Maximum Twist Research Articles

Measured and modelled static and dynamic axial trunk torsion during twisting in males and females

Study of the mechanics of trunk twisting is special interest given epidemiological evidence linking occupational twisting to increased incidence of low back pain. An anatomically detailed, three-dimensional model of the trunk (rib cage, pelvis, five lumbar vertebrae and 50 muscles), was used to predict maximum axial trunk torque. Predicted axial torques were compared with measured torques. Thirty-one (10 male and 21 female) subjects performed maximum effort isometric twisting exertions, at 0° of twist and ±30° of twist together with dynamic exertions, at 30° s −1 and 60° s −1. Females were able to generate approximately two-thirds of the torque of males (males, 97 Nm; females 60 Nm, isometric at 0°). When the trunk was prerotated to 30°, subjects were able to generate greater torque when the effort was toward the 0° position (approximately 105 Nm by males and 68 Nm by females). Experimental data indicated that velocity of rotation and amount of twist are important modulators of axial torque. Changes in muscle length were demonstrated to be minimal from model output as most muscle length changes during a twist from 0° to 30°, measured between the pelvis and the shoulder harness, were less than 1%, although some portions of the abdominal obliques underwent a length excursion of 5%. The small changes in the individual muscle force components that contribute to twist, i.e. the muscle unit vector about the axial twist axis and its moment arm that change as a function of twisted position, do not entirely account for the measured differences in torque, suggesting that additional mechanisms influence axial torque generation.

The history of diclofenac

The purpose in developing diclofenac sodium was to synthesize a nonsteroidal anti-inflammatory drug with high activity and outstanding tolerability. Factors considered were drug transport through biologic membranes, the atomic and spatial structure of the molecule, and the electronic structure. Based on analysis of other nonsteroidal anti-inflammatory drugs, it was postulated that an effective antirheumatic agent should have the following characteristics: an acidity constant between 4 and 5, a partition coefficient of approximately 10, and two aromatic rings twisted in relation to each other. The result was diclofenac sodium, which has an acidity constant of 4.0 and a partition coefficient of 13.4. The structural elements include a phenylacetic acid group, a secondary amino group, and a phenyl ring containing chlorine atoms, which cause maximum twisting of the ring. Experimental and clinical findings obtained to date have indicated that diclofenac sodium was synthesized on well-founded principles.

The history of diclofenac

The purpose in developing diclofenac sodium was to synthesize a nonsteroidal anti-inflammatory drug with high activity and outstanding tolerability. Factors considered were drug transport through biologic membranes, the atomic and spatial structure of the molecule, and the electronic structure. Based on analysis of other nonsteroidal anti-inflammatory drugs, it was postulated that an effective antirheumatic agent should have the following characteristics: an acidity constant between 4 and 5, a partition coefficient of approximately 10, and two aromatic rings twisted in relation to each other. The result was diclofenac sodium, which has an acidity constant of 4.0 and a partition coefficient of 13.4. The structural elements include a phenylacetic acid group, a secondary amino group, and a phenyl ring containing chlorine atoms, which cause maximum twisting of the ring. Experimental and clinical findings obtained to date have indicated that diclofenac sodium was synthesized on well-founded principles.

Effect of the moisture content of viscose textile yarns on their twist uniformity

To obtain viscose textile yarns with a maximum twist uniformity, it is advisable to carry out the twisting operation at a yarn moisture content equal to or greater than 10–12% by wt. Raising the moisture content of a yarn to 17% only slightly affects twist uniformity. Reducing the linear density of the elementary filaments raises the twist uniformity of a viscose complex yarn.

Crack deflection processes—I. Theory

A fracture mechanics approach has been used to predict fracture toughness increases due to crack deflection around second phase particles. The analysis is based on a determination of the initial tilt and the maximum twist of the crack front between particles, which provides the basis for evaluating the deflection-induced reduction in crack driving force. Features found to be important in determining the toughness increase include the volume fraction of second phase, the particle morphology and aspect ratio, and the distribution of interparticle spacing. Predictions are compared with expected surface area increases.

Creep of Pipes Under Axial Force and Twisting Moment

The load-deformational behavior of twisting of pipes in the presence of axial force is examined. Based on the small deformation theory, charts and curves, which relate the twisting moment, axial force, and twist rate per unit length, are presented for the design of pipes with creep. The accuracy of the results are demonstrated by comparing the maximum stress and twist rate due to pure tension of fairly heavy pipes, with that of more exact thick-walled cylinder solutions.

三子糸の幾何学的特性-I

The theory of geometry of the 3-ply cord developed in this paper is based on the assumption that the cylindrical strand in the cord has the form of a simple helix around the cord axis. The geometrical analysis yields a ratio of the helix radius to the ply radius, a/b, with varying helix angle of ply axis, θ, for defining the cross-sectional form of the ply in the cord. As a result, the sectional form of the ply in the cord cross-section can not be regarded as an ellipse in the range of the helix angle of the ply axis of over 30° up to 60°, (θm) maximum cord twist.

