Electrical Loading Conditions Research Articles

Strip electro-mechanical yield model for three equal straight collinear cracks in piezoelectric materials

This paper is devoted to the development of a model to study three straight collinear cracks in piezoelectric materials under the influence of combined electrical and mechanical loading conditions. Mathematical relationships for the size of yield zones with mechanical yielding conditions and the saturation zone sizes to applied electrical field has been established. To make this plausible, two different cases are considered: first when the electrical saturation zones are bigger than the mechanical yield zones while other case in which situation is just opposite. Closed-form analytic expressions are derived for various fracture parameters with the help of well known complex variable method. Numerical results are presented to study the multiple cracks in different piezoelectric materials. Results obtained are reported graphically, analyzed and concluded.

Tracking deep-level defects in degrading perovskite solar cells with a multifactorial approach

In this work, we provide a mechanistic understanding of the degradation of perovskite solar cells in operation by focusing on methylammonium lead triiodide (CH3NH3PbI3 or MAPbI3) and tracking the evolution of electronic defects via photo-induced current transient spectroscopy (PICTS). Moreover, we also record the degradation of its photovaltaic characteristics over time under various electric load and temperature conditions. Using PICTS, we found that bands of trap states, initially highly localized deep within the band gap of the perovskite, widened over the exposure period. This effect was exacerbated with increasing temperature. Further, using the design of experiment methodology for this multifactorial study, we found that two interaction factors (temperature× load & temperature× time) were significant in the degradation of the perovskite cells, validating the importance of our holistic approach. Through these observations, we establish a mechanistic link between deep-level traps and photovoltaic characteristics.

On the electric behaviour of conductive grease inside the contact zone

Conductive grease has been considered as a potential solution in addressing electric erosion issue inside motor bearings. Understanding the conductive grease performance, especially the electric and tribological behaviour is crucial for its application. This paper combines bulk grease characterization and contact film study considering both electrical and tribological loading conditions. The results show that the electric performance for the selected conductive grease sample is electric field dependent, including both frequency and voltage amplitude. Its film impedance inside the contact area is closely related to the external electric field, running condition, and lubrication regime. The following film impedance calculation tells that not only bulk grease electric parameters, but the contact parameter, lubricant film contour and lubrication condition should be considered when performing the overall bearing electrical modelling.

Automatic voltage stabilization system for substation using deep learning

The operating voltage in the substation must be maintained at its rated voltage within the specified standard because a voltage outside the specified range may cause a malfunction of the power facility and interfere with the stable power supply. Therefore, the voltage regulation process to maintain the rated voltage of the substation is essential for the stability of the power system. However, the voltage regulation process is currently performed manually by resident staff. Voltage regulation based on human judgment increases the uncertainty of voltage stabilization and makes efficient operation in consideration of the economic feasibility of power facilities difficult. Therefore, this paper proposes an automatic voltage stabilization system that can automatically perform voltage regulation. Instead of predicting the electrical load or overvoltage conditions studied so far, we focus on more direct, scalable input capacity prediction for an automatic voltage stabilization system. First, the proposed system predicts the input capacity required for a given situation through a trained stacked LSTM model. Second, an optimal regulation plan is derived through an optimization process that considers the economic feasibility of power facility operation. Additionally, the development of the user interface makes it possible to visualize the operation of algorithms and effectively communicate the models? predictions to the user. Experimental results based on real substation data show that the proposed system can effectively automate the voltage regulation process.

Analytical Solution of the Interference between Elliptical Inclusion and Screw Dislocation in One-Dimensional Hexagonal Piezoelectric Quasicrystal

This study examines the interference problem between screw dislocation and elliptical inclusion in one-dimensional hexagonal piezoelectric quasicrystals. The general solutions are obtained using the complex variable function method and the conformal transformation technique. When the screw dislocation is located outside or inside the elliptical inclusion, the perturbation method and Laurent series expansion are employed to derive explicit analytical expressions for the complex potentials in the elliptical inclusion and the matrix, respectively. Considering four types of far-field force and electric loading conditions, analytical solutions for various specific cases are obtained by using matrix operations. Expressions for the phonon field stress, phason field stress, and electric displacement are given for special cases, including the absence of a dislocation, the presence of an elliptical hole, and the interference between a screw dislocation and circular inclusion, as well as the case of a circular hole. The design and analysis of quasicrystal inclusion structures can benefit from the results of this work.

