The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and e...The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.展开更多
Permanent Magnet Synchronous Motors(PMSMs)are widely employed in high-performance drive applications due to their superior efficiency and dynamic capabilities.However,their control remains challenging owing to nonline...Permanent Magnet Synchronous Motors(PMSMs)are widely employed in high-performance drive applications due to their superior efficiency and dynamic capabilities.However,their control remains challenging owing to nonlinear dynamics,parameter variations,and unmeasurable external disturbances,particularly load torquefluctuations.This study proposes an enhanced Interconnection and Damp-ing Assignment Passivity-Based Control(IDA-PBC)scheme,formulated within the port-controlled Hamiltonian(PCH)framework,to address these limitations.A nonlinear disturbance observer is embedded to estimate and compensate,in real time,for lumped mis-matched disturbances arising from parameter uncertainties and external loads.Additionally,aflatness-based control strategy is employed to generate the desired current references within the nonlinear drive system,ensuring accurate tracking of time-varying speed commands.This integrated approach preserves the system’s energy-based structure,enabling systematic stability analysis while enhancing robustness.The proposed control architecture also maintains low complexity with a limited number of tunable parameters,facilitating practical implementation.Simulation and experimental results under various operating conditions demonstrate the effectiveness and robustness of the proposed method.Comparative analysis with conventional proportional-integral(PI)control and standard IDA-PBC strategies confirms its capability to handle disturbances and maintain dynamic performance.展开更多
7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because...7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because of its limited machining space,bad environment and large elongation induced low stiffness.To reduce vibration and improve machined surface quality,a particle damping boring bar,filled with particles in its inside damping block,is designed based on the theory of vibration control.The theoretical damping coefficient is determined,then the boring bar structure is designed and trial-manufactured.Experimental studies through impact testing show that cemented carbide particles with a diameter of 5 mm and a filling rate of 70% achieve a damping ratio of 19.386%,providing excellent vibration reduction capabilities,which may reduce the possibility of boring vibration.Then,experiments are setup to investigate its vibration reduction performance during deep hole boring of 7075 aluminum alloy.To observe more obviously,severe working conditions are adopted and carried out to acquire the time domain vibration signal of the head of the boring bar and the surface morphologies and roughness values of the workpieces.By comparing different experimental results,it is found that the designed boring bar could reduce the maximum vibration amplitude by up to 81.01% and the surface roughness value by up to 47.09% compared with the ordinary boring bar in two sets of experiments,proving that the designed boring bar can effectively reduce vibration.This study can offer certain valuable insights for the machining of this material.展开更多
Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.Howev...Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.展开更多
The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to t...The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to those observed in traditional synchronous generators.In response to this,an improved strategy for lead-lag filter based GFVSG(LLF-GFVSG)is presented in this article.Firstly,the grid-connected circuit structure and control principle of typical GFVSG are described,and a closed-loop small-signal model for GCAP in GFVSG is established.The causes of GCAP dynamic oscillation of GFVSG under the disturbances of active power command as well as grid frequency are analyzed.On this basis,the LLF-GFVSG improvement strategy and its parameter design method are given.Finally,the efficiency of the proposed control strategy in damping GCAP dynamic oscillations under various disturbances is verified using MATLAB simulations and experimental comparison results.展开更多
Active damping(AD)strategy is an economical and efficient method to solve the resonant problem of the permanent magnet synchronous motor(PMSM)drive system with inductor-capacitor(LC)sine wave filter.In this article,th...Active damping(AD)strategy is an economical and efficient method to solve the resonant problem of the permanent magnet synchronous motor(PMSM)drive system with inductor-capacitor(LC)sine wave filter.In this article,the AD methods used in PMSM drive system are classified as inherent damping(ID),state variable feedback,and digital filter.Based on this,the purpose of this article is to provide an overview and analysis of the AD methods on PMSM drive system in recent years,and to comprehensively review,compare,and summarize the stability,dynamic performance,robustness,and algorithm complexity.Furthermore,a new expansion of AD method based on capacitor current feedback with high-pass filter(HPF-CCF)is studied to ensure the effectiveness when the resonant frequency is around sixth of the sampling frequency.The simulation and experimental results validate the effectiveness of theoretical analysis.展开更多
