Pulse Loading Research Articles

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.

Failure analysis of Fiber Metal Laminate channel section column under axial compressive pulse loading

The study aims to analyse the dynamic buckling phenomenon and assess the role of the stress tensor components in the failure process of a short Fiber Metal Laminate column under axial compressive dynamic loading. The investigation is focused on a channel-section profile composed of three aluminium layers and two doubled composite plies [Al/0/90/Al/90/0/Al]. The numerical analysis was performed on the finite element model, which was validated by experimental static buckling tests. Employing a progressive failure algorithm, this analysis incorporated the material property degradation method and Hashin’s criterion as the damage initiation criterion. Failure initiation in metal layers was based on the HuberMises-Hencky failure criterion. Based on the conducted analyses, it was concluded that the dominant forms of destruction in the FML structure are yielding in the metal layers due to excessive compressive stresses and the failure of the matrix in composite plies as a result of compressive and shear stresses. Through a thorough examination of the stress tensor components, critical stresses contributing to aluminum plastic deformation and laminate failure mechanisms were identified.

Optimal transient power sharing method for shipboard MVDC System based on segmented variable step dynamic programming

Supplying power for large pulsed power load with shipboard medium voltage direct current integrated power system has continued to be a challenge. The energy storage device configured in the system can effectively mitigate the power impact on grid and gas turbine gensets, but it also complicates the system operation, requiring advanced power sharing and control strategies for support. In this paper, the control framework of system configured with hybrid energy storage is presented, the objective function to quantify transient power disturbance on gas turbine genset is established, and the segmented variable step dynamic programming method for system transient power sharing is innovatively proposed and employed to derive the optimal transient power-sharing scheme for the rectangular and triangular large pulsed power load conditions. Compared with the conventional approach through MATLAB/Simulink simulation, the scheme derived from segmented variable step dynamic programming demonstrates enhanced utilization of the transient power compensation capability of hybrid energy storage, and leads to a reduction in the power regulation pressure on gas turbine gensets. In the assumption of two typical operating processes, as the results of the power impacts，the transient regulation rate of the genset rotor is reduced from 10.4 % to 9.9 % and from 13.7 % to 8.6 %, respectively, the fatigue damage of shaft system is decreased by 53 % and 94.4 %, respectively, and the maximum inlet relative temperature of gas generator turbine is reduced by 0.015 and 0.139, respectively.

Simulation research on blasting of an open pit mine slope considering elevation conditions and slope shape factors

This study established a numerical model that considers elevation conditions and slope shape factors by the modified Sadovsky formula to analyze the vibration attenuation law of open-pit slopes under blasting vibration conditions. The blasting excavation of a slope in a certain open-pit mine in Yunfu, Guangdong, is selected as an example. Using a numerical model that considers elevation conditions and slope shape factors by the modified Sadovsky formula, a triangular pulse load was utilized to approximate the time-history characteristics of explosion vibration with FLAC3D software. The simulation results showed the radiation range of the blasting vibration seismic wave. By comparison with field monitoring data, the numerical model that considers the slope shape factor had a relative error of ∼10%, while the numerical model that disregards the slope shape factor had a relative error of ∼15%. The relative accuracy of the calculation results of the new numerical model is higher and closer to the actual attenuation law of blasting particle vibration speed, providing more reliable results for slope stability assessment. The peak particle velocities obtained from the numerical simulation results were generally higher than the field monitoring data. These discrepancies might be attributed to the use of simplified models that disregard the discontinuous structural planes within the rock mass. This study provides an important reference for the stability assessment of open-pit slopes under blasting vibration conditions, offering guidance for improving slope stability assessment and related engineering practices.

