Dynamic Response Characteristics Research Articles

Dynamic response characteristics of optical beam deflection in liquid crystal optical phased array

The beam deflector based on liquid crystal optical phased array (LCOPA) is a crucial component of space laser communication systems. Understanding and mastering the beam deflection characteristics under the dynamic response of LCOPA is essential for achieving real-time acquisition and tracking in space laser communication. This paper thoroughly explores the beam deflection characteristics during the dynamic response process by analyzing the dynamic response and far-field diffraction models of LCOPA. It presents the far-field diffraction patterns under the dynamic response of LCOPA and validates the analysis through experiments. This study not only enhances the understanding of the dynamic performance of LCOPA but also provides a theoretical basis for its control in space laser communication systems.

Characterization of Seismic Dynamic Response of Uranium Tailings Dams Based on Discrete Element Method

Tailings dams play a critical role in ensuring the safety of mining operations. However, earthquakes can cause breaches in these dams, resulting in significant casualties and property damage. This study investigates the dynamic response characteristics of uranium tailings dams subjected to seismic loading, employing the discrete element method. It specifically analyzes how seismic wave amplitude, frequency, and the friction angle of tailings sand affect the dams’ dynamic response. The results reveal that the peak ground acceleration ratio (PGAR) exhibits an increasing–decreasing–increasing pattern with elevation. When the friction angle of the tailings sand exceeds 35°, the overall stability of the dam improves. Conversely, a friction angle below 25° significantly increases the risk of dam failure. Additionally, the dam shows a reduced dynamic response to seismic waves with frequencies exceeding 15 Hz. At lower frequencies, deformation and damage are primarily concentrated on the slope face, while at higher frequencies, damage is predominantly located at the bottom of the model. These findings provide a theoretical foundation and reference for the safe operation of tailings dams, highlighting their practical significance.

Dynamic fracture mechanism and fragment characteristics of sandstone specimens with asymmetrical conjugate fissures under static pre-compression

This paper systematically investigates the dynamic mechanical response and fragment characteristics of sandstone with asymmetrical conjugate fissures subjected to preexisting static stress based on the split Hopkinson pressure bar apparatus. The cross-fissured sandstone exhibits significant variations in mechanical behavior when exposed to higher dynamic strain rates under identical static pre-stress. The cross-fissured sandstone with a higher dynamic strain rate is characterized by a greater coupled strength under the same static pre-stress; for a given dynamic load, the highest coupled strength occurs under the static pre-stress of 60% UCS. The failure mode of the cross-fissured sandstone is predominantly governed by the dynamic strain rate, independent of static pre-stress variations considered in this investigation. At lower dynamic strain rates, the specimens typically exhibit a mixed tensile-shear failure mode, characterized by the dominance of larger fragments in the broken specimens. In contrast, under high dynamic impacts, the sandstone tends to fail in a shear-dominated manner, resulting in smaller fragments with a more uniform size distribution. Furthermore, the study explores how varying dynamic strain rates and static pre-stress influence the fragment characteristics of the cross-fissured sandstone. Higher dynamic strain rates and increased static pre-stress generally lead to smaller mean fragment sizes. This phenomenon is quantitatively described by fitting fragment size distributions using the Generalized Extreme Value (GEV) distribution, revealing a decrease in the location parameter (μ) and an increase in fractal dimension. These metrics indicate that higher dynamic strain rates and static pre-stress result in sandstone specimens breaking into smaller fragments with a more homogeneous size distribution. These findings contribute to a deeper understanding of rock dynamics, with potential implications for engineering applications involving similar geological configuration under dynamic loading conditions.

Retraction Notice: Study on Dynamic Response Characteristics of Offshore Floating Wind Turbine Pitch System

The article Study on Dynamic Response Characteristics of Offshore Floating Wind Turbine Pitch System has been retracted at the request of EAI's Research Integrity Committee on the grounds of plagiarism.

