Initial Tension Research Articles

Model-based vibration response analysis and experimental verification of lathe spindle-housing-belt system with rubbing

Vibration response analysis for lathe spindle-housing-belt system with rubbing is performed by finite element method. The emergence of free-running abnormal noise of economical commercial lathes inspires the fusion of the annular rubbing model and spindle-housing-belt system since there is a small clearance between the front bearing cover and shaft to realize good sealing. The longitudinal and transverse dynamic equations for tight and loose sides of the V-belts are established when geometric and material parameters and initial tension of belt are integrated into the belt’s stiffness coefficient. The Lankarani-Nikravesh contact model depending upon intrusion and rotation speeds is used to describe the shaft-housing interaction. The calculated value of the proposed model agrees well with the modal and harmonic excitation test results, measured free-running rotor orbit signal and housing acceleration data with rubbing. It indicates that the model is promising to predict the abnormal noise of the laboratory lathe. Numerical simulations suggest that the belt’s dynamic parameters have a negligible influence on the vibration shape and amplitude of system. When the rubbing force is applied, nonlinear behavior is prone to be triggered by the larger unbalanced excitation. As the higher rotation speed is used, the interaction load is strengthened due to the speed-dependent of the Lankarani-Nikravesh model.

Study on vibration behavior of functionally graded porous material plates immersed in liquid with general boundary conditions

This paper presents a novel energy method for vibration analysis of pre-loaded moving functionally graded material (FGM) plates in fluid. Porosity in plates, fluid–structure interactions and initial tensions are taken into consideration. The first-order shear deformation theory (FSDT) and linear potential flow theory are adopted to formulate the strain energy, kinetic energy and external work functions of the coupled system. The governing equations of the porous FGM plate immersed in liquid are deduced by the Hamilton’s principle and the unified solutions for general boundary conditions are obtained using the modified Ritz method. By comparing the obtained vibration results with those from the commercial software and literature, the accuracy of the proposed model is validated. The effects of axial speed, fluid density, material constituent, initial axial tension and porosity volume fraction on the vibration behaviors of the FGM plate are further discussed. Numerical cases show that the vibration behaviors of the FGM plate are significantly influenced by these key parameters.

Vibration Analysis of Rotating Combined Thin-Walled Shells With Multiple Conical Segments

Abstract In this paper, vibration analysis of rotating combined thin-walled shells with multiple conical segments has been carried out. Considering the centrifugal force, Coriolis force, and initial hoop tension due to rotation, the elastic strain energy and kinetic energy of a single rotating conical shell are expressed based on Love’s first approximation theory. The artificial springs are introduced to simulate the connections of adjacent conical shells and the boundaries of the rotating combined thin-walled shells. Taking characteristic orthogonal polynomial series as the admissible functions, the Rayleigh–Ritz method is employed to derive the frequency equations of the combined shell and corresponding vibration characteristics are then obtained. Given that the cylindrical shell and annular plates can be regarded as conical shells with semi-vertex angles of 0 deg and 90 deg, respectively, the solution given is also available for the vibration analysis of rotating combined thin-walled shells comprised of any segments of cylindrical, conical shell, and annular plate. As examples of rotating combined thin-walled shells with two and five segments, vibrations of rotating conical–conical joined shell and cylindrical–conical–cylindrical–conical–cylindrical joined shell are investigated in the paper. Traveling wave frequencies and corresponding mode shapes are shown, and the effects of rotating speed, circumferential wave number, spring stiffness, and semi-vertex angles on the vibration behavior are given in detail.

