Electromechanical Failure Research Articles

Decoupling the influence of impact energy and velocity on dynamic failure of cylindrical lithium-ion batteries

Ensuring battery safety in electric vehicles during crashes is crucial due to the complexities of battery failure under dynamic loading. This study presents a dynamic test apparatus that isolates the effects of impact energy and velocity. Experiments show that impact energy primarily drives battery failure, with impact velocity also influencing outcomes. Notably, the battery demonstrates mitigated electrical failure within a specific impact energy range, which is lower than the threshold for failure characterized by a sudden voltage drop due to major fractures. The self-discharging rate of the impaired batteries within this range exhibits randomness, likely caused by complex electrode contact conditions following minor separator fractures and subsequent deformation recovery. Interestingly, under similar impact energy, electro-mechanical failure exhibits a nonlinear “severe-mild-severe” pattern as velocity increases, differing from the typical strain-rate effect observed in components like separators. X-ray computerized tomography and dynamic material behavior analysis reveal this anomaly as a competition between strain-rate hardening of materials and inertia effect of electrolyte flow and wound structure. The findings highlight that different factors dominate battery failure under varying impact velocities. This research enhances understanding of the energy- and velocity-dependent responses of lithium-ion batteries, aiding in optimizing battery designs for improved safety during collisions.

Assessing the Effect of Twisting and Twisting Fatigue on ZnO:Al Thin Film Performance on PEN and PET Substrates.

This study examines the electromechanical characteristics of aluminium-doped zinc oxide (AZO) films. The films were produced using the RF magnetron sputtering process with a consistent thickness of 150 nm on various polymer substrates. The study focuses on assessing the electro-mechanical failure processes of coated segments using flexible substrates, namely polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), with a specific emphasis on typical cracking and delamination occurrences. This examination involves conducting twisting deformation together with using standardised electrical resistance measurements and optical microscope monitoring instruments. It was found that the crack initiation angle is mostly dependent on the mechanical mismatch between the coating and substrate. Higher critical twisting angle values are observed for the AZO/PEN film during twisting testing. Relative to the perpendicular plane of the untwisted sample, it was found that cracks initiated at a twist angle equal to 42° ± 2.1° and 38° ± 1.7° for AZO/PEN and AZO/PET, respectively, and propagated along the sample length. SEM images indicate that the twisting motion results in deformation in the thin film material, leading to the presence of both types of stress in the film structure. These discoveries emphasise the significance of studying the mechanical properties of thin films under different stress conditions, as it can impact their performance and reliability in real-world applications. The electromechanical stability of AZO was found to be similar on both substrates during fatigue testing. Studying the electromechanical properties of various material combinations is important for selecting polymer substrates and predicting the durability of flexible electronic devices made from polyester.

Microstructure-driven mechanical and electromechanical phenomena in additively manufactured nanocrystalline zinc oxide

Advances in nanoscale additive manufacturing (AM) offer great opportunities to expand nanotechnologies; however, the size effects in these printed remain largely unexplored. Using both in situ nanomechanical and electrical experiments and molecular dynamics (MD) simulations, this study investigates additively manufactured nano-architected nanocrystalline ZnO (nc-ZnO) with ∼7 nm grains and dimensions spanning 0.25–4 μm. These nano-scale ceramics are fabricated through printing and subsequent burning of metal ion-containing hydrogels to produce oxide structures. Electromechanical behavior is shown to result from random ordering in the microstructure and can be modeled through a statistical treatment. A size effect in the failure behavior of AM nc-ZnO is also observed and characterized by the changes in deformation behavior and suppression of brittle failure. MD simulations provide insights to the role of grain boundaries and grain boundary plasticity on both electromechanical behavior and failure mechanisms in nc-ZnO. The frameworks developed in this paper extend to other AM nanocrystalline materials and provide quantification of microstructurally-drive limitations to precision in materials property design.

