Lateral Vibration Behavior Analysis and TLD Vibration Absorption Design of the Soft Yoke Single-Point Mooring System

Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.

Vibration absorption of parallel-coupled nonlinear energy sink under shock and harmonic excitations

Nonlinear energy sink(NES)can passively absorb broadband energy from primary oscillators.Proper multiple NESs connected in parallel exhibit superior performance to single-degree-of-freedom(SDOF)NESs.In this work,a linear coupling spring is installed between two parallel NESs so as to expand the application scope of such vibration absorbers.The vibration absorption of the parallel and parallel-coupled NESs and the system response induced by the coupling spring are studied.The results show that the responses of the system exhibit a significant difference when the heavier cubic oscillators in the NESs have lower stiffness and the lighter cubic oscillators have higher stiffness.Moreover,the efficiency of the parallel-coupled NES is higher for medium shocks but lower for small and large shocks than that of the parallel NESs.The parallel-coupled NES also shows superior performance for medium harmonic excitations until higher response branches are induced.The performance of the parallel-coupled NES and the SDOF NES is compared.It is found that,regardless of the chosen SDOF NES parameters,the performance of the parallel-coupled NES is similar or superior to that of the SDOF NES in the entire force range.

An electromagnetic semi-active dynamic vibration absorber for thin-walled workpiece vibration suppression in mirror milling

As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.

A novel way for vibration control of FGM fluid-conveying pipes via NiTiNOL-steel wire rope

In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method(GTM)and harmonic balance method(HBM).The harmonic balance solutions and the numerical results are consistent.Also,the linearized stability of the structure is determined.The effects of the structure parameters on the absorption performance are also studied.The results show that the NiTi-ST is an effective means of vibration absorption.Furthermore,in studying the effect of the NiTi-ST,a closed detached response(CDR)is first observed.It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR.This vibration absorption device can be extended to offer more general vibration control in engineering applications.

Experimental study on absorption of blade vibration of honeycomb seal and shunt injection

Honeycomb seals and shunt injection have been proposed to weaken the blade vibration.Honeycombseals,as well as,smooth seals were tested with different seals' clearances and shrouded blades.Theshunt injection was sprayed to the blade tip clearance in the reverse direction of the main flow.Experi-mental results showed that both honeycomb seals and shunt injection had the damping effect for blade vi-bration,and the blade vibration magnitude could be reduced by more than 25 % and 17 %,respectively.When the two methods were adopted synchronously,more than 1/3 of the blade vibration could be re-duced.Consequently,adopting honeycomb seal and superinducing proper shunt injection are two usefulways to minimize vibration of the blade from the viewpoints of avoiding blade rupture and improving therotor stability.

Effect of Changing Anion on the Crystalline Structure, Crystal Structure, Hirschfield Surface, IR and NMR Spectroscopy of Organic Salts and Hybrid Compounds: C6H4(NH3)2Cl2 (I), β-[C6H10N2]2ZnCl4 (II), Respectively

Two organic-inorganic hybrid materials, C6H4(NH3)2∙Cl2 (I) and β-[C6H10N2]2ZnCl4 (II), have been synthesized by hydrothermal method. These two materials are one of the hybrid materials have emerged as one of the most brilliant components classes. These extraordinary compounds synergistically combine the desired physical properties of both organic and inorganic components into a single compound offering the possibility to achieve great improvement over time in terms of science across various sectors. Their structures were determined by XRD pattern investigations and single crystal X-ray diffraction. These two compounds are crystallized in the monoclinic system;C2/c space group. In the both structures, the anionic-cationic entities are interconnected by hydrogen bonding contacts and p-p Interaction forming three-dimensional networks. Intermolecular interactions were investigated by Hirshfeld surfaces and the contacts of the four different chloride atoms in (II) were compared. The vibrational absorption bands were identified by infrared spectroscopy. These compounds were also investigated by solid state13C NMR spectroscopy.

