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Abstract:
The paper presents a novel approach for prototyping and modelling of the Adaptive Tuned Particle Impact Damper (ATPID). After introducing the operation and potential disadvantages of the classical Particles Impact Dampers (PIDs) the authors propose the concept of single-grain controllable damper, which can adapt to actual dynamic excitation by a real-time change of the container height. The investigations focus on the methodology of simplified mathematical modelling of the ATPID damper based on grain physical properties, nonlinear soft contact theory, and control function of the absorber height being a novel component used to optimize dynamic response of the system. The proposed ATPID model is positively verified against the experimental results obtained from the developed test stand including a vibrating beam equipped with the proposed innovative attenuator. The conducted analyses clearly reveal the operating principles of the ATPID damper, the types of grain movement, the influence of shock absorber parameters on the vibrating system response and the energy balance of the system. The solution of the formulated optimization problem aimed at minimization of vibration amplitudes allows to find the optimal damper height for various physical parameters of the grain and the external excitation and to achieve a high efficiency of the proposed damper reaching 90%. In addition, a real-time control strategy providing adaptation of the ATPID damper to changing amplitude of kinematic excitation and effective mitigation of steady-state vibrations is proposed and verified experimentally.

Keywords:
Adaptive Tuned Particle Impact Damper, Damping of vibrations, Semi-active damping, Controllable damper, Control function, Sensitivity analysis, System optimization, Real-time control strategy

Abstract:
Jammed granular systems, also known as vacuum packed particles (VPP), have begun to compete with the well commercialized group of smart structures already widely applied in various fields of industry, mainly in civil and mechanical engineering. However, the engineering applications of VPP are far ahead of the mathematical description of the complex mechanical mechanisms observed in these unconventional structures. As their wider commercialization is hindered by this gap, in the paper the authors consider experimental investigations of granular systems, mainly focusing on the mechanical responses that take place under various temperature and strain rate conditions. To capture the nonlinear behavior of jammed granular systems, a constitutive model constituting an extension of the Johnson–Cook model was developed and is presented. green The extended and modified constitutive model for VPP proposed in the paper could be implemented in the future into a commercial Finite Element Analysis code, making it possible to carry out fast and reliable numerical simulations.

Keywords:
vacuum packed particles, granular jamming, smart materials, Johnson-Cook model

Abstract:
In this paper, we present a novel approach to modeling and analysis of Vacuum Packed Particle dampers (VPP dampers) with the use of Discrete Element Method (DEM). VPP dampers are composed of loose granular medium encapsulated in a hermetic envelope, with controlled pressure inside the envelope. By changing the level of underpressure inside the envelope, one can control mechanical properties of the system. The main novelty of the DEM model proposed in this paper is the method to treat special (pressure) boundary conditions at the envelope. The model has been implemented within the open-source Yade DEM software. Preliminary results are presented and discussed in the paper. The qualitative agreement with experimental results has been achieved.

Keywords:
VPP, discrete element method, Yade DEM, modelling, smart structures, smart materials

Abstract:
A new semi-active damping of vibrations method is presented, which is based on loose granular grains that are placed in a hermetic sleeve that is surrounding a steel beam, forming a complex controllable granular beam structure. Changing the partial pressure inside the structure results in changes of the elastic and dissipative properties of the system resulting from the granules’ jamming mechanism. The paper presents both experimental and theoretical analyses of a vibrating cantilever granular beam system. The linear Bernoulli–Euler beam model with Kelvin–Voigt damping that depends on underpressure is used to describe the behavior of the investigated structure. The proposed strategy of vibrations damping is found to be easy to implement, provides satisfactory damping, and is efficient, but also indicates that a nonlinear beam model may be a better fit.

Keywords:
Special Granular Structures, Semi-active damping of vibrations, Jamming mechanism, Experiments, Modeling, Beam vibrations

Abstract:
The dynamics of an inertially excited steel cantilever beam encapsulated in a hermetic sleeve filled with polypropylene grains is investigated experimentally and theoretically. An electric motor rotating an unbalanced mass is attached at the end of the beam to generate forced vibrations of the system. Changing the underpressure in the sleeve results in changes of the stiffness and dissipative properties of the composite structure, which allow one to control the resonant characteristics of the system. Is is shown that the amplitude of vibrations can be reduced in this way. This innovative semi-active method of vibration damping is based on the jamming mechanism of the granules, and proved to be efficient in the reduction of the free vibrations of the beam, which was studied in the authors' latest paper. In the present work, it is confirmed that the classical Bernoulli–Euler beam model with Kelvin–Voigt damping provides a satisfactory explanation of the observed relation between the vibrations amplitude and underpressure.

Keywords:
Vacuum Packed Particles, semi-active damping, jamming mechanism, inertial excitation