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The aim is to demonstrate the reliability of a population at consecutive points in time, where a sample at each current point must prove that at least 100p$$ p $$% of the devices function until the next point with a probability of at least 1−ω$$ 1-\omega $$. To test the reliability of the population, we flexibilise standard lifetime models by allowing the unknown parameter(s) of the corresponding counting process to vary in time. At the same time, we assign a prior distribution that assumes the parameters to be constant within a certain interval. This flexibilisation has several advantages: it can be applied for all parametric lifetimes; its Markov property allows the efficient derivation of the number of defective devices, even for a large number of testing times; and the inference is less certain and hence more realistic and leads to less frequent acceptance of poor quality populations. On the other hand, the inference is stabilised by the informative prior. Based on the flexibilisation of the homogeneous Poisson process (HPP), we derive acceptance sampling plans to test the future reliability of a population. Applying the zero failure sampling plans on simulations of Weibull processes shows their good frequentist properties and their robustness. In the case of utility meters subject to German regulations (Mess‐ und Eichverordnung (MessEV). 2014: 2010–2073.), application of the derived sequential sampling plans when the conditions of these plans are met can lead to an extension of the verification validity period. These sampling plans protect the consumer better than those from an HPP and are still cost efficient. [ABSTRACT FROM AUTHOR]

The creating of novel models essentially stems from the requirement to appropriate describe survival cases. In this study, a novel lifetime model with two parameters is proposed and studied for modeling more types of data used in different study cases, including symmetric, asymmetric, skewed, and complex datasets. The proposed model is obtained by compounding the exponential and XLindley distributions, and it is regarded as a strong competitor for the widely applied symmetrical and non-symmetrical models. Several characteristics and statistical properties are investigated. The unknown parameters of the recommended model for the complete sample are estimated using two estimation methods; notably, maximum likelihood estimation and Bayes techniques based on several loss functions as well as an approximate tool are used to construct the confidence intervals for the unknown parameters of the suggested model. The estimation procedures are compared using a Monte Carlo simulation experiment to demonstrate their effectiveness. In the end, the applicability and flexibility of the recommended model are conducted using two real lifetime datasets. In our illustration, we compare the practicality of the recommended model with several well-known competing distributions. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are used in a wide range of applications. However, their cycle life suffers from the problem of capacity fade, which includes calendar and cycle aging. The effects of storage time, temperature and partial charge-discharge cycling on the capacity fade of Li-ion batteries are investigated in this study. The calendar aging and cycle aging are presented based on the storage and cycling experiment on LiCoO2/graphite cells under different storage temperature and different ranges of state of charge (SOC). Based on the measurement data, a one-component and a double-component aging model are presented to respectively describe the capacity fade caused by calendar and cycle aging. The calendar aging of LiCoO2/graphite batteries is mainly affected by temperature and SOC during the storage. Mean SOC and change in SOC (ASOC) are the main factors affecting battery degradation during cycling operation. [ABSTRACT FROM AUTHOR]

This paper presents a design optimization for grid-connected modular Active Front-End (AFE) rectifiers with an evaluation of efficiency, lifetime, cost, volume, and weight. This tool optimizes the rectifier switching frequency, component sizing and selection, and the number of parallel converters by designing and evaluating every possible configuration of the AFE rectifier system defined by the end user. The design of the LCL filter, magnetic design of inductors, selection of the inductor core and winding, and selection of SiC switches and MLC capacitors are discussed. Rapid Low-Fidelity (Lo-Fi) electro-thermal and lifetime models that are fast enough to be used in an optimization process have been developed. The rapid Lo-Fi models estimate component losses, temperatures, and lifetime for given load profiles and converter configurations. This Lo-Fi approach accelerates the processing time to generate the thermal data for the converter mission profile and allows us to skip rainflow-counting algorithm to assess the accumulated thermal damage to the SiC switches at the design and development stage. This in turn allows engineers to design converters with a longer predicted lifetime. Moreover, optimization of the grid-side three-phase LCL filter is performed considering efficiency, cost, and volume trade-off between the grid-side and converter-side inductors to achieve up to 50% decrease in losses, and 23% decrease in cost. Moreover, a 21-22% decrease in the system losses, 23-27% decrease in system cost, and tenfold improvement of the system lifetime can be achieved by optimizing the converter switching frequency and number of parallel modules. A 15 kW hardware prototype consisting of three 5 kW AFE rectifier modules is built and used to validate the efficiency from the fast Lo-Fi models. The validation of the detailed loss model and junction temperature swing is performed against a High-Fidelity (Hi-Fi) simulation in MATLAB Simulink environment.

