Dynamic Torsional Vibration Research Articles

Dynamic Torsional Vibration of a Pipe Pile in Radial Heterogeneous Transversely Isotropic Saturated Soil

Dynamic Torsional Vibration of a Pipe Pile in Radial Heterogeneous Transversely Isotropic Saturated Soil

Analysis of deformation and force behavior of pile in double-parameter layered foundation subjected to combined horizontal dynamic load and torsional vibration

Analysis of deformation and force behavior of pile in double-parameter layered foundation subjected to combined horizontal dynamic load and torsional vibration

Study on curing kinetics and behaviours of PGN adhesives.

The curing kinetics between PGN and N100 were studied by Fourier transform infrared spectroscopy and dynamic torsional vibration method. The results showed that the entire curing process of adhesives was divided into three stages. Infrared spectroscopy can only monitor the first and second stages, while dynamic torsional vibration method monitors the second and third stages. Combining the two analysis methods allows the complete monitoring of the entire curing process in this system. Besides, differential scanning calorimeter is not suitable for studying this process.

Multidimensional vibration reduction control of the frame structure with magnetorheological damper

To analyze the multidimensional vibration reduction performance and torsional vibration characteristics of frame structures with magnetorheological damper (MRD), the space models of the reinforced concrete (RC) frame structure with and without MRD, based on the space beam element and shell element model, are established and programmed by using MATLAB software. Then, comparisons on results of modal analysis and dynamic time history response calculated from self-programmed space model and finite element model established by ANSYS software are carried out. The comparison results show that the self-programmed space model is validity and reliability. Finally, the dynamic time history analyses on the structures with and without MRD under bidirectional seismic wave action are presented; the multidimensional dynamic time history response and torsional vibration response between the uncontrolled and the controlled structures are then compared. The comparison results show that MRD can effectively reduce the three-dimensional displacement response and restraint the torsional vibration response of the space frame structure.

Exponential and harmonic forced torsional vibration of single-walled carbon nanotube in an elastic medium

In this study, free torsional vibration and forced torsional vibration analysis under the time-dependent exponential and harmonic torsional loadings in single-walled carbon nanotube are investigated. The SWCNT is embedded in an elastic medium. Eringen's theory among the small-scale theories is selected. The nonlocal differential constitutive relation and corresponding boundary condition are derived via Hamilton's principle. Clamped–clamped boundary condition is utilized. The assumed modes method is employed for the dynamic torsional vibration in order to discretize the derived governing equations. The novelty of this work is devoted to the analysis of forced torsional vibration of a carbon nanotube embedded in an elastic medium under the various loadings. The angular displacement for the resonance frequency neglecting the elastic medium is illustrated. For the free analysis, the first three nondimensional natural frequencies with various small-scale parameters and stiffness of the elastic medium are calculated. The results are compared with another study for the first 10 mode numbers. The effects of the nonlocal parameter, length of carbon nanotube, stiffness of the elastic medium, thickness, time constant, and excitation frequency on the nondimensional and dimensional angular displacements are investigated, dynamically. For the greater values of the stiffness of the medium, the nonlocal parameter becomes negligible. When a time-dependent exponential torque is applied to the model, the angular displacement becomes greater and then lower by an increase in the value of the length, but the nondimensional angular displacement decreases continuously by increasing the value of the length under the time-dependent harmonic loading. Moreover, the angular displacement for a determined time becomes lower first and then becomes greater by increasing the time constant.

A torsional vibration damper based on a serial viscoelastic coupling of its seismic mass

The design of dynamic torsional vibration dampers of piston internal combustion engines is generally based on the principle of a dynamic damper with one degree of freedom in which the coupling of the seismic mass of the damper to the basic dynamic system is realized by a two-parameter parallel rheological model. With known realizations of this principle, it is usually difficult to achieve the optimum value of the respective damper parameters determined from the computational models, which is particularly true for optimal damping values. A dynamic torsional damper, based on the series arrangement principle of the elastic and damping element, offers better design options to achieve the optimum parameters of both the elastic and damping elements.

