An experimental investigation of yarn tension in simulated ring spinning

Yarn tension is a key factor that affects the efficiency of a ring spinning system. In this paper, a specially constructed rig, which can rotate a yarn at a high speed without inserting any real twist into the yarn, was used to simulate a ring spinning process. Yarn tension was measured at the guide-eye during the simulated spinning of different yarns at various balloon heights and with varying yarn length in the balloon. The effect of balloon shape, yarn hairiness and thickness, and yarn rotating speed, on the measured yarn tension, was examined. The results indicate that the collapse of balloon shape from single loop to double loop, or from double loop to triple etc, lead to sudden reduction in yarn tension. Under otherwise identical conditions, a longer length of yarn in the balloon gives a lower yarn tension at the guide-eye. In addition, thicker yarns and/or more hairy yarns generate a higher tension in the yarn, due to the increased air drag acting on the thicker or more hairy yarns.

Application of bending under tension test to determine the effect of tool radius and the contact pressure on the coefficient of friction in sheet metal forming

To quantify the frictional behaviour in sheet forming operations, several laboratory experiments which simulate the real forming conditions are performed. The Bending Under Tension Test is one such experiment which is often used to represent the frictional flow of sheet material around a die or a punch radius. Different mathematical representations are used to determine the coefficient of friction in the Bending Under Tension Test. In general the change in the strip thickness in passing over the die radius is neglected and the radius of curvature to thickness ratio is assumed to be constant in these equations. However, the effect of roller radius, sheet thickness and the surface pressure are also omitted in some of these equations. This work quantitatively determined the effect of roller radius and the tooling pressure on the coefficient of friction. The Bending Under Tension Test was performed using rollers with different radii and also lubricants with different properties. The tool radii were found to have a direct influence in the contact pressure. The effect of roller radius on friction was considerable and it was observed that there is a clear relationship between the contact pressure and the coefficient of friction.

Recent studies on yarn tension and energy consumption in ring spinning

High energy consumption remains a key challenge for the widely used ring spinning system. Tackling this challenge requires a full understanding of the various factors that contribute to yarn tension and energy consumption during ring spinning. In this paper, we report our recent experimental and theoretical research on air drag, yarn tension and energy consumption in ring spinning. A specially constructed rig was used to simulate the ring spinning process; and yarn tension at the guide-eye was measured for different yarns under different conditions. The effect of yarn hairiness on the air drag acting on a rotating yarn package and on a ballooning yarn was examined. Models of the power requirements for overcoming the air drag, increasing the kinetic energy of the yarn package (bobbin and wound yarn) and overcoming the yarn wind-on tension were developed. The ratio of energy-consumption to yarn-production over a full yarn package was discussed. A program to simulate yarn winding in ring spinning was implemented, which can generate the balloon shape and predict yarn tension under a given spinning condition. The simulation results were verified with experimental results obtained from spinning cotton and wool yarns.

Twinning and the ductility of magnesium alloys Part I: “Tension” twins

Magnesium and its alloys do not in general undergo the same extended range of plasticity as their competitor structural metals. The present work is part I of a study that examines some of the roles deformation twinning might play in the phenomenon. A series of tensile test results are reported for the common wrought alloy AZ31. These data are employed in conjunction with a simple constitutive model to argue that View the MathML source twinning (which gives extension along the c-axis) can increase the uniform elongation in tensile tests. This effect appears to be similar to that seen in Ti, Zr and Cu–Si and in the so called TWIP phenomenon in steel.

Influence of low-strain deformation characteristics of high strength sheet steel on curl and springback in bend-under-tension tests

The influence of low-strain deformation behavior on curl and springback in advanced high strength steels (AHSS) was assessed using a bend-under-tension test. The effect of yielding behavior on curl and springback was examined by heat-treating two dual-phase steels to induce yield point elongation, while keeping a relatively constant tensile strength and a constant sheet thickness. A dual-phase and TRIP steel with similar initial thickness and tensile strengths were also examined to investigate the effect of work-hardening on curl and springback. It is shown that while current understanding limits prediction of curl and springback in bending under tension using only the initial sheet thickness and tensile strength, both the yielding and work-hardening behavior can affect the results. Explanations for these effects are proposed in terms of the discontinuous yielding and flow stress in the materials.