The Synchronized Switch Damping(SSD)is regarded as a promising alternative to mitigate the vibration of thin-walled structures in aero-engines,especially for blades or bladed disks.The common manner is to shunt the sw...The Synchronized Switch Damping(SSD)is regarded as a promising alternative to mitigate the vibration of thin-walled structures in aero-engines,especially for blades or bladed disks.The common manner is to shunt the switch circuit independently to a single piezoelectric structure.This paper is aimed at exploring a novel way of using the SSD,i.e.,the SSD is interconnected between two piezoelectric structures or substructures.The damping mechanism,performance,and effective range of the interconnected SSD are studied numerically and experimentally.First,based on a dual cantilever beam finite element model,the time domain and frequency domain modeling and solving methods of the interconnected SSD are deduced and validated.Then,the influence of the amplitude and phase relationship on the damping effect of the interconnected SSD is numerically studied and compared with the shunted SSD.A self-sensing SSD control board is developed,and experimental studies are carried out.The results show that the interconnected SSD establishes an additional energy channel between the corresponding piezoelectric structures.When the amplitudes of the two cantilever beams are different,the interconnected SSD balances the vibration level of each beam.When the amplitudes of the two cantilever beams are the same,if the appropriate interconnection manner is selected according to the phase,the resonance peak can be reduced by more than 30%.When the vibration is in-phase/out-of-phase,the damping generated by the interconnected SSD in a cross/parallel manner is even more significant than the shunted SSD.Furthermore,this novel connection scheme reduces the number of SSD circuits in half.Finally,for engineering applications,we implement the proposed damping technology to the finite element model of a typical dummy bladed disk.A piezoelectric damping ratio of 13.7%is achieved when the amount of piezo material is only 10%of blade mass.Compared with traditional friction dampers,the major advancements of the interconnected SSD are:(A)it can reduce the vibration level of blades without friction interface;(B)the space constraint is overcome,i.e.,the vibration energy is not necessarily dissipated independently in one sector or through physically adjacent blades,and instead,the dissipation and transfer of vibrational energy can be realized between any blade pair.If a specific gating circuit is adopted to adjust the interconnection manner of the SSD,vibration mitigation under variable working conditions with different engine orders will be expected;(C)designers do not need to worry about the annoying nonlinearities related to working conditions anymore.展开更多
For the solution of peridynamic equations of motion,a meshless approach is typically used instead of utilizing semi-analytical or mesh-based approaches.In contrast,the literature has limited analytical solutions.This ...For the solution of peridynamic equations of motion,a meshless approach is typically used instead of utilizing semi-analytical or mesh-based approaches.In contrast,the literature has limited analytical solutions.This study develops a novel analytical solution for one-dimensional peridynamic models,considering the effect of damping.After demonstrating the details of the analytical solution,various demonstration problems are presented.First,the free vibration of a damped system is considered for under-damped and critically damped conditions.Peridynamic solutions and results from the classical theory are compared against each other,and excellent agreement is observed between the two approaches.Next,forced vibration analyses of undamped and damped conditions are performed.In addition,the effect of horizon size is investigated.It is shown that for smaller horizon sizes,peridynamic results agree well with classical results,whereas results from these two approaches deviate from each other as the horizon size increases.展开更多
Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtua...Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtual inertia for frequency support,but the larger inertia would worsen the synchronization stability,referring to keeping synchronization with the grid during voltage dips.Thus,this paper presents a transient damping method of VSGs for enhancing the synchronization stability during voltage dips.It is revealed that the loss of synchronization(LOS)of VSGs always accompanies with the positive frequency deviation and the damping is the key factor to remove LOS when the equilibrium point exists.In order to enhance synchronization stability during voltage dips,the transient damping is proposed,which is generated by the frequency deviation in active power loop.Additionally,the proposed method can realize seamless switching between normal state and grid fault.Moreover,detailed control design for transient damping gain is given to ensure the synchronization stability under different inertia requirements during voltage dips.Finally,the experimental results are presented to validate the analysis and the effectiveness of the improved transient damping method.展开更多
This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered ...This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.展开更多
