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An analytical rheological‐dynamical visco‐elastic solution of one‐dimensional longitudinal continuous vibration of bars has been developed and used to evaluate the validity of the classical analytical elastic solutions. As it is well known, the resonance occurs only in the continuous or singledegree‐of‐freedom ideal elastic system when the excitation frequency ωP is equal to the one of the natural frequency of the bar. However, owing to the visco‐elastic nature of materials and frequency dependence of the damping factor it is useful to consider separately the situations arising when the is positive (system is stable) and when it is negative. Negative damping factor means that the complementary solution of the response would not die away (system is unstable because of the factor e). Rheologic behavior of the bar can be characterized by one parameter, i.e. dynamic time of retardation TK D=1/ω, like in a single‐degree‐of‐freedom spring mass system. RDA model has the same phase angle as a simple single‐degree‐of‐freedom spring mass system with damping in the steady state vibration and from that the damping factor is obtained. This paper provides description of the dynamic magnification factor and the transmissibility of several metallic materials using RDA similitude and could be concluded that an ideally effective antivibration mount material should satisfy at least two requirements: first, it should posses a relatively large damping factor; and second, it should possess a damping factor that either remains constant or decreases only slowly with frequency.

The present investigation is concerned with the utilisation of the finite element technique for predicting the natural frequencies and the modal damping factor (also called the loss factor) of anisotropic fibre‐reinforced composite laminated plates. The simple definition of the modal damping factor is defined as the ratio of the strain energy dissipated per radian of vibration, in the mode of interest, to the total strain energy of the entire laminate at maximum displacement during the same cycle. Results for the vibration and damping analysis of multi‐layered plates obtained by the present methods are compared with the results obtained by other authors and with the results of experiments.

As an important part of the rotor system, the damping coefficient of ball bearing has a great influence on the dynamic characteristics of the system. This study aims to propose a theoretical calculation method and an experimental test method to obtain the damping coefficient of ball bearing.

Based on Hertzian contact theory and elastohydrodynamic lubrication theory, the point contact oil film damping analysis model of ball bearing is established. The comprehensive damping calculation method considering external radial load, centrifugal force, ball spin, rotational speed and lubricating oil film is derived. The multigrid method is used to obtain the oil film pressure and thickness distribution in the contact zone. The variation trend of comprehensive damping with bearing radial load, rotational speed, oil film thickness and viscosity is analyzed. The test platform is designed and the influencing factors of damping are tested.

The validity of the model and reliability of the test device are verified by comparing the good consistency obtained in the work. The results show that the comprehensive damping of ball bearing increases with the increase of radial load and decreases with the increase of rotational speed.

At present, the existing bearing damping model can achieve approximate calculation of damping, but the factors considered in these models are not comprehensive enough. Besides, few studies exist regarding test platform of bearing damping, and a perfect test plan has not yet been formed. In this paper, the comprehensive damping calculation model of ball bearing is improved, and a complete experimental scheme is proposed to provide reference for the comprehensive damping theory and experimental research of bearing.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0342/

The purpose of this study is to provide some references about applying the semi-active particle damper to enhance the stability of the pipe structure.

This paper establishes the dynamical models of semi-active particle damper based on traditional dynamical theory and fractional-order theory, respectively. The semi-active particle damping vibration isolation system applied in a pipe structure is proposed, and its analytical solution compared with G-L numerical solution is solved by the averaging method. The quantitative relationships of fractional-order parameters (a and kp) are confirmed and their influences on the amplitude-frequency response of the vibration isolation system are analyzed. A fixed point can be obtained from the amplitude-frequency response curve, and the optimal parameter used for improving the vibration reduction effect of semi-active particle damper can be calculated based on this point. The nonlinear phenomenon caused by nonlinear oscillators is also investigated.

The results show that the nonlinear stiffness parameter p will cause the jump phenomenon while p is close to 87; with the variation of nonlinear damping parameter μ, the pitchfork bifurcation phenomenon will occur with an unstable branch after the transient response; with the change of fractional-order coefficient k_p, a segmented bifurcation phenomenon will happen, where an interval that k_p between 18.5 and 21.5 has no bifurcation phenomenon.

This study establishes a mathematical model of the typical semi-active particle damping vibration isolation system according to fractional-order theory and researches its nonlinear characteristics.

Usual definitions of damping in oscillatory modes are reviewed, a new definition is proposed and it is suggested that the latter offers certain advantages to both the theoretical and the practical worker in this field. An Appendix contains response formulae for three fundamental types of disturbance. These can be used for the derivation of the various expressions characterizing dynamic properties of any mode that is equivalent to a damped system of one degree of freedom. A collection of formulae, numerical tables and graphs permit a quick comparison to be made between the different definitions of damping.

