Dynamic Response Characteristics Research Articles

Instability mechanism and failure criteria of large-span flexible PV support arrays under severe wind

Compared with independent flexible PV support, the entire structure force performance and transfer mechanism of inter-row cables and inter-span rods of flexible PV support arrays are more complex, it is easy to have large vibration or even instability failure under strong wind. In this study, the three-span and five-row flexible PV support array of a 66 MW Fishery-PV Complementary demonstration site in the eastern coastal region of China is used as the research object. The rigid body pressure measurement wind tunnel test was designed and carried out, and the wind pressure distribution characteristics of the PV panels surface were analyzed. A three-dimensional explicit dynamics model of the flexible PV support array considering inter-row cables and inter-span rods is established, and the wind-induced dynamic response characteristics and instability processes of the large-span flexible PV support array are effectively simulated. Finally, the instability mechanism of the large-span flexible PV support array is revealed, and the dual failure criteria based on structural deformation and energy increment are proposed. Results demonstrated that the maximum values of displacement and von Mises stress of the large-span flexible PV support array are concentrated in the 1st row of the span in the windward side. The array under 0° and 180° wind direction angles induces local instability and failure at wind speeds of 51 m/s and 46 m/s due to the failure of the 1st row of triangular rods and crossed diagonal rods on the windward side, respectively, and the rods instability mechanisms are Eulerian buckling mechanism and Limit point buckling mechanism, respectively. When the axial compression ratio [Δ] > 0.1 or the strain energy increment [ΔU] > 1.0 × 105J of the instability rod, the structure will be locally destabilized. This paper presents a systematic work around the wind-induced response and instability characteristics of the large-span flexible PV support array, the results are of significance for the engineering application of solar energy generation structures.

On the 3D fluid behavior during CBM coproduction in a multi pressure system: Insights from experimental analysis and mathematical models

To investigate the dynamic response characteristics of coalbed methane (CBM) reservoirs with multi pressure system induced by coproduction, physical simulation experiments were conducted on CBM coproduction under both conventional and constant-rate coproduction modes using a self-built experimental platform. The results showed that constant-rate coproduction can significantly extend the stable coproduction period of CBM compared to conventional coproduction, but it may have an inhibitory effect on certain reservoirs, which is negatively correlated with the initial reservoir pressure. Constant-rate coproduction can cause disturbance effects on reservoir pressure, leading to an increase in the expansion resistance of the pressure-reduction funnel during coproduction, and even the appearance of the pressure-buildup funnel of low-pressure reservoirs. A calculation principle for the 3D fluid flow parameters was developed by considering the dynamic permeability and the pressure gradient of the reservoir. The 3D fluid flow parameters were employed to quantitatively characterize the spatial and temporal evolution of fluid relative flow velocity and deflection angle in the reservoir during coproduction. Near the far end of the wellbore, the fluid flowed nearly horizontally, while near the wellbore, the fluid flowed towards or away from the wellbore center due to different levels of disturbance.

Nonlinear energy harvesting from rotating system

A simple electromagnetic energy harvester with a cubic nonlinear stiffness is proposed and dynamic responses as well as the potential power harvested are studied in this paper. The proposed nonlinear electromagnetic vibration energy harvester can be installed on a host base that is rotating at a constant speed and vibrating vertically. Considering the combination of the vertically vibrating and rotating frequency of the host base, the 1:1 primary resonance is investigated by the method of multiple scales. The dynamic characteristics of responses in terms of system parameters are studied and bifurcation curves are constructed. In addition to possessing the resonance characteristics, some saddle–node bifurcations occur for the steady-state solutions under certain conditions. Moreover, the effects of system parameters on the output average power are investigated as well. The results of analysis show that multiple frequency bands and parameter regions exist where a large power can be harvested due to the nonlinear resonances. Introducing the nonlinearity not only can increase the power output but also expand the frequency bands and parameter regions to harvest more power. A carefully selected system parameters can help to optimize the average power harvested in the design.

