Dynamic Response Characteristics Research Articles

Design, modeling and performance analysis of a deformable double-float wave energy converter for AUVs

Autonomous underwater vehicles (AUVs) are one of the most important means of ocean exploration. However, the restricted energy supply poses a significant challenge to the advancement and practical application of AUVs. Based on the structural characteristics, this paper proposes a novel AUV, which integrates a deformable double-float wave energy converter (WEC), called DFWEC-AUV. The DFWEC empowers the AUV to capture wave energy to supply itself by oscillating double-float form in power generation mode. The structural design, focusing on the deformable float (DeF) and the onboard damping plate (DP), and the working principle, including mode switching and energy capture, are firstly introduced. Then, a double-float dynamic model of DFWEC-AUV oscillating in regular waves is established to reveal the energy capture mechanism in both frequency-domain and time-domain. Finally, the influence of the presence of DP, structural parameters (diameter of DP and deployment angle of DeF) and power take-off (PTO) system damping coefficient on the dynamic response characteristics and energy capture performance is analyzed. In addition, to verify the effectiveness of the performance analysis, a comparative simulation of parameter optimization is carried out under actual wave excitation. The results show that the addition of onboard DP is able to effectively enhance the energy capture performance of DFWEC-AUV, as well as increase the energy capture bandwidth. Moreover, the larger the diameter of the DP is, the greater the performance improvement of DFWEC-AUV is. Conversely, increasing the deployment angle of the DeF does not necessarily lead to better power capture performance. Additionally, it is observed that waves of a particular period are consistently associated with an optimal PTO damping coefficient, which leads to superior power capture performance. In comparative simulation, the energy capture performance of DFWEC-AUV after parameter optimization is increased by 4.7 times.

Numerical analysis on dynamic response and damage threshold characterization of deep rock mass under blasting excavation

The excessive destruction of surrounding rock in deep tunnel will change the original environmental state and destroy the natural ecological balance. Research on the dynamic response characteristics and damage thresholds of rock masses in deep environments plays a crucial role in determining the excavation range of blasted rock and establishing safety construction scheme. This study employs numerical simulation techniques to investigate the dynamic response characteristics of surrounding rock under different ground stress conditions. By introducing the dynamic ultimate tensile strength criterion, critical fracture stress threshold, and maximum damage radius of rock under coupled dynamic-static loading conditions are determined. The research shows that under uniaxial ground stress condition, increasing ground stress inhibits damage to the surrounding rock and the extension of cracks in the excavation area, while imposing restrictions on the attenuation rate of explosive stress. Under bidirectional equal ground stress condition, an increase in lateral pressure coefficient inhibits the development of damage zones along the excavation contour, yet enhances the extension of cracks in the maximum principal stress direction. Moreover, when lateral pressure coefficient becomes excessively large, the attenuation rate of explosive stress significantly increases. Based on the threshold values of peak particle velocity (PPV), the functional relationship is established to predict safety criteria for deep blasting excavation.

Research on impact resistance of new suspended elastic safety net system

In order to reduce the direct injuries caused by falling from height, we propose a new type of suspended elastic safety net system suitable for pylon assembly construction. Analyze the correlation between damping and toughness of the protection system, establish the falling object motion control method, and construct the mechanism model of the protection system accordingly. Full-scale impact tests are carried out using test pylons on transmission line projects. Test data is collected using high-speed cameras and dynamic data acquisition equipment to analyze the key impact dynamic response characteristics of the test model. The experimental results show that the system has three working stages. In the first stage, the elastic safety net is transformed from an initial equilibrium state, where it is subjected only to its gravity, to a taut state. In the second stage, as the elongation of the system continues to increase in the direction of impact, the internal forces transmitted by the net to the elastic rod and the supporting rope gradually increase until the energy dissipating devices connected to the elastic rod are activated. In the third stage, additional elongation of the system is provided by activating the support springs in the bearing supports. Based on the failure modes observed in the tests, the key factors leading to the breakdown of the system are investigated. A new numerical simulation method is developed which is not only capable of predicting the load-bearing capacity of an elastic safety net system under the impact of a falling object, but also accurately simulates the main operating characteristics, such as buckling of the elastic rods, activation of the energy-absorbing devices, and deformation of the net ropes. The numerical simulation model was evaluated using the experimental results, and the numerical response of the system was in good agreement with the experimental data.