In this article,the global attractors of 2D g-Navier-Stokes equations are obtained in the space of C_(Hg) and CVg respectively.When the external force f is sufficiently small,the studies indicate that the global attra...In this article,the global attractors of 2D g-Navier-Stokes equations are obtained in the space of C_(Hg) and CVg respectively.When the external force f is sufficiently small,the studies indicate that the global attractor in C_(Hg) is equal to the global attractor in C_(Vg).展开更多
The outstanding comprehensive mechanical properties of newly developed hybrid lattice structures make them useful in engineering applications for bearing multiple mechanical loads.Additive-manufacturing technologies m...The outstanding comprehensive mechanical properties of newly developed hybrid lattice structures make them useful in engineering applications for bearing multiple mechanical loads.Additive-manufacturing technologies make it possible to fabricate these highly spatially programmable structures and greatly enhance the freedom in their design.However,traditional analytical methods do not sufficiently reflect the actual vibration-damping mechanism of lattice structures and are limited by their high computational cost.In this study,a hybrid lattice structure consisting of various cells was designed based on quasi-static and vibration experiments.Subsequently,a novel parametric design method based on a data-driven approach was developed for hybrid lattices with engineered properties.The response surface method was adopted to define the sensitive optimization target.A prediction model for the lattice geometric parameters and vibration properties was established using a backpropagation neural network.Then,it was integrated into the genetic algorithm to create the optimal hybrid lattice with varying geometric features and the required wide-band vibration-damping characteristics.Validation experiments were conducted,demonstrating that the optimized hybrid lattice can achieve the target properties.In addition,the data-driven parametric design method can reduce computation time and be widely applied to complex structural designs when analytical and empirical solutions are unavailable.展开更多
On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston ...On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston resonance state of the moonpool under wave excitation and the non-resonance state of the moonpool under wave-current excitation.A novel damping device specifically designed and fabricated for stepped moonpools has been developed.Before and after the installation of the damping device,the free surface response characteristics of the moonpool and heave motion response characteristics of the hull are compared.The findings show a clear correlation between the current speed and heave response characteristics of the hull.During the seakeeping design phase of the drilling vessel,the current speed is an additional critical factor that cannot be disregarded,alongside the moonpool effect.A correlation exists between the fluid dynamics occurring within the moonpool and the heave motion of the vessel hull.A reduction in the amplitude of the motion of the moonpool water results in a decrease in the heave motion of the hull.This study provides a reference for alleviating the seakeeping of a drill ship’s heave response and enhancing the safety and efficiency of the operation.展开更多
Magnonics and magnonic materials have attracted widespread interest in the spintronics community and demonstrate potential for applications in the next generation of information technology.Recent advances in manganite...Magnonics and magnonic materials have attracted widespread interest in the spintronics community and demonstrate potential for applications in the next generation of information technology.Recent advances in manganite thin films highlight their promise for magnonics,in which enhanced film quality and strain control of spin and electronic structures play a crucial role in reducing magnetic damping.Here,we report the fabrication of La_(0.67)Sr_(0.33)MnO_(3) thin films of varying quality via pulsed laser deposition.The quality of epitaxial films is characterized using atomic force microscopy and x-ray diffraction.A pronounced fourfold anisotropy in the magnetic damping(with a ratio of about 150%)is observed,where the minimum damping occurs along the[110]crystalline orientation.Notably,improved sample quality significantly reduces the magnetic damping at low temperatures.The highest-quality sample,featuring atomic-scale terraces,exhibits a magnetic damping of~2.5×10^(-3)at 5 K.Our results not only demonstrate effective reduction of low-temperature magnetic damping in high-quality correlated oxide systems but also provides a strategy and material platform for exploring novel quantum phenomena and for designing low-temperature magnonic devices.展开更多
This paper investigates the impact of the model top and damping layer on the numerical simulation of tropical cyclones(TCs)and reveals the significant role of stratospheric gravity waves(SGWs).TCs can generate SGWs,wh...This paper investigates the impact of the model top and damping layer on the numerical simulation of tropical cyclones(TCs)and reveals the significant role of stratospheric gravity waves(SGWs).TCs can generate SGWs,which propagate upward and outward into the stratosphere.These SGWs can reach the damping layer,which is a consequence of the numerical scheme employed,where they can affect the tangential circulation through the dragging and forcing processes.In models with a higher top boundary,this tangential circulation develops far from the TC and has minimal direct impact on TC intensity.By comparison,in models with a lower top(e.g.,20 km),the damping layer is located just above the top of the TC.The SGW dragging in the damping layer and the consequent tangential force can thus induce ascent outside the eyewall,promote latent heat release,tilt the eyewall,and enlarge the inner-core radius.This process will reduce inner-core vorticity advection within the boundary layer,and eventually inhibits the intensification of the TC.This suggests that when the thickness of the damping layer is 5 km,the TC numerical model top height should be at least higher than 20 km to generate more accurate simulations.展开更多