[Display omitted] The exponential growth of stationary energy storage systems (ESSs) and electric vehicles (EVs) necessitates a more profound understanding of the degradation behavior of lithium-ion batteries (LIBs), with specific emphasis on their lifetime. Accurately forecasting the lifetime of batteries under various working stresses aids in optimizing their operating conditions, prolonging their longevity, and ultimately minimizing the overall cost of the battery life cycle. Accelerated aging, as an efficient and economical method, can output sufficient cycling information in short time, which enables a rapid prediction of the lifetime of LIBs under various working stresses. Nevertheless, the prerequisite for accelerated aging-based battery lifetime prediction is the consistency of aging mechanisms. This review, by comprehensively summarizing the aging mechanisms of various components within LIBs and the battery degradation mechanisms under stress-accelerated conditions, provides a reference for evaluating the consistency of battery aging mechanisms. Furthermore, this paper introduces accelerated aging-based lifetime prediction models and offers constructive suggestions for future research on accelerated lifetime prediction of LIBs. [ABSTRACT FROM AUTHOR]

Bond wire failure, primarily wire neck breakage, in power LED devices due to thermomechanical fatigue is one of the main reliability issues in power LED devices. Currently, the standard testing methods to evaluate the device's lifetime involve time-consuming thermal cycling or thermal shock tests. While numerical or simulation methods are used as convenient and quick alternatives, obtaining data from material lifetime models with accurate reliability and without experimental fatigue has proven challenging. To address this issue, a mechanical fatigue testing system was developed with the purpose of inducing mechanical stresses in the critical region of the bond wire connection above the ball bond. The aim was to accelerate fatigue cracks at this bottleneck, inducing a similar failure mode as observed during thermal tests. Experimental investigations were conducted on Au, Cu, and Pd-coated Cu bonding wires, each with a diameter of 25 µm, using both low- and high-frequency excitation. The lifetime of the wire bond obtained from these tests ranged from 100 to 1,000,000 cycles. This proposed testing method offers material lifetime data in a significantly shorter timeframe and requires minimal sample preparation. Additionally, finite element simulations were performed to quantify the stresses at the wire neck, facilitating comparisons to conventional testing methods, fatigue test results under various operating conditions, material models, and design evaluations of the fine wire bond reliability in LED and microelectronic packages. [ABSTRACT FROM AUTHOR]

The creating of novel models essentially stems from the requirement to appropriate describe survival cases. In this study, a novel lifetime model with two parameters is proposed and studied for modeling more types of data used in different study cases, including symmetric, asymmetric, skewed, and complex datasets. The proposed model is obtained by compounding the exponential and XLindley distributions, and it is regarded as a strong competitor for the widely applied symmetrical and non-symmetrical models. Several characteristics and statistical properties are investigated. The unknown parameters of the recommended model for the complete sample are estimated using two estimation methods; notably, maximum likelihood estimation and Bayes techniques based on several loss functions as well as an approximate tool are used to construct the confidence intervals for the unknown parameters of the suggested model. The estimation procedures are compared using a Monte Carlo simulation experiment to demonstrate their effectiveness. In the end, the applicability and flexibility of the recommended model are conducted using two real lifetime datasets. In our illustration, we compare the practicality of the recommended model with several well-known competing distributions.

