Strain Measurement on Composites: Effects due to Strain Gauge Misalignment

Abstract: The present work analyses the errors affecting the strains measured by misaligned strain gauges installed on orthotropic‐composite laminae. Various analytical relationships are derived showing that, besides the fibre and strain gauge orientations, the misalignment error in unidirectional off‐axis orthotropic composite samples depends also on the lamina stiffness properties (E₁, E₂, ν₁₂, G₁₂). If the fibres are aligned with the loading axis, it is found that the higher Poisson's ratio ν₁₂ is the only elastic property influencing the misalignment error. Experimental results are shown confirming the theoretical predictions.     

对数滚子偏斜时的弹流润滑研究

针对工程上滚子摩擦副偏斜的问题,研究了对数滚子偏斜时的弹流润滑特性。研究表明,偏斜后接触区出现大端和小端,大端处的压力增大而膜厚减小,小端处的压力减小而膜厚增大,并且这一趋势随着偏斜角的增大而趋于明显。偏斜现象总体上将恶化滚子的润滑状态。在同样的偏斜角下,滚子长径比越大,偏斜的影响越显著。适当增大对数滚子的凸度量可减弱偏斜现象的影响,因此,对于易发生偏斜的工况,设计时可适当增大滚子凸度量以补偿偏斜因素的影响。     

栅对准误差对双栅MO SFET 性能影响的分析

对栅MOSFET是一种非常有发展前途的新型器件，它具有跨导高、亚阈值特性优异、短沟道特性好等优点，但是目前自对准的双栅MOSFET的工艺制作相当困难。本文中分析了双栅MOSFET的正、背面栅存在对准误差时，对器件的表态及动态特性的影响，并提出了一种改善这种影响的方法。     

光纤与波导器件的联接技术

文中就如何增大耦合效率和工艺容差的问题作了具体的分析,在此基础上,评述了现 有的几种能够获得较低插入损耗的光纤和波导的固定联接技术。     

Compressive strength of unidirectional fiber composites with matrix non-linearity

A study has been made of the effect of fiber misalignment and non-linear behavior of the matrix on fiber microbuckling and the compressive strength of a unidirectional fiber composite. The initial fiber misalignment constituted the combined axial and shear stress state in the matrix, and the state of stress just prior to the buckling was considered to be the initial state of stress in bifurcation analysis. The expression for the critical microbuckling stress was found to be the same as that for the elastic shear-mode microbuckling stress except that the matrix elastic shear modulus was replaced by the matrix elastic-plastic shear modulus. Incremental theory of plasticity and deformation theory of plasticity were used to model the matrix non-linearity. The analysis results showed reasonable correlation with available experimental data for AS4/3501-6 and AS4/PEEK graphite composites with 2° to 4° range of initial fiber misalignment.     

带钢连续处理机组中带钢纠偏设备设计与应用研究

对纠偏检测、执行原理进行研究,给出了纠偏设备执行纠偏动作时,带钢由运动扭曲而对其边缘带来的拉伸应力的校核方法,提出了带钢纠偏执行装置设计的重点和难点,为带钢处理机组的纠偏设备设计提供理论和实践两方面的参考和借鉴.     

机、泵轴对中的评估与调整

轴系不对中是导致机械设备故障的主要原因。电机与泵的轴不对中又可以分为3种情况：平行不对中、偏角不对中和平行偏角不对中。文中利用机械故障诊断的方法,提取联轴器的径向振动信号,对信号进行处理和分析,以判断电机与泵轴对中的情况,提供对中调整的依据。利用频谱仪提取的频谱图,对照调整良好的频谱图,可以评估轴系对中的情况。     

计及轴颈轴向运动的径向滑动轴承润滑分析

以轴-径向滑动轴承系统为研究对象,综合考虑轴颈轴向运动和倾斜,建立了倾斜轴颈的轴承的流体动力润滑模型,采用有限差分法求解Reynolds方程,分析了不同的轴颈倾角、转速、偏心率和轴承间隙下的轴颈轴向运动对倾斜轴颈的轴承润滑性能的影响规律。结果表明：轴颈轴向运动对倾斜轴颈滑动轴承润滑特性影响显著,且影响程度与轴颈倾角和转速有直接的关系,倾角越大,对轴承润滑性能的影响越大,转速越低,对轴承润滑性能的影响越显著;轴承间隙越小,对轴承润滑性能的影响越大。     

Misalignment effects on steady‐state and dynamic behaviour of compliant journal bearings lubricated with couple stress fluids

This work concerns the steady‐state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro‐continuum theory, a modified form of the Reynolds equation is derived. The displacement field at the fluid film–bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load‐carrying capacity, power loss, side leakage flow, misalignment moment, critical mass and whirl frequency are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Mechanical degradation of proton exchange membrane during assembly and running processes in proton exchange membrane fuel cells with metallic bipolar plates

The mechanical degradation of the proton exchange membrane (PEM) is one of the main aspects affecting the lifetime of proton exchange membrane fuel cells (PEMFCs). It was observed in our previous study that the stress/strain distribution in the PEM of fuel cells with metallic bipolar plates (BPPs) is more complex, owing to manufacturing and assembly errors of the BPPs. The present study further concentrates on the stress/strain evolution in the membrane of fuel cells throughout the assembly and running processes by a finite element model. In membranes at the joint area between the gasket and gas diffusion layers, a serious stress concentration aggravated as the misalignment displacement increases. As for the membrane in reaction area, the plastic strain reaches highest level at the center of the groove after hygrothermal loading. The maximum stress is mainly relevant to the temperature and humidity and has little concern with the misalignment. The model and results of this study offer guidance regarding the design of PEMFC. Owing to the stress concentration, an additional protection should be set in the joint area, and the assembly error should be limited within 0.05 mm.