Investigation of fibre tension and fibre breakage in siumulated fibre opening processes

To reveal the mechanism of fibre damage and breakage in the fibre opening processes, the fibre tension during the interaction between a fibre and a pinned beater has been investigated. Details of the interacting force variations and incident of fibre breakage have been closely examined. Many factors which influence the fibre/pin interacting force have been elucidated. The results highlight the causes of fibre damage and breakage by fibre/pin interactions.

Slip during tension testing of Mg-3A1-1Zn sheet

The activation of slip and twinning deformation modes in Mg-3Al-1Zn alloy was investigated by means of both in-situ and ex-situ methods at ambient temperature using electron back scattering diffraction (EBSD). The results confirm the importance of non-basal slip and c-axis compression double twinning. During tensile deformation of rolled sheet, 63% of the observed slip traces were ascribed to prismatic slip, 33% to basal slip and 4% to <c+a> slip. Prismatic slip was frequently observed in grain interiors. The density of twinning was quantified in samples tested along transverse, extrusion and rolling directions at failure. The values in the range of 0.02-0.18 twins per square micron were found depending on sample orientation. The results show the effect of twinning on failure.

Characteristics of the contraction twins formed close to the fracture surface in Mg-3A1-1Zn alloy deformed in tension

Characteristics of the “contraction” twins, formed close to the fracture surface in Mg–3Al–1Zn alloy deformed in tension approximately perpendicular to the grain c-axes, are investigated using transmission electron microscopy. The grain c-axis contractions were largely accommodated by {1011}-{1012} source double-twins in a variant characterized by 38° ⟨1210⟩ source twin/matrix misorientation in conjunction with dislocation slip. A possible interpretation of the observed preference for this variant formation is given and some crystal plasticity modelling is performed to elucidate the matter.

Emulsions and microcapsules with substances having low interfacial tension, methods of making and using thereof

Disclosed are emulsions and microcapsules that comprise one or more substances with a low interfacial tension. Methods of making the emulsions and microcapsules as well as methods of using them are also disclosed. In some embodiments microbial oil is used. In some embodiments marine oil is used. In some embodiments the emulsion has a pH of greater than 6,0. In some embodiments the emulsion has a pH of less than 5,0.

Schools as sites of race relations and intercultural tension

Australia’s education system endeavours to provide an environment in which students can learn in a safe and comfortable manner, free of fear of verbal or physical abuse. However, for many schools, the ability to create this safe environment has been undermined by a recent rise in society-wide intercultural tensions that inevitably permeate the school boundary. Empirical data from a national project about racism among Australian youth provides evidence that these intercultural tensions are generating an unsettling level of verbal, and in some cases, physical abuse in Australian secondary schools. These project findings inform the discussion presented in this paper that schools, as sites of intercultural relations, reflect wider societal attitudes. Nevertheless, this paper also contends that schools as microcosms of social realities have the potential to change social attitudes gradually, including those about diversity, culture and race. To do so, schools need to be supported by teacher education programs which explore the ways in which issues of race, culture and diversity can be incorporated in the content choice in school curriculum. This will influence positively the way in which graduating teachers approach diversity and inter-cultural tensions within their own classrooms and the wider school.

The effect of skin passing on the material behavior of metal strip in pure bending and tension

The metal strip used in roll forming has often been preprocessed by (tension or roller) leveling or by skin-pass rolling, and as a consequence, may contain residual stresses. These stresses are not well observed by the tensile test, but could have a significant effect on the bending and springback behavior. With the advent of improved process design techniques for roll forming, including advanced finite element techniques, the need for precise material property data has become important. The major deformation mode of roll forming is that of bending combined with unloading and reverse bending, and hence property data derived from bend tests could be more relevant than that from tensile testing.

This work presents a numerical study on the effect of skin passing on the material behavior of stainless steel strip in pure bending and tension. A two dimensional (2-D) numerical model was developed using Abaqus Explicit to analyze the affect of skin passing on the residual stress profile across a section for various working conditions. The deformed meshes and their final stress fields were then imported as pre-defined fields into Abaqus Standard, and the post-skin passing material behavior in pure bending was determined. The results show that a residual stress profile is introduced into the steel strip during skin passing, and that its shape and stress level depend on the overall thickness reduction as well as the number of rolling passes used in the skin passing process. The material behavior in bending and the amount of springback changed significantly depending on the skin pass condition.