19—SELF-TWIST SPINNING: PROTOTYPE DEVELOPMENT

The development of self-twist spinning as a system of forming staple-fibre yarns has been dependent on the use of simultaneously oscillating and rotating rubber-covered rollers for the insertion of alternating twist. Design aspects of the mounting and driving of such rollers are described, and some parameters affecting the way in which they twist staple-fibre strands are investigated.     

Some Remarks on the Removal of Adhered Particles by Oscillating Air Flows

On the background of technical concepts for the removal of particles from moving textiles by linear as well as oscillating air flows, some theoretical remarks on particle adhesion forces and the hydrodynamical and acoustic forces acting on particles are given. As the main removal forces in linear air flows, drag and lift are taken into consideration and analytical expression derived from the Bernoulli equation. For a hypothetical example of particles in the size range from below 0.5 to 7 μm on a cotton fiber, hydrodynamic forces are compared to van der Waals interaction, electrostatic forces and capillary forces. In this work, a special focus is placed on the application of high-frequency oscillating air flows which results in a direct coupling of ultrasound to the particles. The theoretical calculation of resulting forces showed that the detachment threshold is determined not only by sound intensity level, but also by the frequency of the ultrasonic wave. If capillary forces act, the coupling of ultrasound alone does not suffice to detach particles within the considered size range.     

Combined effects of surface roughness and couple stresses on static and dynamic behaviour of squeeze film lubrication of porous journal bearings

Abstract

The combined effects of surface roughness and the couple stresses on the static and dynamic characteristics of squeeze film lubrication in porous journal bearings with no journal rotation are theoretically studied. The Stokes couple stress fluid model is considered to model the lubricants with additives. The surface roughness on the porous journal bearing is mathematically modelled by a random variable with non-zero mean, variance and skewness. The generalised stochastic Reynolds type equation is derived for the problem under consideration. The applied load is considered as a sinusoidal function of time to simulate the bearings operating under cyclic loads. The closed form expressions for the bearing characteristics are obtained for the short porous journal bearings. It is observed that the negatively skewed surface roughness and couple stresses improve the performance of the porous journal bearings as compared to the smooth journal bearings with Newtonian lubricants. However, the presence of positively skewed surface roughness on the bearing surface affects its performance.     

自润滑轴承的特性及其在水电站水轮机中的应用

本介绍了日本OILS公司OILLESSBEARINGS自润＃500P及德国GLACLER公司DEVA－BM产品的金相组织、自润滑特性，阐述了它们在水力发电设备上的应用，描述了它们的实际装配安装方法，介绍了使用寿命计算方法进行寿命计算。     

25—INCREASING THE RATES OF FABRIC PRODUCTION OF WEFT-KNITTING MACHINERY: PART III: MEASUREMENT OF THE NEEDLE FORCES

When information is required about the forces acting on the needles in different cam systems, it is clearly more desirable to measure these forces directly than to measure the over-all machine torque.

This paper describes a method for measuring the needle forces directly, and an examination is made of some of the information obtained from the force-measuring device used.     

两种滑动轴承的应用和比较

通过对液体静压和液体动静压两种轴承的理论分析和实际应用比较，说明了液体动静压滑动轴承的优点。