Optimal design of structure in rheological models: an automotive application to dampers with high viscosity silicone fluids

Dynamic torsional vibration dampers are for a long time inherent integral components of internal combustion engines. One of the most common types of the dynamic dampers is a silicone damper. It has been, for many years, perceived as an exclusively viscous damper, thus it has been constructed and designed according to this perception. When compared to other types of dynamic dampers of the similar size with flexible components used for their construction, the standard viscous damper has a lower damping effect. Moreover, this damper type has been a significantly cheaper and simpler solution. Current silicone oils with high nominal viscosity, having not only the expected damping properties, but also significant elastic characteristics under alternate shear stress, enable construction of dynamic dampers with a higher damping effect than a viscous damper. Frequency and temperature dependent complicated rheological properties of high viscosity silicone fluids can only be identified experimentally using a suitable dynamic viscometer. However, the measured frequency dependencies of both components of the complex shear modulus are only defined for harmonic loading while internal combustion engine load is periodic and contains several tens harmonics. The key to the solution is therefore to find suitable multiparameter rheological models comprised of linear elastic and damping elements that would approximate in the specified frequency range both components of the complex shear modulus. Such a complicated task can be solved using efficient optimization algorithms. This article focuses on the mathematical description of convolute rheological properties of high viscosity silicone liquids and also contains an example of the application of created rheological models in the complex dynamic model of a V10 diesel engine. A computational tool for the determination of stiffness and damping coefficients of the multi-parameter rheological model was created and solved in the optimization software GAMS by means of the CONOPT solver. The possibility of these modern technologies is shown by the comparison of computation models and experimentally set torsional vibration spectres with standard viscous damper and damper utilizing a high viscosity silicone oil.

Calibration exercise of a Hardin-type resonant column

This technical note presents the calibration exercise of a Hardin-type resonant column of fixed–partly fixed ends, which is capable of exerting dynamic torsional vibration on the specimen. The apparatus uses a mechanical system connected to the drive mechanism which works as a massless torsional spring–dashpot and can apply axial load of compression or extension to the specimen. Thus, the vibration of this system follows the physics of oscillators (spring-type model), which is highly strain-rate dependent. The calibration exercise led to the estimation of the apparatus rotational inertia (JA). The calibration exercise was carried out using aluminium bars of known stiffness and of variable dimensions covering a range of frequencies from about 60 to 95 Hz, as well as real soil specimens, which were used as calibration rods covering an additional range of frequencies from about 85 to 170 Hz. This allowed a wide range of frequencies to be captured, which are representative of resonant frequencies of soil specimens of 70 mm dia. and 140 mm long. For the real soil specimens, which were used as calibration rods, the rotational stiffness necessary for the estimation of JAwas estimated from bender elements inserted into the resonant column. It was shown that JAwas frequency dependent, which is in alignment with the vibration of oscillators.

Parametric resonances for torsional vibration of excited rotating machineries with nonconstant velocity joints

The shaft system is a rotating machinery with many applications due to its high speed. The angle between shafts may not be zero. So the shafts can be connected to each other through a nonconstant velocity U-joint, which transforms a constant input angular velocity into a periodically fluctuating velocity. Consequently, the mechanism is parametrically excited and may face resonance conditions. Herein, a power transmission system including three elastic shafts is considered. The polar inertia moment of each shaft is modeled as a dynamic system with two discrete disks at the shaft ends. The equations of motion consist of a set of Mathieu–Hill differential equations with periodic coefficients. The dynamic stability and torsional vibration of the shaft system are analyzed. The system geometry and inertia moment effect are the main issues in this contribution. Parametric instability charts are achieved via the monodromy matrix technique. The graphical numerical results are validated with the frequency analytical results. Finally, the stability regions are shown in the parameter spaces of velocity, misalignment angles and the inertia of disks. The results demonstrated that by changing the system inertia and geometry, stabilizing the whole system is possible. Moreover, to check the precision of the model, the results are compared with a basic single-disk model, which is prevalent in two-shaft systems.

