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This paper aims to investigate post-buckling responses of shell-like structures using an implicit conservative-decaying time integration dynamic scheme.

In this work, the authors have proposed the use of a four-node quadrilateral flat shell finite element with drilling rotational degree of freedom within the framework of an updated Lagrangian formulation mutually with an implicit conservative-dissipative time integration dynamic scheme.

Several numerical simulations were considered to evaluate the accuracy, robustness, stability and the capacity of the considered time integration scheme to dissipate numerical noise in the presence of high frequencies. The obtained results illustrate a very satisfying performance of the implicit conservative-dissipative direct time integration scheme conjointly with the quadrilateral flat shell finite element with drilling rotation.

The authors have investigated the potential of the implicit dynamic scheme to deal with unstable branches after limit points in the non-linear post-buckling response of shell structures with no need for structural damping. The capability of the studied algorithm to study buckling and post-buckling behaviour of thin shell structures is illustrated through several numerical examples.

A method for non‐linear static and dynamic analysis of flexible systems submerged in water is outlined. The systems considered here include cable and beam elements, as well as buoys and clump weights. Contact and lift‐off between members and the sea floor is also accounted for. The formulation used allows for very large deformations and material non‐linearities. Hydrostatic buoyancy and hydrodynamic drag forces are considered throughout the analyses. These capabilities have been implemented in the general purpose non‐linear finite element program FENRIS. Aspects concerning efficient solution of the non‐linear static and dynamic equations are discussed. In particular, an efficient start‐up procedure for analysis of highly flexible systems is described. The paper shows applications involving static and dynamic analysis of a floating structure kept in place by six mooring lines and a flexible riser system.

A simple numerical algorithm is developed for the implementation of the harmonic balance method to analyse periodic responses of a general dynamic system having geometrical non‐linearities of the quadratic and cubic types. The resulting non‐linear algebraic equations which are not explicitly determined are solved by non‐linear equation routines available in most mathematical libraries. Various non‐linear responses, such as the combinational resonances of a hinged‐clamped beam, the non‐linear effect on degenerate vibration modes of a square plate and the non‐linear oscillation of thin rings, are presented to demonstrate the versatility of the algorithm.

This paper aims to present a new method for identification of some flight modes, including natural and non-standard modes, and extraction of their characteristics, directly from measurements of flight parameters in the time domain.

The Hilbert-Huang transform (HHT), as a novel prevailing tool in the signal analysis field, is used to attain the purpose. The study shows that the HHT has superior potential capabilities to improve the airplane flying quality analysis and to conquer some drawbacks of the classical method in flight dynamics.

The proposed method reveals the existence of some non-standard modes with small damping ratios at non-linear flight regions and obtains their characteristics.

The paper examines only airplane longitudinal dynamics. Further research is needed regarding lateral-directional dynamic modes and coupling effects of the longitudinal and lateral modes.

Application of the proposed method to the flight test data may result in real-time flying quality analysis, especially at the non-linear flight regions.

First, to utilize the empirical mode decomposition (EMD) capabilities in real time, a local-online algorithm is introduced which estimates the signal trend by the Savitzky-Golay sifting process and eliminates it from the signal in the EMD algorithm. Second, based on the local-online EMD algorithm, a systematic method is proposed to identify flight modes from flight parameters in the time domain.

The purpose of this study is to examine the dynamic performance of an orifice-compensated three-pad hydrostatic squeeze film damper.

A numerical model has been developed and presented to study the effect of eccentricity ratio and pressure ratio on the static and dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper. It is assumed that the fluid flow is incompressible, laminar, isothermal and steady-state. The finite difference method has been used to solve Reynolds equation governing the lubricant flow in film thickness of hydrostatic bearing. The numerical results obtained are discussed, analyzed and compared between three- and four-lobe hydrostatic journal bearings available in the literature.