Modulating the mass sensitivity of graphene resonators via kirigami

The unique mechanical properties of graphene make it an excellent candidate for resonators. We have used molecule dynamic to simulate the resonance process of graphene. The kirigami approach was introduced to improve the mass sensitivity of graphene sheets. Three geometric parameters governing the resonant frequency and mass sensitivity of Kirigami graphene NEMS were defined. The simulation results show that the closer the kirigami defect is to the center of the drum graphene, the higher the mass sensitivity of the graphene. The kirigami graphene shows up to about 2.2 times higher mass sensitivity compared to pristine graphene. Simultaneously, the kirigami graphene has a higher out-of-plane amplitude and easy access to nonlinear vibrations, leading to higher mass sensitivity. Besides, the kirigami structure can restrict the diffusion of gold atoms on graphene under high initial velocity or large tension condition. It is evident that a reasonable defect design can improve the sensitivity and stability of graphene for adsorption mass.

Relative permeability of two-phase flow through rough-walled fractures: Effect of fracture morphology and flow dynamics

This paper considers the influence of geometry and flow conditions on the relative permeability of wetting and non-wetting components of multiphase flows through fractures. Using an explicit immiscible two-phase fracture-flow model, 945 multiphase flow simulations were conducted on artificially-generated fracture geometries. These simulations accounted for the effects of initial fracture roughness, confining stress, pressure gradient, surface tension and volume fraction on the fracture flow. Time averaged relative permeabilities were recorded for both the wetting and non-wetting phases in each of the simulations.The simulation results demonstrate that relative permeability curves are strongly influenced by contact area, fracture morphology and competition between viscous and capillary forces. Increasing the normal stress creates more contact in the fracture plane, which increases interference between the fluid phases. The effect is more pronounced in fractures with strongly correlated apertures where the chance of fluid trapping is increased. The relative importance of viscous forces compared to capillary forces was investigated by applying different pressure gradients to the fluids. Increasing the pressure gradient tends to cause the flow paths to segregate and the relative permeability curves approach the linear model, in agreement with experimental results.From these observations, two new relative permeability models were introduced to describe the behavior of wetting and non-wetting phases in fractures. The performance of the new models were compared to other published relative permeability models for fracture geometries. The new models were found to more accurately predict the relative permeability when compared to the other available models for both the wetting and non-wetting phases.

Meshless Chebyshev RPIM Solution for Free Vibration of Rotating Cross-Ply Laminated Combined Cylindrical-Conical Shells in Thermal Environment.

This paper provides a numerical solution to the vibration of a rotating cross-ply laminated combined conical-cylindrical shell in the thermal environment. Its numerical discrete solution method uses the meshless method. The combined shell assumed the temperature independence of material property is divided to the fundamental conical and cylindrical shell substructures, and the theoretical formulation for each substructure is derived based on the first order shear deformation theory (FSDT) and Hamilton’s principle. The effects of the initial hoop tension and temperature change are considered through the kinetic energy reflecting the effects of centrifugal and Coriolis forces and additional strain energy by the nonlinear part of the Green–Lagrange strains. The substructures are then assembled according to the continuity conditions. The boundary and continuity conditions are simulated by introducing artificial virtual spring technology. The displacement component in the theoretical formulation is approximated using a meshless Chebyshev-RPIM shape function. The reliability of the method is verified by comparing with mature and reliable results. The free vibration characteristics of the rotating combined conical-cylindrical shell structure under various sizes, speeds and temperatures are given by numerical examples.

Influence of temperature gradient of slab track on the dynamic responses of the train-CRTS III slab track on subgrade nonlinear coupled system

Temperature is an important load for ballastless track. However, there is little research on the system dynamic responses when a train travels on a ballastless track under the temperature gradient of ballastless track. Considering the moving train, temperature gradient of slab track, gravity of slab track, and the contact nonlinearity between interfaces of slab track, a dynamic model for a high-speed train runs along the CRTS III slab track on subgrade is developed by a nonlinear coupled way in ANSYS. The system dynamic responses under the temperature gradient of slab track with different amplitudes are theoretically investigated with the model. The results show that: (1) The proportions of the initial force and stress caused by the temperature gradient of slab track are different for different calculation items. The initial fastener tension force and positive slab bending stress have large proportions exceeding 50%. (2) The maximum dynamic responses for slab track are not uniform along the track. The maximum slab bending stress, slab acceleration, concrete base acceleration appear in the slab middle, at the slab end, and at the concrete base end, respectively. (3) The maximum accelerations of track components appear when the fifth or sixth wheel passes the measuring point, and at least two cars should be used. (4) The temperature gradient of slab track has a small influence on the car body acceleration. However, the influences on the slab acceleration, concrete base acceleration, fastener tension force are large, and the influence on the slab bending stress is huge.