The paper is devoted to establishing the long-time behavior of solutions to the extensible beam equation with rotational inertia and nonlocal strong damping.Within the theory of asymptotical smoothness,we investigate ...The paper is devoted to establishing the long-time behavior of solutions to the extensible beam equation with rotational inertia and nonlocal strong damping.Within the theory of asymptotical smoothness,we investigate the existence of the attractor by using the contractive function method and more detailed estimates.展开更多
Ni-Mn-Ga-Cu microwires,with diameter of 20-80 μm,length of 30-150 mm and fined columnar grains,were produced by melt-extraction technique.The damping capacity of the extracted micro wires was investigated by stretchi...Ni-Mn-Ga-Cu microwires,with diameter of 20-80 μm,length of 30-150 mm and fined columnar grains,were produced by melt-extraction technique.The damping capacity of the extracted micro wires was investigated by stretching a micro wire under a tensile stress using dynamic mechanical analyzer.The damping capacity of the martensite and austenite phases shows a weak frequency dependence but a strong strain amplitude dependence.The damping capacity(Tanδ) of the martensite and austenite phases reaches 0.08 and 0.04,respectively,under strain amplitude of 0.5% and frequency of 1 Hz.The high damping capacity of the martensite phase is related to the high mobility of martensite twin boudaries,while that of austenite phase to the motion of dislocations.The ferromagnetic Ni-Mn-Ga-Cu micro wires,with high ductility and damping capacity,may act as promising materials for microscale devices,systems and composite fillers for passive dissipation of undesired vibrations and noises.展开更多
The Fe–Mn damping alloys possess considerable damping capacity,but their yield strength is rather low.The 800 MPa Fe–Mn alloy with expected damping capacity was designed by the combination of grain refinement and ε...The Fe–Mn damping alloys possess considerable damping capacity,but their yield strength is rather low.The 800 MPa Fe–Mn alloy with expected damping capacity was designed by the combination of grain refinement and ε-martensite introduction.The yield strength can be greatly raised to around 700 MPa by refining grain size from 88.4 to 1.8μm.Although there exist numerous stacking faults in the fine-grained alloy,the damping capacity is strongly deteriorated due to the suppression of thermally activated ε-martensite.We demonstrate that the stacking faults cannot provide effective contribution to damping capacity and hence introduce a considerable volume fraction of stress/strain-induced ε-martensite to raise damping sources,including ε-martensite and γ/ε interfaces,etc.,by a small pre-strain.From this,the damping capacity can be improved,and the yield strength can be further enhanced from nearly 700 MPa to around 800 MPa.Thus,the combination of high yield strength and good damping capacity is realized.展开更多
The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction...The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction of BCC phase increases while that of FCC decreases with increasing the Al content.When the content of Al is 0.54,the alloy is composed of 82.1vol.%BCC matrix and 17.9vol.%FCC phase.Wherein the FCC phase is distributed on the BCC matrix,forming a structure where the hard BCC matrix is surrounded by soft FCC phase.This results in a hindering effect on the propagation process of vibration waves.The damping performance of Al0.54CrFe_(3)Ni alloy,characterized by an internal friction of Q^(-1) is as high as 0.059,is higher than that of most FeCr damping alloys.The volume fraction of the BCC phase and the peculiar distribution of the FCC phase are identified as the key factors affecting the damping capacity.In addition,the Al0.54CrFe3Ni alloy exhibits a high yield strength of 811.16 MPa.展开更多
Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibra...Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.11961059,1210502)the University Innovation Project of Gansu Province(Grant No.2023B-062)the Gansu Province Basic Research Innovation Group Project(Grant No.23JRRA684).
文摘The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.
基金supported in part by an International Research Partnership“Electrical Engineering-Thai French Research Center(EE-TFRC)”under the project framework of the Lorraine Universite´d’Excellence(LUE)in cooperation between Universite´de Lorraine(France)and King Mongkut’s University of Technology North Bangkok(year 2021-2024/2025-28)by the National Research Council of Thailand(NRCT)under Research Team Promotion Grant(Senior Research Scholar Program)under Grant No.N42A 680561by the NSRF via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation under Research project Grant No.B41G680025.