Optimizing electric vehicle charging schedules and energy management in smart grids using an integrated GA-GRU-RL approach

Introduction: Smart grid technology is a crucial direction for the future development of power systems, with electric vehicles, especially new energy vehicles, serving as important carriers for smart grids. However, the main challenge faced by smart grids is the efficient scheduling of electric vehicle charging and effective energy management within the grid.Methods: To address this issue, we propose a novel approach for intelligent grid electric vehicle charging scheduling and energy management, integrating three powerful technologies: Genetic Algorithm (GA), Gated Recurrent Unit (GRU) neural network, and Reinforcement Learning (RL) algorithm. This integrated approach enables global search, sequence prediction, and intelligent decision-making to optimize electric vehicle charging scheduling and energy management. Firstly, the Genetic Algorithm optimizes electric vehicle charging demands while minimizing peak grid loads. Secondly, the GRU model accurately predicts electric vehicle charging demands and grid load conditions, facilitating the optimization of electric vehicle charging schedules. Lastly, the Reinforcement Learning algorithm focuses on energy management, aiming to minimize grid energy costs while meeting electric vehicle charging demands.Results and discussion: Experimental results demonstrate that the method achieves prediction accuracy and recall rates of 97.56% and 95.17%, respectively, with parameters (M) and triggers (G) at 210.04 M and 115.65G, significantly outperforming traditional models. The approach significantly reduces peak grid loads and energy costs while ensuring the fulfilment of electric vehicle charging demands and promoting the adoption of green energy in smart city environments.

Impact of the Porosity and Elastic Foundation on Frequency and Buckling Response of Bidirectional Functionally Graded Piezoelectric Porous Plate

This work presents a thermoelectric vibration and buckling behavior of a bidirectional functionally graded piezoelectric porous (BD-FGPP) plate resting on the elastic foundation with arbitrary boundary conditions. The variation of the material properties in the FGPP plate is bidirectional, i.e. along longitudinal and thickness directions, using the modified power law distributions. Also, the BD-FGPP plate carries various porosity distributions, i.e. even, uneven and symmetric center types. The governing equation of the FGPP plate has been obtained through Hamilton’s principle and solved through a higher-order finite element approach. The correctness and usefulness of the current technique are confirmed and compared with existing model outcomes available in the literature. A comprehensive parametric study has investigated the effect of the elastic foundations, porous exponent with various porosity distributions, bidirectional material exponent, temperature change, electrical loading and boundary conditions. The attained results are more valuable for designing functionally graded piezoelectric-based smart structures by considering the porosity distribution in a thermoelectric environment.

Thermodynamically consistent volumetric–deviatoric decomposition-based phase-field model for thermo-electro-mechanical fracture

Using a volumetric–deviatoric decomposition of strain, we propose a novel phase-field model for thermo-electro-mechanical fracture and provide an open-source finite element implementation of the proposed model. Considering displacement, electric potential, temperature field, and phase-field variable, we have obtained the governing partial differential equations (PDEs), by utilizing the virtual power principle. We have obtained the constitutive relations for the necessary thermodynamic fluxes on satisfying the first and second laws of thermodynamics. The proposed model can accommodate any dissipative effect, such as viscous damping, whenever necessary, in a thermodynamically consistent manner. We have developed open-source finite element codes for the proposed model using the Gridap package in Julia. Here, we have used the proposed model for fracture simulation in transversely isotropic material and functionally graded material for compact tension and three-point bending tests. We have considered variations in thermal and electrical loading conditions and investigated the corresponding changes in the structural responses. For the functionally graded specimens, we have also considered the variation in the material property gradation directions, along with the thermal and electrical boundary conditions to evaluate their effect on the structural responses of specimens.