Flexural–torsional modeling and equilibria of three-dimensional axially moving beams

The equilibrium equations for the coupled flexural–flexural–torsional–extensional mechanics of an axially moving beam with initial tension are studied. The form of the governing equations is discussed, and numerical solutions are presented for two types of boundary misalignment that both result in out-of-plane flexural–torsional equilibria. Solutions to the governing equations are obtained while retaining all non-linear terms. With all non-linear terms, the governing equations cannot be expressed in first-order form and appear to be missing boundary conditions, thus complicating the numerical solution. The results are compared to an existing reduced model, thereby confirming previously employed simplifying assumptions. Finally, an alternative form of the equations of motion is derived that are simpler and consists of only polynomial non-linearities. The new equations are shown to capture the behavior studied with only a small reduction in accuracy compared to other models.

A closed-form solution for the wind-induced responses of transmission lines considering the failure of adjacent towers

Some towers in transmission lines may collapse first under the gust wind and have pulling effects on conductors, which may trigger the cascade failure when the unbalanced force on the adjacent tower is large. Thus, a closed-form solution is proposed to predict conductor responses induced by both the failed tower and wind loads. The total wind-induced response is divided into the mean component affected by support displacement and fluctuating component around the static equilibrium, which can be determined by nonlinear static analysis and influence line, respectively. The equilibrium iteration method and trapezoidal equivalent wind pressure are proposed to correct the response distortion caused by the large deformation and non-uniform wind pressure. Then, the power spectral density and root mean square of responses considering three-dimensional correlation are provided. Finally, parameter analysis investigates the influence of support displacement, initial horizontal tension, and horizontal span on reaction force and gust response factor (GRF). The results show that the proposed closed-form solution has high accuracy and efficiency, and the influence of large deformation and wind pressure forms on the wind-induced responses cannot be ignored. Moreover, both the lateral reaction force and GRF are significantly sensitive to the lateral support displacement.

Analysing an Interactive Problem-Solving Task Through the Lens of Double Stimulation

Problem-solving activities have been studied from a diversity of epistemological perspectives. In problem-solving activities, the initial tensions of a problematic situation led to a cognitive dissonance between conflicting motives and instruments to reach the activity goal. We analyze problem-solving in the continuation of Sannino and Laitinen’s (2015) approach to the analysis of a decision-forming apparatus. The originality of this study is in consideration of the materialistic nature of double stimulation that appears during the activity of the CreaCube problem-solving task. This activity engages the participant in solving tasks with interactive robotic instruments. To solve a task, the subject is required to build interactive robotic modules into a specific configuration which will cause the artifact to move from an initial position to a predetermined final position. The conflict of stimuli in the CreaCube is strong and observable because of the tangibility of the artifact, which is manipulated by the participant into different configurations with the goal of solving the task. We discuss double stimulation in relation to the artifactual interactive affordances of educational robotics.

Analysis of Energy Loss on a Tunable Check Valve through the Numerical Simulation

The article presents a study of the flow through a tunable check valve used as a hydraulic lock in a system with an actuator. Special attention is given to energy losses of the liquid stream in the poppet gap. In the first stage of the research, CFD methods were used to determine the speed and pressure distributions for the fixed values of the input flow rate and the poppet position. The values of the jet angle and pressures determined based on the CFD results were used to build a simulation model of the entire hydraulic system in Matlab/Simulink environment. The influence of the spring parameters pressing the poppet against the valve seat on the pressure drop and thus on the amount of energy lost was investigated. In particular, the spring stiffness and initial tension were studied. The obtained results were used to develop guidelines for constructing a valve prototype. Finally, the results of simulation tests were verified based on the actual valve characteristic obtained on a test bench.