The Thermodynamic Responses of FG Conical/Cylindrical/Annular Panels with Circumferentially Variable Dimensions

This paper is the first to develop a meshless thermodynamic model with circumferentially variable dimensions to analyze the thermal-vibration mechanisms of typical functionally graded (FG) panel-type structures, mainly including conical, cylindrical, and annular panels. The longitudinal variation of the panel-type structure’s circumferential dimensions is taken into account according to specific rules. The Thin Plate Inverse Mapping (TPIM) meshless shape functions are introduced to characterize the displacement components associated with each substructure. Thermodynamic equations are formulated based on FSDT thermo-elastic theory as well as Hamilton’s principle. Rectangular and exponential pulse loads are taken into consideration for forced vibration analysis in this formulation. Numerical convergence and comparative cases are provided. Solutions from the literature and finite element simulation results are utilized for comparison, revealing that the percentage differences observed are all less than 0.025%. This confirms the reliability and accuracy of the developed analysis model. In conclusion, a detailed investigation is conducted on the influences of geometrical dimensions, boundary conditions, as well as thermal and external loads on the thermodynamic behaviors of FG panel-type structures with circumferentially variable dimensions.

Evaluating the vertical stiffener effects on the dynamic behavior of a cylindrical intake tower under pulse loading

Evaluating the vertical stiffener effects on the dynamic behavior of a cylindrical intake tower under pulse loading

A multi-objective configuration optimization method of passive hybrid energy storage system for pulse loads operating under very low temperatures

The lithium-ion battery energy storage system currently widely used faces a problem of rapid degradation of electrical performance at very low temperatures (such as −40 °C), making it difficult to meet the power supply requirements of high-power pulse loads in low-temperature environments. To address this issue, this paper proposes a multi-objective configuration optimization method for passive lithium-ion battery-supercapacitor hybrid energy storage systems (HESS) based on an electro-thermal-aging coupling model, in order to achieve non-preheating power supply for pulse loads under low temperatures. Firstly, an electro-thermal-aging coupling model for the passive HESS is established to accurately describe the dynamic characteristics during discharge. Subsequently, aiming at the low-temperature application requirements of high-power pulse loads, a multi-objective configuration optimization model is established based on the coupling model with the objectives of minimizing the mass and the minimum operating ambient temperature of the HESS; a solving method of the optimization model is designed based on the non-dominated sorting genetic algorithm with elite strategy. Finally, a case study is conducted on configuration optimization for a certain type of pulse load. The optimization results show that when the minimum operating temperature is consistent and below 0 °C, the passive HESS compared with the lithium-ion battery energy storage system can reduce the system mass by more than 23% and the acquisition cost by more than 18% while maintaining basically consistent single-pulse costs. When the minimum operating temperature is lower, the advantages of the HESS are even more significant.

Non-intrusive fault detection in shipboard power systems using wavelet graph neural networks

Naval shipboard power systems (SPS) are rapidly embracing electrification, resulting in loads that generate pulsation currents and encounter substantial transients. However, conventional time-based features alone are inadequate for effectively monitoring and safeguarding these loads against faults. This highlights the critical requirement for advanced machine learning based methods to discern and differentiate between the various transient stages within the load profile. In this paper, we propose a Wavelet Graph Neural Network (WGNN) model for non-intrusive fault detection in SPS. The fault detection system leverages the dynamic model of the SPS to train and test performance with varying fault scenarios. The underlying structure and the interdependence among component states in the SPS network are effectively captured using the WGNN model, resulting in accuracies over 99% for intrusive fault detection and 97% for non-intrusive fault detection. The developed WGNN model has also shown to be robust in the presence of pulse loads and noise, achieving an accuracy of over 95%. At the end, a real-time simulation of the proposed method is validated on a hardware-in-the-loop system, guaranteeing the high fidelity and low latency of the proposed approach. These findings validate the effectiveness of the proposed WGNN model for fault detection and real-world applications in SPS.

A wideband harmonic self-mitigation controller of the VSG-based islanded microgrid without harmonic extraction

In virtual synchronous generator (VSG)-based islanded microgrid, voltage harmonics induced by nonlinear loads seriously degrade system power quality. Existing harmonic mitigation controllers mainly rely on the extracted harmonic components to control, and generally have the weakness that can only mitigate harmonics with known frequencies. To better improve the power quality of the islanded microgrid, a wideband harmonic self-mitigation controller (WHSMC) is proposed in this paper, which can effectively mitigate wideband voltage harmonics above the fundamental frequency without extracting harmonics. Firstly, based on the impedance method, the reason why nonlinear loads will cause voltage harmonics in the islanded microgrid is analyzed in detail. Secondly, by establishing the impedance model of VSG with the proposed WHSMC, the mechanism how the proposed WHSMC mitigates voltage harmonics without knowing the harmonic frequency in advance is theoretically revealed. Finally, the effectiveness of the proposed WHSMC is verified through simulation and experimental results. The experiments indicate that the voltage total harmonic distortion (THD) can decrease from 7.02 % to 3.41 % under nonlinear load disturbance and from 8.27 % to 3.99 % under pulse load disturbance.