Power Optimization of Systems for Direct Thermal to Electrical Energy Conversion

Thermoelectric generators (TEGs) offer the possibility of extracting electrical power from any heat source, including low-enthalpy heat. The operation of thermoelectric generators is closely related to not only thermal factors but also the electrical load conditions. Consequently, simulations of TEG-based thermoelectric systems require the adequate modeling of both thermal and electric phenomena. In this paper, the developed TEG model is presented and verified through the design of a complete thermoelectric system able to optimize the extraction of electrical power according to the thermal conditions. The system consisted of a TEG, a properly designed low-cost DC/DC converter, and an energy storage element. The DC/DC converter was controlled by a specific algorithm that optimized the electrical power extraction following the maximum power point. The choices adopted for the system design, the implementation of the DC/DC converter, and the algorithm development were verified with experimental measurements.

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

Double superposition hypothesis for smart composite plates-two approaches

Structural failure in laminated composites is primarily due to the interlaminar debonding that results due to the transverse shear stresses and such scenario arises due to their inaccurate prediction by various shear deformation theories. In order to predict such stresses accurately and in a simple yet effective manner, the global local theories are employed. In this study, two such theories have been used for static response of smart laminated plates under electromechanical loading. Though both theories use the same principle of double superposition, one of them has been observed to predict better accuracy for all laminated plates subjected to both mechanical loading and electric potential loading conditions. The effect of inclusion of the piezoelectric coefficient in the transverse displacement assumption has been observed to yield much improved response.

Vibration response analysis of the bi-directional porous functionally graded piezoelectric (BD-FGP) plate

The current paper investigates the free vibration characteristics of the bidirectional functionally graded piezoelectric (BD-FGP) porous plate subjected to thermal and electrical loading. The properties of the plate vary as power-law distributions in two directions, that is, longitudinal and transverse directions. The BD-FGP plate is considered to be porous of two types even type and uneven type. The governing equation of the BD-FGP plate is attained with the Von Karman nonlinear strains associated with the FSDT displacement field and Hamilton’s principle. Also, the 9-noded Lagrange quadrilateral element with seven degrees of freedom (DOFS) discretized the BD-FGP plate and solved it by the higher-order finite element (HOFE) method. The present formulation's convergence and accuracy are confirmed by comparing the attained results with the literature. The influence of the various parameters includes thickness ratios, porous exponent, volume fraction exponent, electrical loading, thermal loading, and support conditions. The investigations of the current study show that the material variations in both directions, that is, longitudinal and transverse, have significant importance in the design and development of modern smart structures and their components of engineering applications.

In-situ temperature monitoring of a lithium-ion battery using an embedded thermocouple for smart battery applications

Uncertainty in the measurement of key battery internal states, such as temperature, impacts our understanding of battery performance, degradation and safety and underpins considerable complexity and cost when scaling-up battery components into complete systems. Our research presents a systematic methodology for the engineering of a commercially available cylindrical cell format to accept in-cell instrumentation. We have developed bespoke cell opening methods and unique fixtures that facilitate a reliable instrumentation process. Extensive experimental results are presented that highlight the performance of both the sensor and the lithium-ion battery are not adversely affected by instrumentation. Our modified test cells were evaluated the energy capacity and impedance for a range of different electrical loading conditions and compared to a set of reference or unmodified batteries. The longer-term implications of embedding instrumentation within a battery are also evaluated with cell performance evaluated after a period of calendar and cyclic ageing. Our study demonstrates the importance of internal temperature monitoring during cell operation by comparing internal and surface temperatures measurements. We found that the internal temperature is consistently and notably higher than surface temperature during cell characterisation and when the cell was electrically loaded with a dynamic real-world profile derived from an electric vehicle. No significant effect on the electrochemical performance of the instrumented cells was observed. Measurement data demonstrates that there is a negligible reduction in energy capacity and only a marginal increase in internal resistance.

