Tension Distribution Research Articles

Innovative Solution for Reducing Yarns Hairiness on Ring Spinning Machines

ABSTRACT Yarn’s hairiness represents a continuous challenge for spinning technologies. To keep this aspect under control, an almost perfect combination between the construction and performance of the machines, the control of the technological processes through appropriate settings, and the experience of the producers are required. As a consequence, the researchers were preoccupied to adapt or modify the ring frame to produce yarns with a lower degree of hairiness. Spinning triangles as a very demanding area exert a crucial impact both on the distribution of fiber tension and their spatial location in the staple yarn structure. Our study encompasses yarn hairiness reduction employing a device composed of two bars. Various combinations of spindle speeds and contact angles between yarns and bars were tested to examine their effects on yarn hairiness. The study was completed with the optimization of technological parameters using a central, composite, rotating program with two independent variables (spindle speed and contact angle) to establish mathematical models and optimize technological parameters for the reduction of hairiness. The effectiveness and efficiency of this device consist of the easy execution and installation on the existing machines in spinning mills without any constructive adjustments and additional energy consumption.

Distributions of tension and torsion in a threaded connection

Threaded connection is a common structure in engineering applications, and its load distribution plays a critical role on the static and dynamic performances of the system. Although Sopwith (1948) studied the tension distribution along a thread helix, a model that includes the tension and torsion distributions in threaded connections is still missing. In this paper, we establish a comprehensive model which takes tension–torsion coupling into consideration for thread connection for the first time. In the proposed model, the bolt and nut are considered as two linearly elastic bodies with a tension–torsion coupling deformation, and deformation of the thread is calculated by the modified theory of the trapezoidal cantilever beam model. Based on the compatibility condition of these deformations, tension–torsion coupling equilibrium equations for the threaded connection can be built up. Our theoretical analysis shows that the proposed model agrees with the Sopwith’s theory when the lead angle of the threaded connections is sufficiently small. However, the torque neglected by the Sopwith’s theory must be taken into account in the cases of threaded connections with large lead angles. In addition, we perform a three-dimensional finite element analysis to demonstrate the validity of the proposed model. Finally, influence of geometrical and material parameters on load distribution is investigated. The finding of this work may provide a new insight into the fastening and anti-loosening design for threaded connections.

Overall Design of Multi-module Offshore Floating Bridge and a Method for Random Analysis of Anchor Tension

This paper proposes a multi-module floating bridge design for offshore applications and establishes a coupled motion response analysis method for the anchoring system of the floating bridge. Time-domain coupled analysis is performed under the combined effects of wind, wave, and current loads, resulting in the maximum tension of the anchor chain in random waves. Using the typical island and reef sea area of Zhoushan, China as an example, the randomness of waves is considered, and a random sampling method is adopted. The main configuration, connection structure, and mooring system design schemes are presented, and the maximum tension of the anchoring system is numerically calculated and analyzed. The random distribution of the maximum anchor chain tension is obtained, the goodness-of-fit test is conducted for the fitting results, and the main degree-of-freedom motion response is analyzed under different exceedance probabilities. The results show that the multi-module offshore floating bridge meets the design requirements, and the statistical characteristics of the maximum tension of the anchor chain under random waves conform to the Gumbel distribution. The mode of the random distribution of the maximum anchor chain tension increases by 7.65% when fully loaded compared to the unloaded condition. In different exceedance probability scenarios, there are significant differences in the maximum tension of the anchor chain and the motion response of the main degrees of freedom of the floating bridge.

Vibration response analysis technique for elevator wire rope

Wire rope is an element often used in transportation infrastructure and systems such as bridges, elevators, ropeways, funiculars and so on. Generally, wire ropes require a high level of safety because they suspend heavy and important components such as roadways in bridges, cages and cabins in elevators, ropeways and funiculars. In addition to dead loads like roadways, wire ropes are subjected to dynamic loads caused by earthquakes, wind and moving cars, etc. Therefore, it is important to accurately simulate the dynamic response of wire ropes to dynamic loads to ensure safety of wire ropes. This paper deals with techniques for vibration response analyses of wire ropes. Techniques in this paper specially focused on a transverse vibration of wire ropes for elevators because their response is complicated by the moving cage and tension distribution. Vibration response analysis techniques using the difference method and a simplified mass point model will be introduced in this paper.