Dynamic Response and Rock Damage of Different Shapes of Cavities under Blasting Loads

In order to investigate the dynamic response and rock mass damage characteristics of cavities with different shapes under blasting loads, this paper, through a combination of model tests and numerical simulations, studies the stress distribution, strain, failure modes, and blasting fragment size distribution of cavities with different shapes subjected to blasting loads. The results show that under the action of blasting loads, the presence of cavities with different shapes significantly affects the blasting effects and rock mass damage. Spherical cavities exhibit excellent blast resistance, whereas rectangular and triangular cavities are prone to stress concentration at their tips, which in turn promotes rock mass damage and failure. Subsequent analysis of the blasting fragment sizes reveals that rectangular and triangular cavities yield more favorable blasting results than spherical cavities. The research findings provide important theoretical foundations and practical guidance for the design and construction of underground engineering blasting, contributing to enhancing engineering safety and promoting the sustainable development of the underground engineering industry.

Dynamic response characteristics of backfill under blasting disturbance simulated through a three-dimensional model

During mining operations, the backfill body is subject to significant disturbance due to large-volume blasting, resulting in stress concentration and vibration response within the backfill. This alters energy distribution, leading to the continuous development, expansion, and accumulation of damage, potentially culminating in instability and collapse. Blasting disturbance in stopes is the main cause of filling instability and ore dilution. It is crucial to study the failure mechanism of filling bodies under blasting load to guide actual mine production. In this study, a custom mold was created to establish an innovative three-dimensional model of an ore-backfill system subject to explosion loading. Simultaneous detonation was selected as the control group and delayed detonation was selected as the experimental group. Monitoring and analysis methods, such as a high-speed camera system, MATLAB software, and vibration monitors, were utilized to investigate the impact of delay time on the dynamic response characteristics of the backfill. The results show that the dynamic fracture process of the backfill is mainly divided into four stages: initial crack initiation stage, crack development stage, crack expansion stage, and backfill collapse stage. The difference in delay time on the dynamic fracture process of the backfill is mainly reflected in two aspects: time effect and crack distribution. The surface flatness after delayed detonation is higher by 20.5% as compared with that after simultaneous detonation. The average damping rate during delayed detonation decreases by 19.7% as compared with that after simultaneous detonation, the frequency distribution of the single stage is more uniform, and the instantaneous peak energy during delayed detonation is 0.76 times that during simultaneous detonation. The maximum crushing size, average crushing size, and bulk crushing size after delayed detonation are reduced by 25%, 15.26%, and 9.23%, respectively, compared with that after simultaneous blasting. Thus, delayed detonation effectively improves the crushing effect while reducing the degree of damage to the backfill.

Active Control for Construction Stability of Suspension Arch Rib Segments Based on ARID System

In response to the issues of vibrations affecting the construction safety, speed, and accuracy of suspended structures due to dynamic disturbances during lifting, environmental disturbances, and improper operator actions, this paper investigates the application of the Active Rotary Inertia Driver (ARID) system for double-rope suspended structures, namely analyzes, and applies control to the vibration response of double-rope suspended structures under external excitations. Taking the double-rope suspended structure as an example, a dynamic analytical model of the double-rope suspended structure is established based on D’Alembert’s principle. Through shake table tests, the dynamic response characteristics and vibration control effects of the double-rope suspended structure under various external excitations are studied, and the influence of the twisting radius of the suspended structure on the control effect is analyzed. The experimental results show that the ARID control system achieves significant control effects on the swing and torsional vibrations of the suspended structure, which validates the accuracy of the theoretical model for the ARID control system and demonstrates its feasibility for practical applications.

An Ionization-Based Aerosol Sensor and Its Performance Study.

In recent years, with the rapid development of new energy vehicles, the safety issues of lithium-ion batteries have attracted attentions from all sectors of society. Research has found that during the thermal runaway process of lithium-ion batteries, aerosol emissions usually occur earlier than other gases. Accurate and timely measurement of these aerosol concentrations can help to warn the power battery pack fires. However, existing aerosol sensors are unable to meet the requirements of real-time monitoring and high precision. This article proposes an ionization mechanism based aerosol sensor that works at principles of field emission, field charging and gas discharge, and investigates its static and dynamic response characteristics. The sensor is manufactured and assembled using Microelectro Mechanical Systems processing technology. The sensor exhibits superior performances in terms of range, sensitivity, nonlinearity, repeatability, response time, and other aspects. The study provides a new solution for current aerosol detection with great potential for application.