Atomistic modeling of the coupling between electric field and bulk plastic deformation in fcc metals

A notable impediment in maintaining high electric fields in accelerating structures is the onset of breakdown events. While bulk mechanical properties of the materials are known to significantly affect the breakdown propensity, the underlying mechanisms coupling electric fields to bulk plastic deformation in experimentally relevant thermal and electrical loading conditions remain to be identified at the atomic scale. We present the results of large-scale molecular dynamics simulations (MD) to investigate a possible mode of coupling. Specifically, we consider the activation of Frank-Read sources, which leads to dislocation multiplication, under the combined action of biaxial thermal stresses caused by rf losses and surface tractions induced by electric fields. With the help of a charge-equilibration formalism incorporated in a classical MD model, we show that the creation of surface slipped steps can couple to electric fields in a way that enhances local stresses and facilitates further activation of existing dislocation sources. We quantify the possible enhancement of surface slip under typical microstructural parameters of annealed copper. We show that such a mechanism could potentially promote breakdown precursor formation at very high electric fields, but that its impact is limited at fields typical of the operation of accelerator structures. In this regime, thermal stresses caused by rf losses are expected to be the main drivers of plastic deformation.

Electrothermal Performance of Heaters Based on Laser-Induced Graphene on Aramid Fabric.

Nanostructured heaters based on laser-induced graphene (LIG) are promising for heat generation and temperature control in a variety of applications due to their high efficiency as well as a fast, facile, and highly scalable fabrication process. While recent studies have shown that LIG can be written on a wide range of precursors, the reports on LIG-based heaters are mainly limited to polyimide film substrates. Here, we develop and characterize nanostructured heaters by direct writing of laser-induced graphene on nonuniform and structurally porous aramid woven fabric. The synthesis and writing of graphene on aramid fabric is conducted using a 10.6 μm CO2 laser. The quality of laser-induced graphene and electrical properties of the heater fabric is tuned by controlling the lasing process parameters. Produced heaters exhibit good electrothermal efficiency with steady-state temperatures up to 170 °C when subjected to an input power density of 1.5 W cm–2. In addition, the permeable texture of LIG–aramid fabric heaters allows for easy impregnation with thermosetting resins. We demonstrate the encapsulation of fabric heaters with two different types of thermosetting resins to develop both flexible and stiff composites. A flexible heater is produced by the impregnation of LIG–aramid fabric by silicone rubber. While the flexible composite heater exhibits inferior electrothermal performance compared to neat LIG–aramid fabric, it shows consistent electrothermal performance under various electrical and mechanical loading conditions. A multifunctional fiber-reinforced composite panel with integrated de-icing functionality is also manufactured using one ply of LIG–aramid fabric heater as part of the composite layup. The results of de-icing experiments show excellent de-icing capability, where a 5 mm thick piece of ice is completely melted away within 2 min using an input power of 12.8 W.

Combined electromechanical dynamic fracture behavior of lead zirconate titanate (PZT)

AbstractCoupon specimens of poled and depoled lead zirconate titanate (PZT) are examined under combined stress wave and electric loading conditions. Mode‐I crack initiation and fracture behavior is examined using ultrahigh‐speed imaging and two‐dimensional digital image correlation. The dynamic critical stress intensity factor () is extracted using measured displacement fields ahead of the impulsively loaded crack tip, and compared between poled and depoled plates that were either under no electric field, positive 0.46 kV/mm electric field, or negative 0.46 kV/mm electric field. Poled specimens had a poling direction and applied electric field direction normal to the crack front. The addition of an electric field resulted in a crack‐enhancing effect, where the dynamic fracture toughness of poled specimens under 0.46 kV/mm was almost half that of samples with no electric field. Depoled samples experienced almost no change in dynamic fracture toughness with the addition of an electric field.