Distribution of Oxygen Tension on Microvessels and in Tissue of Rat Brain Cortex at Severe Arterial Hypocapnia

Arterial hypocapnia (AH), induced by voluntary or forced hyperventilation of the lungs, is accompanied by a decrease in cerebral blood flow (due to an increase in the arteriole tone) and an increase in the affinity of hemoglobin for oxygen. As a result, an insufficient oxygen supply to cortical tissue take place and zones with a critically low oxygen tension (pO2) are formed in brain tissue. The distribution of pO2 to cerebral cortex during AH has not been studied enough. The aim of the work was to evaluate the effectiveness of oxygen supply to brain tissue at the level of arterial and venous microvessels at AH. To do this, the following tasks were set: 1) to study the distribution of the pO2 on the arterial and venous microvessels of the rat cerebral cortex; 2) to analyze tissue pO2 profiles near the walls of these microvessels. On anesthetized Wistar rats under conditions of forced hyperventilation (PaCO2 = 17.1 ± 0.7 mm Hg), the distribution of oxygen tension on the wall of pial and radial arterioles with a lumen diameter of 7–70 μm and on the wall of pial and ascending venules with a lumen diameter of 7–300 µm was studied. In tissue, near the wall of cortical arterioles and venules with a lumen diameter of 10–20 μm, tissue pO2 profiles were measured. Measurements of pO2 during spontaneous breathing of the animal with air served as a control. All pO2 measurements were made using platinum polarographic microelectrodes with a tip diameter of 3–5 μm. Visualization of the electrode tip and microvessels was carried out using a LUMAM-K1 microscope with epiobjectives of the contact type. This work presents for the first-time direct measurements of pO2 on the walls of arterioles and venules of the rat cerebral cortex and in tissues at different distances from the walls of these microvessels at AH. It has been shown that AH results in significant decrease in the oxygen supply to cerebral cortex, that is manifested by a significant drop of the pO2’s on venous microvessels and in tissue in the immediate vicinity of the studied microvessels. It has been shown, that the role of arterioles as a direct source of oxygen to brain tissue, is significantly reduced during arterial hypocapnia. Forced hyperventilation results in significant deterioration of oxygen supply to cerebral cortex, despite elevated pO2 values in the systemic arterial blood and in blood of systemic cerebral veins (sagittal sinus).

Experimental study of multi-buoy-assisted moored ship motion at open berth

Cable breaking and fender failure are frequently reported for the traditional moored ship at open berths. An effective mooring system is necessary to optimize the distribution of cable tension and reduce the impact force acting on the fender. In this paper, a multi-buoy-assisted mooring system is proposed to improve the safety performance of the moored ship. Based on the traditional mooring system, two or four buoys are added in the offshore direction of the ship and connected to the ship with the additional mooring lines. Physical model tests of a 180,000-dwt bulk cargo ship are carried out with the different mooring conditions. The cable tensions, the fender reaction forces and the corresponding ship motions in six degrees of freedom are measured under the different mooring conditions. By adjusting the number of buoys and the pretension of the buoy-assisted mooring lines, an effective mooring system for the tested ship is developed. The experimental results indicate that the developed mooring system can effectively prevent the cable breakage and the fender damage under the present test conditions. In addition, although the motion amplitude of the multi-buoy-assisted moored ship increases slightly, the motion velocity of the ship is considerably small, and the influence is limited for the load and unload operations of the bulk cargo ship.