Correlating ballast resilient modulus with particle movement through SmartRock sensing

The resilient modulus of ballast is a key parameter in assessing track quality and is influenced by various loading conditions, such as deviator stress, bulk stress, loading frequency, and confining pressure. These factors, when incorporated into different models, can sometimes complicate their application in track maintenance planning. Therefore, a simplified model that collectively considers these factors would be beneficial in practical applications for estimating the ballast resilient modulus. This study utilizes smart sensing technology, SmartRock, to track particle movement during large-scale triaxial cyclic loading tests, exploring the potential correlation between ballast resilient modulus and particle motion. The findings indicate that the settling acceleration of ballast particles significantly impacts the ballast resilient modulus. This effect is dependent on the applied cyclic loading pulses, an aspect previously overlooked in research. Consequently, an index termed the Cyclic Loading and Acceleration Index (CLAI) has been introduced. CLAI integrates the effects of deviator stress, loading frequency, loading pulses, and settling acceleration. Based on CLAI, a simplified model for ballast resilient modulus has been developed and validated.

Formation of Wave Fields in a Metal Melt under the Influence of Magnetic-Pulse Loading and Discharge Current Pulses

Based on mathematical modeling, a study of the wave fields in molten aluminum formed by the action of a pulse, electric discharge and combined sources was carried out. A comparative analysis of their influence on the wave fields in the melt was performed. An increase in the intensity of the wave fields under the influence of a combined method of loading the melt was registerd. The occurrence of cavitation in the melt under the influence of the considered sources of pressure pulses has been determined. The energy features of the action of pressure fields on the melt are noted. The influence of the mass of the melt on the pressure fields arising in it is shown.

Dynamic Power Balancing Control Method for Energy Storage DC/DC Parallel Supply System With Low-Frequency Pulsed Load

Dynamic Power Balancing Control Method for Energy Storage DC/DC Parallel Supply System With Low-Frequency Pulsed Load

Evaluation of self-sensing material behaviour: Insights from cyclic and pulse load testing

Recent advancements in materials engineering have addressed challenges in integrating sensory properties into metallic components, notably through Self-Sensing Materials (SSMs) embedding piezoelectric particles like Barium Titanate (BT) via Friction Stir Processing (FSP). This study explores self-monitoring metallic parts obtained by incorporating BT particles in AA5083-H111 plate via FSP, evaluating their behaviour under cyclic and pulse loads for real-time operational insights. The study explores how manufacturing processes affect SSMs’ electrical voltage response, focusing on FSP’s impact on different nugget regions, investigating polarization direction, electrode positioning, thickness effects, and performance under pulse loads. Findings indicated consistent electrical responses across specimens, with sensitivity affected by polarization direction and thickness. There was no evidence of electrical voltage response for constant loads. The pulse and cyclic loads triggered an electrical response, exhibiting a piezoelectric behaviour. The study highlights the intricate relationship between specimen features and piezoelectric properties, offering insights into optimizing SSM performance.