Non-Invasive Method-Based Estimation of Battery State-of-Health with Dynamical Response Characteristics of Load Surges

Battery state-of-health (SOH) estimation is an effective approach to evaluate battery reliability and reduce maintenance costs for battery-based backup power supply systems. This paper proposes a novel SOH estimation method for batteries, which only uses the response characteristics of load surges and is, therefore, non-destructive to the estimated battery and its system. The discrete wavelet transform (DWT) method based on multi-resolution analysis (MRA) is used for wavelet energy features extraction, and the fuzzy cerebellar model neural network (FCMNN) is introduced to design the battery SOH estimator. The response voltage signals to load surges are used in the training and detection process of the FCMNN. Compared to conventional methods, the proposed method only exploits characteristics of online response signals to the inrush currents rather than injecting interference signals into the battery. The effectiveness of the proposed method is validated by detailed simulation analysis and experiments.

Multi-objective cooperation optimization research on dynamic response and energy loss of high-speed solenoid valve for diesel engine injector

The dynamic response and operational reliability of high-speed solenoid valve (HSV) for diesel engine injector are the main indicators to measure their performance. At high-frequency, the eddy current energy and Joule energy generated by the HSV will be converted into heat, which has a significant impact on the service life of HSV. The optimization of HSV involves the interaction between energy loss and the dynamic response of HSV. To optimize the HSV dynamic response time considering energy loss, the HSV work process simulation model was established in this paper, and the model was verified based on armature lift experimental data. Without changing the structural parameters of the HSV, the four parameters of electroconductibility, spring stiffness, damping coefficient, and coil resistance were selected as the key parameters affecting the dynamic response and energy loss. The response surface models (RSMs) of opening response time, closing response time, eddy current energy and Joule energy of the HSV were constructed by using the smoothing spline-analysis of variance method. The multi-objective cooperation optimization of HSV under the interaction of dynamic response characteristics and energy loss was completed by using non-dominated sorting genetic algorithms. After optimization, the opening and closing response times of HSV were reduced by 15.1% and 16.6% respectively, while the eddy current energy and Joule energy were reduced by 5.2% and 48.4% respectively. In this paper, the dynamic response and energy loss were jointly optimized. The presented results provide theory instruction for multi-objective cooperative optimization of HSV.

Dynamic Response of Bridge–Tunnel Overlapping Structures under High-Speed Railway and Subway Train Loads

With the rapid development of high-speed railroads and subways, there has been an increasing number of bridge–tunnel overlapping structures. To study the dynamic response characteristics of bridge–tunnel structures under the synergistic effects of the vibration generated by high-speed railway and subway trains, the dynamic response characteristics of a bridge–tunnel structure under single-point vibration loading was analyzed by conducting numerical simulations and model tests, with the frequency response function and peak acceleration as the evaluation indices. The dynamic response characteristics of the overlapping structure under moving vibration loads of the high-speed railway and subway trains were further analyzed. The results showed that the dynamic response of the bridge–tunnel overlapping structure increased with the increase in the frequency under the full frequency domain single-point sweep vibration load. The dynamic response of the tunnel hance near the pile foundation side was significantly greater than the vault and invert. Compared with the effect of high-speed train loads alone, the dynamic response of the bridge–tunnel overlapping structure under the synergistic effects of high-speed railways and subways increased significantly and varied at different locations. This investigation provides theoretical support for the design and construction of bridge–tunnel overlapping structures under the synergistic effects of high-speed railways and subways, contributing to improving engineering quality and safety.

Research on Vibration Characteristics of a Flexible Vehicle-Ladder Track System

As a means of vibration reduction, the ladder track has seen broad implementation in urban rail transit. However, issues such as increased vibration noise, rail corrugation, and fastener failure have been observed in certain sections of the ladder track during later operation. To investigate the mechanisms behind these phenomena and provide comprehensive insights into the system's response to various operational conditions, this study employed vehicle-track coupled dynamic theory to establish a three-dimensional finite element model of the flexible vehicle-ladder track system. The vibration transmission and dynamic response characteristics of the vehicle-ladder track system were analyzed. The findings revealed that the vehicle-track resonance and anti-resonance phenomena were more prominent in the medium- to low-frequency range. At specific frequencies, the wheelset exhibited various vibration modes, and the fastener force was found to closely correlate with the ladder vibration mode. Furthermore, the influence of speed on diverse components of the vehicle-ladder track system, in terms of maximum vibration and the dominant vibration frequency range, differed considerably. This study provides a more comprehensive and reasonable exploration of the modeling and dynamic behavior of vehicle-ladder track systems.