Topology Optimization of a Femoral Stem in Titanium and Carbon to Reduce Stress Shielding with the FEM Method

Arthroplasty is commonly performed to treat advanced osteoarthritis or other degenerative joint conditions; however, it can also be considered for young patients with severe joint damage that significantly limits their functionality and quality of life. Young patients are still at risk of aseptic mobilization and bone resorption due to the phenomenon of stress shielding that causes an uneven distribution of tensions along the femoral contact surface prosthesis. This phenomenon can be limited by choosing the material of the prosthesis appropriately or by varying its stiffness, making sure that its mechanical behavior simulates that of the femur as much as possible. The aim of this study is to evaluate the mechanical strength of a prosthesis optimized both in shape and material and compare the results with a standard titanium prosthesis. Methods: Through three-dimensional modeling and the use of finite element method (FEM) software such as ANSYS, the mechanical behavior of traditional prosthesis and prosthesis optimized topologically respecting the ASTM F2996-13 standard. Results: With topological optimization, there is a stress reduction from 987 MPa to 810 MPa with a mass reduction of 30%. When carbon fiber is used, it is possible to further reduce stress to 509 MPa. Conclusions: The reduction in stress on the femoral stem allows an optimal distribution of the load on the cortical bone, thus decreasing the problem of stress shielding.

Data-Driven Dynamics Modeling and Control Strategy for a Planar n-DOF Cable-Driven Parallel Robot Driven by n + 1 Cables Allowing Collisions

Abstract Scholars have proposed to allow collisions of cables with the base, the end-effector, or obstacles to expand the workspace of cable-driven parallel robots (CDPRs) in recent years. However, allowing collisions also leads to new challenges in kinematics and dynamics modeling for CDPRs. To this end, this article focuses on a planar fully constrained n-degree-of-freedom (DOF) CDPR driven by n + 1 cables allowing collisions and develops a data-driven dynamics modeling strategy. The data-driven dynamics modeling strategy can address the collisions and optimal tension distribution issues simultaneously. Based on the data-driven dynamics modeling strategy, this article proposes a data-driven dynamics-based control strategy for the planar CDPR allowing collisions. A planar two-DOF CDPR prototype driven by three cables is established to evaluate the data-driven dynamics modeling strategy and data-driven dynamics-based control strategy.

Effect of modified γ-Fe2O3 magnetic nanoparticles on the stability of heavy oil-in-water emulsions

The effects of modified γ-Fe2O3 magnetic nanoparticles having various sizes at different mass fractions on the stability of heavy oil-in-water emulsions were compared. The zeta potential, wettability, oil-water interfacial tension, apparent viscosity, and oil droplet distribution of the emulsions were measured. The optimal size of the γ-Fe2O3(-COOH) magnetic nanoparticles was 2–3 μm, and this resulted in the lowest water-separation rate (23.72% at 4 hours), greatest electrostatic repulsion, weakest hydrophilic effect, lowest interfacial tension, greatest migration resistance, and smallest and most uniform oil droplet distribution. In addition, the stability of the emulsions increased and then decreased as the mass fraction of γ-Fe2O3 (-COOH) magnetic nanoparticles increased because of the increased electrostatic repulsion and decreased migration resistance. This in-depth analysis of the effect of modified magnetic nanoparticle size on the stability of oil-in-water emulsions provides comprehensive theoretical support for achieving viscosity and resistance reduction in an environmentally friendly manner.

Numerical assessment of interstand tensions in continuous hot rolling processes of flat and long products

The paper deals with the calculation of interstand tensions in continuous rolling mills.In the rolling mill industry, continuous measurement and data collection of roll forces, roll torques, temperatures and roll velocities is possible. However, the important process parameter of interstand tensions is not directly measurable and no direct calculation of the interstand tensions is possible. The interstand tensions couple the effects of subsequent roll gaps and should therefore by known for a holistic recalculation of the process. It is straightforward to calculate the effects of the tensions on roll forces, torques and the stock velocity. The inverse problem of calculating the acting interstand tensions including their effects from the process parameters is of greater interest but also of a higher complexity, because the interactions between all the stands in the rolling mill must be regarded. The present paper aims at filling this research gap by presenting a mathematical model to solve the inverse problem by a linearization of the tensions influences in the rolling mill. The present model does not require measured roll forces or torques to find the interstand tensions, only the rotational velocities of the rolls and the rolling parameters (material, temperature, pass schedule or pass design) must be known. Tension-dependent spread is considered by an empirical sub-model. Results are shown for the tension distributions in strip and rod mills. The results indicate that the present friction conditions and the entry size of the rolled stock have a high impact on the tension distributions.