Impact dynamics and polarization mechanism of BaxSr1−xTiO3 particles reinforced polydimethylsiloxane composites

AbstractBaxSr1−xTiO3 (BST) ceramics have excellent performance of electromechanical conversion, however, the application of BST ceramics in the field of sensing is restricted by the brittle fracture, electromechanical failure, and collateral damage of BST under impact. In this article, unpolarized BST particles reinforced polydimethylsiloxane (PDMS) composites‐BST/PDMS with excellent mechanical properties, flexibility and flexoelectric coefficient have been prepared. Experimental study on the dynamic mechanical behavior and polarization characteristics of BST/PDMS composites under different impact velocity, element ratio and content of BST are carried out. Furthermore, the three‐phase model have been developed, based on that, impact deformation, stress behavior and polarization response have been investigated. The results show that, the duration of elastic deformation stage increases with increasing of BST content, but maximum stress decreases; time‐history curves of polarization voltage are approximately a “sine” function distribution, polarization voltages of Ba0.75Sr0.25TiO3/PDMS are higher than that of Ba0.25Sr0.75TiO3/PDMS; flexoelectric coefficient increases with increasing of BST content, and μzzzz is larger than that of μxxzz and μxzxz; addition of BST particle leads to greater strain gradient, and increases the polarization voltage of PDMS matrix; electric field at the interface increases due to the dielectric effect, which improves the ability of charge migration, voltage difference of 20% Ba0.75Sr0.25TiO3/80% PDMS caused by interfacial potential is smaller (about 9.3%) compared with 10% Ba0.75Sr0.25TiO3/90% PDMS. This work is significant for the development of flexible intelligent sensing materials.Highlights The mechanical behavior and polarization characteristics of BST/PDMS are studied. The polarization voltages of BST/PDMS (x = 0.75) are higher than BST/PDMS (x = 0.25). The flexoelectric coefficient increases with increasing of BST content.

A peridynamic model for electromechanical fracture and crack propagation in piezoelectric solids

This paper presents for the first time an approach to the problem of electromechanical fracture and crack propagation in piezoelectric solids with peridynamics. Fracture in piezoelectric ceramics is an important problem in engineering due to its complexity. The majority of the computational models available on the literature rely on sharp crack representations, which have difficulties dealing with complex crack patterns, or rely on diffusive crack models, such as the phase-field fracture model, that can predict complex patterns but does not represent cracks in a discrete way. On the other hand, peridynamics has been designed to solve this problems and is able to simulate discrete cracks as well as complex crack phenomena like fragmentation and branching. We present a novel approach to the implementation of different electric crack face boundary conditions in a peridynamic way, by a field selective bond breaking approach. Moreover, it is also presented the first electromechanical failure criterion for fracture in piezoelectric ceramics. We develop an energy based failure criterion due to its generality and wide range of applications. These approaches are presented in a way such that they are valid for any type of peridynamic formulation. The used numerical model is implemented using correspondence-based peridynamics with the linear piezoelectricity constitutive setting, using a meshfree discretization and solved quasi-statically with an implicit incremental-iterative scheme. Numerical examples are presented to demonstrate the capabilities of these new approaches and assess the performance of the model against experimental results. The model is capable of numerically predicting complicated fracture behaviour and crack propagation in an intrinsic/autonomous way, as demonstrated by the results.

Tunable pure shear deformation of voltage/charge loaded dielectric elastomers

The pure shear mode can achieve a large and stable deformation in the actuation of dielectric elastomers (DEs). In this paper, based on our previously designed deformation controller, we propose the method of tuning two inplane stresses and applied voltage/charge to realize precise pure shear deformation, by deducing the governing equations of voltage- and charge-loaded DEs. The evolution of electromechanical stabilities of voltage- and charge-loaded DEs under pure shear deformation mode is considered. The maximum stable electromechanical deformation related to electromechanical failures is simultaneously calculated. It is found that the stable deformation and parameter variation tendency have different dependency for the loading modes of DEs. The critical conditions of occurrence of possible electromechanical failures are also clarified. This research can be utilized to beforehand select the tension stresses and applied voltage/charge to strengthen the electromechanical stability of DEs in pure shear deformation mode.