It was found that the influence of eccentricity ratio on dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper appears to be essentially controlled by the concentric pressure ratio. It was also found that the three-pad hydrostatic squeeze film damper has higher stiffness than three and four-lobe hydrostatic journal bearings.

In fact, the results obtained show that this type of hydrostatic squeeze film damper provides hydrostatic designers a new bearing configuration suitable to control rotor vibrations.

The supercritical propulsion shaft equipped with a dry friction damper has been designed for a polish ultra light helicopter named IS‐2. Models of the shaft and the damper and some results of analysis of the shaft flexural vibrations are presented.As it turned out the shaft vibrations strongly depend on parameters of the damper (especially on the damper gap) and can be regular or chaotic. There are two main cases: the damper with a small gap and the damper with a big gap, when compared to shaft eccentricity.

A numerical investigation has been undertaken to study fluid flow and heat transfer through artificially rib‐roughened channels. Such flows are of particular interest in internal cooling of advanced gas turbine blades. The main objective is to test the suitability of recently developed variants of the cubic non‐linear k‐ε model for the prediction of cooling flows through ribbed passages. The numerical approach used in this study is the finite‐volume method together with the SIMPLE algorithm. For the modelling of turbulence, the Launder and Sharma low‐Re k‐ε model and a new version of the non‐linear low‐Re two equation model that have been recently shown to produce reliable thermal predictions in impinging jet flows and also flows through pipe expansions, have been employed. Both models have been used with the form of the length‐scale correction term to the dissipation rate originally proposed by Yap and also more recently developed differential version, NYap. The numerical results over a range of flow parameters have been compared with the reported experimental data. The mean flow predictions show that both linear and non‐linear k‐ε models with NYap can successfully reproduce the distribution of the measured streamwise velocity component, including the length and width of the separation bubble, formed downstream of each rib. As far as heat transfer predictions are concerned, the recent variant of the non‐linear k‐ε leads to marked improvements in comparison to the original version of Craft et al. Further improvements in the thermal prediction result through the introduction of a differential form of the turbulent length scale correction term to the dissipation rate equation. The version of the non‐linear k‐ε that has been shown in earlier studies to improve thermal predictions in pipe expansions and impinging jets; it is thus found to also produce reasonable heat transfer predictions in ribbed passages.

In the vibration reduction field, constrained stand-off layer damping cylindrical shell plays an important role. However, due to the lack of accurate analysis of its damping characteristics, this hinders its further research and application. Therefore, the purpose of this paper is concerned with an accurate solution for the vibration-damping characteristics of a constrained stand-off-layer damping cylindrical shell (CSDCS) under various classical boundary conditions and conducts a further analysis.

Based on the Rayleigh–Ritz method and the Hamilton principle, a dynamic model of CSDCS is established. Then the loss factor and the frequency of CSDCS are obtained. The correctness and convergence behavior of the present model are verified by comparing the calculation results with the literature. By using for various classical boundary conditions without any special modifications in the solution procedure, the characteristics of CSDCS with S-S, C-C, C-S, C-F and S-F boundaries are discussed.

The Rayleigh–Ritz method is effective in handling the problem of CSDCS with different boundaries and an accurate solution is obtained. The boundary conditions have an important influence on the vibration and damping behavior of the CSDCS.

Based on the Rayleigh–Ritz method and Hamilton principle, a dynamic model of CSDCS is established for the first time, and then the loss factor and frequency of CSDCS are obtained. In addition, the effectiveness of adding the stand-off layer between the base shell and the viscoelastic layer is confirmed by discussing the characteristics of CSDCS with S-S, C-C, C-S, C-F and S-F boundaries.

THE simplest type of aircraft power control is probably that shown in FIG. 1. The dynamics of this type of servo have been discussed in papers by Harpur and others, and it is shown that if the valve has cither zero or positive overlap the servo will be unstable with inertia loading. Harpur suggested the following methods of stabilizing the servo:

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.