Analysis of Pressure Pulsation and Structural Characteristics of Vertical Shaft Cross-Flow Pumps

In order to study the pressure pulsation characteristics and structural dynamic response characteristics of a vertical shaft cross-flow pump, this study used a computational fluid dynamics (CFD) numerical simulation method to analyze the pressure pulsation characteristics of the inlet passage, impeller, and guide vane positions of the vertical shaft cross-flow pump device. At the same time, this study analyzed the equivalent stress–strain characteristics of the impeller and guide vane of a vertical shaft cross-flow pump based on fluid structure coupling technology and comprehensively analyzed the deformation modes of the impeller blades and guide vanes under dynamic water flow. This research shows that due to the influence of rotor–stator interaction, the amplitude of pressure pulsation at the interface between the impeller and guide vane of the pump device is the largest and that the main frequency distribution at this position is relatively complex. The non-uniformity of stress distribution at the impeller position gradually decreases with an increase in the radial distance. The high stress and strain zones of the impeller and guide vane are concentrated at the root of the blade. This study can provide reference for hydraulic optimization design and stable operation of similar pump devices.

On quasi-steadiness of transverse galloping of rectangular cylinders at Reynolds numbers below 10,000

Forced transverse oscillations are used to investigate the quasi-steady behavior of a rectangular cylinder with a side ratio of 2 at Reynolds numbers less than 10,000 (based on cylinder thickness). To this end, phase-averaged measurements of the transverse force acting on the oscillating cylinder at different phases of motion are compared to the mean force acting on the static cylinder at different angles of attack. The force data are complemented with boundary-layer-resolved measurements of the streamwise velocity using single-component molecular tagging velocimetry. The experiments are conducted for two Reynolds numbers of 2,500 and 7,500, two oscillation amplitudes of 20 % and 50 % of the cylinder thickness, and reduced velocities in the approximate range of 2–30 times the reduced velocity corresponding to the vortex shedding frequency. The results show that the reduced velocity threshold required to attain quasi-steady behavior is strongly dependent on Reynolds number in the investigated range. The effect is such that the lower the Reynolds number, the higher the threshold. This behavior is linked to viscous effects which render the shear layer too slow to adapt to the cylinder motion with decreasing Reynolds number. A most pronounced effect is observed at the lowest reduced velocity and Reynolds number, where the shear layer reattaches on the side of the cylinder during the cycle at an angle of attack less than half that exhibited for the static cylinder. Overall, the study shows that in addition to the time scale associated with vortex shedding, when the Reynolds number is sufficiently low, a viscous time scale characteristic of the shear layer dynamic response should be included in determining the validity of quasi-steadiness.

Quasi-Static Model Test of Pile-Supported Wharf under Cyclic Lateral Loading

The pile-supported wharf (PSW) is one of the most common structures in harbor engineering. To investigate the dynamic response characteristics of the PSW, a quasi-static model test of a PSW–ground system under cyclic lateral loading is conducted. The deformation and damage processes of piles and the sand stratum are observed and obtained. The hysteresis characteristics of the PSW–ground system and the response characteristics of piles are systematically explored. The strain energy of the pile group on the sloping ground is calculated and analyzed. The results show that there are two peak bending moments on the pile, and the maximum one occurs at the pile top. The pile embedded depth and the loading direction strongly affect the strain energy distribution of the pile group. Under downslope direction loading, the center piles have the largest strain energy percentage. The strain energy extends from the center piles to the outside piles with the increase in loading displacement amplitude. The test results indicate that the landside pile and center pile should be strengthened during seismic design.