文摘Permanent Magnet Synchronous Motors(PMSMs)are widely employed in high-performance drive applications due to their superior efficiency and dynamic capabilities.However,their control remains challenging owing to nonlinear dynamics,parameter variations,and unmeasurable external disturbances,particularly load torquefluctuations.This study proposes an enhanced Interconnection and Damp-ing Assignment Passivity-Based Control(IDA-PBC)scheme,formulated within the port-controlled Hamiltonian(PCH)framework,to address these limitations.A nonlinear disturbance observer is embedded to estimate and compensate,in real time,for lumped mis-matched disturbances arising from parameter uncertainties and external loads.Additionally,aflatness-based control strategy is employed to generate the desired current references within the nonlinear drive system,ensuring accurate tracking of time-varying speed commands.This integrated approach preserves the system’s energy-based structure,enabling systematic stability analysis while enhancing robustness.The proposed control architecture also maintains low complexity with a limited number of tunable parameters,facilitating practical implementation.Simulation and experimental results under various operating conditions demonstrate the effectiveness and robustness of the proposed method.Comparative analysis with conventional proportional-integral(PI)control and standard IDA-PBC strategies confirms its capability to handle disturbances and maintain dynamic performance.
基金supported by the Scientific Research Program of Tianjin Education Committee(No.2022ZD030)。
文摘7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because of its limited machining space,bad environment and large elongation induced low stiffness.To reduce vibration and improve machined surface quality,a particle damping boring bar,filled with particles in its inside damping block,is designed based on the theory of vibration control.The theoretical damping coefficient is determined,then the boring bar structure is designed and trial-manufactured.Experimental studies through impact testing show that cemented carbide particles with a diameter of 5 mm and a filling rate of 70% achieve a damping ratio of 19.386%,providing excellent vibration reduction capabilities,which may reduce the possibility of boring vibration.Then,experiments are setup to investigate its vibration reduction performance during deep hole boring of 7075 aluminum alloy.To observe more obviously,severe working conditions are adopted and carried out to acquire the time domain vibration signal of the head of the boring bar and the surface morphologies and roughness values of the workpieces.By comparing different experimental results,it is found that the designed boring bar could reduce the maximum vibration amplitude by up to 81.01% and the surface roughness value by up to 47.09% compared with the ordinary boring bar in two sets of experiments,proving that the designed boring bar can effectively reduce vibration.This study can offer certain valuable insights for the machining of this material.
基金Supported by the National Natural Science Foundation of China(Nos.52222904 and 52309117)China Postdoctoral Science Foundation(Nos.2022TQ0168 and 2023M731895).
文摘Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.
基金supported by the Key Laboratory of Modern Power System Simulation and Control&Renewable Energy Technology(Northeast Electric Power University)Open Fund of China under Grant MPSS2024-08.
文摘The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to those observed in traditional synchronous generators.In response to this,an improved strategy for lead-lag filter based GFVSG(LLF-GFVSG)is presented in this article.Firstly,the grid-connected circuit structure and control principle of typical GFVSG are described,and a closed-loop small-signal model for GCAP in GFVSG is established.The causes of GCAP dynamic oscillation of GFVSG under the disturbances of active power command as well as grid frequency are analyzed.On this basis,the LLF-GFVSG improvement strategy and its parameter design method are given.Finally,the efficiency of the proposed control strategy in damping GCAP dynamic oscillations under various disturbances is verified using MATLAB simulations and experimental comparison results.
基金supported in part by the National Natural Science Foundational of China under Grants 62373363 and 52007190
文摘Active damping(AD)strategy is an economical and efficient method to solve the resonant problem of the permanent magnet synchronous motor(PMSM)drive system with inductor-capacitor(LC)sine wave filter.In this article,the AD methods used in PMSM drive system are classified as inherent damping(ID),state variable feedback,and digital filter.Based on this,the purpose of this article is to provide an overview and analysis of the AD methods on PMSM drive system in recent years,and to comprehensively review,compare,and summarize the stability,dynamic performance,robustness,and algorithm complexity.Furthermore,a new expansion of AD method based on capacitor current feedback with high-pass filter(HPF-CCF)is studied to ensure the effectiveness when the resonant frequency is around sixth of the sampling frequency.The simulation and experimental results validate the effectiveness of theoretical analysis.