MULTI-GRANULE IMPACT MODEL OF NOPD AND ITS NUMERICAL SIMULATIONS

Aiming at the impaction among granules of non obstructive particle damping(NOPD), the vibration absorption model for vertical impact of granules is established by adopting Hertz contact theory. The numerical simulation of the granules movement process is proceeded, and the vibration response of a free free uniform beam is obtained for the case when all granules act on it. Through this method, the effect on vibration absorption of impaction is investigated. The simulational data show that multi gra nule vertical impaction is not sensitive to the movement clearance. The vibration absorption is also very well when the clearance changes within a large range. Therefore, the phenomenon that the vibration magnitude may increase if the clearance in a single impact body is improperly selected will not happen. The effect of vibration suppression in the range of middle and high frequencies(2 500~6 000 Hz) is better than that in the range of low frequency(<2 500 Hz). It indicates that the effect on vibration absorption of multi granule can well restrain the vibration of middle and high frequencies.

Theoretical studies of vibrationally resolved absorption and emission spectra: From a single chromophore to multichromophoric oligomers/aggregates

Absorption and photoluminescence spectroscopies are useful tools to study the photo-physical properties of materials. The theoretical methods for calculation of the spectra of molecules/supermolecules and aggregates, whose structures can differ significantly, are reviewed from the viewpoint of computational efficiency. Several model compounds/multimers are taken as examples for the spectral calculations. The numerical results achieve a satisfactory agreement between the theory and experiment.

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

In the semiconductor manufacturing industry,the dynamic model of a controlled object is usually obtained from a frequency sweeping method before motion control.However,the existing isolators cannot properly isolate the disturbance of the inertial force on the platform base during frequency sweeping(the frequency is between 0 Hz and the natural frequency).In this paper,an adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system(DSASAVIS)is proposed.This system has a significant anti-resonance characteristic;that is,the vibration amplitude can drop to nearly zero at a particular frequency,which is called the anti-resonance frequency.The proposed controller is designed to add an adjustable anti-resonance frequency to fully use this unique anti-resonance characteristic.Experimental results show that the closed-loop transmissibility is less than−15 dB from 0 Hz to the initial anti-resonance frequency.Furthermore,it is less than−30 dB around an added anti-resonance frequency which can be adjusted from 0 Hz to the initial anti-resonance frequency by changing the parameters of the proposed controller.With the proposed controller,the disturbance amplitude of the payload decays from 4 to 0.5 mm/s with a reduction of 87.5%for the impulse disturbance applied to the platform base.Simultaneously,the system can adjust the anti-resonance frequency point in real time by tracking the frequency sweeping disturbances,and a good vibration isolation performance is achieved.This indicates that the DSA-SAVIS and the proposed controller can be applied in the guarantee of an ultra-low vibration environment,especially at frequency sweeping in the semiconductor manufacturing industry.

Response regimes of narrow-band stochastic excited linear oscillator coupled to nonlinear energy sink

This paper draws attention to the issue of the vibration absorption of nonlinear mechani- cal system coupled to nonlinear energy sink （NES） under the impact of the narrow band stochastic excitation. Firstly, based on the complex-averaging method and frequency detuning methodology, response regimes of oscillators have been researched under the linear impact of coupling a nonlinear attachment with less relativistic mass and an external sinusoidal forcing, of which results turn out that the quasi-periodicity response regime of system which occurs when the external excitation amplitude exceeds the critical values will be the precondition of the targeted energy transfer. Secondly, basing on the path integration method, vibration suppression of NES has been researched when it is affected by a main oscillator with a narrow band stochastic force in the form of trigono- metric functions, of which results show that response regimes are affected by the amplitude of stochastic excitation and the disturbance strength. Finally, all these conclusions have been approved by the numerical verification and coincided with the theoretical analysis; meanwhile, after the com- paring analysis with the optimal linear absorber, it turns out that the NES which is affected by the narrow band stochastic force could also suppress the vibration of system with a better effect.