Polyamidoamine dendrimers as curing agents: The optimum polyamidoamine concentration selected by dynamic torsional vibration method and thermogravimetric analyses

AbstractPolyamidoamine (PAMAM) dendrimers were investigated as curing agents in bisphenol A epoxy resin systems. The cure behavior of epoxy resin/PAMAM at varying components was investigated by a dynamic torsional vibration method (DTVM); the thermal behavior of the materials was characterized by means of thermogravimetric (TGA) analyses. The DTVM results show that 10/100 parts of the resin (phr) PAMAM was the optimum concentration for 1.0, 3.0, and 5.0 G PAMAM dendrimers/resin systems in our experiment. Also, the TGA results agreed with the conclusions made by the DTVM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1430–1434, 2007

Cure Behavior of Epoxy Resin E51–Melamine Phosphate (MP)–MeTHPA–2,4-EMI Halogen-free Fire Retardant Composite by the Dynamic Torsional Vibration Method

The cure behavior of epoxy resin E51–melamine phosphate (MP)–methyltetrahydrophthalic anhydride (MeTHPA)–2-ethyl-4-methyl-imidazole (2,4-EMI) halogen-free fire retardant composite at varying temperatures and MP loading is investigated by the dynamic torsional vibration method (DTVM). The dynamic parameters, such as gelation time tg, apparent activation energy Ea, and curing rate k are estimated as well. The theoretical prediction is in good agreement with the experimental results obtained by the DTVM. The results show that the rate of cure reactions depends distinctly on the cure temperature. At low MP loadings, the tg for the systems does not change obviously, while at higher MP loadings, it has a remarkable increase. Furthermore, the Flory's gelation theory and the Avrami equation are used to describe the cure behavior of the halogen-free fire retardant composite system.

Cure behavior of epoxy resin/CdS/2,4-EMI nanocomposites investigated by dynamic torsional vibration method (DTVM)

Epoxy resin/CdS nanocomposite was prepared by a novel method and its cure behavior was investigated by the HLX-II Resin Curemeter based on the dynamic torsional vibration method (DTVM). The non-equilibrium thermodynamic fluctuation theory, the Avrami equation and the Flory’s gelation theory have been used to analysis the cure behavior of the composite systems with different CdS and cure agent loadings at various temperatures. The results show that the addition of CdS nanoparticles reduces the gel time tg, but has little effect on the mechanism of the cure reaction. The theoretical prediction is in good agreement with the experimental results. The Avrami exponent of n decreases a little when the temperature increases.

Tracing the sol–gel transformation by dynamic torsional vibration method

Tracing the sol–gel transformation by dynamic torsional vibration method

Cure behavior of UP/Org‐MMT/MEKP/cobalt octoate nanocomposites by the dynamic torsional vibration method

AbstractThe cure behavior of unsaturated polyester(UP)/organo‐montmorillonite (Org‐MMT)/methyl ethyl ketone peroxide (MEKP)/cobalt octoate intercalated nanocomposites at varying temperatures and Org‐MMT loadings was investigated by the Dynamic Torsional Vibration Method (DTVM). The apparent kinetic parameters of the cure reaction, including the gelation time tg, apparent activation energy Ea, and curing rate, etc., were estimated by Flory's gelation theory, non‐equilibrium thermodynamic fluctuation theory, and Avrami equation. The theoretical prediction is in good agreement with the experimental results obtained by the DTVM. The gelation time tg increases, and the rate of curing reaction decreases, with increasing Org‐MMT loadings, but there is no obvious effect of Org‐MMT on the apparent activation energy Ea and the curing process of nanocomposites. A two‐step cure process of UP was observed due to the addition of Org‐MMT. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1–7, 2005

Behavior of polyamidoamine dendrimers as curing agents in bis‐phenol A epoxy resin systems

AbstractPolyamidoamine (PAMAM) dendrimers with different generations (0–5) were investigated as curing agents in epoxy resin systems. Flory's gelation theory and the Avrami equation were used to predict the cure behavior of epoxy resin/PAMAM/imidazole at various temperatures and PAMAM concentrations. The theoretical prediction is in good agreement with the experimental results obtained from the dynamic torsional vibration method. Copyright © 2004 Society of Chemical Industry