Dynamic Feature Identification of Carbon-Fiber-Reinforced Polymer Laminates Based on Fiber Bragg Grating Sensing Technology

Carbon-fiber-reinforced polymer (CFRP) composites have many advantages, and have been widely used in aerospace structures, buildings, bridges, etc. The analysis of dynamic response characteristics of CFRP composite structures is of great significance for promoting the development of smart composite structures. For this reason, vibration experiments of CFRP laminates with surface-attached fiber Bragg grating (FBG) sensors under various dynamic loading conditions were carried out. Time- and frequency-domain analyses were conducted on the FBG testing signals to check the dynamic characteristics of the CFRP structure and the sensing performance of the installed sensors. The results show that the FBG sensors attached to the surface of the CFRP laminates can accurately measure the dynamic response and determine the excited position of the CFRP laminates, as well as invert the strain distribution of the CFRP laminates through the FBG sensors at different positions. By performing Fourier transform, short-time Fourier transform, and frequency domain decomposition (FDD) on the FBG sensing signals, the time–frequency information and the first eight modal frequencies of the excited CFRP structure can be obtained. The modal frequencies obtained by different excitation types are similar, which can be used for structural damage identification. The research in this paper clarifies the effectiveness and accuracy of FBG sensors in sensing the dynamic characteristics of CFRP structures, which can be used for performance evaluation of CFRP structures and will effectively promote the design and development of intelligent composite material structures.

Study on dynamic response characteristics of impact of freeze-thaw saturated marble in plateau area.

To study the effects that the perennial freeze-thaw environment exerts on the dynamic mechanical properties of marble, which characterizes the Qinghai-Tibet Plateau, impact tests were conducted, and saturated marble was utilized; thus, we analyzed the effect of different loading rates on its dynamic compressive strength, fragmentation pattern, and energy-absorbing density. The results indicate the following: (1) When 42.02s-1 ≤[Formula: see text]≤ 49.20s-1, the degree of fragmentation and the fractal dimension of saturated state marble is greater than that of the dry state marble; when [Formula: see text]<42.02s-1 or [Formula: see text]>49.20s-1, the dry state marble exhibits greater fragmentation than the saturated marble; (2) When the saturated state marble is subjected to a specific fractal dimension, the energy-absorbing density of the marble that characterizes the saturated state is great compared with the dry state, and when the fractal dimension increases, the energy-absorbing densities that characterize the two states gradually converge. (3) The effect of water on the mechanical properties of marble has an obvious rate dependence, showing a weakening effect at low strain rates and a strengthening effect at high strain rates. In regard to the analysis pertaining to the dynamic fracture mechanism of marble under the influence of the freeze-thaw environment that characterizes the plateau, the aforementioned experimental results exhibit considerable significance.

Experimental study on the vibration characteristics of fluid–structure coupling in the transition process of flexible bending pipes

The flexible bending pipes with large aspect ratios are more likely to cause large vibrations in the extraction of offshore oil and gas resources, which can accelerate the fatigue damage of the pipes. In order to explore the characteristics of fluid–structure coupling vibration during the transition period after the flexible bending pipe starts to transport fluid, an experimental platform of flexible bending pipes fluid–structure coupling vibration was created. The strain and vibration displacements of the pipe were measured by a resistance strain gauge and a high-speed camera system, respectively. According to the measure results, the largest values of stress and strain both were discovered at the pipe's two ends, and the maximum values of vibration displacement and vibration velocity were found in the middle of the pipe. The phenomenon indicates that the two ends of the pipe are more prone to fatigue damage. Moreover, the dynamic response and dynamic characteristics of the pipeline during the transition process were investigated. In addition, the effects of fluid flow rate, pipe wall thickness and different pipes on the dynamic response and dynamic characteristics of the pipe were also investigated in the present work.

Research on Design and Control Strategy of Novel Independent Metering System

The independent metering system used in the combination of traditional cartridge proportional valves employs an excessive number of components, which increases the complexity of the control strategy. To address this problem, a novel independent metering system based on pilot hydraulic control was developed. Following the pressure and flow requirements, the structure and valve body size of the two spools were designed. The effect of the parameter change in the control valve on the dynamic response characteristics of the main spool was investigated by simulation. A control strategy was developed based on load force direction prediction and two-chamber pressure switching to verify the feasibility of working mode switching during load direction change. As indicated by the results, compared with the mode switching control strategy of the traditional independent metering system, the proposed control strategy could effectively reduce the number of mode switching and ensure the continuity of the actuator operation. Compared with the traditional load-sensitive valve control system, the proposed pilot-controlled independent metering system achieved an average energy-saving efficiency of 47.27%. This study provides technical reference for the low energy consumption, high efficiency, and sustainable development of hydraulic systems.