Insights from an electro-mechanical heart failure cell model: Role of SERCA enhancement on arrhythmogenesis and myocyte contraction

Background and objectiveStructural and electrical remodeling in heart failure predisposes the heart to ventricular arrhythmias. Computer modeling approaches, used to complement experimental results, can provide a more mechanistic knowledge of the biophysical phenomena underlying cardiac pathologies. Indeed, previous in-silico studies have improved the understanding of the electrical correlates of heart failure involved in arrhythmogenesis; however, information on the crosstalk between electrical activity, intracellular Ca2+ and contraction is still incomplete. This study aims to investigate the electro-mechanical behavior of virtual failing human ventricular myocytes to help in the development of therapies, which should ideally target pump failure and arrhythmias at the same time. MethodsWe implemented characteristic remodeling of heart failure with reduced ejection fraction by including reported changes in ionic conductances, sarcomere function and cell structure (e.g. T-tubules disarray). Model parametrization was based on published experimental data and the outcome of simulations was validated against experimentally observed patterns. We focused on two aspects of myocardial dysfunction central in heart failure: altered force-frequency relationship and susceptibility to arrhythmogenic early afterdepolarizations. Because biological variability is a major problem in the generalization of in-silico findings based on a unique set of model parameters, we generated and evaluated a population of models. ResultsThe population-based approach is crucial in robust identification of parameters at the core of abnormalities and in generalizing the outcome of their correction. As compared to non-failing ones, failing myocytes had prolonged repolarization, a higher incidence of early afterdepolarizations, reduced contraction and a shallower force-frequency relationship, all features peculiar of heart failure. Component analysis applied to the model population identified reduced SERCA function as a relevant contributor to most of these derangements, which were largely reverted or diminished by restoration of SERCA function alone. ConclusionsThese simulated results encourage the development of strategies comprising SERCA stimulation and highlight the need to evaluate both electrical and mechanical outcomes.

Influence of loading rate and out of plane direction dependence on deformation and electro-mechanical failure behavior of a lithium-ion pouch cell

Understanding the behavior of lithium-ion battery cells under complex load situations that can occur in vehicle crash scenarios is important to integrate the cells in the best possible way in an electrified vehicle. Since individual cell components partly show highly anisotropic material behavior, this work investigates whether a direction-dependent behavior is present on cell level when loaded in the out-of-plane direction, which has not been investigated so far. Cylindrical indentation tests in out-of-plane direction were performed on a 41 Ah NMC pouch cell under laboratory conditions. Thereby, impactor orientation, loading speed and electrolyte quantity were varied in order to study the respective influences both, separately as well as in interaction with each other. Component tensile tests with different directions and speeds were carried out. The results were compared with those of the cell tests for a better understanding of the observed electro-mechanical behavior. It could be shown that the investigated cell shows a significant out-of-plane direction dependence at low-speed loading (1 mm/s). This results in an approximately 23 % lower failure strain when the impactor is aligned along the long side of the cell compared to its alignment along shot side. Strain rate influences cell behavior, resulting in higher stiffness and lower failure strain at higher loading speeds (3000 mm/s). Furthermore, the out-of-plane direction dependence is reduced at higher loading speed, which is in direct contrast to the observations of the tensile tests. This is attributed to viscosity effects during high-speed loading, since the liquid electrolyte affects the mechanical cell behavior, as shown by the experiments with reduced electrolyte quantity. This study shows that the out-of-plane direction dependence should be taken into account for the evaluation of the crash safety of a lithium-ion pouch cell.

Phase field modeling of coupling evolution of fracture and dielectric breakdown in ferroelectric materials

Ferroelectric materials have attracted increasing attention due to their distinguished electromechanical coupling properties. Fracture and dielectric breakdown are two main failure behaviours of ferroelectric materials, which may occur simultaneously under large mechanical and electrical loads. Understanding the coupling evolution of fracture and dielectric breakdown is crucial for the application of ferroelectric materials under complex electromechanical environments. In the present study, a phase field model with multiple order parameters is developed to investigate the coupling evolution behaviours of fracture and dielectric breakdown of ferroelectric materials subjected to the mechanical and electrical loadings. In the phase field model, coupled electromechanical degradation functions are proposed to model the interface boundary conditions of fracture and dielectric breakdown. Generalized configurational forces of fracture and dielectric breakdown are obtained from the phase field model to analyse the driving forces for the evolution of fracture and dielectric breakdown. The interaction between fracture and dielectric breakdown is predicted by using the phase field model with a set of interface boundary conditions. The simulation results show that dielectric breakdown occurs at impermeable crack tips due to the concentrated electric field, while the stress distribution around the crack tip and the driving force of crack propagation are influenced by dielectric breakdown. The attraction of crack to electrical treeing path and the deflection of electrical treeing to crack path are predicted during the coupling evolution of fracture and dielectric breakdown. The results of this work provide an in-depth insight into the electromechanical coupling failure of fracture and breakdown of ferroelectric materials. The developed model framework can be employed to investigate more complex electromechanical coupling failures of dielectric, piezoelectric and ferroelectric materials and structures.