ALTERNATE TWISTING BY INTERMITTENT AIR-VORTEX

In the previous paper, it has been reported the twisting mechanism and the twist distributions caused by the air-jet false twister.In this paper it is shown that the filament yarn can be twisted by the new twister designed by using the air-jet false twister, in which the air can be supplied intermittently.Generally yarn twisting was thought to take place usually in the form of real twisting (especially in the case of spun yarn), however several new spinning methods (fasciated yarn by Du Pont., ST yarn by Repco Co. and etc.) have been developed recently to overcome the difficulty of speed limitation due to real yarn twisting.The apparatus in this paper can be used easily as one of the high speed methods for the twisting of fleece and the convergence of filaments.The twist distributions along the twisted yarn axis are discussed in the case of using one twister and two twisters, when the air was supplied in a form of step changes and intermittently. The results are as follows:1) The twist distribution at the step input of the air is more variable at the time of start than at stoppage.2) The intermittent supply of the air generates the alternate twists in the yarn, and the ratio of the lengths between the alternating points of the twist direction does not always agree with the ratio of the time of air supply to interruption.3) The twist number of the alternate twist varies in accordance with the ON-OFF ratio of the supplied air. There exists an optimum ON-OFF ratio which generates the maximum twist.4) In the plied yarn the twist appears more under the tensionless than under the tension of twisting process.

Twist Flow in Ring Spinning

A simple and easy method for measuring the twist density in the yarn between the roller-nip and thread-guide of a ring spinning frame has been compared with the high speed photography technique and has been shown to be reliable. Measurements using the method have brought out the influence of such factors as doff-stage, chase cycle, etc. on this twist density. It has been shown, for example, that there is, over the chase, a peri odic variation in the twist density—the maximum twist density is at the nose of the chase and is slightly more than or almost equal to the mechanical turns per inch, while the minimum is at the shoulder and is about two to three turns per inch less than the mechanical twist. The collected data show that while, in general, the twist density in the roller nip—thread guide yarn is determined by both the yarn tension and the balloon shape, the balloon shape becomes increasingly important with decreasing balloon height. Also, an increase in yarn tension, accompanied by a change in balloon shape, which renders the angle of yarn wrap less at the traveller and more at the thread guide, results in a reduction of the twist density in the roller nip—thread guide yarn or, at best, leaves it unaltered.

Variants of canonical formalism

Canonical formalism is presented in invariant notation as one of a family of solutions of the problem of finding infinite-dimensional subgroups of the group of all time-independent flows of points in a real n-dimensional space. When the problem is restricted to a local study with the flows restricted to such as are specified by a flow vector field with analytic components, and a geometry in the first-order neighborhood of each point specified by a real irreducible Lie group of n by n matrices is required to be preserved by the motions, then a limited number of classes of solutions appear (theorems of E. A. Ruh and Y. Matsushima). Ordinary canonical formalism is produced from one of these classes by an extra assumption of flatness. It is shown that, if the flatness assumption is replaced by one of maximum twist, no motions at all are possible.

高Cr-Niオーステナイト鋼の高温変形能

The “hot-twist ductility” of highly alloyed austenitic steels such as AISI type 309, 310 and 330 was studied. Effects of alloying elements, melting practices, and grain size of these steels on the “hot-twist value” at testing temperatures ranging from 1, 000 to 1, 300°C were mainly investigated by torsion testing at a rate of 200 rpm.Fully austenitic specimens showed twist value curves of a convex type at testing temperatures, while two-phase specimens had much lower twist values than the former, nearly constant through all testing temperatures. With the former specimens, a transcrystalline fracture was observed at temperatures lower than that showing maximum twist value, while an intercrystalline fracture was shown at temperatures higher than that.In the case of type 310 steel, the higher the carbon content of specimen, the lower was its twist value. On the other hand, the maximum twist value was obtained with 0.2% C specimen in the case of type 309 steel. This difference was attributed to the fact that the ductility of these steels depended upon the stability of austenitic structure.Besides, effects of Si, Ni, Cr, N and Nb contents on twist value were explained. Comparing vacuum-melted with air-melted specimens, the effect of melting atmosphere was not so clear than that of alloying elements. Addition of small quantity of Al improved hot-twist ductility, while addition of large amount of Al as well as B up to 0.01% in the form of Fe-B much impaired ductility.In the case of high-C steels, the increase of annealing temperature which resulted in grain-coarsening decreased the hot-twist value owing to the increase of solubility of C atoms, while no change of the hot-twist value were observed with very low-C steels. Therefore, it was concluded that grain size itself did not affect the hot ductility.

An Investigation of Mechanical Strength of Yarn or Cord Twisted with Other Kinds of Filaments

The object of this study is to discover the most effective law of blending and the maximum limitation on the mechanical strength of a blended yarn or cord composed of two kinds of continuous filaments. In the case of tensile rupture, the fibers making up a blended yarn resist the rupture most effectively if the mixing rate of the fibers of low extensibility is under 25% and the twist on the blended yarns is more than half the permissible maximum twist. In the case of flexing fatigue, an ideal blended cord is obtainable if the parameter of S-N diagrams and the mechanical model of the constituent fibers of the blended cord satisfy equation (27). The tensile strength or fatigue life of even the most effective blended yarn or cord is less than that of the mathematical mean of the constituent fibers. The amount of work (the degree of toughness) needed for the tensile rupture of the yarn or cord exceeds the mathematical mean of the constituent fibers.