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torsional Vibrations of a Cantilever with Lateral Friction in a Resonance Friction Microscope

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Chinese Physics Letters 2012年第1期29卷 53-55页

作者： CHEN Jian-Song GE Yun ZHANG Hui School of Mechanical Engineering Southeast UniversityNanjing 211189 School of Electronics Science and Engineering Nanjing UniversityNanjing 210093 Laboratory of Modern Acoustics Institute of AcousticsNanjing UniversityNanjing 210093

A model of fundamental torsional vibration of a cantilever with lateral friction is presented by using the harmonic balance *** model demonstrates that the torsional vibration has close relations with the lateral friction threshold,the lateral contact stiffness and the torsional vibration amplitude of the *** the threshold is larger than a product of the stiffness and the vibration amplitude,the lateral friction is a linear force with the *** the lateral friction threshold is less than the product,the motions of the tip on the sample can be stick-slip or slip *** results are useful to optimize and to manipulate the fundamental flexural vibration of the piezo-cantilever,and give an insight into the tribological characterization of the interface in a resonance friction microscope.

关键词： friction torsional cantilever

Boundary layer flow of Maxwell fluid due to torsional motion of cylinder: modeling and simulation

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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 667-680页

作者： M.KHAN A.AHMED J.AHMED Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This paper investigates the boundary layer flow of the Maxwell fluid around a stretchable horizontal rotating cylinder under the influence of a transverse magnetic *** constitutive flow equations for the current physical problem are modeled and analyzed for the first time in the *** torsional motion of the cylinder is considered with the constant azimuthal velocity *** partial differential equations(PDEs)governing the torsional motion of the Maxwell fluid together with energy transport are simplified with the boundary layer *** current analysis is valid only for a certain range of the positive Reynolds ***,for very large Reynolds numbers,the flow becomes ***,the governing similarity equations are simplified through suitable transformations for the analysis of the large Reynolds *** numerical simulations for the flow,heat,and mass transport phenomena are carried out in view of the bvp4c scheme in *** outcomes reveal that the velocity decays exponentially faster and reduces for higher values of the Reynolds numbers and the flow penetrates shallower into the free stream *** is also noted that the phenomenon of stress relaxation,described by the Deborah number,causes to decline the flow fields and enhance the thermal and solutal energy transport during the fluid *** penetration depth decreases for the transport of heat and mass in the fluid with the higher Reynolds *** excellent validation of the numerical results is assured through tabular data with the existing literature.

关键词： torsional motion Maxwell fluid magnetic field stretchable rotating cylinder bvp4c scheme

torsional RIGIDITY OF SHELLS OF REVOLUTION

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Applied Mathematics and Mechanics(English Edition) 1990年第5期11卷 403-412页

作者：钱伟长 1. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University of Technology Shanghai

In this paper, the general equations of equilibrium for axisymmetrical deformation including the torsional deformation of revolutional shells are derived. It is shown that the shearing stress distribution due to torsion is independent of other stress components including those of membrane stress and bending stress. In this paper, the torsional deformation is considered to be represented by membrane action only, and also by the combined action of bending membrane deformation. It is shown that the main contribution of torsional rigidity is that related to membrane action.

关键词： Mathematical Models Mathematical Techniques Numerical Methods Stresses torsional

torsional wave frequency in heterogeneous earth crust lying over dry sandy semi-infinite substratum

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Applied Mathematics and Mechanics(English Edition) 2019年第10期40卷 1399-1412页

作者： S.K.VISHWAKARMA R.KAUR T.R.PANIGRAHI Department of Mathematics Birla Institute of Technology and SciencePilani Hyderabad Campus

The present study is carried out to investigate the transference of torsional surface waves in a heterogeneous anisotropic crust lying over a dry sandy half-space. The rigidities and densities as well as the initial stress are assumed varying as a function of depth in both the media. These variations are the product of the polynomial function of depth in degree n (n ∈ R) and the exponential function of depth. Following the theory of elastic waves, the mathematical model is established. Separation of variables is used to obtain the displacement in the layer and the half-space. Intrinsic boundary conditions are imposed to derive the dispersion equation. The inhomogeneity parameters associated with the rigidity, the density, and the initial stress of the medium are found to have substantial influence on the phase velocity of the torsional surface wave. The graphical presentations are drawn to exhibit the findings. The results thus obtained are significant for the investigation and characterization of torsional surface wave in the heterogeneous anisotropic layer.

关键词： hypergeometric function Laguerre function torsional wave inhomogeneity gravity initial stress sandy medium

torsional Models of Two-ply Yarn

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Journal of China Textile University(English Edition) 1998年第1期15卷 31-37页

作者：蔡家辉石济民卢明德 G.A.Carnaby Hongkong Polytechnic Univ Hongkong Hong Kong

In this paper,the vector equation of a generaliseddoubly wound helix was ***’s pliedyarn geometry could be obtained as a special case ofthe generalised doubly wound *** shortest fi-bre length around the surface of a helical tube(formed by fibre helices)was determined by apply-ing variational *** fibre length as calcu-lated by using Treloar’s geometry was compared in-directly with the shortest possible fibre length at dif-ferent levels of yarn deformation when some of Tre-loar’s rigid geometrical constraints were *** idea based on non-concentric circles was intro-duced to approximate the fibre helix movement in atwo-ply yarn.A torsional model of two-ply yarnwas developed and the theoretical predictions werecompared with some preliminary experimental re-sults.