Dataset Generation Based on 1D-CAE Modeling for Fault Diagnostics in a Spacecraft Propulsion System

The objective of this study is to generate a classified dataset of valve faults and bubble contamination anomalies in the propellant supply pipe of spacecraft propulsion systems. The dataset is available in PHMAP23, and the paper intends to describe its characteristics. The dataset includes time and pressure information and has been generated through numerical simulations using SimlationX, a 1D-CAE software. The condition of the propulsion system is reflected by the characteristics of the pressure dynamic response generated by the water hammer in the supply pipe caused by the rapid opening and closing of the downstream solenoid valve. Therefore, accurate classification of anomalies and faults can be achieved by extracting characteristics from the pressure dynamic response waveform.

A collaborative training approach for multi energy systems in low‐carbon parks accounting for response characteristics

AbstractExisting researches lack systematic design of the operation mechanism and overall implementation process of park oriented multi‐state energy system; The existing researches on multi‐state energy systems ignored the dynamic response characteristics of load and the coupling effect of units considering the impact of carbon emissions, and did not go deep into the collaborative management of multiple multi state energy system parks. To this end, this paper first proposes a two‐stage multi‐energy system operation architecture for low carbon parks, and establishes a mathematical model considering carbon emissions, operating costs and other objectives. The response space of load is optimized by considering the dynamic interaction characteristics of load response and the coupling characteristics of unit operation. Then, considering the problems of data security and training efficiency, F‐DDPG technology is used to conduct collaborative training for multiple campus systems. Finally, an example is given to prove the effectiveness of the method, which is not only conducive to reducing the operating cost of the system and the carbon emissions on the supply side, but also improves the convergence of model training. In the case of collaborative training in multiple parks, the method in this paper converges faster and has better economic benefits.

Optimization Design of Lubrication Performance of Planetary Gear Transmission

Due to the need to clarify the interaction between tooth surface lubrication characteristics and dynamic behavior, it is necessary to consider the influence of time-varying characteristics of lubrication contact on dynamic behavior and the effect of dynamic gear tooth force on lubrication characteristics, establish a friction dynamics coupling analysis model for spur gears, and achieve accurate prediction of dynamic response and lubrication characteristics. In this paper, the planetary gear transmission system model is built, the planetary gear transmission system model is solved, and the lubrication performance of planetary gear transmission is analyzed.

Denoising for Dynamic Vision Sensor Based on Augmented Spatiotemporal Correlation

To effectively denoise the output events of Dynamic Vision Sensor (DVS) in real-time, a denoising method based on augmented spatiotemporal correlation is proposed. In addition, this paper also presents a novel method to evaluate the performance of event denoising. By classifying the events and noise based on their spatiotemporal properties, we use the dynamic response characteristics of DVS under different cases to augment the spatiotemporal correlation, and construct two event filters to process different kinds of events. To benchmark event denoising, we exploit the low-latency of DVS to temporally synchronize raw event stream through motion compensation and obtain the ideal response probability of DVS to quantify the plausibility of events and measure the denoising accuracy. Experiments in various scenes validate that the denoising method is effective at reducing noise with high accuracy and little computational cost, which significantly outperforms the state-of-the-art methods. Moreover, the evaluation method can quantify the denoising accuracy and benchmark different denoising methods objectively and comprehensively.

Dynamic Effect of the Earth Fissure Sites in the Yuncheng Basin, China

Earth fissures are widely distributed worldwide, and the Fenwei Basin in China is one of the regions with the most significant number and scale of fissures in the world. The Yuncheng Basin is an important constituent basin of the Fenwei Basin in China, where earth fissures are densely developed and cause severe damage. In particular, the impact of earth fissures on the seismic response of the site is still unknown and is an urgent problem that needs to be solved. Based on microtremor tests, three types of typical earth fissure sites in the Yuncheng Basin were selected for field testing. Through spectrum analysis, the dynamic response characteristics of the earth fissure sites were determined. The results show that the dynamic response of the site is significantly affected by the earth fissures. The dynamic response strength of the site is the largest on both sides of the earth fissures, and it decreases and gradually stabilizes with increasing distance from the fissures. The influence range of the earth fissures on the hanging side is slightly longer than the heading side.