Dynamic response characteristics and economic analyses of two solar-assisted multi-generation systems

Efficient use of solar energy can alleviate the depletion of fossil energy and global warming. In this paper, two solar-aided combined cooling, heating and power systems are proposed and dynamically modeled. The main difference between the two systems is whether the solar energy is stored. A rotor speed-temperature-fuel control system is established, which is suitable for both systems. A control system for solar heat collection process is developed. Energy, exergy and techno-economic analyses are carried out to evaluate the thermodynamic and economic performances. The dynamic responses under direct normal irradiation perturbation and load perturbation are also investigated. The result shows that compared with the system without energy storage, the system with energy storage has higher primary energy utilization rate, exergy efficiency and fuel saving rate, but the economic performance is poorer. The rotor speed-temperature-fuel control system can guarantee a short equilibrium time and a small overshoot for power generation process. When electrical load disturbance occurs, the stabilization times of the output power, cooling energy supply and thermal energy supply are 30 s, 675 s and 770 s, respectively. Under the regulation of the solar heat collection control system, the maximum overshoot of the outlet thermal oil temperature of the parabolic trough solar collector is 2.6 % with a stabilization time of 83 s when the direct normal irradiation step disturbance occurs.

Study on high temperature dynamic characteristics and mesoscopic simulation of HFRC under dynamic and static combined loading

The Φ50mm SHPB system was used to carry out three-dimensional dynamic and static combined loading tests on hybrid fiber reinforced concrete (HFRC) treated at different temperatures (25 °C, 200 °C, 400 °C) under different confining pressure ratios (0, 0.1, 0.2, 0.3). The temperature effect, confining pressure effect and failure characteristics of HFRC under impact load were studied. The effect of fiber was equivalently treated in mortar, and the meso-aggregate model of HFRC considering aggregate, mortar and interfacial transition zone (ITZ) was established. The simulation results were compared with the experimental results. The results showed that the higher the confining pressure ratio, the more significant the temperature effect of peak stress is. The higher the temperature is, the less obvious the enhancement effect of confining pressure on peak stress is. Compared with the influence of confining pressure on dynamic peak strain, the influence of temperature effect on dynamic peak strain is higher. The established three-dimensional meso-aggregate model and calculation method can accurately reflect the dynamic response characteristics of HFRC at different temperatures and confining pressure ratios. Prestress will affect the internal stress distribution of the specimen, thus affecting the compression failure characteristics of the specimen. The confining pressure can constrain the damage course of the specimen and has a good protective effect on the specimen.

Delamination and Dynamic Response Characteristics of CFRP Laminate Under Laser Shock

Delamination and Dynamic Response Characteristics of CFRP Laminate Under Laser Shock

Dynamic response characteristics of linear translation stage: A review

This paper explores the various factors that influence the dynamic response of a linear translation stage. The dynamic behavior of a linear translation stage is dominated by various factors such as friction, stiffness and resonant frequency. Friction behavior hinges on the preload level, while vibration behavior is dominated by the resonant frequency of the stage. Dynamic stiffness depends on the bearing preload and the mechanical properties of the linear motion stage. Damping is influenced by the linear bearing preload, friction, and the lubricant film. The preload applied to the rolling element bearings plays a key role in the dynamic response of the system since it influences friction, damping, resonant frequency, and stiffness of the linear translation stage.

Study on the Dynamic Response Characteristics of Surrounding Rock Mass of Underground Caverns under Blast load

Study on the Dynamic Response Characteristics of Surrounding Rock Mass of Underground Caverns under Blast load

Study on the flooding characteristics of a deep-water submarine based on δ plus-smoothed particle hydrodynamics method and graphic processing units acceleration

The process of a damaged ship flooding is a complicated free surface flow problem. There is a complex coupling effect between the ship cabin and the flow inside and outside of the cabin. In this paper, a GPU (graphic processing unit)-δ+-SPH (smoothed particle hydrodynamics) numerical model for the cabin flooding in deep-water environments is developed based on GPU parallel acceleration technology and Nvidia's CUDA (compute unified device architecture). First, the computational accuracy and efficiency of this numerical model are verified by experiments results on the water flooding of a simple damaged cabin model. Furthermore, the flooding characteristics of a submarine cabin are analyzed, considering different numbers of damaged cabins, depths, and opening positions. Finally, the progressive flooding and the dynamic response characteristics of a full-scale submarine model are investigated. The results show that the process of progressive flooding in a submarine cabin is characterized by its rapidity and intensity. Different factors, for example, damaged cabin numbers, cabin depths, and opening positions, have great influences on the process of flooding and the motion of the submarine cabin. This study can offer valuable technical assistance in the post-damage remediation process.

Comparing the Perceived Intensity of Vibrotacitle Cues Scaled Based on Inherent Dynamic Range.