Study on fracture cause of porcelain insulator of 220KV transmission line

Porcelain insulators are widely used in EHV and UHV lines because of their excellent mechanical properties. Recently, the porcelain insulator of a 220kV transmission line tension tower in Shandong Province broke, which directly affected the safe and stable operation of the power grid. In order to analyse the fracture cause of porcelain insulator, the insulation resistance test, electromechanical damage composite test, morphology analysis and metallographic structure analysis of faulty string insulator and adjacent string insulator are carried out in this paper. The results show that the insulation resistance and electromechanical failure load test of porcelain insulator meet the standard requirements, and the electrical performance is normal. The fracture of porcelain insulator is mainly caused by the damage of iron cap. The raw material of broken porcelain insulator iron cap is gray cast iron, and its mechanical properties are far lower than those of nodular cast iron or malleable cast iron required by the standard, which is easy to be damaged in the process of stress; At the same time, there are casting defects in the iron cap of the broken porcelain insulator, and there are micro cracks before hot galvanizing. With the stress of the insulator string during operation, the cracks gradually expand, which eventually leads to the fracture failure of the iron cap and the broken string. The relevant research process can provide reference for the quality control of porcelain insulator fittings.

Research and Design of Remote Online Supervision System of Coal Mine Electromechanical Equipment

Increasing the supervision of coal mine electromechanical equipment is an urgent need to ensure the safe production of coal mines. This paper designs and develops a coal mine electromechanical equipment supervision system, which includes four parts: mine-side monitoring subsystem, mine-side data acquisition and transmission module, local-side data analysis and storage module, and coal mine electromechanical equipment supervision platform. It realizes coal mine ventilator, drainage pump, air compressors, hoists and other major electromechanical equipment online monitoring and equipment failure analysis. The system satisfies the remote online inspection and management of equipment by multi-level departments, reduces the possibility of enterprise accidents, innovates the supervision mode, and improves the efficiency of supervision.

Research on real-time risk monitoring model along the water transfer project: a case study in China

Abstract With the continuous operation of a water transfer project, especially under the general trend of global climate change in recent years, extreme weather occurs frequently, and the project's operation process will be tested by natural disasters, structural damage, electromechanical equipment failure, water pollution and other risks. Therefore, the risk management of the water transfer project is of great significance to ensure the long-term operation of the project. As one of the four largest cross-century projects in China, the operation risk of the South-to-North Water Transfer Project has attracted great attention. In this paper, a system dynamic model (SDM) for simulating real-time risk is presented. Based on the linear and directional characteristics of water transfer project and the known risk level of single buildings, DYNAMO language is embedded to connect the risks of various points on the line, and a model for real-time monitoring the risk changes along the line is constructed. The what-if analysis performed by the SDM shows the importance of human intervention to the deterioration and spread of dangerous situations in the process of engineering damage.

Insights from an Electro-Mechanical Heart Failure Cell Model: Role of SERCA Enhancement on Arrhythmogenesis and Myocyte Contraction

Insights from an Electro-Mechanical Heart Failure Cell Model: Role of SERCA Enhancement on Arrhythmogenesis and Myocyte Contraction

Stray Flux Analysis for the Detection and Severity Categorization of Rotor Failures in Induction Machines Driven by Soft-Starters