Investigation of the effect of loading pulses on the ballast resilient modulus with SmartRock in a large-scale triaxial test

Ballast resilient modulus is a key metric for assessing track resiliency and guiding railroad maintenance. Large-scale triaxial tests are used to determine the ballast resilient modulus and mechanical properties. Replicating complex train-induced loading pulses from field observations in a laboratory setting is challenging owing to technical limitations. Consequently, laboratory tests often employ simplified half-sine and haversine loading pulses with various rest intervals to simulate real-world conditions. However, the effects of different pulses on the obtained ballast resilient modulus remain unclear. In this study, large-scale triaxial tests were conducted using SmartRock sensors to investigate the effects of various cyclic loading pulses on the resilient modulus of the railroad ballast. A new index, called the cyclic loading duration ratio (CLDR), was introduced to categorize these pulses. The results revealed that the resilient modulus correlated with the CLDR, with its impact contingent upon the deviator stress. A CLDR value of 0.20 emerged as a critical threshold, yielding the lowest resilient modulus. Values below this threshold resulted in an increased resilient modulus owing to the consequential large axial acceleration. This study provides insights into the micromechanical resilience reactions of railroad ballast under diverse loading pulses and offers guidance for pulse selection in triaxial testing.

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra.

Pulsating hydraulic fracturing has been an environmentally friendly method to improve the permeability of rock formations to stimulate gas production and reduce hazard risks. It has the advantage of fracturing the reservoir with lower cracking pressure and less water volume, as the mechanical strength of rock materials has been reduced by the hydraulic pulse pressure. Many researchers have found significant changes in hard rocks after cyclic loading. However, the existing work still cannot clearly explain the mechanism of the rock damage by pulsating hydraulic fracturing within a short-time experiment. To solve the issue, an investigation of the effects of pulsating hydraulic fracturing on CBM production has been carried out in lab and field applications. Results indicate that the long-term hydraulic pulse pressure can cause a linear decline in cracking pressure directly measured in the lab. It plays an essential role in the permeability enhancement by generating more flow channels for CBM production. The low-field NMR quantitatively evaluates the increase in porosity, which reveals significant incremental ratios of over 20% in the porosity of macropores, mesopores, and micropores of coal caused by fatigue damage. It is first proven that hydraulic pulse pressure has a significant influence on the porosity components of macropores, mesopores, and micropores. To validate the effectiveness of the technique on the field scale, a field application of pulsating hydraulic fracturing has been carried out in a coal mine. It shows that gas production has been largely enhanced with a long and stable production stage and higher gas flux after the applied pulsating load. The gas concentration and gas flux of the fractured boreholes are about 2 times that of the nonfractured boreholes. This work provides an investigation of the effects of pulsating hydraulic fracturing on CBM production, which gives a better understanding of the mechanism for the engineers in the field.

A Novel Laboratory Technique for Measuring Grain‐Size‐Specific Transport Characteristics of Bed Load Pulses

AbstractAlthough several laboratory studies on the propagation of bed load pulses were carried out in the last decades, most studies neglect grain‐size‐specific aspects or use invasive measurement techniques. To remedy the situation, we present a novel, time‐efficient and non‐destructive laboratory technique to investigate grain‐size‐specific transport characteristics of bed load pulses. The method consists of a through‐water, high‐resolution image acquisition followed by the application of a supervised color classification algorithm (Gaussian Maximum Likelihood Classification). The analyzed bed load pulse consisted of five different grain size classes of dyed quartz sand and gravel, each having a unique color. The initial experimental bed was uni‐colored and contained the same size fractions as the augmented pulse. Quality assessment based on a confusion matrix approach and basic random sampling showed a high classification performance. By statistically analyzing the temporal and spatial color distribution of the experimental reach, characteristic parameters to describe the propagation behavior were determined. The bed load pulse presented in the application example initially showed strong deviations in the grain‐size‐specific advection and dispersion, and advection proved to be predominant in the transport process.

Features of functional behavior of TiNi shape memory alloy after uniaxial high speed magnetic pulse tension

This study investigates the influence of high strain rate on the functional properties of TiNi shape memory alloys. Specimens were deformed in tensile mode using a magnetic pulse loading setup equipped with an optical system to measure the loading time. The technique allows to obtain different strain rates without changing the working part of the specimens, i.e. the residual strains remained the same. The results show that the shape memory effect decreases by 10–25% with increasing strain rate. However, a high strain rate has a positive effect on the two-way shape memory, which increases by 10–25%.