Curing Study of a Toughened Epoxy System Using the Dynamic Torsional Vibration Method

Epoxy resins are widely used as adhesives or as the matrix of high-performance composites and the monitoring for quality of their cure process is of great interest. In this paper, the cure kinetics of an epoxy/polyamide system was successfully studied using the dynamic torsional vibration method (DTVM) by measuring the change in mechanical properties (torque) during the cure. The experimental data were analyzed by the non-equilibrium thermodynamic fluctuation theory and the Avrami method. The results from dynamic mechanical thermal analysis (DMTA) reveal that the fully cured specimens of epoxy resin/polyamide exist in the rubbery plateau state at the applied cure temperature. With increasing cure temperature, the equilibrium torque drops, the gel time decreases and the cure reaction takes less time to complete. After the gel point, the same curing mechanism occurs at various cure temperatures. The effect of increasing hardener concentration on the rate of cross-linking at a given cure temperature was also examined. Excess polyamide increases the number of cross-linking points, and hence enlarges the Avrami exponent n.

Cure behavior of epoxy resin/MMT/DETA nanocomposite

The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict the gel time tg and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation time tgand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60°C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent activation energy of the cure reaction after gelation point. There is no special curing process required for the formation of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.

Centrifugal Pendulum Vibration Absorbers: An Experimental and Theoretical Investigation

This paper presents results from tests completed on a rotor system fitted with pendulum-type centrifugal torsional vibration absorbers. A review of the associated theoretical background is also given and the experimental and theoretical results are compared andcontrasted. An overview of the test apparatus is provided and itsunique features are discussed. To the best knowledge of the authors,this is the first time that a systematic study of the dynamic behaviorof torsional vibration absorbers has been undertaken in a controlledenvironment.

Cure Behavior of Epoxy Resin-Montmorillonite-2-Ethyl-4-Methylimidazole Nanocomposite

Understanding of the mechanism and kinetics of cure for polymer-layered silicate nanocomposites is now the interest of research. The objective of this investigation is to determine the effects of polymer-layered silicate on the cure kinetics of an epoxy resin. The cure process of epoxy resin-organo-montmorillonite (Org-MMT)-2-ethyl-4-methylimidazole (2,4-EMI) nanocomposite with different Org-MMT loadings was in situ monitored with a technique of dynamic torsional vibration method (DTVM) in the isothermal mode. The gel time tg and the completed cure time tc can be read directly from the isothermal cure curve, and the results show that the addition of Org-MMT reduces the tg and increases the rate of curing reaction. The apparent activation energy Ea of cure reaction was estimated by the nonequilibrium thermodynamic fluctuation theory as well. With increasing of cure temperature, the tg decreased and correspondingly, the cure rate was accelerated. In addition, the theoretical prediction was in good agreement with the experimental results obtained by DTVM.

Cure kinetics of epoxy-based nanocomposites analyzed by Avrami theory of phase change

The effect of montmorillonite on the cure kinetics and the structure of epoxy resin/organo-montmorillonite (Org-MMT)/methyltetrahydrophthalic anhydride (MeTHPA)/2-ethyl-4-methyl-imidazole (2,4-EMI) nanocomposites are investigated by X-ray diffraction (XRD) and the dynamic torsional vibration method (DTVM). The XRD result indicates that an exfoliated nanocomposite was obtained. The experimental data obtained from DTVM are explained by the Avrami theory of phase change, and show that the theoretical prediction is in good agreement with the experimental results. No special formation mechanism for epoxy resin/Org-MMT/MeTHPA/2,4-EMI nanocomposite is observed. The addition of Org-MMT reduces the gelation time t g, and increases the rate of the curing reaction and the value of the kinetic constant k. The half-time t 1/2 of cure after the gel point decreases with increasing cure temperature, while the values of kinetic constant k rise as the cure temperature increases. The nanocomposite has a larger value of k and smaller value of n comparing with the epoxy resin/MeTHPA/2,4-EMI system without Org-MMT.