The condition monitoring of induction motors (IM), is an important concern for industry due to the widespread use of these machines. Magnetic Flux Analysis, has been proven to be a reliable method of diagnosing these motors. Among the IM types, squirrel-cage motors (SCIM) are one of the most commonly used. In many industrial applications, the IM are driven by different types of starters, quite often by soft-starters. Despite rotor damages are more prone to occur in line-started motors, these kind of failures have been also reported in those ones driven by soft-starters. Related to this, the use of these type of starters may introduce some harmonic components, that could veil the magnetic flux signature of the different rotor faults. So, the aim of this study is to confirm if the Stray Flux Analysis technique maintains its reliability in these cases. Thus, this article presents the results of soft-started induction motors start-up tests, both in healthy and faulty motors. The fault components are detected by analyzing the stray flux during the starting and the study is complemented by analyzing the stray flux during the steady-state. In addition to the failure patterns, numerical indicators have been found so the identification of the failures is not only qualitative, but also quantitative. The results confirm the potential of the technique for detecting electromechanical failures in soft-started SCIMs.

Development of a multifunctional nanoindenter integrated in-situ Scanning Electron Microscope - application to the monitoring of piezoresponse and electro-mechanical failures

The rising complexity of multi-material structures integrated into multi-functional devices requires the development of dedicated characterization tools capable of simultaneously monitoring different physical magnitudes with a relevant spatial resolution. This paper reports the development and the application of an original instrument based on a nanoindenter coupled with fine electrical measurements and integrated in-situ a Scanning Electron Microscope (SEM). The performances and capabilities of this home-developed instrument are illustrated through two different case studies.First, a micrometer-scale piezoelectric structure made up of wurtzite-single crystalline AlN islands grown on top of conductive Si pillars is tested. In-situ SEM imaging is used to precisely position the indenting probe on these individual islands, while the instrument sensitivity and repeatability are used to monitor their low-signal piezoresponse. Effective piezoelectric coefficients are also extracted for different loading/unloading conditions.Secondly a Si3N4/AlSiCu/SiO2 stack, which is standardly integrated as a passivation structure on top of microelectronic chips, is electrically and mechanically stressed and monitored up to its failure. The mechanical failure mechanisms (buried or emerging cracks) are discriminated thanks to the real-time SEM imaging of the indentation test. The instrument high sensitivity is used to monitor early current leakages that are attributed to conduction paths induced by mechanical failures.Combining high electro-mechanical sensitivity and precise probe positioning appears as an efficient way to monitor and analyze low-level electrical responses of small-scale structures. This approach paves the way to the fine characterization of micro/nano-systems displaying mechanically-driven electrical properties (conduction mechanism, leakage, breakdown,) like 2D-materials, dielectrics in microelectronic devices, strain-sensors, enamelled Litz wires,…

Low-cycle electro-mechanical fatigue of dielectric elastomers: Pure-shear experiments and life-prediction model

Dielectric elastomers (DEs) often suffer from fatigue failure during electro-mechanical cyclic loading, which significantly constrains the applications of DE-based devices. In this work, we first carried out a series of electro-mechanical fatigue tests, where the pure-shear DE specimen was loaded with a constant voltage and cyclic stress with various stress levels. It was found that the DE under large cyclic deformation is vulnerable to the low-cycle fatigue in the failure mode of electric breakdown, and the fatigue life is significantly affected by the applied stress amplitudes and mean stresses. An electro-mechanical fatigue failure model was then developed to predict the low-cycle electro-mechanical fatigue life of DEs in a pure-shear cyclic loading mode by using a configurational stress-based damage predictor and an electro-mechanically coupled constitutive model. This work is expected to help guide the safe design and evaluation of DE-based devices.

Construction of intelligent query system for metro electromechanical equipment faults based on the knowledge graph

The intelligent inquiry system for metro electro-mechanical equipment faults based on the knowledge graph can effectively consolidate various semi-structured failure messages, and can provide users with quick, accurate and high-quality intelligent inquiry services such as equipment fault causes-researching and solutions-delivering, which could be really relevant to this research field and application areas. The recorded date which related to metro electromechanical equipment failures were in this research collected, consolidated and converted, so that these failures could be stored in our databases. In this context, various functions of the intelligent inquiry system have been implemented, including: natural language question analysis, language Cypher-based question and answer design, Naive Bayesian classification based on characteristic core words, and user interaction interface realization. The experimental results show that the system can effectively solve the problems related to fault handling in metro mechanical and electrical equipment, thus improving the efficiency of equipment fault maintenance.