Modeling of static reliability assessment in dielectric elastomer transducers subject to electric loads

In recent years, Dielectric Elastomer Transducers (DETs) have been of top-notch interest as an alternative solution to conventional mechatronic transduction systems, thanks to their features as low-cost and affordable materials, silence operation, low-power consumption, and high level of energy density. Generally, in their most uncomplicated layout, these devices form an electrostatic system, composed of a Dielectric Elastomer (DE) membrane, embedded between two opposite compliant electrodes, constituting a highly deformable capacitor capable of transforming electrical energy into mechanical and vice versa. However, DETs applicability is strongly affected by several engineering constraints. One of their principal failure modes is related to the electrical breakdown of the DE membrane, which occurs when an applied input electrical load exceeds the dielectric strength of the DE. In order to address this problem, the materials and the input load conditions must be chosen appropriately to assure a desired lifetime of operation. For this purpose, this work proposes a preliminary static reliability assessment procedure to evaluate the failure probability of a DET for static events as the electrical breakdown, with specific electric input load conditions. The resulting reliability model comprises the stochastic comparison of the dielectric strength of the DE material with the extreme values distribution of electrical loads in a specific period, aiming to forecast the reliability evaluation for a more extended period, multiple of the original one.

Creep evaluation and temperature dependence in self-sensing micro carbon polymer-based composites for further development as an Internet of Things Sensor device

This article investigates the dependency of temperature on electrical resistance (R) change in micro carbon fiber polymer composites (MCFPC), for further development as an Internet of Things sensor from previous research works. Three mixtures were prepared using Dow Corning’s Silastic 145 as base polymer and made vary fiber content weight percentages: fiber diameter to length ratio ∅⁄l 0.13 and carbon fiber content of 13%; ∅⁄l:0.66 and carbon fiber contents of 40% and 50%. Composites tested were submitted to temperature loading, with a constant strain of 0.0%, for assessment of R when a change in the composite’s temperature occurs. The composite response was observed to follow an Arrhenius function, for temperatures ranging from −10°C to 40°C. The apparent activation energy was calculated to evaluate further differences between carbon fiber contents and the sensitivity factor, [Formula: see text] due to temperature is determined. The specimens were also tested with a constant strain of 2.86% to assess creep. It was found that creep and R, over the period of time in the analysis, best fit a discrete latent variable model. The sensitivity factor change is determined in regard to stress relaxation, [Formula: see text]. The properties of MCFPC investigated here can be used to establish relationships between electrical resistance outputs and environmental loading conditions for this type of composites, enabling the possibility of deployment as part of a management system network for structural monitoring with real-time data acquisition.

Numerical Investigation on Crack Detection Technique for Electric Connector with Joule Heating Effect

Using the electro-thermo-structural coupled-field finite element analysis, the crack detection technique with the Joule heating effect for the electric connector is studied and discussed. The physical behavior of the electric connector with an edge crack is investigated numerically. The electric current density, Joule heating temperature and structural deformation are obtained. As a result, the electric current concentration and Joule heating effect can induce a local hot spot or hot band region around the crack tip. Furthermore, the crack tip location can be determined according to the temperature distribution. For the accurate crack detection, two better electric loading conditions are found as follows: (a) shorter electric operating time (tp), (b) larger electric current (I0). The optimal condition , I0 = 100 A and tp = 0.001 s, is found for this crack detection research.

Ultrasonic inspection of lithium-ion batteries to detect cell safety and prevent thermal runaway

Accurately monitoring the safety of lithium-ion batteries to prevent a thermal runaway (TR) event is of utmost importance especially in high-power applications such as electric vehicles. The fire caused by a lithium-ion battery is particularly difficult to extinguish because of its continuous emittance of highly flammable gas and its extremely high temperature. Current battery management systems (BMS) only monitor cell safety by measuring voltage, current, and temperature on the module level. Because the BMS operates on the module-level as opposed to the cell-level, these metrics can fail to predict a TR event, which may begin with individual cell failures. We report on the viability of early detection of cell damage by simultaneously monitoring voltage, current, temperature, mechanical clamping force, and ultrasonic wave transmission through individual battery cells under various electrical, mechanical, and thermal loading conditions. Time- and frequency-domain features of the acoustic signals transmitted along three propagation paths and excitation frequencies between 0.1 and 1 MHz are monitored and correlated with electrical, temperature, and force sensor data under mechanically clamped overcharge and thermal abuse scenarios. Early indicators of damage in the ultrasonic signals are presented and discussed with respect to propagation paths and known damage mechanisms in lithium-ion batteries.