负载对超声加工声学系统特性的影响

以一维超声振动系统为研究对象,以点、线、面三种不同的加载方式对工件进行加载,研究了负载对超声加工声学系统特性的影响。实验表明,当以点、线的加载方式对工件进行加载时,载荷的变化对声学系统特性各参数的影响不大;而当加载方式为面接触时,机械品质因数Qm、谐振频率fs和动态电阻R随着载荷F的增大有明显的增大趋势,动态电容C和最大电导Gmax却随着载荷F的增大而减小。     

基于转速耦合的适配功率电机动力性能分析计算

适配功率电机是一种适用于城市重载电动汽车的新型驱动电机,具有转速耦合的特点。以6极适配功率电机为研究对象,阐述了适配功率电机设计原理及适用工况,运用电磁场理论及电机学理论知识,对适配功率电机动力输出性能进行对比分析计算,计算得出同一转速下减匝工作状态更能节约车载有限电能,并运用仿真分析软件进行验证。同时研究结果表明,与满匝工作状态相比,适配功率电机工作在减匝状态的机械特性更硬。最后,通过样机试验例证了以上理论计算与仿真分析的正确性,证明该电机设计模型是可行的。     

PREDICTION OF MECHANICAL PROPERTY OF WHISKER REINFORCED METAL MATRIX COMPOSITE: PART-I. MODEL AND FORMULATION

Whisker reinforced metal matrix compositespossess good transverse strength,low cost,high workability and other properties over unre-inforced alloys.They are applied increasingly inaerospace,automotive,electronics,sportinggoods and many other areas.Creation of thosecomposites has led to the development of newtest methods,manufacturing techniques,predic-tion theory and design practices[1,2 ] .　　The pioneer works on prediction of the elas-tic moduli of composite were traced back toVoigt[3] and …     

Numerical investigation on leakage and rotordynamic performance of the honeycomb seal with swirl-reverse rings

Honeycomb seals are a crucial component to restrict the leakage flow and improve system stability for the turbomachines and aero-engines. In this work, the leakage and rotordynamic performance of honeycomb seals with the Swirl-Reverse Ring(SRR) is predicted by employing the approach of Computational Fluid Dynamics(CFD) and the multifrequency whirling model theory.Numerical results show that the positive preswirl flow and circumferential velocity can be effectively weakened for the honeycomb seal...     

BAS粘接碳化硅材料的性能

采用原位生成钡长石为烧结助剂,研究BAS/SiC复相陶瓷的低温无压液相烧结工艺,制备高致密度的陶瓷材料。通过XRD、SEM及力学试验机等研究烧结温度、BAS含量对复相碳化硅陶瓷的致密化、组织结构及力学性能的影响。结果表明:在1800℃温度下原位生成了BAS相,运用无压液相烧结法制备出了密度达到3.2g/cm3的BAS/SiC复相陶瓷;陶瓷中BAS以六方结构析出、SiC颗粒均匀分布;烧结温度不宜超过1800℃,温度过高将促使碳化硅颗粒长大,损伤陶瓷材料抗弯强度和断裂韧度;当复相BAS/SiC陶瓷中BAS质量分数为30%时,弯曲强度达到413MPa,模量达到210GPa,断裂韧度达到5.03MPa.m1/2。     

Effect of the protrusion shape on gas ingestion of two sealing structures

The windage loss caused by protrusion in a rotor–stator cavity has been studied in detail, and there are abundant fitting formulas that have been summarized to calculate the moment coefficients. Some other theorists have emphasized its effect on the sealing efficiency, proposing that installation of protrusion could alleviate gas ingestion. However, the protrusion shape which is an influential factor on the sealing efficiency has not been focused in previous research. Using the experimental method of measuring CO₂ volume fraction, cavity pressure, and power consumption, we investigated the effects of several typical protrusion shapes on various parameters for two sealing structures, in order to obtain the optimal shape. Results showed that a variation of the protrusion shape had little impact on the static pressure, but the total pressure and the sealing efficiency increased in different degrees. Furthermore, even though the hexagon shape resulted in the highest sealing efficiency, we observed that the drop shape had the best overall performance in all of the eight models, which could result in higher efficiency of the turbine cavity. The combination of a radial seal structure and protrusion could improve sealing efficiency better.     

大缝隙密封的几种异型截面橡胶密封结构的有限元分析

针对大缝隙密封要求,利用有限元方法,考虑了橡胶材料的非线性影响,分别对矩形、椭圆形、骨形、塔形和月形硅橡胶密封件和相应的O形密封圈的压缩变形过程、压缩反力、接触应力和性能特点进行分析,计算结果与压缩试验结果基本一致,证明有限元方法可应用于该类橡胶密封结构的设计分析。密封模拟试验结果表明,塔形和矩形密封圈可在较大缝隙时（大于5mm）保证良好的气密性,弥补了传统0形密封圈的不足。     

丁腈橡胶/酚醛树脂/受阻酚AO80阻尼橡胶贮存稳定性研究

在丁腈橡胶(NBR)中添加酚醛树脂(PR)和受阻酚AO80,制备共混橡胶,采用示差扫描量热(DSC),傅立叶红外光谱(FTIR),扫描电子显微镜(SEM)和粘弹谱仪(DMTA)等方法表征其结构,研究其阻尼机理.研究结果表明:在共混橡胶中,除NBR硫化交联网络外,还包含NBR/AO80的超分子氢键网络、NBR/PR的络合作用、AO80与PR分子间作用、AO80分子聚集体及在AO80相中的NBR分子等多种微观作用形式.复杂的分子作用形式使硫化胶分子间摩擦增大,提高了阻尼性能.但随贮存时间延长,AO80聚集结晶,造成硫化橡胶阻尼性能的不稳定.     

CMP加工过程中加工载荷对液膜厚度的影响分析

本文采用激光诱导荧光技术(LIF)来研究抛光参数对化学机械抛光加工区液膜厚度的影响.研究表明,抛光液膜厚度随着抛光载荷的增加而减少,减小的趋势随抛光载荷的提高而减缓.同时液膜厚度随着抛光速度的增加而变大.通过抛光参数的变化对抛光液液膜厚度影响的分析,为改善CMP加工工艺提供理论性的依据.     

聚碳酸酯SHPB系统测量泡沫铝合金动态压缩性能

为更加合理、有效地使用泡沫铝,了解其动态冲击下的力学性能是必要的。为提高泡沫材料分离式霍普金森压杆（SHPB）实验的有效性和精度,采用聚碳酸酯SHPB实验系统对泡沫铝合金进行了动态压缩实验,给出了不同冲击速度下的压缩应力 应变曲线,并研究了泡沫铝合金的动态压缩力学特性和变形机制。实验结果表明,高孔隙率的泡沫铝合金的应变率敏感性不强,其动态屈服强度可用静态压缩的实验结果代替。但本结论能否向其他泡沫铝推广,尚有待进一步研究。