Eddy Effect and Dynamic Response of High-Speed Solenoid Valve with Composite Iron Core.

To alleviate the Eddy effect of the high-speed solenoid valve (HSV) and improve its dynamic response speed, a novel HSV with a composite iron core is presented. The time-step finite element method is used to establish and verify the numerical simulation of HSV coupling multiple physical fields. Then, the Eddy effect and dynamic response characteristics of the conventional and composite HSVs are further compared and analyzed. The results showed that the Eddy current loss in the main pole was the largest for the conventional HSV, accounting for 72.5% and 64.4% in the actuation and release processes, respectively. It was found that the Eddy effect of the composite HSV was obviously weakened, and the total Eddy current losses in the actuation and release processes were reduced by 58.8% and 38.7%, respectively. Meanwhile, the actuation response time and release response time of the composite HSV were shortened by 15.6% and 18.5%, respectively. In addition, increasing the peak voltage further shortened the actuation response time of the composite HSV, but had no significant effect on the response time of the conventional HSV.

Dynamic response analysis of a monopile-supported offshore wind turbine under the combined effect of sea ice impact and wind load

The existence of drifting ice is a key challenge for structural design of offshore wind turbines (OWTs) in cold regions. To better understand the structural behavior of OWT under combined sea ice impact and wind load effects, this paper investigates the dynamic response of a monopile-supported OWT using the nonlinear finite element method. The interaction between the OWT and ice impact, wind loads and soil contact are addressed in the developed numerical models in LS-DYNA. The coupling between the main program and the aerodynamic damping model is achieved by a user-defined load subroutine. To calibrate and verify the ice material model and the simulation technique, model test data are used of ice impacts with a nearly vertical monopile foundation. In the case study, numerical simulations of the interaction between a typical 5-MW monopile-supported OWT and an ice sheet are performed under various combined load scenarios. The dynamic response characteristics are presented and the effects of ice drifting speed and mean wind speed are elucidated by statistical methods. Finally, insights into the ice loads are obtained by comparing the simulation results against two international design standards. The present study contributes to an improved understanding of load effects of monopile OWTs in cold regions.

Dynamic response characteristics and damage modes of multifunctional layered hydrogen storage vessels under impact loads

Hydrogen storage vessels in hydrogen refueling stations are densely arranged, so high-speed fragments generated by explosion accidents may endanger adjacent vessels. It is of great significance to explore the dynamic responses and damage modes of hydrogen storage vessels under impact loads to promote the intrinsic safety development of hydrogen storage vessels. In this paper, a finite element analysis model is developed for simulating the dynamic responses of vessels under the impact of fragments. The influences of the number of winding layers, impact velocity, fragment mass, and fragment shape are investigated. The results show that fragment impact is a kind of local damage behavior with two typical stages of hitting and rebounding. The impact resistance of vessels increases with the number of winding layers. Impact velocity and fragment mass are positively related to deformation and damage. Conical fragments have stronger damage abilities, while spherical fragments cause greater deformation.

Dynamic Response of Thick Laminated Shells using Higher-Order Theory

In this paper, the dynamic characteristics of thick cross-ply laminated composite cylindrical shells are studied using a higher-order displacement model. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in the slope of the in- plane displacements at any interface. The effect of inplane and rotary inertia terms is included. The analysis is carried out using finite element approach. The governing equations derived using Lagrange's equations of motion are solved employing Newmark's direct integration technique for transient response analysis. The influences of various terms in the higher-order displacement field on the free vibrations, and transient dynamic response characteristics of cylindrical composite shells subjected to thermal and mechanical Loads are analysed.

Evaluating the impact of higher-mode and inelastic dynamic responses of concrete frames on the performance of seismic intensity measures

The accuracy of seismic risk-based evaluation depends on the selected seismic intensity measures (IMs). The performance of the selected IM is commonly assessed based on efficiency and sufficiency criteria, which reflect the ability of the IM to reduce epistemic uncertainty and avoid bias, respectively. Although various characteristics of structural dynamic response affect IM performance to different extents, the current literature determines IM suitability based on the overall response. This study examines the impact of two dynamic response characteristics, namely higher-mode effect and nonlinearity, on the efficiency and sufficiency of a comprehensive set of common and advanced IMs. Two correlation-based measures are then proposed to explicitly evaluate the effect of higher-mode effect and nonlinearity using statistical tests. The results show that the developed statistical measures can explain the inefficiency and insufficiency of an IM based on dynamic characteristics of response. In addition, while the IM’s efficiency and sufficiency changes for different structures and ground motion sets, vector-valued and energy-based scalar IMs provide more consistent performance. Lastly, the impact of higher-mode response and nonlinearity is more pronounced on IMs efficiency than IM sufficiency.