Heat transfer characteristics of vertical condensers under unsteady boundary conditions: Dynamic modeling, experiment validation, and parametric analysis

A dynamic model has been developed to predict the coupled heat transfer characteristics of vertical condensers under varying boundary conditions. The model predictions closely matched the experimental data, with normalized mean bias error and root mean square error metrics below 3%. It was observed that variations in the inlet temperature of the secondary-side coolant did not immediately affect the outlet coolant temperature, exhibiting a noticeable lag phase before gradually adjusting to new conditions. Even after the inlet coolant stabilized, the outlet coolant temperature continued to rise until reaching a steady state after a defined period. The dynamic changes in the condensate film thickness and local heat flux density were categorized into three stages: lag, transitional, and steady. These stages showed differing response and transition times across various locations of the condenser. The bottom of the condenser pipeline demonstrated the shortest response time for condensate film thickness variation but the longest transition time. Additionally, the study investigated the influence of geometric parameters on the dynamic response characteristics of condensers. It was found that longer condenser tubes, lower wall thermal diffusivity, and thicker condensing walls resulted in extended transition times for condensate mass flow at the condenser bottom.

Dynamic Characteristics of Pressure-Balanced Metal Bellows in Fluid–Structure Interaction

As a flexible component in high-pressure vessels and pipeline systems, bellows experience significant fluid–structure interaction effects under high-speed internal fluids and external vibrations. Nevertheless, their dynamic response mechanisms coupled with fluid–structure interaction mentioned below have not yet been clarified so far. In this work, a novel pressure-balanced metal bellow (PBMB) for low-stiffness and high-pressure resistance is firstly proposed. Several fluid–structure interaction models were considered to study the dynamic response characteristics of the PBMB. An experimental platform associated with fluid–structure interaction was established to validate the effectiveness of its vibration attenuation performance. The results indicate that the PBMB has an obvious vibration attenuation effect in the range of 5–90[Formula: see text]Hz, and super-harmonic and sub-harmonic resonance phenomena occur in the range of 90–200[Formula: see text]Hz. Under constant fluid conditions, fluid density, viscosity, flow velocity, and pressure are positively correlated with the response amplitude of the PBMB. The response of the PBMB oscillates at the fluid entry point due to both pulsating flow velocity and pulsating pressure. After several cycles, the response caused by pulsating flow velocity gradually decays and stabilizes. Thus, the impact of pulsating frequency on the stability of the response of bellows is insignificant during the initial cycles.

Dynamic response and failure characteristics of the fluid-filled concave multicell structure under combined blast and fragments loading

The deformation and damage characteristics of the fluid-filled concave multicell structure under the charge explosion with preset fragments are investigated to assess its performance against combined blast and fragments loading. The failure characteristics of the structure, the propagation process of loads, and the dynamic response characteristics of the structure are analyzed using experimental research and SPH-ALE numerical simulation. The results indicate that the deformation of the structure, caused by the explosion of a charge with preset fragments, is 400% greater than the deformation caused by the explosion alone. The propagation of the load is influenced by the panels of the structure and the irregular regions where fluid is filled. The deformation and failure of the fluid-filled concave multicell structure occur in two stages. The failure mode of this structure can be seen as a combination of the failure modes of individual single-cell structures, based on the method of fluid filling. The strength distribution of the structure plays a crucial role in determining the failure of the fluid-filled concave multicell structure.

Riding safety prediction of a high-speed train running on transition zone under foundation settlement

The settlement of piers and subgrade bending deformation are widely recognized as common issues in the transition zones of high-speed railway bridges. This study aims to investigate the settlement behavior within these transition zones and its impact on the dynamic interaction between trains and the track. To achieve this, a vehicle-track-transition zone mapping relationship model is developed to analyze both the settlement behavior and the resulting dynamic response characteristics. The study employs the finite element method and multi-body dynamics to construct the simulation model. Settlement effects are simulated using the Newton-Raphson iterative method, with the additional rail deformation caused by foundation settlement serving as the excitation for the vehicle-track-transition zone dynamic interaction system. In the numerical analysis, the dynamic effects of three key factors—train speed, transition zone length, and the amplitude of foundation settlement—are examined based on the performance of the vehicle-track-transition zone interaction. The time-frequency technique is utilized to comprehensively reveal and clarify the spatial-frequency characteristics of system responses influenced by settlement excitation. Moreover, the relationship between the safety-based settlement threshold and these three factors is calibrated.