The charging modules of Electric vehicles (EVs) always run in a complex and variable state. As the weakness in the reliable operation of charging modules, the accurate lifetime prediction of aluminum electrolytic capacitors (Al-caps) is important for the later maintenance and reliability design. The hotspot temperature calculation method and lifetime model limit the accuracy of aluminum electrolytic capacitors lifetime prediction methods, which cannot meet the increasing requirements for reliability. In order to solve the problems above, this paper has proposed a hotspot temperature calculation method based on the ripple current with frequency characteristics and the cooling conditions on the heat generation and thermal conductivity of the capacitors. Furthermore, the lifetime model under reference voltage has been constructed with 3D surface fitting toolbox, which describes the trends of capacitor lifetime with ambient temperature and hotspot temperature under the constant voltage condition. Considering the variation of voltage, the multiple lifetime model of capacitor is established with a voltage correction coefficient. With the proposed method, it can be realized about the real-time lifetime prediction of capacitors under multiple operating profiles such as ripple current, thermal dissipation conditions, ambient temperature and operating voltage. Finally, the effectiveness of the proposed method is verified with the annual profiles of a 30 kW EV charging module. [ABSTRACT FROM AUTHOR]

Bond wire failure, primarily wire neck breakage, in power LED devices due to thermomechanical fatigue is one of the main reliability issues in power LED devices. Currently, the standard testing methods to evaluate the device’s lifetime involve time-consuming thermal cycling or thermal shock tests. While numerical or simulation methods are used as convenient and quick alternatives, obtaining data from material lifetime models with accurate reliability and without experimental fatigue has proven challenging. To address this issue, a mechanical fatigue testing system was developed with the purpose of inducing mechanical stresses in the critical region of the bond wire connection above the ball bond. The aim was to accelerate fatigue cracks at this bottleneck, inducing a similar failure mode as observed during thermal tests. Experimental investigations were conducted on Au, Cu, and Pd-coated Cu bonding wires, each with a diameter of 25 µm, using both low- and high-frequency excitation. The lifetime of the wire bond obtained from these tests ranged from 100 to 1,000,000 cycles. This proposed testing method offers material lifetime data in a significantly shorter timeframe and requires minimal sample preparation. Additionally, finite element simulations were performed to quantify the stresses at the wire neck, facilitating comparisons to conventional testing methods, fatigue test results under various operating conditions, material models, and design evaluations of the fine wire bond reliability in LED and microelectronic packages.

Solder fatigue is among the predominant failure modes observed in power electronic modules. Under service conditions power electronic parts are exposed to repeated temperature swings originating from resistance heating. In consequence of a mismatch of the coefficients of thermal expansion, thermomechanical stresses are generated at material interconnects. Nevertheless, lifetimes of up to 30 years are requested for high reliability applications. Therefore, there is a demand for accelerated testing methods. However, due to strain rate dependence of inelastic deformations theoretical lifetime modeling is necessary to compare the results of accelerated test methods with usual service conditions. The present study reports on a mechanical testing method operating at the ultrasonic frequency of 20 kHz. During testing samples are exposed to repeated bending deformations until the solder joint finally breaks. The number of cycles to crack initiation is determined for different temperatures ranging from room temperature to 175 °C. Thereafter, an FEM computer simulation of the fatigue experiment is performed, where the visco-plastic Anand model serves as material model of the solder. The time to crack initiation in the solder is evaluated with a model of damage accumulation, which combines the Coffin-Manson model with a multiaxial version of the Goodman relation. It is demonstrated that this model can be applied to the solder alloys PbSnAg, Sn3.5Ag and SnSbAg.

Abstract Lithium‐ion technologies have become the most attractive and selected choice for battery electric vehicles. However, the understanding of battery aging is still a complex and nonlinear experience which is critical to the modeling methodologies. In this work, a comprehensive lifetime modeling twin framework following semi‐empirical methodology has been developed to predict the crucial degradation outputs accurately in terms of capacity fade and resistance increase. The constructed model considers all the relevant aging influential factors for commercial nickel manganese cobalt (NMC) Li‐ion cells based on long‐term laboratory‐level investigation and combines both the cycle life and the calendar life aspects. To demonstrate robustness, the model is validated with a real‐life worldwide harmonized light‐duty test cycle (WLTC). The model can precisely predict the capacity fade and the internal resistance growth with a root‐mean‐squared error (RMSE) of 1.31% and 0.56%, respectively. The developed model can be used as an advanced online tool forecasting the lifetime based on dynamic profiles.