Electromechanical deformation and failure of multilayered films

AbstractLayer thickness was found to have a significant effect on the irreversible electromechanical deformation and the failure mechanism in polycarbonate (PC)/poly (vinylidene fluoride) (PVDF) multilayered films when subjected to an electrical impulse in a DC needle‐plane configuration. Three distinct regions of behavior were observed. Region I comprised thick layer systems that exhibited only irreversible center deformation. The improvement to failure resistance compared to the monolithic films was attributed to the interphase between the two components. Region II films with an intermediate layer thickness showed both an irreversible center deformation and a treeing mechanism which were observed to simultaneously occur. The surface treeing mechanism, similar to the lightning treeing phenomena in nature, occurs only at impact rates. The tree morphology showed large amounts of plowing, indicating that this damage mechanism can dissipate a large amount of energy prior to electromechanical fracture of the film. Region III films comprise ultrathin layers in the nanoscale and showed no treeing. The unique interphase region between these ultrathin layers was estimated to be at least ten percent of the overall layered structure. These films behaved similar to monolithic materials with improved electromechanical failure characteristics. This work complements the enhanced dielectric performance of multilayer films observed in earlier investigations.

Evaluation of the Correlation Coefficient as a Prognostic Indicator for Electromechanical Servomechanism Failures

In order to identify incipient failures due to a progressive wear of a primary flight command electromechanical actuator, several approaches could be employed; the choice of the best ones is driven by the efficacy shown in fault detection/identification, since not all the algorithms might be useful for the proposed purpose. In other words, some of them could be suitable only for certain applications while they could not give useful results for others. Developing a fault detection algorithm able to identify the precursors of the abovementioned electromechanical actuator (EMA) failure and its degradation pattern is thus beneficial for anticipating the incoming malfunction and alerting the maintenance crew such to properly schedule the servomechanism replacement. The research presented in the paper was focused to develop a fault detection/identification technique, able to identify symptoms alerting that an EMA component is degrading and will eventually exhibit an anomalous behavior, and to evaluate its potential use as prognostic indicator for the considered progressive faults (i.e. frictions and mechanical backlash acting on transmission, stator coil short circuit, rotor static eccentricity). To this purpose, an innovative model based fault detection technique has been developed merging several information achieved by means of Fast Fourier Transform (FFT) analysis and proper "failure precursors" (calculated by comparing the actual EMA responses with the expected ones). To assess the performance of the proposed technique, an appropriate simulation test environment was developed: the results showed an adequaterobustness and confidence was gained in the ability to early identify an eventual EMA malfunctioning with low risk of false alarms or missed failures.

Elaboration of a method of electromechanical drive systems status estimation (at an example of a roll-table roller) by application statistical analysis of electric motor current signal

Loss enhancement because of extraordinary stoppage of technological equipment due to breakage of separate equipment units is an actual task. Existing methodologies of equipment status estimation, based on planning systems, instrumental checks, and personal experience do not ensure always revealing of the incipient of breakdown status in separate elements of the equipment, which often results in breakdown situations and extraordinary repairs. Studies of analysis statistical methods application were accomplished for early revealing indications of electromechanical equipment failure at an example of predicting breakdown status of rollers of rolling mill roll-table. As a parameter under the study, the current signal was chosen, measured at the electric motor of a roller, since it reacts practically without inertia on external oscillations in mechanical part of the facility. The variations of the current curve form reflect any variations of the equipment operation character. From this point of view, the electrical motor itself can be considered as a technical mean of diagnostics of mechanical oscillations in the load with a short response time. Statistical analysis of electric motors current data within one month of roll-table rollers operation, within which 14 jams took place, was carried out. Based on the results of the analysis it was determined, that the process of the jams intensification for various rollers has a similar character. A possibility wa shown to predict the developing and identification of a roller defect by a type of a jam several hours before commencement of the breakdown status, based on one parameter – the load current. Based on sampling of the rollers statistical data in various operation modes and mark of breakdown stops, it is possible to learn the nonlinear machine model for classification of a roller breakdown degree by extracted from the distribution form of statistical current characteristics. The elaborated models in the form of software products and machine codes can be implemented in algorithms of existing at a plant automation systems and technological process and equipment status control systems.