Plasticity enhancement in pure magnesium achieved based on initial twin orientation regulation

In the short communication, the ductility of pure magnesium was enhanced about 3 times at room temperature compared with the initial material based on the proposed concept of shear strain-induced twin orientation regulation (SITOR). The initial tension twin orientation inclines about 30° to the TD-ND plane which is regulated by the introduced shear deformation so that a larger Schmid factor of basal slip is achieved. Due to the promotion of basal slip, the plasticity of pure Mg is improved obviously.

The optimal tension for the reconstruction of the distal radioulnar ligaments.

This study aimed to investigate the optimal tension for the reconstruction of the distal radioulnar ligaments (DRULs) in the treatment of the distal radioulnar joint (DRUJ) instability. A total of eight human cadaver upper extremities were used. First, the Tekscan sensor film system was used to measure the contact characteristics of the intact DRUJ. Following this, the DRULs were resected, and the measurement was repeated. The DRULs were then reconstructed according to Adams' procedure, and the contact forces under different initial tension were compared with that of the intact group to obtain the optimal tension. At that point, the contact force of the DRUJ was close to normal. The reliability of the obtained tension was verified by translational testing, which reflected the stability of the DRUJ. In the neutral position, the contact force, area, and pressure inside DRUJ were 0.51 ± 0.10N, 64.08 ± 11.58 mm2, and 8.33 ± 2.42kPa, respectively. After the DRULs were resected, they were 0.19 ± 0.02N, 41.75 ± 5.01 mm2, and 4.86 ± 1.06kPa, respectively. The relationship between the tension and contact force was linear regression (Y = 0.0496x + 0.229, R2 = 0.9575, P < 0.0001). According to the equation, when the tension was 3.64-7.68N, the contact force was close to normal. There was no statistical difference in the stability of the reconstructed DRUJ under this tension compared with the intact group (P = 0.08). By comparing the contact forces under different reconstruction tensions with the normal value, we obtained the optimal tension, which can provide the theoretical basis for the clinical treatment of chronic DRUJ instability.

Free vibration analysis of a spinning functionally graded spherical–cylindrical–conical shell with general boundary conditions in a thermal environment

Based on the first-order shear deformation theory (FSDT) for shells, the free vibration of a spinning functionally graded (FG) spherical–cylindrical–conical (SCC) shell with arbitrary boundary conditions subjected to a thermal environment is investigated. The centrifugal forces, the Coriolis forces, and the initial hoop tension caused by spin are all considered in the theoretical modeling. The model is analyzed using the domain decomposition method. The penalty method is used to model the continuity and arbitrary boundary conditions. Validity study is performed by comparing with the results from finite element analyses for special cases. Finally, the effects of the power-law index, the temperature loads, the spinning speed, and the geometrical parameters on the free vibration characteristics, as well as the influences of structural configuration on the critical spinning speed, are investigated. It is found that the configuration of a spinning SCC shell has significant effect on its natural frequency and critical speed under a fixed shell weight. The natural frequencies approximately converge into three values with increases in the circumferential wave number. The FG–SCC shell’s cone angles at which the minimum and maximum natural frequencies occur are not affected by the spinning speed and the power-law index.

