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Technique for creation of polycrystalline computer materials is presented. The method considered allows for the obtaining of not only polycrystalline particle packings with various grains sizes but also the creating of materials with the preset value of porosity. Plate impact experiments were performed to compare strength properties of mono- and polycrystalline computer materials and also to investigate...
This paper deals with simplified mathematical models of the dynamic systems with weak non-linearities and described by complex continuous transfer functions without jumping. We consider only the first approximation of the steady state forced vibration where the complex amplitude corresponds to the same frequency as the harmonic excitation. The iterative smoothing of the above system from the measured...
Dynamic properties of simple mechanical 1 DOF system containing soft stop is described and analyzed. The proposed general dynamical impact model respects the nonlinearity of the restoring contact force between solid bodies as function of deformation and velocity. It describes the real behavior of impacting system more exact than the piecewise linear model or the Kelvin–Voigt model and even model based...
A p-version, hierarchical finite element for moderately thick isotropic plates is derived and free vibrations are studied. The effects of the rotatory inertia, transverse shear and geometrical non-linearity, due to moderately large displacements, are taken into account. The time domain free vibration equations of motion are obtained by applying the principle of virtual work, and are mapped into the...
Aspects of drill-string vibrations in the context of a recently developed integrated model of a drill-rig assembly based on the Cosserat theory of rods are discussed. Computer simulations are used to compare existing rotary feedback strategies currently in use to optimise drilling performance where torsional slip-stick vibrations are a hazard. Guided by the wave nature of axial and torsional vibrations...
A two degrees of freedom model of two coupled suspension systems characterised by piecewise linear stiffness has been studied. The system, representing a pantograph current collector head, is shown to be sensitive to changes in excitation and system parameters, possessing chaotic, periodic and quasiperiodic behaviour. The coupled system has a more irregular behaviour with larger motions than the uncoupled...
A novel experimental rig capable of generating a versatile dynamic loading has been designed and tested to overcome the shortcomings of conventional fatigue testing machines such as the difficulty in providing zero crossing aperiodic loading. The main principle of this new design is based on two, single degree of freedom based excited oscillators, where inertial forces act on a specially designed...
This paper describes current research into the mathematical modelling of a vibro-impact ground moling system. Due to the structural complexity of such systems, in the first instance the dynamic response of an idealised impact oscillator is investigated. The model is comprised of an harmonically excited mass simulating the penetrating part of the mole and a visco-elastic slider, which represents the...
Ground anchorage systems are used extensively throughout the world as supporting devices for civil engineering structures such as bridges and tunnels. The condition monitoring of ground anchorages is a new area of research, with the long term objective being a wholly automated or semi-automated condition monitoring system capable of repeatable and accurate diagnosis of faults and anchorage post-tension...
In this paper we investigate the nonlinear dynamics of a cantilever elastic pipe that contains pulsatile flow. The equation of motion was derived by using Hamiltonian action function. We use Galerkin's technique to include only finite number of spatial modes in the solution. The stability chart of the time-varying system was computed in the space of the relative perturbation amplitude of the...
A systematic investigation of the dynamics of an offshore system is presented using two different approaches. The multiple scales method and path following techniques in combination with numerical integration of the equations of motion are applied in order to analyze the dynamics of a periodically forced floating crane in frequency and time domain, respectively.
Time series data from stochastic processes described by the Langevin equation are analyzed. Analysis is based on estimation of the deterministic and random terms of the Langevin equation from data. The terms are presented as fields and inspected visually. Forming a model of the process, the terms are also used to reconstruct the deterministic and stochastic process trajectories. The deterministic...
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