Methods for multi-segment continuous cable analysis

Cables are invaluable members for some applications of engineering. The specialty is due to its behavior under transverse loads. Having almost no rigidity in transverse direction makes cables different from other structural elements. In most applications, cables are assumed to be two force members. However, not only its weight but also its application with roller supports makes them different structural elements. Generally, cables are assembled as single-segmented cables (SSC) where they are fixed at their ends. However, in most of the SSC applications, cables have intermediate supports which can be rollers or sliders. These type of cable applications are called as multi-segment continuous cables (MSCC). In MSCC systems, the cable fixed at its ends and supported by a number of intermediate rollers. Total length of cable is constant, and the intermediate supports are assumed to be frictionless and stationary. In this problem, the critical issue is to find the distribution of the cable length among the segments in the final equilibrium state, so reactions at all supports can be found. Two methods are proposed for the segment length adjustment based on the stress continuity among the cable. These methods are named as direct stiffness method and tension distribution method (relaxation method). Results calculated from the proposed methods are verified by both the reference benchmark problems and commercial finite element program.

DESIGN OF WEARABLE TENSEGRITY STRUCTURES FOCUSING ON THE TENSION PROPAGATION FUNCTION THROUGHOUT THE BODY

AbstractHumans are able to perform skilful movements by coordinating muscles throughout the body. It has been revealed that not only neural mechanisms but also direct and dynamic interactions between body parts contribute to muscular coordination. Tensegrity, accurately biotensegrity, can be considered to the basic mechanism for the interactions. Tensegrity structures are composed of tensile and compressive components, and are lighter and more flexible than existing rigid structures. The authors investigated designing wearable tensegrity structures for extending human motor ability, especially assisting in carrying heavy objects. Based on Flemons' spine model, we devised a columnar tensegrity structure that can be expanded to the size of the whole body, and connected each of four columns to the front and back of the body on right and left side. The wearable tensegrity structures can deform flexibly due to tension distribution when external force is applied, and follow the human motions in twisting trunk and walking. Experimental results in carrying heavy objects showed that some muscle activities around hip and knee tended to decrease by using the structures when those joints extended.

Passive Dynamics of the Head, Neck and Forelimb in Equine Foetuses-An Observational Study.

Passive dynamics is an aspect of locomotion which is entirely dependent on the mechanical configuration and linkages of adjacent body segments. Tension distribution along mechanical linkages enables the execution of movement patterns with reduced need for complex neurological pathways and may play a role in reestablishing postural stability following external disturbances. Here we demonstrate a uni-directional mechanical relationship between the equine forelimb, head and neck, which may have implications for balance and forelimb loading in the horse. These observations suggest that forelimb, head and neck movement coordination (observed in the horse during unrestrained locomotion) is significantly influenced by the mechanical linkages between body segments, rather than being entirely dependent on neurological input as previously thought. This highlights the potential significance of research directed at investigating passively induced movements in understanding common locomotory patterns. Additionally, it suggests a mode of postural control which may provide instantaneous adjustments to postural disturbances, thus promoting rapid and efficient locomotion.

Analysis of the upper tail of the short-term extreme tension distribution of mooring line by the peaks-over-threshold method

The consistency of the upper tail of the extreme response distribution plays an important role in the accuracy of the extreme response prediction. Although the peaks-over-threshold method has a high data utilization of the response time series, the consistency of the upper tail of the extreme response distribution was not thoroughly investigated, especially for the inherent randomness of the short-term sea state. This study aims to estimate the upper tail of the short-term extreme tension distribution of the mooring line considering the short-term variability by the peaks-over-threshold method. The consistency of the extreme tension distribution tail is quantified by a relative error compared with the global maximum method, and the theoretical optimal threshold is defined by minimizing the largest relative error among the tail quantiles for different thresholds. Results from a case study for the mooring line of the fish cage indicate that the effect of the random seed is significant for consistency in the prediction of the distribution tail of the short-term extreme tension. And the generalized Pareto distribution model combined with the L-moments method is recommended for the theoretical optimal threshold. These findings provide some useful suggestions for the preliminary design of the mooring line for offshore structures.

