Performance analysis of an integrated tangential microfilter‐fermenter

A specially designed bioreactor including an axial microfilter for cell retention was evaluated for continuous‐flow operation with selected liquid media as controls and in aerobic cultivations of Saccharomyces yeasts. In the initial tests, performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time and microfilter type (i.e. membrane or porous metal). The bioreactor did not perform satisfactorily when viscous extracellular polymer was present in the liquid. In the continuous‐flow culture enabling cell retention, Saccharomyces cerevisiae yeast cell concentrations were enhanced by as much as 16‐fold over ordinary batch growth. Concomitant filtration rates were stable over operating times of up to 130 h and hence were independent of the cell concentration. The maximum steady‐state flux was enhanced at rotational speeds up to 400‐700 rpm ranging from 22 to 42 L m^?2 h^?1. Higher rotation rates offered no further improvements. The maximum stabilized flux was independent of operating pressure. Pressure increases caused momentary flux improvements, which rapidly declined and eventually restabilized. Copyright © 2006 Society of Chemical Industry     

JT9D—7R4G2型发动机八级压气机盘及叶片失效原因分析

通过对失效的第八级压气机盘和叶片观察和金相分析，探讨了该失效件断裂的原因。结果表明，微动磨损引起疲劳断裂。     

WJ5AI发动机中央传动锥齿轮组件故障分析及改进措施

通过对ＷＪ５ＡＩ发动机中央传动锥齿轮组件故障进行调查、分析，阐明了原中央传动锥齿轮组件结构设计存在不安全因素。中央传动锥齿轮与轴的配合紧度小，圆柱销在变化载荷作用下传递扭矩，与其孔的配合表面产生微动磨损，微动磨损进一步发展造成了中央传动锥齿轮组件传扭失效。     

2号初轧机轧辊锯齿型磨损产生原因及机理分析

宝钢条钢厂2号初轧机轧辊的锯齿型磨损对辊耗、钢坯质量有一定的影响。本文试分析了该锯齿型磨损的产生原因及产生机理，并在实践中进行了验证。     

Mechanical and experimental investigation on nuclear fuel fretting

A mechanical approach to the nuclear fuel fretting problem is studied in this paper to find a possible and efficient way of a wear restraint. Two different contours of the spacer grid spring and dimple were developed to increase the contact area. Fretting wear experiments were carried out for the developed springs and tube specimens. Contact forces of 10 and 30 N, and slip displacements of 50–100 μm were applied under the environment of air as well as water at room temperature. Wear scars on the rods were examined to observe the effect of the mechanical approach on the wear. Especially, the influence of a contour deviation which occurred during fabrication and the wear particle accumulation in the clearance region were investigated in detail. It was found that the contact shape influenced the feature and the behavior of the length, width and volumetric shape of the wear. For the model of fuel fretting wear, equivalent depth (D_e) is suggested as a new parameter that can represent the wear severity.     

Wear analysis of Cu–Al coating on Ti–6Al–4V substrate under fretting condition

Fretting behavior of Cu–Al coating on Ti–6Al–4V substrate was investigated with and without fatigue load. Soft and rough Cu–Al coating resulted in abrasive wear and a large amount of debris remained at the contact surface, which caused an increase in tangential force during the fretting test under gross slip condition. Fretting in the partial slip condition also showed the wear of coating. To characterize wear, dissipated energies during fretting were calculated from fretting loops and wear volumes were obtained from worn surface profiles. Energy approach of wear analysis showed a linear relationship between wear volume and accumulated dissipated energy. This relationship was independent of fatigue loading condition and extended from partial slip to gross slip regimes. As an alternate but simple approach for wear analysis, accumulated relative displacement range was correlated with the wear volume. This also resulted in a linear relationship as in the case of accumulated dissipated energy suggesting that the accumulated relative displacement range can be used as an alternative parameter for dissipated energy to characterize the wear. When the maximum wear depth was equal to the thickness of Cu–Al coating, harder Ti–6Al–4V substrate inhibited further increase in wear depth. Only when a considerable energy was supplied through a large value of the applied displacement, wear in the substrate material could occur beyond the thickness of coating.     

Theoretical Substantiation of the Slip Index Approach to Fretting

A theoretical basis is presented for a previous fully empirical development of the unified approach to fretting that was based on a new similarity criterion termed slip index. It is shown that the slip index can be analytically derived from any friction loop geometry and hence, can be used for the characterization of any fretting system.     

切向极化同轴压电陶瓷圆片堆的扭转振动研究

利用压电陶瓷的压电及运动方程。研究了切向极化压电陶瓷细棒及同轴压电陶瓷堆的扭转振动。推出了单一压电陶瓷细棒扭转振动的机电等效图及其输入电阻抗。并得出了其频率方程。在此基础上，利用四端网络理论，研究了切向极化同轴压电陶瓷圆片堆的扭转振动特性，并得出了其网络方程及机电等效图。文中还给出了截面扭转系数以及压电陶瓷细棒扭转振动的机电耦合系数等概念。     

A friction energy approach to quantifying lubrication under fretting sliding

The problem of a proper lubrication under low‐speed small oscillatory movement can be a decisive factor for the reliability of various components. There is a need to characterise the lubricious behaviour of the interface under oil‐bath fretting wear conditions for ball bearing applications. Fast and reliable methods to quantify this behaviour for broad range of mechanical conditions are proposed and validated. Pure sliding reciprocation induces mixed lubrication mode. It was found that transient film profiles depend on the non‐Newtonian response of the oils and the type of motion. Running‐in period has a crucial importance for the tribofilm formation, and is a result of the interplay of the oil‐sliding surfaces interface and is directly connected with the total energy dissipated from the contact region. The stability of structured tribofilm in steady‐state period relies on the balance between the competitive processes: replenishment of the oil to the contact and ejection of the oil pending the oscillatory movement. The phenomenon of starvation was observed when the system was moved away from dynamical equilibrium and the growth of the dissipated energy was spotted. A proposed methodology provides the evaluation of the lubrication properties of the oil in a quantitative way. Copyright © 2010 John Wiley & Sons, Ltd.     

季节性冻土环境下混凝土短桩基础抗冻拔研究

结合寒冷地区某公园人工湖船台工程,通过现场试验,确定船台桩基切向冻胀力作用下的摩阻力值和上拔位移.对船台桩基采用刚性套筒或柔性套筒的抗冻拔方案建立试验船台,并和现场不采用抗冻拔措施的船台比较,发现采用加套筒方案,试验船台在寒期内产生的位移平均值为2-3mm,较自然冻拔船台位移小90%.考虑精密水准测量精度±2mm,船台基本上没有冻拔位移,证明抗冻拔措施成功、有效.