汽车动力传动系统扭转振动的研究

本文对汽车动力传动系统进行了讨论分析和试验研究。提出了汽车动力传动系统的力学模型,用试验方法确定了模型中的全部参数。对系统进行了自由振动和强迫振动计算,在数据处理中采用了谱分析的方法。对不同形式的扭振减消措施的减消效果进行了试验研究。     

Thermal Transport in Nanoporous Yttria-Stabilized Zirconia by Molecular Dynamics Simulation

Yttria-stabilized zirconia (YSZ) is widely used as thermal barrier coatings (TBCs) to reduce heat transfer between hot gases and metallic components in gas-turbine engines. Porous structure can generally reduce the lattice thermal conductivity of bulk material, so porous YSZ can be potentially used as TBCs with better thermal performance. In this work, we investigate the thermal conductivity of nanoporous YSZ using the nonequilibrium molecular dynamics (NEMD) simulation, and comprehensively discuss the effects of cross-sectional area, pore size, structure length, porosity, Y₂O₃ concentration and temperature on the thermal conductivity. To compare with the results of the NEMD simulation, we solve the heat diffusion equation and the gray Boltzmann transport equation (BTE) to calculate the thermal conductivity of the same porous structure. From the results, we find that the thermal conductivity of YSZ has a weak dependence on the structure length at the length range from 10 to 26 nm, which indicates that the majority of heat carriers have very short mean free path (MFP) but there exists small percentage (about 3%) of phonons with longer MFP (larger than 10 nm) contributing to the thermal conductivity. The thermal conductivity predicted by NEMD simulation is smaller than that of solving heat diffusion equation (diffusive limit) with the same porous structure. It shows that the presence of pores affects phonon scattering and further affects the thermal conductivity of nanoporous YSZ. The results agree well with the solution of gray BTE with a average MFP of 0.6 nm. The thermal conductivity of nanoporous YSZ weakly depends on the Y₂O₃ concentration and temperature, which shows the phonons with very short MFP play the major contribution to the thermal conductivity. The results help to better understand the heat transfer in porous YSZ structure and develop better TBCs.     

营口港某码头腐蚀与防护状况调查与分析

对营口港某码头的腐蚀与防护状况进行了调查,调查内容包括钢管桩外观状况、涂层厚度、壁厚、保护电位和阴极保护系统等。结果表明,大部分钢管桩整体状态良好,无明显的涂层破损和局部腐蚀,壁厚和涂层厚度满足要求,保护电位正常。但少部分钢管桩存在涂层的局部破损,部分钢管桩因整流器损坏或输出电流偏低导致保护电位不足。     

离合器扭振减振器性能参数计算公式探讨及其弹性特性表达

离合器扭振减振器是消减汽车动力传动系扭振的一个十分有效的装置,但其设计方法问题,在国内尚未得到较好的解决。本文对减振器,尤其是多级非线性减振器结构设计中,计算性能参数的基本公式,进行了必要的修正和补充,并给出了用解析式表达减振器弹性特性的方法。     

秦北牵引变电所设计特点

以秦北牵引变电所设计为事例，介绍单相变压器AT供电牵引变电所及既有电气化铁路改造的设计原则和设计特点。