基金funded by the Major Projects of AeroEngines and Gas Turbines,China(Nos.J2019-IV-0005-0073 and J2019-IV-0023-0091)the Aeronautical Science Foundation of China(No.2019ZB051002)+1 种基金China Postdoctoral Science Foundation(No.2021M700326)the Advanced Jet Propulsion Creativity Center,China(Nos.HKCX2020-02-013,HKCX2020-02-016 and HKCX2022-01-009).
文摘The Synchronized Switch Damping(SSD)is regarded as a promising alternative to mitigate the vibration of thin-walled structures in aero-engines,especially for blades or bladed disks.The common manner is to shunt the switch circuit independently to a single piezoelectric structure.This paper is aimed at exploring a novel way of using the SSD,i.e.,the SSD is interconnected between two piezoelectric structures or substructures.The damping mechanism,performance,and effective range of the interconnected SSD are studied numerically and experimentally.First,based on a dual cantilever beam finite element model,the time domain and frequency domain modeling and solving methods of the interconnected SSD are deduced and validated.Then,the influence of the amplitude and phase relationship on the damping effect of the interconnected SSD is numerically studied and compared with the shunted SSD.A self-sensing SSD control board is developed,and experimental studies are carried out.The results show that the interconnected SSD establishes an additional energy channel between the corresponding piezoelectric structures.When the amplitudes of the two cantilever beams are different,the interconnected SSD balances the vibration level of each beam.When the amplitudes of the two cantilever beams are the same,if the appropriate interconnection manner is selected according to the phase,the resonance peak can be reduced by more than 30%.When the vibration is in-phase/out-of-phase,the damping generated by the interconnected SSD in a cross/parallel manner is even more significant than the shunted SSD.Furthermore,this novel connection scheme reduces the number of SSD circuits in half.Finally,for engineering applications,we implement the proposed damping technology to the finite element model of a typical dummy bladed disk.A piezoelectric damping ratio of 13.7%is achieved when the amount of piezo material is only 10%of blade mass.Compared with traditional friction dampers,the major advancements of the interconnected SSD are:(A)it can reduce the vibration level of blades without friction interface;(B)the space constraint is overcome,i.e.,the vibration energy is not necessarily dissipated independently in one sector or through physically adjacent blades,and instead,the dissipation and transfer of vibrational energy can be realized between any blade pair.If a specific gating circuit is adopted to adjust the interconnection manner of the SSD,vibration mitigation under variable working conditions with different engine orders will be expected;(C)designers do not need to worry about the annoying nonlinearities related to working conditions anymore.
文摘For the solution of peridynamic equations of motion,a meshless approach is typically used instead of utilizing semi-analytical or mesh-based approaches.In contrast,the literature has limited analytical solutions.This study develops a novel analytical solution for one-dimensional peridynamic models,considering the effect of damping.After demonstrating the details of the analytical solution,various demonstration problems are presented.First,the free vibration of a damped system is considered for under-damped and critically damped conditions.Peridynamic solutions and results from the classical theory are compared against each other,and excellent agreement is observed between the two approaches.Next,forced vibration analyses of undamped and damped conditions are performed.In addition,the effect of horizon size is investigated.It is shown that for smaller horizon sizes,peridynamic results agree well with classical results,whereas results from these two approaches deviate from each other as the horizon size increases.
文摘Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtual inertia for frequency support,but the larger inertia would worsen the synchronization stability,referring to keeping synchronization with the grid during voltage dips.Thus,this paper presents a transient damping method of VSGs for enhancing the synchronization stability during voltage dips.It is revealed that the loss of synchronization(LOS)of VSGs always accompanies with the positive frequency deviation and the damping is the key factor to remove LOS when the equilibrium point exists.In order to enhance synchronization stability during voltage dips,the transient damping is proposed,which is generated by the frequency deviation in active power loop.Additionally,the proposed method can realize seamless switching between normal state and grid fault.Moreover,detailed control design for transient damping gain is given to ensure the synchronization stability under different inertia requirements during voltage dips.Finally,the experimental results are presented to validate the analysis and the effectiveness of the improved transient damping method.
基金the postdoctoral research grant received from the University of Glasgow for the partial financial support for this research work。
文摘This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.