Capacity loss over time is a critical issue for lithium-ion batteries powering battery electric vehicles (BEVs) because it affects vehicle range and performance. Driving cycles have a major impact on the ageing of these devices because they are subjected to high stresses in certain uses that cause degradation phenomena directly related to vehicle use. Calendar capacity also impacts the battery pack for most of its lifetime with a capacity degradation. The manuscript describes experimental tests on a lithium-ion battery for electric vehicles with up to 10% capacity loss in the WLTP CLASS 3B driving cycle. The lithium-ion battery considered consists of an LMO-NMC cathode and a graphite anode with a capacity of 63 Ah for automotive applications. An internal impedance variation was observed compared to the typical full charge/discharge profile. Incremental capacitance (IC) and differential voltage (DV) analysis were performed in different states of cell health. A lifetime model is described to compute the total capacity loss for cycling and calendar ageing exploiting real data under some different scenarios of vehicle usage. [ABSTRACT FROM AUTHOR]

• The effect of surface underconstraint on energy input for surfaces and interiors under identical stress is quantified via representative volume element simulation. • A low cycle fatigue lifetime model is established considering differences in fatigue resistance at various failure sites based on fracture mechanics. • The mechanism of internal inclusions' reduced dominance in fatigue failure compared to surface roughness at high stress levels is quantitatively revealed. The mechanism behind why internal defects are less competitive than surface roughness in low cycle fatigue (LCF) failure is still an issue for inclusion-containing powder metallurgy (PM) superalloys. Differentiating the differences in applied energy and fatigue resistance at various failure sites is crucial to addressing this issue. This study first captures the dependence of failure site on applied loading from the fractographic observations to quantify the characteristics such as surface roughness, internal defects, and sub-surface facets. Subsequently, an LCF lifetime model is developed based on fracture mechanics principles, considering the difference in applied energy and cracking energy requirements due to underconstraint degree at different sites. A representative volume element (RVE) with similar grain characteristic is then established, and different boundary conditions are applied to describe the energy differences around internal and surface. By comparing the energy at different failure sites, the model predicts the tendency of failure sites under varying loading conditions. The developed LCF lifetime model distinguishes energy input and fatigue resistance differences at surface, sub-surface, and interior of the specimen, which reduces the lifetime prediction error from a scatter band of 9 times to within 3 times. [ABSTRACT FROM AUTHOR]

Battery degradation is one of the key barriers to the correct deployment of electric vehicle technology. Therefore, it is necessary to model, with sufficient precision, the State of Health (SoH) of batteries at every moment to know if they are useful as well as to develop operating strategies aimed at lifetime maximization. This paper presents a commercial electric vehicle with a nickel-cobalt-manganese (NCM) battery cell model that is composed of electrical and degradation submodels given by cycling aging. The studied cell is an LG Chem E63 cell, which is used in Renault Zoe electric vehicles. This degradation model is based on experimental results that are interpolated in the Hermite Cubic Interpolation Polynomial (PCHIP), with the exception of the number of cycles, whose impact is determined by a potential law. Temperature and C-rate are found to be the most influential factors in the aging of these batteries. The degradation model developed presents an RMSE of 1.12% in capacity fade and 2.63% in power fade. Furthermore, an application of the model is presented, in which high demanding (highway), average demanding (mixed), and low demanding (urban) driving environments are analyzed in terms of degradation.

