Toshiyasu Kinari

Polyester "Shingosen" Fabrics Characterized by Dynamic Drape Coefficient with Swinging Motion

The static and dynamic drape behavior of polyester Shingosen fabrics is investigated using the new mechanical parameter of dynamic drapability, that is, the dynamic drape coefficient with swinging motion Dd. The Dd of the Peach Face fabric is small and that of the New Worsted fabric is large. On the other hand, there are almost no differences between each group of Shingosen fabrics in node numbers and conventional static drape coefficients. In classifying production characteristics, yam-processing fabrics show larger values of Dd than other fiber-production and fabric-finishing samples. In classifying fiber characteristics contractile fiber and ultra-fine fiber Shingosen fabrics show smaller values of Dd than irregular fiber fabrics.

Changes in the Static and Dynamic Drape Coefficients of Polyester Fabrics Through the Finishing Stages

Static and dynamic drape behaviors of polyester woven fabrics are s died through representative finishing stages using two sets of fabrics with different conditions of relaxation and weight reduction. The node number n, the revolving drape increase coefficient Dr, and the dynamic drape coefficient Dd increase through the finishing stages, especially with relaxation. The static drape coefficient D, and revolving drape coefficient at 200 rpm D 200 decrease through the finishing stages, especially with relaxation. These parameters do not change much after dyeing and raising. The effect of elaxation in a washer is stronger than in a jet-dyeing machine for these parameters. The e fect of weight reduction on D, and D 200 appears clearly: the former increases and the latter decreases with a higher ratio of weight reduction.

Defect-induced anisotropy in mechanical properties of nanocrystalline metals by molecular dynamics simulations

The influence of defects in nanograins, e.g. stacking faults and twinnings, on mechanical properties of nanocrystalline materials is studied by molecular dynamics simulations. Two types of many-body interatomic potential based on aluminium are adopted to investigate the influence of stacking fault energy on the deformation mechanism of nanocrystalline metals: one accurately reproduces the energy value of stacking faults for aluminium; the other underestimates the energy value for aluminium. Three different deformation processes are performed to nanocrystalline models with high or low stacking fault energy, and crystal slips occur in both models. In the case of the high stacking fault energy, crystal deformation occurs by perfect dislocations and no defects exist in the grains. Therefore, the strength almost recovers after relaxation. On the other hand, for low stacking fault energy, stacking faults remain through the grains after the crystal slips by partial dislocations. Consequently, these defects cause anisotropy in the mechanical properties of the simulated nanocrystalline metals.

Dislocation-Grain Boundary Interactions by the Quasicontinuum Method

The interactions between edge dislocations and the grain boundary have been studied by using quasicontinuum simulations. With an increase in the shear strain, dislocation pile-up is created and local stress concentration occurs at the head of the pile-up. The relationship between the stress concentration and the number of dislocations in the pile-up is discussed.

Mechanics of Disk-Type False Twisting Part I: Yarn Path and Friction Force on a Single Disk

False twisting by means of a friction disk unit is an efficient technology used worldwide to manufacture synthetic fiber yarns that are textured. This paper proposes a new theory to analyze the yam path and the friction force exerted on the running yarn over a single friction disk. We do not apply discrete methods, but treat the system in a continuous manner using three-dimensional vector analysis and differential geometry.

Collective grain deformation of nanocrystalline metals by molecular dynamics simulations

The collective grain movement of nanocrystalline metals and its temperature dependence are studied by using molecular dynamics simulations. First, a unit structure that consists of eight aluminium grains in the regular hexagonal shape with 5 nm grain size is prepared, and then an analysis model is made by arranging the same 144 unit structures in the two-dimensional periodicity. Thus the total number of grains is 1152. Various collective grain deformations occur at different temperatures under tensile loading. In the case of 100 K, shear bands formed by the collective grain deformation can be observed remarkably. On the other hand, in the case of 300 or 500 K, no remarkable inhomogeneous deformation such as shear bands occurs. This might be due to the different accommodation mechanism for geometrical misfits by local shear deformation at each different temperature. In order to investigate the effect of the collective grain deformation on the macro-scale mechanical properties, the stress–strain curve for the model with 144 unit structures and an averaged strain–stress curve for the 60 cases of a model with one unit structure are compared. Consequently, it is found that the inhomogeneous plastic deformation mode such as a shear band can influence the strength of nanocrystalline metals.