基金Supported by the National Natural Science Foundation of China(11971378)Shaanxi Fundamental Science Research Project for Mathematics and Physics(23JSY050)Shaanxi Innovative Training Program for College Students(S202410719114)。
文摘In this article,the global attractors of 2D g-Navier-Stokes equations are obtained in the space of C_(Hg) and CVg respectively.When the external force f is sufficiently small,the studies indicate that the global attractor in C_(Hg) is equal to the global attractor in C_(Vg).
基金supported by National Natural Science Foundation of China(Grant No.52375380)National Key R&D Program of China(Grant No.2022YFB3402200)the Key Project of National Natural Science Foundation of China(Grant No.12032018).
文摘The outstanding comprehensive mechanical properties of newly developed hybrid lattice structures make them useful in engineering applications for bearing multiple mechanical loads.Additive-manufacturing technologies make it possible to fabricate these highly spatially programmable structures and greatly enhance the freedom in their design.However,traditional analytical methods do not sufficiently reflect the actual vibration-damping mechanism of lattice structures and are limited by their high computational cost.In this study,a hybrid lattice structure consisting of various cells was designed based on quasi-static and vibration experiments.Subsequently,a novel parametric design method based on a data-driven approach was developed for hybrid lattices with engineered properties.The response surface method was adopted to define the sensitive optimization target.A prediction model for the lattice geometric parameters and vibration properties was established using a backpropagation neural network.Then,it was integrated into the genetic algorithm to create the optimal hybrid lattice with varying geometric features and the required wide-band vibration-damping characteristics.Validation experiments were conducted,demonstrating that the optimized hybrid lattice can achieve the target properties.In addition,the data-driven parametric design method can reduce computation time and be widely applied to complex structural designs when analytical and empirical solutions are unavailable.
基金supported by the National Natural Science Foundation of Jiangsu Province,China(Grant No.BK20231255).
文摘On the basis of the model tests,this paper explores the coupled hydrodynamic performance of the moonpool and the hull.This study aims to compare and analyze the variation in the hull heave response between the piston resonance state of the moonpool under wave excitation and the non-resonance state of the moonpool under wave-current excitation.A novel damping device specifically designed and fabricated for stepped moonpools has been developed.Before and after the installation of the damping device,the free surface response characteristics of the moonpool and heave motion response characteristics of the hull are compared.The findings show a clear correlation between the current speed and heave response characteristics of the hull.During the seakeeping design phase of the drilling vessel,the current speed is an additional critical factor that cannot be disregarded,alongside the moonpool effect.A correlation exists between the fluid dynamics occurring within the moonpool and the heave motion of the vessel hull.A reduction in the amplitude of the motion of the moonpool water results in a decrease in the heave motion of the hull.This study provides a reference for alleviating the seakeeping of a drill ship’s heave response and enhancing the safety and efficiency of the operation.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406500,J.Z.,2021YFA0718700,J.Z.)the National Natural Science Foundation of China(Grant Nos.T2350005,J.Z.,12404119,Y.Z.,52225205,J.Z.)+1 种基金the Beijing Natural Science Foundation(Grant No.Z240008,J.Z.)the Fundamental Research Funds for the Central Universities(Y.Z.and J.Z.)。
文摘Magnonics and magnonic materials have attracted widespread interest in the spintronics community and demonstrate potential for applications in the next generation of information technology.Recent advances in manganite thin films highlight their promise for magnonics,in which enhanced film quality and strain control of spin and electronic structures play a crucial role in reducing magnetic damping.Here,we report the fabrication of La_(0.67)Sr_(0.33)MnO_(3) thin films of varying quality via pulsed laser deposition.The quality of epitaxial films is characterized using atomic force microscopy and x-ray diffraction.A pronounced fourfold anisotropy in the magnetic damping(with a ratio of about 150%)is observed,where the minimum damping occurs along the[110]crystalline orientation.Notably,improved sample quality significantly reduces the magnetic damping at low temperatures.The highest-quality sample,featuring atomic-scale terraces,exhibits a magnetic damping of~2.5×10^(-3)at 5 K.Our results not only demonstrate effective reduction of low-temperature magnetic damping in high-quality correlated oxide systems but also provides a strategy and material platform for exploring novel quantum phenomena and for designing low-temperature magnonic devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.42475016,42192555 and 42305085)the China Postdoctoral Science Foundation(Grant No.2023M741615)the 2023 Graduate Research Innovation Project of Hunan Province(Grant No.CX20230011)。
文摘This paper investigates the impact of the model top and damping layer on the numerical simulation of tropical cyclones(TCs)and reveals the significant role of stratospheric gravity waves(SGWs).TCs can generate SGWs,which propagate upward and outward into the stratosphere.These SGWs can reach the damping layer,which is a consequence of the numerical scheme employed,where they can affect the tangential circulation through the dragging and forcing processes.In models with a higher top boundary,this tangential circulation develops far from the TC and has minimal direct impact on TC intensity.By comparison,in models with a lower top(e.g.,20 km),the damping layer is located just above the top of the TC.The SGW dragging in the damping layer and the consequent tangential force can thus induce ascent outside the eyewall,promote latent heat release,tilt the eyewall,and enlarge the inner-core radius.This process will reduce inner-core vorticity advection within the boundary layer,and eventually inhibits the intensification of the TC.This suggests that when the thickness of the damping layer is 5 km,the TC numerical model top height should be at least higher than 20 km to generate more accurate simulations.
