped fibers, which provides an efficient preparation method of ANF. The comprehensive study on the processes accelerated by different alcohols revealed that the preparation time of ANF in the mixed medium of dimethyl sulfoxide (DMSO)-alcohol (20:1 in volume) was shorten to 45 min and 75 min for methanol (ethanol) and isopropanol, respectively. However, the nanofibers prepared in DMSO-IPA exhibited the minimum in axial and radial dimensions, providing the finest and most uniform diameter of 16 nm. The corresponding ANF films through vacuum assisted filtration also showed the highest tensile strength of 150 MPa, in comparison with those of the ANF films prepared using other alcohols, which were about 110 MPa. Furthermore, ANF/silicon hybrid films were prepared by the ionic ring-opening reaction followed by the alkoxysilane condensation and nanoparticle fabrication. By changing the organo functional groups in the alkoxysilane, the surface of the films were adjustable in a wide contact angle range from 56° (hydrophilic) to 150° (superhydrophobic), suggesting the amendable interfacial properties potential applicable to composite fabrication with most of the resin matrix.     

负载换流逆变器驱动电励磁同步电机无速度传感器模型预测控制方法

负载换流逆变器(LCI)驱动电励磁同步电机控制系统广泛应用于中高压场合,在应对干扰和负载变化上,较大的系统惯性系数和较低的开关频率导致其动态响应性能欠佳.该文提出一种基于LCI驱动电励磁同步电机的无速度传感器模型预测控制方法.首先根据LCI的数学模型建立预测状态方程,同时给出合适的代价函数和约束条件;然后分析负载换相模式下的控制矢量模型,给出速度观测器的设计方法和参数选择依据,并针对负载变化对速度观测产生的影响进行分析和补偿.同时该观测器还能够同时实现逆变桥输入电压和端电压相位的观测;最后,通过3.75kW的LCI驱动电励磁同步电机实验平台对提出的无速度传感器模型预测控制方法进行实验验证.结果表明所提出的控制方法能够有效提升系统的动态响应性能,所设计的观测器具有可行性,速度观测结果在额定阶跃负载下误差小于13°.     

一种制备纳米复合镀层的新方法

研究了一种制备纳米复合镀层的新方法--在直流电镀过程中对电镀液施加强磁场以代替机械搅拌来制备Ni/Al2O3纳米复合镀层,考察了镀层的结构,并对镀层性能进行了研究.结果表明,在强磁场下可以制得纳米复合镀层;与未加磁场的纯镍镀层相比,施加磁场后镀层的晶体结构发生了择优取向;当磁场强度为8T时,复合镀层的磨损率仅为纯镍镀层的25%,其耐蚀性与Q235钢相比提高56.3%,与纯镍镀层相比提高46.8%.强磁场对电镀液起到较好的搅拌作用,通过影响镀层中纳米微粒的含量,使镀层结构发生变化,进而影响镀层的性能.     

机械合金化Al-Cu-Fe准晶相形成的研究进展

综述了机械合金化A1-Cu-Fe准晶相的形成机理及热力学稳定性方面的研究进展.     

车顶蒙皮焊接工艺改进

西安某汽车厂客车蒙皮组焊件焊接采用CO2焊,生产效率低,焊接变形大,表面处理难度大,质量难以保证,使产品的质量和产量受到严重的制约,为此必须进行工艺改进.通过采用全自动缝焊焊接工艺及选择合理的工艺参数,在保证结构和强度的前提下,使蒙皮组焊件焊接表面质量大幅度提高,劳动强度大幅度下降,生产效率提高数倍.     

退火温度对铜合金-镍复合材料组织与力学性能的影响

对3种铜合金-镍复合材料进行了不同温度的退火处理，通过力学拉伸试验和电子探针(EPMA)观察与分析，研究了退火温度对3种复合材料的金相组织、元素扩散以及力学性能的影响。结果表明，经300℃以上温度退火处理后，3种复合材料的抗拉强度、屈服强度和硬度均随退火温度的升高而降低，而伸长率则随退火温度的升高而增大，铜合金与镍之间的Cu／Ni元素均发生了扩散，但主要是铜元素向镍层的扩散。合适的退火温度有利于提高复合材料的综合性能。     

基于TMS320C6678的多核程序加载研究与实现

针对多核D SP系统程序加载复杂的问题,基于T MS320C6678对多核程序加载进行了研究与设计。从一级引导程序出发,设计并优化了多核程序内容存储格式。设计了简洁的二级引导程序,以修正一级引导程序只识别主核程序入口地址,而从核入口地址缺失的现象。为了快速生成特定格式的多核程序内容,设计了多个工具用于添加S PI启动参数表、DDR3启动表、从核程序入口地址以及完成程序内容格式的转换。实现了S PI Flash多核程序加载以及基于I2C主模式的Nand Flash多核程序加载。