Mechanics of Disk-Type False Twisting Part II: Yarn Path and Yarn Inclination Angle in a Multiple-Disk Spindle Unit

A triple-stack multiple-disk spindle unit is used widely in actual draw texturing processes. In this kind of friction false twisting process, the angle of inclination (angle between yarn path and disk axis) is an important factor that determines yarn tension and twisting torque over the disk surface. This paper proposes a new theory that will give a more precise angle of inclination using differential geometry. The basic assumptions are that the disk profile is represented as an outer surface of a torus, and the yarn path over the disk surface forms a geodesic line. The angle of inclination is calculated by this theory in the actual range of the disk diameter, the radius of the disk edge, and the distance between two neighboring disk axes. The inclination angle obtained by this theory gives smaller values than the angles obtained by previous studies, but the experimental data agree best with the value calculated by this theory. We also explain how to calculate the entry angle (the angle of wrap) and the limiting value of the angle of wrap to guarantee smooth contact of the yarn with the disk periphery. The effect of the profile represented by the radius of the disk on the angle of inclination, and the angle of wrap is also investigated.

IMPACT TENSILE PROPERTIES OF SUPER FIBER YARNS

ABSTRACT A new impact tensile testing apparatus based on the one-dimensional elastic-stress-waves theory has been developed. It is mainly composed of an input bar to transmit load to the specimen and to measure dynamic elongation of the specimen, a pair of load cells to measure the load of the specimen and a striker energized by compressed air. It is designed to investigate dynamic mechanical properties of super fiber yarns, such as aramid fiber and carbon fiber that have small breaking elongation compared with most synthetic fibers. Using this apparatus and an universal testing machine, stress-strain curves of several kinds of aramid fiber yarns and a carbon fiber yarn are obtained at the strain rates ranging from 10-3/s to 103/s.

Atomic Simulations on the Grain Subdivision of a Crystalline Metal

The relationship between grain subdivision mechanisms of a crystalline metal and the strain gradient under severe plastic deformation is studied by using molecular dynamics simulations in quasi two dimensions. Two problems are simulated for single crystal models: (a) uniaxial tensile and compressive deformation and (b) localized shear deformation. In the case of uniaxial deformation, a large number of dislocation pairs with opposite Burgers vectors are generated under deformation, but most dislocations are vanished due to pair annihilation under relaxation. Therefore, no dislocation boundary can be formed. On the other hand, in case of localized shear deformation with large strain gradient, dislocation boundaries are formed between undeformed and deformed regions. These dislocations can be regarded as geometrically necessary dislocations. Consequently, the importance of the strain gradient to make grain boundaries under plastic deformation can be confirmed by atomic simulations.

Development of an Auto-Doffer for Covering Machines. Part 7. Success Improvement and Air-Power Saving on the Yarn Drawing-in Based on Analysis of Yarn Running Behavior.

It is important to improve the rates of success on drawing-in operation of the auto-doffer for the covering machine. Saving air consumption for drawing-in operation can bring about the total energy saving on the doffing operations. In this report, various conditions on the drawing-in operations are investigated in order to improve its success rates and to reduce its air consumption. Experiments were performed with changing supplied pressures for the injector and for the ejector, yarn feed speeds and their working time. Acting forces such as the air drag on a spandex yarn were measured and the behaviors of a running yarn were observed during the drawing-in operations. Results obtained are as follows : (1) Each yarn has the unique drawing-in condition in order to improve the rate of success. The higher pressure does not always bring about the higher rate of success for the injector, but for the ejector within the limits of these experiments.(2) The fine tuning in the working time of the injector or the ejector is not so significant because the yarn in the hollow spindle is extended cyclically by the turbulent air flow. The governing factor for the successful drawing-in operation is the yarn capture at the suction entrance. Yarn feed tuning by means of some pooling devices is prefer to the yarn feed rollers.(3) The velocity of air jet from subsonic to sonic region is the most efficient for drawing-in operation. Further pressure causes the air flow disturbance that may induce the yarn troubles.