The dynamic response of solid oxide fuel cell fueled by syngas during the operating condition variations

This work investigates the dynamic characteristics of solid oxide fuel cell (SOFC) under variation operating conditions and complements the dynamic response characteristics on SOFC operating end. The dynamic characteristics is significant to dynamic operation and performance control. The classical appropriate transfer functions are proposed to capture the practical changing process of operating conditions for the first time. The dynamic multi-physical field model is developed as a mapping function to obtain the dynamic characteristics. The SOFC will be stabilized again within 100 s after the flow rate variations, which means that SOFC can be in another stable operation. The current density obviously goes through an overshoot phase and then gradually reaches stability caused by cathode flow rate variation. While, the change of anode flow does not cause overshoot. It is also found that the “fuel starvation” phenomenon also does not exist during flow rate variations, which means the “fuel starvation” hardly needs to be considered under non-extreme changes in operating conditions. The step function is used to simulate the change process of syngas composition. The increase in current density can be divided into two stages, which last about 100 s totally. The variation amplitude of current density due to the fuel composition variation is relatively small, which means the change in fuel composition doesn't cause a very dramatic response. The cell length has relative significance influence on the dynamic characteristic. This dynamic model could also be used to simulate the dynamic response of SOFC with different geometric structures, especially those with large changes in length and direction. This work is expected to uncover the dynamic response characteristics of SOFC under the variations of operating parameters, and to provide data support and theoretical guidance for SOFC under variable operating conditions and performance control.

Shake Test on Light Combat Helicopter

This paper deals with the Shake test (Ground Vibration Test) performed on a Light Combat Helicopter (LCH) at Rotary Wing Research and Design Centre, Hindustan Aeronautics Limited, Bangalore. Modal characteristics (frequency, mode shape and damping) and dynamic response characteristics of the prototype LCH have been determined experimentally. Tests are conducted with helicopter resting on landing gear and helicopter in free-free condition. Single input excitation and multipoint output data acquisition is used for determination of modal parameters. Multipoint excitation and multipoint output data acquisition is used for the dynamic response measurement to access the effectiveness of the Anti Resonance Isolation System (ARIS) of LCH. The test setup, instrumentation, data acquisition and analysis procedures are enumerated herein. The modal parameters are comparable to the finite element modal results. It is shown experimentally that, ground resonance condition does not occur and this has been proved during the ground run of the helicopter.

A new approach to aircraft ditching analysis by coupling free surface lattice Boltzmann and immersed boundary method incorporating surface tension effects

This study primarily addresses the phenomenon of aircraft ditching. This phenomenon presentspresenting a significant challenge for numerical simulations due to its highly nonlinear and multiphase-coupled water entry impact problem involving fluid-structure interaction. Traditional numerical methods have difficulties and deficiencies in free surface evolution and accuracy. An improved iterative velocity correction scheme has been presented by coupling the single-phase free surface-lattice Boltzmann method (FS-LBM) based on the volume of fluid method with the immersed boundary (IB) method to simulate water entry impact issues. Notably, this model incorporates the effect of surface tension, enhancing its ability to accurately simulate various phenomena, such as rolling, breaking, splashing, and fusion with the free surface in gas-liquid-solid multi-physical field conditions. Through the correction of the boundary force of the interface lattice and the gas lattice and the improved scheme, the non-slip boundary is satisfied, and the particle penetration is prevented. Furthermore, several benchmark tests have been conducted to verify the rationality and feasibility of the FS-LBM-IB method in simulating aircraft ditching. A scaled model of an aircraft has been developed to investigate the dynamic response characteristics of aircraft ditching at a specific attitude angle, with the simulation results confirming the accuracy of the FS-LBM-IB method in predicting the secondary head-up of the aircraft under suction force. This research highlights the efficiency of the FS-LBM-IB method as a novel approach for simulating aircraft ditching behavior.