在线振动监测与故障诊断的一种新途径

文中由应力强度因子导出含裂纹单元的刚度矩阵,从而提出了一种有限元法.将该法用于单边裂纹悬臂梁,计算了应变响应.用时域法识别了模态参数,并考虑了裂纹闭合的影响.分析了应变响应对故障的敏感度,计算结果表明,应变响应相对于位移响应而言,对故障更敏感.本文还提出了一种判别函数,该函数对于损伤检测,比现有几种判别函数更有效.最后,给出了一种在线振动监测与故障诊断新方法.     

A critical evaluation of numerical solutions to the ‘Benchmark’ surface-flaw problem

Recent precise, elastic numerical solutions to a surface flaw in a plate under remote tension and bending have been compared to arrive at a ‘best estimate’ of the stress-intensity-factor variation along the flaw border. The geometry of the semielliptical surface flaw examined had a depth to length ratio of 0.25 (a/2c=0.25) and 25- and 75-percent relative crack depths (a/t=0.25, 0.75). The analysis methods used to determine the solutions included: Schwarz alternating technique, finite-element method and boundary-integral-equation method. The derived best-estimate curve for the stress-intensity factor is believed within 3 percent of the actual value along the crack front. The best-estimate curve compared well with scarce experimental data (±10 percent). The difference between the best-estimate curve and experiment is thought largely due to differences in geometry and Poisson's ratio.     

气缸垫对机体受力和缸套变形影响的实验研究

某四缸柴油机在试制中出现机体裂纹现象，为保证内燃机正常工作，机体裂纹问题急待处理．应用力学理论对此进行分析，得出机体裂纹是由机体受力不均匀引起的结论．同时采用实验应力分析方法，对两种四缸柴油机机体进行了对比实验研究，在实验中发现了缸垫对机体受力和缸套变形的影响，从而提出了一种有效的改进方法，使机体的应力有明显下降，并不再出现裂纹，也未出现漏油、漏气和活塞拉缸等不良现象，大大提高了产品可靠性．     

SYNTHESIS AND CHARACTERIZATION OF SURFACE-HYPERBRANCHED MAGNETITE NANOPARTICLE FOR BOVINE SERUM ALBUMIN IMMOBILIZATION

A hyperbranched polyamidoamine polymer was synthesized on the surface of magnetite nanoparticles to enhance bovine serum albumin (BSA) immobilization efficiency. The amount of immobilized bovine serum albumin (BSA) on the surface-hyperbranched magnetite nanoparticle was up to 2.5 times as much as that of magnetite nanoparticle modified with only amino silane.     

坡面流及土壤侵蚀动力学（II）——————土壤侵蚀

介绍了坡面土壤侵蚀的基本特征和主要类型, 综述了坡面土壤侵蚀动力学过程和预报模型等方面的研究进展, 包括土壤表层结皮、雨滴溅蚀、片流侵蚀、细沟侵蚀、坡面流输沙、土壤侵蚀界限坡度, 以及土壤侵蚀预报模型等. 并简要讨论了土壤侵蚀动力学研究的发展趋势.     

双周期圆截面纤维复合材料平面问题的解析法

结合双准周期Riemann边值问题理论与Eshelby等效夹杂原理，为双周期圆截面纤维复合材 料平面问题发展了一个实用有效的解析方法，获得了问题的全场级数解并与有限元结果进行 了比较. 该方法为非均匀材料的力学性质分析和复合材料等新材料的微结构设计提供了 一个有效的计算工具，也可用来评估有限元等数值与近似方法的精度.     

SURFACE MODIFICATION AND DISPERSION OF NANODIAMOND IN CLEAN OIL

The effect of different kinds of surfactants on the size distribution of nanodiamond particles in clean oil was studied.Results show that the dispersing stability of nanodiamond modified with surfactangts YS-1 and SB-18 simulta-neously is much better than those modified with either of them because of synergism of the surfactangts.And the particle size distribution in the system can be improved remarkably after the adoption of hyperdispersants such as SA-E and SA-F.Anchoring groups of those hyperdispersants can be bonded with the particle surface by chemical and/or hydrogen bonding and their soluble chains are well compatible with the dispersion media.As a result,the particles are uniformly distrbuted in the system owing to the steric stabilization.A very stable clean-oil based nanodiamond suspension with an average particle size of around 53.2 nm was prepared.     

相变材料接触熔化的研究

对有关相变材料接触熔化的研究成果进行了全面的综述, 内容包括:封闭空间的接 触熔化、围绕热源的接触熔化、滑动接触熔化、滚动接触熔化、冰的压力熔化、接 触熔化的量级分析与修正、由液体边界层内的热扩散引起的熔化、不连续接触点上 熔化与润滑、固体内部传热的影响、玻璃的软化与接触熔化.     

振动翼型和襟翼的绕流特性研究

用数值模拟手段详细地研究了振动翼型和襟翼的绕流问题,数值模拟的出发方程为Euler和N-S方程,格式为Bcam-Warming格式的改进型。数值实验主要针对流场的二大特性进行的,即振动对激波的影响和振动对分离的抑制作用,结果表明:(1)随翼型或襟翼的振动激波强度和位置也相应地变化但这一变化滞后于攻角的变化;(2)振幅加大激波强度的变化和激波运动范围也加大;(3)振动频率越高对激波的影响反而较低频时要小;(4)流动条件的不同可使升力回线的走向发生变化;(5)振动对分离有明显的抑制作用。     

镍钛记忆合金自补偿磨粒磨损性能研究

研究了高临界温度镍钛记忆合金一维自补偿磨粒磨损特性.结果表明,在一定温度下,镍钛记忆合金在摩擦过程中具有形状恢复能力,从而产生一维磨损自补偿作用.超弹状态镍钛记忆合金具有热弹性马氏体相变、高阻尼、应力感生马氏体、超弹性、高应变硬化指数和时效弥散析出强化等特性,这使得硬度较低的镍钛合金的耐磨性能远优于硬度较高的淬火45#钢.利用超弹状态镍钛记忆合金的磨损自补偿作用可望开发出新型抗磨形状记忆合金产品.