Nonlinear transient response of magneto-electro-elastic cylindrical shells with initial geometric imperfection

Exploring the nonlinear mechanical behaviors of structures under external excitation is significant. This article, for the first time, attempts to demonstrate the transient response of imperfect magneto-electro-elastic (MEE) cylindrical shells under pulse load in thermal environment by time history curves and phase trajectories. Using Love's thin shell theory and Maxwell's equations, expressions for displacement-, electric-, and magnetic- fields are obtained. Combining Hamiltonian principle and Galerkin method, the nonlinear dynamic equations of cylindrical shells are derived, and Runge-Kutta method is employed to solve the whole problem. Subsequently, the transient responses under various parameters including BaTiO3 vol fraction, geometric imperfection, electrical potential, magnetic potential, prestress, viscoelastic foundation, positive phase duration, damping coefficient, maximum blast load, geometrical parameter, temperature variation and various pulse loads are presented in numerical analysis in the forms of time history curves and phase trajectories. Finally, the conclusion advocates that the BaTiO3 vol fraction, geometric imperfection and dimensions of cylindrical shells have significant impacts on the transient response.

Influence of dapagliflozin on cardiovascular remodeling in hypertensive patients with accompanying type 2 diabetes

Aim. To compare the results of 12-week treatment of patients with stage II hypertension (HTN) with accompanying diabetes mellitus (DM) type 2 between the combination of metformin + dapagliflozin and metformin monotherapy by studying changes in the elastic properties of the common carotid arteries (CCA), echocardiographic indicators, 24-hour ambulatory blood pressure monitoring (ABPM) and laboratory parameters of lipid and carbohydrate metabolism. Materials and methods. 24 patients with stage II HTN with type 2 DM were involved in the study, the average age was 60.4 years, 50 % – men. Patients in the first group were randomized to receive metformin, and the second group – to receive a combination of metformin and dapagliflozin. At inclusion and after 3 months of treatment, basic anthropometric data, laboratory indicators of lipid and carbohydrate metabolism, ABPM, echocardiography, and indicators of CCA local stiffness were studied. Statistical analysis was performed, the probability of differences is at the level of p < 0.05. Results. In both observation groups, there was a comparable decrease in SCORE 2-Diabetes range, glucose and glycated hemoglobin, total cholesterol, LDL cholesterol, average daily systolic blood pressure (SBP), daily SBP load, day and night pulse BP, as well as an increase in speed systolic movement of the lateral fibrous ring of the mitral valve (S lat). Only in the metformin + dapagliflozin group a decrease in the adipose tissue level, the average daily diastolic blood pressure (DBP), the burden of DBP, the size of the left atrium and right ventricle, an increase in the movement speeds of the medial (e’med), lateral (e’lat) ring of the mitral and of the tricuspid (e’tk) valve in the period of early diastolic filling of the ventricles, velocities of systolic movement of the medial fibrous ring of the mitral (S med) and tricuspid (S tk) valves, a decrease in the ratio E/e’, and an improvement in the elastic properties of general carotid arteries were observed. Conclusions. In persons with HTN stage II with DM type 2 the addition of dapagliflozin to the treatment regimen was associated with better control of blood pressure, improvement of diastolic function and longitudinal contractility of the left ventricle, elastic properties of CCA.

Energy Storage Systems: Technologies and High-Power Applications

Energy storage systems are essential in modern energy infrastructure, addressing efficiency, power quality, and reliability challenges in DC/AC power systems. Recognized for their indispensable role in ensuring grid stability and seamless integration with renewable energy sources. These storage systems prove crucial for aircraft, shipboard systems, and electric vehicles, addressing peak load demands economically while enhancing overall system reliability and efficiency. Recent advancements and research have focused on high-power storage technologies, including supercapacitors, superconducting magnetic energy storage, and flywheels, characterized by high-power density and rapid response, ideally suited for applications requiring rapid charging and discharging. Hybrid energy storage systems and multiple energy storage devices represent enhanced flexibility and resilience, making them increasingly attractive for diverse applications, including critical loads. This paper provides a comprehensive overview of recent technological advancements in high-power storage devices, including lithium-ion batteries, recognized for their high energy density. In addition, a summary of hybrid energy storage system applications in microgrids and scenarios involving critical and pulse loads is provided. The research further discusses power, energy, cost, life, and performance technologies.