基金Supported by the National Natural Science Foundation of China(Grant Nos.1210150211961059)the University Innovation Project of Gansu Province(Grant No.2023B-062).
文摘The paper is devoted to establishing the long-time behavior of solutions to the extensible beam equation with rotational inertia and nonlocal strong damping.Within the theory of asymptotical smoothness,we investigate the existence of the attractor by using the contractive function method and more detailed estimates.
基金financially supported by the Ministry of Science and Technology Bureau of Harbin(No.2011RFQXG001)
文摘Ni-Mn-Ga-Cu microwires,with diameter of 20-80 μm,length of 30-150 mm and fined columnar grains,were produced by melt-extraction technique.The damping capacity of the extracted micro wires was investigated by stretching a micro wire under a tensile stress using dynamic mechanical analyzer.The damping capacity of the martensite and austenite phases shows a weak frequency dependence but a strong strain amplitude dependence.The damping capacity(Tanδ) of the martensite and austenite phases reaches 0.08 and 0.04,respectively,under strain amplitude of 0.5% and frequency of 1 Hz.The high damping capacity of the martensite phase is related to the high mobility of martensite twin boudaries,while that of austenite phase to the motion of dislocations.The ferromagnetic Ni-Mn-Ga-Cu micro wires,with high ductility and damping capacity,may act as promising materials for microscale devices,systems and composite fillers for passive dissipation of undesired vibrations and noises.
基金supported by Fundamental Research Funds for Central Universities(Grant No.N2107009)Reviving-Liaoning Excellence Plan(Grant No.XLYC2203186).
文摘The Fe–Mn damping alloys possess considerable damping capacity,but their yield strength is rather low.The 800 MPa Fe–Mn alloy with expected damping capacity was designed by the combination of grain refinement and ε-martensite introduction.The yield strength can be greatly raised to around 700 MPa by refining grain size from 88.4 to 1.8μm.Although there exist numerous stacking faults in the fine-grained alloy,the damping capacity is strongly deteriorated due to the suppression of thermally activated ε-martensite.We demonstrate that the stacking faults cannot provide effective contribution to damping capacity and hence introduce a considerable volume fraction of stress/strain-induced ε-martensite to raise damping sources,including ε-martensite and γ/ε interfaces,etc.,by a small pre-strain.From this,the damping capacity can be improved,and the yield strength can be further enhanced from nearly 700 MPa to around 800 MPa.Thus,the combination of high yield strength and good damping capacity is realized.
基金supported by the Natural Science Foundation of Liaoning Province(No.2022-BS-181).
文摘The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction of BCC phase increases while that of FCC decreases with increasing the Al content.When the content of Al is 0.54,the alloy is composed of 82.1vol.%BCC matrix and 17.9vol.%FCC phase.Wherein the FCC phase is distributed on the BCC matrix,forming a structure where the hard BCC matrix is surrounded by soft FCC phase.This results in a hindering effect on the propagation process of vibration waves.The damping performance of Al0.54CrFe_(3)Ni alloy,characterized by an internal friction of Q^(-1) is as high as 0.059,is higher than that of most FeCr damping alloys.The volume fraction of the BCC phase and the peculiar distribution of the FCC phase are identified as the key factors affecting the damping capacity.In addition,the Al0.54CrFe3Ni alloy exhibits a high yield strength of 811.16 MPa.
基金The Fundamental Research Funds for the Central Universities(JD2423)。
文摘Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.