Seismic response investigation of prestressed anchor cable supporting rock slope with weak interlayer in Qinghai-Tibet Plateau, China

Earthquake-induced rock landslides in the eastern mountains of the Tibetan Plateau, especially landslides with weak interlayers pose a significant threat to major construction projects. Prestressed anchor cable is one of the main reinforcement methods of rock slopes. This paper combines shaking table model tests and numerical simulation to study the reinforcement effect and dynamic response characteristics of prestressed anchor cables applied to rock slopes with weak interlayers under strong earthquakes. The research results show that prestressed anchor cables can effectively reinforce slopes with weak interlayers. A small cable inclination, a small spacing and a high prestress are recommended in the seismic reinforcement design of prestressed anchor cable. In addition, the characteristics of slope progressive damage and prestress loss under the earthquake are found by the shaking table test. The results have been applied in hazard prevention and control of rock slopes on the Chengdu-Lanzhou Railway at the eastern Qinghai-Tibet Plateau.

Comparative study on dynamic responses of ballasted and ballastless tracks at critical velocity

High-speed railways are becoming ubiquitous worldwide, demanding increased operational speeds. Yet, as trains near critical speeds, dynamic stress and embankment displacement escalate, jeopardizing safety. While significant strides have been made in studying these critical speeds, capturing the dynamic characteristics of all track responses remains elusive. This study presents a coupled train-track-ground model employing a 2.5D finite element approach integrated with a nonlinear soil model to investigate the influence of embankment and foundation properties on the critical speeds for both ballasted and ballastless tracks. The research resulted in the development of unified Dynamic Amplification Factor curves that consistently represent the dynamic behavior of various tracks as observed in multiple studies. Additionally, the applicability of simplified theoretical models for calculating critical speeds, such as the elastic half-space foundation and track-foundation models, was assessed. The findings suggest that the simplified models are suitable only under specific conditions. This research provides valuable perspectives on optimizing train speeds and ensuring the safety of diverse track types.

Liquid microlens compound structure for enhanced sub-micron resolution imaging and accelerated reconfigurable deformation manipulation

The optical observation of sub-micron structures encounters significant challenges due to the inadequate spatial shape matching of optical devices and the limitations imposed by diffraction. These factors result in suboptimal imaging resolution and the introduction of defocus distortion. One approach to mitigating these limitations involves utilizing a liquid microlens (LML) assisted microscope, which offers real-time and localized control capabilities. However, the dynamic tuning of LML is subject to volatility and instability, adversely affecting sub-micron resolution imaging. To address this issue, a contour-following coating inspired by the natural cornea is applied to the droplet's surface, resulting in the formation of liquid microlens compound structures (LMLCS). Firstly, photoresist microholes are fabricated on the optical disc. Then, liquid self-assembly technology is used to fill glycerol in the microholes. At last, a conformal spreading method of UV-curable adhesive precursor film is developed to ensure the combination of the microlens bilayer structure. Through the application of optical information transmission theory, finite difference time domain (FDTD) method, and the principle of Abbe microscopic imaging, the imaging magnification process and sub-micron resolution characteristic of the LMLCS are revealed. Remarkably, the obtained focal width at half maximum (FWHM) of 1.54 μm is smaller than the theoretical value, enabling reconfigurable sub-micron resolution observation and 1.63 times imaging magnification of 226 nm grating lines under the optical microscope. Compared with unencapsulated LML, this compound structure exhibits better sub-micron resolution capability, greater imaging magnification, and faster adaptive dynamic response characteristics. Consequently, the LMLCS introduces exciting prospects for exploring optical sub-micron measurement and sensing devices with exceptional performance.

Responses analysis and structural optimization of a semisubmersible platform based on the Taguchi experiment method

Responses analysis and structural optimization of a semisubmersible platform based on the Taguchi experiment method

Characteristic Study of a Typical Satellite Solar Panel under Mechanical Vibrations.