Radial and Axial Displacement of the Initially-Tensioned Orthotropic Arterial Wall Under the Influence of Harmonics and Wave Reflection

Abstract This study examines radial and axial displacement of the arterial wall under the influence of harmonics and wave reflection for the role of axial wall displacement in pulsatile wave propagation. The arterial wall is modeled as an initially-tensioned thin-walled orthotropic tube. In conjunction with three pulsatile parameters in blood flow, a free wave propagation analysis is conducted on the governing equations of the arterial wall and no-slip conditions at the blood-wall interface to obtain the frequency equation and pulsatile parameter expressions under different harmonics. The influence of wave reflection is then added to pulsatile parameter expressions. With the harmonic values of measured pulsatile pressure and blood flow rate at the ascending aorta in the literature, the waveforms of radial wall displacement, axial wall displacement, and wall shear stress are calculated under different orthotropicity and axial initial tension. The developed theory and calculated results indicate that (1) difference in waveform between blood flow rate, wall shear stress, and axial wall displacement is caused by harmonics, rather than wave reflection; (2) Axial wall displacement does not affect blood flow rate, radial wall displacement, and wall shear stress; (3) Besides wall shear stress, radial wall displacement gradient also contributes to axial wall displacement and its contribution is adjusted by axial initial tension; (4) different wave reflections only noticeably affect the maximum and minimum values of wall shear stress; and (5) The amplitude and waveform of axial wall displacement are predominantly dictated by axial elasticity and axial initial tension, respectively.

The tension of the iliopsoas tendon more than doubles during extension of the dysplastic hip in open reduction.

The role of the iliopsoas as an obstructing and re-dislocating factor in developmentally dislocated hips is unclear. The purpose of this article is to determine the change in the iliopsoas' tension during flexion and extension when performing an open reduction. We evaluated 34 hips undergoing an anterior open reduction for a developmental dislocation. At the time of surgery, we identified the iliopsoas, and before sectioning it as part of the open reduction, we measured the tension while cycling the reduced hip through flexion and extension. We performed statistical analysis using Pearson and Spearman correlation tests. We created an initial tension artificially at 20 N with the hip held in 90º of flexion, which then doubled to a mean of 42 N when placed in extension. We found a significant increase in tension when the hip went below 20º of flexion. We also found the correlation between the angle of the hip and the force of tension to be statistically significant ( P = 0.003). This study provides quantitative support that the tension of the iliopsoas tendon increases significantly in extension when performing an open reduction of a developmentally dislocated hip.

Constitutive model for cyclic behavior of mild steel under various strain amplitudes

To enable accurate simulation of steel material under various loadings, cyclic behaviors of mild steel Q235 were extensively investigated through experimental analysis and constitutive modeling in this work. The studied steel was tested under cyclic loading protocols with constant strain amplitudes and variable strain amplitudes. The evolutions of stress amplitude, effective stress and back stress components, and elastic stiffness during the whole cyclic loading history are quantitatively scrutinized. The results demonstrate that mild steel exhibits cyclic capacity depended strongly on strain amplitude. Besides, the strain history effect depends on both the historical maximum strain amplitude and the target unloading strain amplitude, indicating the existence of a critical state for the incomplete evanescence of strain memory surface to be activated. An abrupt drop of effective stress at onset of plastic straining is observed in experimental tests and contributes to the early re-yielding of the reversed curve. Furthermore, elastic stiffness in the cyclic loading phase differs much from that in initial tension. Based on those observations, a new constitutive model with robust ability to predict hysteretic behavior of structural steel under complex loading paths is proposed. This model considers the strain range dependence and the strain history dependence effects. In addition, a new method to identify the yield points of hysteretic loops is proposed in this paper to enable simulations of back stress with the Armstrong-Frederick hardening model without considering the strain range dependence effect. The validity of this model is demonstrated through comprehensive comparison between simulated results and experimental data.