A Rate-Dependent Cell Microinjection Model Based on Membrane Theory.

As an effective method to deliver external materials into biological cells, microinjection has been widely applied in the biomedical field. However, the knowledge of cell mechanical property is still inadequate, which greatly limits the efficiency and success rate of injection. Thus, a new rate-dependent mechanical model based on membrane theory is proposed for the first time. In this model, an analytical equilibrium equation between the injection force and cell deformation is established by considering the speed effect of microinjection. Different from the traditional membrane-theory-based model, the elastic coefficient of the constitutive material in the proposed model is modified as a function of the injection velocity and acceleration, effectively simulating the influence of speeds on the mechanical responses and providing a more generalized and practical model. Using this model, other mechanical responses at different speeds can be also accurately predicted, including the distribution of membrane tension and stress and the deformed shape. To verify the validity of the model, numerical simulations and experiments were carried out. The results show that the proposed model can match the real mechanical responses well at different injection speeds up to 2 mm/s. The model presented in this paper will be promising in the application of automatic batch cell microinjection with high efficiency.

25 The potential impact of female body shape on rider posture and scores received from dressage judges

The ideal female body image in equestrianism has been perceived as a slighter physique, resulting in riders and coaches perceiving that dressage judges have a preferred bias toward smaller riders, impacting the overall competition scores. This research aimed to identify certain aspects of rider body shape (BS) that enhance rider posture both physically and subjectively via dressage judge scoring, also to identify if judge bias was present toward rider physique. Aspects of rider posture were measured, including upper body position, rein tension, stirrup force and weight distribution. Measurements of rider volunteers (n = 20) were taken including height, weight, torso height, arm and leg length, reflective markers were used for postural analysis. Riders rode an equine simulator for 30 s in walk, trot and canter left and were recorded on video. Dressage judges (list 1–5, n = 11) were asked to score riders on a scale of one (very bad) to 10 (excellent) for different postural aspects. Kendall's Coefficient of Concordance assessed level of agreement among judges scores, and Regression Analysis made comparisons between BS aspects, judge scores and quantifiable data of rider posture. The results indicated that body mass index (BMI), height, or rider confidence was not related to judges’ scores. There was a moderate agreement overall for all thejudges (Kendall's Coef = 0.466195), higher-level judges showed a substantial agreement (Kendall's Coef = 0.672543) compared with lower-level judges who showed a moderate agreement (Kendall's Coef = 0.476772). A relationship between torso height and judge score indicated that riders with a shorter torso scored higher for upper body position (DF = 1; R-sq(adj) = 22.66%; F-Value = 5.52; P = 0.034); no relationship was found between rider posture (the range around the vertical) and torso height. Riders with longer legs in proportion to their height scored higher from judges for lower leg security (DF = 1; R-sq(adj) = 19.52%; F-Value = 5.61; P = 0.029). Rider leg length was significantly related to stirrup force, indicating that riders with longer legs produced greater force onto the stirrups (DF = 1; R-sq(adj) = 21.04%; F-Value = 6.06; P = 0.023). This identified that judges appeared not to have a rider size bias, contradicting previous rider perceptions. Certain aspects of rider BS were suggested to impact rider ability from the scores received by judges, such as a shorter torso enhancing upper body posture and leg length enhancing the security of the lower leg. Future research investigating further performance indicators or limiters is needed to identify aspects that may enhance rider performance.

Deformation of soft microbeam caused by wetting of droplet

Owing to the complexity of interaction on the solid–liquid interface, the wetting-induced deformation of micro-structure or soft matter is an open question. In this paper, a new model is developed to characterize the flexural deformation of microbeams with different supports induced by droplet wetting. Unlike the existing models, in this model it is no longer necessary to presuppose the distribution of the capillary tension and Laplace pressure on the wetted interface. The deflection of the microbeam due to wetting under different support conditions is solved analytically and compared with the results calculated by existing models. The results show that the capillary force that causes the microbeam to bend is not a self-equilibrium force system, but the assumption of the self-equilibrium traction in wetting-induced deformation is a good approximation. In addition, when the ratio of the size of the capillary tension zone to the wetted segment of the microbeam takes 0.55, the deflection curves calculated by the new model are agreement with those by the existing models.