The study aims to investigate the influence of fabric hybridization, stacking sequences and matrix materials on the tensile strength and damping behavior of jute/carbon reinforced hybrid composites.

The hybrid composites were fabricated with different sequences of fabric plies in epoxy and polyester matrix using a hand layup technique. The tensile and vibration characteristics were evaluated on the hybrid laminated composite models using finite element analysis (FEA), and the results were validated experimentally according to ASTM standards. The surface morphology of the fractured specimens was studied using the scanning electron microscope.

The experimental results revealed that the position of jute layers in the hybrid composites has a significant influence on the tensile strength and damping behavior. The hybrid composite with jute fiber at the surface sides and carbon fibers at the middle exhibited higher tensile strength with superior damping properties. Further, it is found that the experimental results are in good coherence with the FEA results.

The less weight and low-cost hybrid composites were fabricated by incorporating the jute and carbon fabrics in interply configurations. The influences of fabric hybridization, stacking arrangements and matrix materials on the tensile and vibration behavior of jute/carbon hybrid composites have been numerically evaluated and the results were experimentally validated.

This paper describes a parallel algorithm for the dynamic relaxation (DR) method. The basic theory of the dynamic relaxation is briefly reviewed to prepare the reader for the parallel implementation of the algorithm. Some fundamental parallel processing schemes have been explored for the implementation of the algorithm. Geometric Parallelism was found suitable for the DR method when using transputer‐based systems. The evolution of the parallel algorithm is given by identifying the steps which may be executed in parallel. The structure of the parallel code is discussed and then described algorithmically. Two geometrically non‐linear parallel finite element analyses have been performed using different mesh densities. The number of processors was varied to investigate algorithm efficiency and speed ups. Using the results obtained it is shown that the computational efficiency increases when the computational load per processor is increased.

The purpose of this study is to bring down collective information about various issues encountered in modelling of rotor systems.

The most important and basic part of “rotor dynamics” is the study related to its different modelling techniques which further involves the analysis of shaft for understanding the system potential, competence and reliability. The issues addressed in this study are classified mainly into two parts: the initial part gives out a vast overview of significant problems as well as different techniques applied to encounter modelling of rotor systems, while the latter part of the study describes the post-processing problem that occurs while performing the dynamic analysis.

The review incorporates the most important research works that have already placed a benchmark right from the beginning as well as the recent works that are still being carried out to further produce better outcomes. The review concludes with the modal analysis of rotor shaft to show the importance of mathematical model through its dynamic behaviour.

A critical literature review on the modelling techniques of rotor shaft systems is provided from earliest to latest along with its real-time application in different research and industrial fields.

The purpose of this paper is to present and demonstrate the efficiency of utilization of a new approach for estimating parameters of micromechanical gyros (MMG) during their operation. It is shown that the main sources of errors are due to the following three factors: measurement errors of micron deviations of the sensitive element, unknown actual value of difference between the frequencies of primary and secondary oscillations and unknown value of damping constant for the axis of secondary oscillations. The estimation of the last two factors during the operation leads to a significant increase of accuracy of MMG. The solution of the problem is presented in the current paper.

To solve this problem, an original two-level algorithm intended for use in the embedded MMG controller is considered. The identification of the internal MMG parameters is carried out at the first stage. At the second stage, an MMG model is created, based on the results of identification of parameters at the first stage. This model is used as a basis for synthesis of a Kalman filter for estimating the angular velocity. The ways of simplifying identification algorithms and filtering for the purpose of their practical implementation are shown.

This paper presents the research results on the effectiveness of the proposed algorithms. Results of simulation are used to confirm the effectiveness of the proposed algorithm in reducing the effect of changes in the design parameters of MMG on the accuracy of the angular velocity measurements.

Proposed algorithms can be used in embedded MMG controllers.

This paper presents a new approach for improving the accuracy of MMG by using a built-in algorithm for estimating parameters during system operation.

VARIATION IN “TYPICAL VALUE” PARAMETERS IT has previously been shown that the effect of freeing the controls on the lateral stability of an aircraft may be taken account of by changes both in the values of the derivatives lp, lr, np and nr (wing), which hitherto have had typcial values, and also of the variables x, y and t themselves. It is therefore desirable to have information on the effect on the stability boundaries of changes in these derivatives. It may also happen that the values of yv and tan Θo in the case of a particular aircraft may be known to differ from those here adopted in the drawing of stability charts. The versatility of these charts (later to be given) will therefore be considerably increased if rules are expounded for assessing the effects of changes in any of those derivatives which were formerly fixed. This we proceed to do.