Free Vibration Analysis of a Spinning Composite Laminated Truncated Conical Shell under Hygrothermal Environment

This paper is concerned with free vibration characteristics of a spinning composite laminated truncated conical shell subjected to hygrothermal environment. Hygrothermal strains are introduced into the constitutive law of single-layer material, and fiber orientation lies symmetrically with respect to the midplane of the composite shell. Considering the spin-induced Coriolis and centrifugal forces, as well as initial hoop tension, the governing equations of free vibration of the composite conical shell with hygrothermal effects are derived on the basis of Love’s thin-shell theory and Hamilton’s principle. The solution of the equations is derived using the Galerkin approach. Then, a detailed parametric study on natural frequencies and critical spinning speeds is numerically performed. Results indicate that the Coriolis force induces an asymmetric influence on natural frequencies of forward and backward traveling waves, while the centrifugal force enhances the frequencies of both traveling waves symmetrically. Initial hoop tension plays a major role in the increase of critical spinning angular speed. Temperature, moisture concentration, and design parameters show the significant influence on the free vibration characteristics of the conical shell, and thermal expansion deformation is nonnegligible in the free vibration analysis.

Numerical assessment of ultrasound supported coalescence of water droplets in crude oil

In this study, a numerical assessment of the coalescence of binary water droplets in water-in-oil emulsion was conducted. The investigation addressed the effect of various parameters on the acoustic pressure and coalescence time of water droplets in oil phase. These include transducer material, initial droplet diameter (0.05–0.2 in), interfacial tension (0.012–0.082 N/m), dynamic viscosity (10.6–530 mPas), temperature (20–100 °C), US (ultra sound) frequency (26.04–43.53 kHz) and transducer power (2.5–40 W). The materials assessed are lead zirconate titanate (PZT), lithium niobate (LiNbO3), zinc oxide (ZnO), aluminum nitride (AlN), polyvinylidene fluoride (PVDF), and barium titanate (BaTiO3). The numerical simulation of the binary droplet coalescence showed good agreement with experimental data in the literature. The US implementation at a fixed frequency produced enhanced coalescence (t = 5.9–8.5 ms) as compared to gravitational settling (t = 9.8 ms). At different ultrasound (US) frequencies and transducer materials, variation in the acoustic pressure distribution was observed. Possible attenuation of the US waves, and the subsequent inhibitive coalescence effect under various US frequencies and viscosities, were discussed. Moreover, the results showed that the coalescence time reduced across the range of interfacial tensions which was considered. This reduction can be attributed to the fact that lower interfacial tension produces emulsions which are relatively more stable. Hence, at lower interface tension between the water and crude oil, there was more resistance to the coalescence of the water droplets due to their improved emulsion stability. The increment of the Weber number at higher droplet sizes leads to a delay in the recovery of the droplet to spherical forms after their starting deformation. These findings provide significant insights that could aid further developments in demulsification of crude oil emulsions under varying US and emulsion properties.

The effects of initial graft tension on femorotibial relationship following anatomical rectangular tunnel anterior cruciate ligament reconstruction using bone–patellar tendon–bone graft

BackgroundThe purpose of this study was to elucidate the effects of the difference of initial graft tension on the femorotibial relationship on an axial plane and its chronological change following anatomical anterior cruciate ligament (ACL) reconstruction. MethodsA total of 63 patients who underwent anatomical ACL reconstruction were included in this study. The graft was fixed at full knee extension with manual maximum (higher graft tension; group H) and 80 N (lower graft tension; group L) pulls in 31 and 32 patients, respectively. The femorotibial positional relationship in axial computed tomography at 1 week and 1 year postoperatively were retrospectively evaluated. The side-to-side differences (SSDs) and the amount of changes of SSDs over 1 year were compared between groups. ResultsThe SSDs of the external rotational angle of the tibia in group H were significantly larger than those in group L at postoperative 1 week (2.7 ± 3.9° vs. 0.3 ± 3.3°; P < 0.01). The amount of internal rotational changes of SSDs of the internal–external rotational angles over 1 year in group H was significantly larger than that in group L (−3.6 ± 3.9° vs. − 0.3 ± 2.7°; P < 0.01). No significant differences were observed on the anterior–posterior translation distance and medial–lateral shift distance. ConclusionThe application of higher initial graft tension resulted in excessive external rotation of the tibia to the femur at 1 week postoperatively in anatomical ACL reconstruction, and the excessive early external tibial rotation had resolved over 1 year.