As the most common energy source of spacecraft, photovoltaic (PV) power generation has become one of the hottest research fields. During the on-orbit operation of spacecraft, the influence of various uncertain factors and the unbalanced inertial force will make the solar PV wing vibrate and degrade its performance. In this study, we investigated the influence of mechanical vibration on the output characteristics of PV array systems. Specifically, we focused on a three-segment solar panel commonly found on satellites, analyzing both its dynamic response and electrical output characteristics under mechanical vibration using numerical simulation software. The correctness of the simulation model was partly confirmed by experiments. The results showed that the maximum output power of the selected solar panel was reduced by 5.53% and its fill factor exhibited a decline from the original value of 0.8031 to 0.7587, provided that the external load applied on the panel increased to 10 N/m2, i.e., the vibration frequency and the maximal deflection angle were 0.3754 Hz and 74.9871°, respectively. These findings highlight a significant decrease in the overall energy conversion efficiency of the solar panel when operating under vibration conditions.

Dynamic response characteristics of microchannel evaporator in a mechanically pumped two-phase loop under hypergravity environment

The unique hypergravity environment and severe heat-dissipation requirements of modern fighter aircrafts pose serious challenges to the potential utilization of mechanically pumped two-phase loops (MPTLs), which are an efficient cooling technology. The microchannel evaporator is a key component of the MPTL system, and understanding its startup and operation characteristics is of great significance for design and optimization. In this context, an experimental MPTL system is built and fixed on a rotating platform, which is designed to generate hypergravity ranging from 0 g0 to 15.0 g0 (g0 = 9.8 m·s−2). The dynamic-response characteristics of the temperature, pressure, and flow rates during the startup and operation of the microchannel evaporator under various hypergravity conditions are investigated. The results indicate that different startup modes, namely gradual startup under low hypergravity and overshoot startup under high hypergravity, are achieved on the microchannel evaporator, even if the flow rate and heat flux are not changed, which is completely different from that under normal gravity. These two startup modes can be quantitatively recognized by two dimensionless numbers: the boiling number (Bo) and Froude number (Fr). A larger Bo or 1/Fr, which corresponds to a larger heat flux or hypergravity; both conditions contribute to the startup mode of the microchannel evaporator shifting from gradual to overshoot startup. During the operation of a microchannel evaporator, the competition between the elevated saturation temperature of the fluid and the induced Coriolis and centrifugal forces caused by hypergravity determines the wall-temperature variation of the evaporator. The dynamic wall temperature decreases under hypergravity below 2.5 g0, is stable with small fluctuations under hypergravity from 4.7 g0 to 7.5 g0, and increases for hypergravity larger than 11.0 g0.

Dynamic Response Characteristics of Rotating and Fixed Components of the Kaplan Turbine under Low and Medium Heads

Dynamic Response Characteristics of Rotating and Fixed Components of the Kaplan Turbine under Low and Medium Heads

Transient thermal management of laser systems using Plate-Fin phase change heat Exchangers: Experimental and computational study

To mitigate transient thermal shocks in lasers and reduce thermal stresses caused by temperature fluctuations, the use of phase change materials (PCMs) in thermal management systems is a viable solution. This study proposes an innovative two-dimensional transient heat transfer model specifically designed for plate-fin phase change heat exchangers (PFPCHEs). The model meticulously simulates the complex heat transfer phenomena within the heat exchanger, including fluid convection, solid thermal conduction, and the phase change processes of PCM. The convective heat transfer coefficient between fluid and plate is calculated using the Wieting correlation. An advanced pulse-mode experimental test platform was constructed to validate the model, dynamically monitoring and recording outlet temperatures and heat exchange performance for stringent experimental comparison. The research explores the impact of key operating parameters such as initial temperature, flow rate, and inlet temperature of the cooling cycle on the performance of the heat exchanger, providing valuable design and control strategies for transient thermal management of laser systems. The experimental results confirm that the model accurately predicts the dynamic response characteristics and temperature distribution of PFPCHEs under multi-cycle pulse loads, with 96% of the predictions within a 10% error margin. A significant finding is that the initial temperature has negligible influence on the heat transfer characteristics when it is below the solid phase temperature of the PCM. Moreover, by meticulously adjusting the flow rate and inlet temperature of cooling cycle, it is possible to effectively maintain the stability of the outlet temperature throughout the entire pulse cycle. This is crucial for minimizing temperature fluctuations within the thermal management system and extending the service life of electronic components.