关键词： Two-ply yarn yarn modelling doubly wound helix shortest path jammed region fibre radial movement fibre lateral movement inter-ply compres-sion fibre tensile energy torsional property

Numerical studies of the hydrodynamic damping of a vibrating hydrofoil in torsional mode

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Journal of Hydrodynamics 2021年第2期33卷 347-360页

作者： Yong-shun Zeng Zhi-feng Yao Biao Huang Fu-jun Wang Qin Wu Ruo-fu Xiao Guo-yu Wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing 100083China School of Mechanical and Vehicular Engineering Beijing Institute of TechnologyBeijing 100081China

The vortex-induced vibration may lead to a premature failure of hydraulic mechanical systems,especially under the resonance condition in the torsional *** predict the structural fatigue life,a careful consideration of the dynamic response to the hydraulic excitations is essential in the design *** study focuses on the numerical investigation of the relationship between the flow velocity,the added mass and the hydrodynamic damping,particularly,with respect to a Donaldson-type hydrofoil,vibrating in the first torsional mode.A two-way fluid-structure interaction(FSI)method is used to predict above two *** flow velocity is in the range of 0 m/s-20m/*** evaluate the hydrodynamic damping ratio,an identification method is proposed,based on a modified version of the logarithmic decay *** relative deviations of the simulated natural frequencies and hydrodynamic damping ratios as compared with the experimental data for the first torsional modes,are within 8.1%and 16.6%,*** analysis results show that the added mass coefficient for the first torsional mode is in the range of 1.59-1.86,and is around 44%of that for the first bending *** trends of the boundary layer thickness and the wake width against the reduced velocity are found to be opposite to that of the hydrodynamic damping *** theoretical equation for predicting the hydrodynamic damping ratio is modified,which is shown to be more reliable due to its consideration of the velocity independent hydrodynamic damping phase.

关键词： torsional mode hydrodynamic damping added mass hydrofoil Donaldson trailing edge

torsional Properties and Torque Relaxation of Cashmere Yarn

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Journal of Donghua University(English Edition) 2002年第3期19卷 68-72页

作者：侯秀良刘启国王善元 College of Textiles Dong Hua UniversityShanghai200051 Nantong Institute of Technology Nantong226007

By means of a torque testing apparatus with heat case and steam, the torque-twist relationship and torque-relaxation of cashmere yarn are investigated in comparison with wool yarn under two conditions of standard state and heating and steaming state, and the effect of pre-tension on the torque-relaxation of cashmere yarn is also *** shows that (1) the torque of cashmere yarn is lower than that of wool yarn under the same conditions, (2) the torques of wet cashmere and wool yarns are both lower than that of cashmere and wool yarns under standard conditions, (3) the torque hysteresis for cashmere yarn is smaller and its level and rate of torque relaxations are lower than that of wool yarn, and (4) the percentage of residual torque of cashmere yarn increases with increasing pre-tensions (630 cN).

关键词： cashmere yarn, wool yarn, torsional properties,torque, relaxation.

INTERACTION CURVES OF LINEARLY INTENSIFYING POLYMERIC MATERIALS UNDER TENSILE-torsional STRESS

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Chinese Journal of Polymer Science 2000年第6期18卷 485-493页

作者：詹茂盛 Department of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

Theoretical and experimental research has been performed on the interaction curves and stress paths of crystalline polymeric materials PE and POM under tensile-torsional stress with a linearly intensifying model and i... 详细信息

关键词： crystalline polymeric material interaction curve tensile torsional stress

torsional negative stiffness mechanism by thin strips

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Theoretical & Applied Mechanics Letters 2019年第3期9卷 206-211页

作者： Jinyou Li Kangjia Fu Yongpeng Gu Zhihua Zhao School of Aerospace Engineering Tsinghua University

Negative stiffness mechanisms have great application potential in different fields, such as vibration isolation, energy absorption and mesh antenna unfolding. Although numerous compliant mechanisms with negative stiffness features have been implemented in literature, the designing work remains in its infancy, and proposing an original design strategy may open a new avenue for the future inventions. In this study, inspired by a toy, we developed a novel type of compliant mechanism composed of thin strips, possessing negative stiffness property under torsion. The negative stiffness feature is achieved by large deformation of the strips rather than mechanical buckling. As a consequence, the obtained negative stiffness segment covers a significantly long range. Demonstrated with examples, it was shown that the proposed mechanisms could be combined with other compliant mechanisms to realize long-range unusual torque-angle relationships, which can be used in different applications.

关键词： Negative stiffness Compliant mechanism Strip torsional spring Flexible multibody system