Collision enhanced hyper-damping in nonlinear elastic metamaterial

Nonlinear elastic metamaterial, a topic which has attracted extensive attention in recent years, can enable broadband vibration reduction under relatively large amplitude. The combination of damping and strong nonlinearity in metamaterials may entail auxetic effects and offer the capability for low-frequency and broadband vibration reduction. However, there exists a clear lack of proper design methods as well as a deficiency in understanding properties arising from this concept. To tackle this problem, this paper numerically demonstrates that the nonlinear elastic metamaterials, consisting of sandwich damping layers and collision resonators, can generate very robust hyper-damping effect, conducive to efficient and broadband vibration suppression. The collision-enhanced hyper damping is persistently present in a large parameter space, ranging from small to large amplitudes, and for small and large damping coefficient. The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials. We report the design concept, properties and mechanisms of the hyper-damping and its effect on vibration transmission. This paper reveals new properties offered by nonlinear elastic metamaterials, and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.

Tool Bits with Elastic Damping Inserted Elements Formed by Semi-Inserts with Different Rigidity

Vibration during turning is a consequence of premature tool wear and an increase in the roughness of parts. The designs of tool bits that increase their durability, reduce vibrations arising during the cutting process, and improve the quality of processing are of practical and scientific interest. Existing developments of vibration-damping bits with elastic damping inserts of constant rigidity, in which a holder or mandrel with a cut-off insert is installed, do not meet the requirements for the efficiency of vibration reduction due to the impossibility of the necessary vibration damping; the consumption of insert materials is high. Innovative designs of tool bits with inserts formed by semi-inserts with different rigidity are proposed, which allows improving the quality of processing by increasing the efficiency of vibration damping, reducing material consumption, because the length of the semi-inserts is less than half the length of the full insert. The tool bits can be used in the area of cutting materials, mechanical engineering and tool manufacturing.

Energy Efficient Strategy Development of Steam Turbine through Vibration Reduction Using ANN and SVM Approaches

The energy efficiency of a power plant is largely determined by the vibrations of bearings that hold the shaft rotating at high speed which need to be critically controlled. This study presents the relative vibration modeling of a shaft bearing that is installed in a 660 MW supercritical steam turbine system. The operational data in raw form after being cleaned using machine learning based visualization and extensive data processing helped in training and validation of SVM and ANN models which are then compared by external validation tests. The model with best results is then used for the simulations of constructed operating scenarios. The ANN has been further tested for the complete operational load range (353 MW to 662 MW) which predicted the reduction in relative vibrations. Moreover, the validated ANN model has been used to develop many strategies of vibration reduction which helped in achieving more than 4% reduction in relative vibrations. Subsequently, an operational strategy that predicts a significant reduction in the bearing vibration levels is selected. For confirmation of the accuracy of prediction by ANN process model, the selected strategy has been used with the actual power plant. This assures the significant reduction of bearing vibration less than the alarm limit.

OPTIMAL PIEZOELECTRIC SHUNT DAMPER USING ENHANCED SYNTHETIC INDUCTOR: SIMULATION AND EXPERIMENTAL VALIDATION

Piezoelectric material has the ability to convert mechanical energy to electrical energy and vice versa, making it suitable for use as an actuator and sensor. When used as a controller in sensor mode, the piezoelectric transducer is connected to an external electrical circuit where the converted electrical energy will be dissipated through Joule heat; also known as piezoelectric shunt damper (PSD). In this work, a PSD is used to dampen the first resonance of a cantilever beam by connecting its terminal to an RL shunt circuit configured in series. The optimal resistance and inductance values for maximum energy dissipation are determined by matching the parameters to the first resonant frequency of the cantilever beam, where R = 78.28 k? and L = 2.9 kH are found to be the optimal values. To realize the large inductance value, a synthetic inductor is utilized and here, the design is enhanced by introducing a polarized capacitor to avoid impedance mismatch. The mathematical modelling of a cantilever beam attached with a PSD is derived and simulated where 70% vibration reduction is seen in COMSOL. From experimental study, the vibration reduction obtained when using the piezoelectric shunt circuit with enhanced synthetic inductor is found to be 67.4% at 15.2 Hz. Results from this study can be used to improve PSD design for structural vibration control at targeted resonance with obvious peaks. ABSTRAK: Material piezoelektrik mempunyai keupayaan mengubah tenaga mekanikal kepada tenaga elektrik dan sebaliknya, di mana ia sesuai digunakan sebagai penggerak dan pengesan. Apabila digunakan sebagai alat kawalan dalam mod pengesan, piezoelektrik disambung kepada litar elektrik luaran di mana tenaga elektrik yang ditukarkan akan dibebaskan sebagai haba Joule; turut dikenali sebagai peredam alihan piezoelektrik (PSD). Kajian ini menggunakan PSD sebagai peredam resonan pertama pada palang kantilever dengan menyambungkan terminal kepada litar peredam RL bersiri. Rintangan optimal dan nilai aruhan bagi tenaga maksimum yang dibebaskan terhasil dengan membuat padanan parameter pada frekuensi resonan pertama palang kantilever, di mana R = 78.28 k? dan L = 2.9 kH adalah nilai optimum. Bagi merealisasikan nilai aruhan besar, peraruh buatan telah digunakan dan di sini, rekaan ini ditambah baik dengan memperkenalkan peraruh polaris bagi mengelak ketidakpadanan impedans. Model matematik palang kantilever yang bersambung pada PSD telah diterbit dan disimulasi, di mana 70% getaran berkurang pada COMSOL. Hasil dapatan eksperimen ini menunjukkan pengurangan getaran yang terhasil menggunakan litar peredam piezoelektrik bersama peraruh buatan menghasilkan 67.4% pada 15.2 Hz. Hasil dapatan kajian ini dapat digunakan bagi membaiki rekaan PSD berstruktur kawalan getaran iaitu pada resonan tumpuan di puncak ketara.

Investigation of Floating Transportation Equipment for the Offshore Wind Power

This paper presents a floating transportation equipment (FTE) for the negative pressure suction bucket foundation (NPSBF) of offshore wind turbines, and the basic design and main transportation means are introduced. The hydrodynamic characteristics of integrated FTE-NPSBF structure are comprehensively studied. The ability of FTE as a transportation aid to provide stability for the NPSBF is verified, and the vibration reduction measures under the condition of wave resonance during the floating transportation process are given.