Wearable devices increasingly incorporate vibrotactile feedback notifications to users, which are limited by the frequency-dependent response characteristics of the low-cost actuators that they employ. To increase the range and type of information that can be conveyed to users via vibration feedback, it is crucial to understand user perception of vibration cue intensity across the narrow range of frequencies that these actuators operate. In this paper, we quantify user perception of vibration cues conveyed via a linear resonant actuator embedded in a bracelet interface using two psychophysical experiments. We also experimentally determine the frequency response characteristics of the wearable device. We then compare user perceived intensity of vibration cues delivered by the bracelet when the cues undergo frequency-specific amplitude modulation based on user perception compared to modulation based on the experimental or manufacturer-reported characterization of the actuator dynamic response. For applications in which designers rely on user perception of cue amplitudes across frequencies to be equivalent, it is recommended that a perceptual calibration experiment be conducted to determine appropriate modulation factors. For applications in which only relative perceived amplitudes are important, basing amplitude modulation factors on manufacturer data or experimentally determined dynamic response characteristics of the wearable device should be sufficient.

Dynamic characteristics of ISRFT blowout considering camber angle under typical driving conditions

Run-flat tires are a significant way to prevent the tire blowout traffic accidents and the inserts supporting run-flat tire (ISRFT) can successfully address the problem of zero-pressure driving after the tire blowout. The dynamic response characteristics must be developed using a reasonable tire model since the characteristics of vehicles fitted with this run-flat tire following tire blowout differ from those of normal tires (NT). In this paper, steady-state mechanical characteristics tests were carried out to obtain the mechanical characteristics after the theoretical analysis of the zero-pressure rolling for the ISRFT. Secondly, a dynamics model based on the UniTire model was developed for ISRFT with the consideration of camber angle. Finally, the effect of various camber angles on the tire blowout parameters of vehicles equipped with ISRFT and NT was compared using three sets of typical working conditions, which demonstrated the superiority of the ISRFT. The results indicate that the optimal characteristic of the vehicle equipped with ISRFT compared to vehicles equipped with NT is improved by 14.02% under steering conditions and 12.75% under double lane change conditions. This study provides a foundation for improving the autonomous characteristics of vehicles.

Experimental study on multi-body coupling system for twin-barge hydraulic lifting shipwreck salvaging system

The twin-barge lifting method, applied in the overall salvaging scheme of ‘SEWOL’, is one of the main approaches for salvaging large-tonnage shipwrecks. A model experiment for the twin-barge lifting shipwreck salvaging system was conducted for three typical salvaging stages. Based on the experimental results, this study investigated the coupled dynamic response characteristics of the multi-body system consisting of the shipwreck and twin barges. The coupling effects between the multi-body system were discussed to understand the complex dynamic behaviour in twin-barge salvaging system, utilizing spectrum and statistical analysis. Additionally, this study considered the influence of the environment direction on the barge motion. It was revealed that the multi-body system exhibits significant shielding, which greatly affects the heave, roll, and pitch motions, particularly for beam and quarter seas. The maximum sling tension, including the case of single lifting sling broken, was also analysed to ensure safety under extreme conditions. Finally, it is advisable to perform salvage operations in head seas considering motion response amplitude, and to conduct the salvage in beam seas from the perspective of lifting slings safety. This study is of great significance for improving the safety of large-tonnage wreck salvage operations, promoting the development of research on multi-body system.

Fault feature extraction method of rolling bearings based on coupled resonance system with vibrational resonance-assisted enhanced stochastic resonance

Stochastic resonance (SR), as a signal processing method that is able to use noise to enhance weak periodic signals, provides effective technical support for the detection of weak signals. However, due to the constraints of potential functions or control means, the detection results of a single SR system on weak signals often fails to achieve the desired effect. Through the interaction between different subsystems, SR under the action of multiple systems can obtain rich dynamic response characteristics and improve the detection ability of weak signals. Therefore, this paper proposes a fault feature extraction method of rolling bearings based on a coupled resonance system with vibrational resonance (VR)-assisted enhanced SR. First, a SR system based on a matched steady-state potential model is constructed, which has the ability to alleviate the phenomenon of output saturation to some extent compared with the classical bistable SR. Second, inspired by the synergy of multiple systems, a coupled resonance system with VR-assisted enhanced SR is constructed by combining VR control and SR control, which has the dual advantages of VR and SR and performs well in weak signal detection. Finally, simulation experiment and fault data of rolling bearings are adopted to analyze the suggested method, and the comparison results with other SR methods verify its practicality and superiority.