Modeling the temperatures of traveler and ring in ring spinning

Ring spinning is the dominant system of manufacturing high-quality yarns in the textile industry. Spinning parameters affect the spinning tension distribution and consequently the temperatures of the ring/traveler system. Excessive traveler heat will limit the spindle speed and the efficiency of yarn production. This study modeled the effect of the traveler weight, yarn count, twist level and spindle speed on the temperatures of the traveler and ring during ring spinning. The finite element method was used to model the temperatures of the ring and the traveler for different spinning parameters. The experimental ring temperature and maximum traveler temperature from the validated model were recorded based on the experimental design. The results show that spindle speed, traveler weight and yarn count had a statistically significant effect on the temperatures of the traveler and the ring, with the spindle speed having the strongest effect. The twist level of yarn, within the range examined, had no statistically significant influence on the traveler and ring temperatures. For a given spindle speed, the traveler weight and yarn count have a significant effect on the maximum temperature of the traveler, and the temperature change is more pronounced at a higher spindle speed.

Equilibria of liquid drops on pre-stretched, nonlinear elastic membranes through a variational approach

We study the equilibrium of planar systems consisting of sessile and pendent drops on pre-stretched, nonlinear elastic membranes. The membrane experiences large deformations due to both capillary forces and the drop's weight. The membrane's surface energies are allowed to depend upon stretches in the membrane. We minimize the free energy of the system to obtain the governing equations. This recovers all equations found by force balance, in addition to an extra condition that must hold at the triple point. The latter closes the system's mathematical description and defines a unique equilibrium given the membrane's material and pre-stretch, and the properties of drop's fluid and its volume. The extra condition simplifies to continuity of stretches at the triple point when the surface energies are strain-independent. We then solve these coupled nonlinear equations to obtain the global equilibria of the drop–membrane system. We report the effects of drop's volume and membrane's pre-tension on the system's geometry and tension distribution in the membrane. Through this, we align the theory closely with experiments, which will then allow the use of the present system both as an elastocapillary tension probe and as a device to measure solid surface energies.

Purifying Fe-based amorphous alloys to enhance glass-forming ability by designing a novel refining slag

• A novel refining slag design strategy was proposed for Fe-based amorphous alloys. • The designed SiO 2 -CaO-Al 2 O 3 -B 2 O 3 refining slag was effective in enhancing the GFA. • Inclusions with small lattice disregistry can promote the heterogeneous nucleation. • The enhanced GFA is due to the reduced impurities and inclusions after refining. Designing low melting point and low basicity refining slag suitable for Fe-based amorphous alloys and understanding the inclusions’ formation, removal, influencing mechanisms are quite vital in the fields of metallurgy and materials. In this study, a novel 13%SiO 2 -32%CaO-30%Al 2 O 3 -25%B 2 O 3 (wt.%) refining slag was designed after careful calculations of the liquid phase region, slag-metal equilibrium, surface tension, viscosity, deoxidation capability and sulfur distribution ratio. After refining with our designed slag, the content of impurities and the number density of inclusions in a representative Fe 83 Si 2 B 15 (at.%) amorphous alloy were significantly reduced. Moreover, the glass-forming ability (GFA) of the alloy was also enhanced, enabling the preparation of amorphous ribbons with a lower cooling rate. Based on the impurities in Fe-based amorphous alloys as well as the calculated oxide and sulfide free energy diagrams, CaO, SiO 2 , Al 2 O 3 oxides and CaS, TiS, MnS sulfides will form in the master alloy. The high melting point inclusions in the melt are generally removed via a floatation-separation-absorption process and the Mn, Ti, S impurities are removed via slag-metal interface reactions during refining. As for the detrimental effect of inclusions on glass formation, the small lattice disregistry between Ti, Mn-containing inclusions and primary α-Fe gains reveal that these inclusions are effective in promoting the heterogeneous nucleation, and therefore greatly deteriorate the GFA. These findings are important and provide an ideal solution to purifying the Fe-based amorphous alloys by refining and enhancing the GFA for industrial production.