Lithium‐ion technologies have become the most attractive and selected choice for battery electric vehicles. However, the understanding of battery aging is still a complex and nonlinear experience which is critical to the modeling methodologies. In this work, a comprehensive lifetime modeling twin framework following semi‐empirical methodology has been developed to predict the crucial degradation outputs accurately in terms of capacity fade and resistance increase. The constructed model considers all the relevant aging influential factors for commercial nickel manganese cobalt (NMC) Li‐ion cells based on long‐term laboratory‐level investigation and combines both the cycle life and the calendar life aspects. To demonstrate robustness, the model is validated with a real‐life worldwide harmonized light‐duty test cycle (WLTC). The model can precisely predict the capacity fade and the internal resistance growth with a root‐mean‐squared error (RMSE) of 1.31% and 0.56%, respectively. The developed model can be used as an advanced online tool forecasting the lifetime based on dynamic profiles. [ABSTRACT FROM AUTHOR]

Capacity loss over time is a critical issue for lithium-ion batteries powering battery electric vehicles (BEVs) because it affects vehicle range and performance. Driving cycles have a major impact on the ageing of these devices because they are subjected to high stresses in certain uses that cause degradation phenomena directly related to vehicle use. Calendar capacity also impacts the battery pack for most of its lifetime with a capacity degradation. The manuscript describes experimental tests on a lithium-ion battery for electric vehicles with up to 10% capacity loss in the WLTP CLASS 3B driving cycle. The lithium-ion battery considered consists of an LMO-NMC cathode and a graphite anode with a capacity of 63 Ah for automotive applications. An internal impedance variation was observed compared to the typical full charge/discharge profile. Incremental capacitance (IC) and differential voltage (DV) analysis were performed in different states of cell health. A lifetime model is described to compute the total capacity loss for cycling and calendar ageing exploiting real data under some different scenarios of vehicle usage.

In the present paper, we consider the estimation problem for the scaled Muth distribution under Type-II censoring scheme. In order to estimate the model parameters α and β, the maximum likelihood, the least-squares, and the maximum spacing estimators are derived. To show estimation efficiencies of the estimators obtained with this paper, we present an extensive Monte-Carlo simulation study in which the estimators are compared according to bias and mean squared error criteria. Furthermore, we evaluate the applicability of the scaled Muth distribution by taking into account both full and Type-II censored data situations by an analysis conducted on a real-life dataset. [ABSTRACT FROM AUTHOR]

Concentrating solar power plant designers are interested in supercritical CO2 (sCO2) for the power block to achieve > 50% electrical efficiency at > 700 °C. The goal of this project was to develop a long-term (> 100 kh) lifetime model for sCO2 compatibility using 10–15 kh laboratory exposures. Three Ni-based alloys (625, 282 and 740H) and an advanced austenitic stainless steel were evaluated in long-term exposures at 700–800 °C using 500-h cycles in laboratory air, 0.1 MPa industrial grade (IG) CO2 and 30 MPa supercritical IG CO2 and using 10-h cycles in 0.1 MPa IG CO2 and O2. Mass change data and quantification of the oxide scale thickness and depth of internal attack after 1000–10,000 h exposures at 750 °C indicate that these materials are compatible with the sCO2 environments with modeling used to predict long-term behavior. Comparison of the 0.1 and 30 MPa 500-h cycle results did not show a significant effect of pressure on the reaction, and no significant internal carburization was observed under these conditions, even for the stainless steel, suggesting that chromia scales may be better C diffusion barriers than expected. For the Ni-based alloys, thermal cycling to simulate the solar duty cycle did not result in scale spallation after 15 kh in 10-h cycles or 4 kh in 1-h cycles at 750 °C. However, the stainless steel specimens formed an Fe-rich oxide after ~ 1500-h cumulative exposure time in both 1- and 10-h cycles. [ABSTRACT FROM AUTHOR]

Concentrating solar power plant designers are interested in supercritical CO2 (sCO2) for the power block to achieve > 50% electrical efficiency at > 700 °C. The goal of this project was to develop a long-term (> 100 kh) lifetime model for sCO2 compatibility using 10–15 kh laboratory exposures. Three Ni-based alloys (625, 282 and 740H) and an advanced austenitic stainless steel were evaluated in long-term exposures at 700–800 °C using 500-h cycles in laboratory air, 0.1 MPa industrial grade (IG) CO2 and 30 MPa supercritical IG CO2 and using 10-h cycles in 0.1 MPa IG CO2 and O2. Mass change data and quantification of the oxide scale thickness and depth of internal attack after 1000–10,000 h exposures at 750 °C indicate that these materials are compatible with the sCO2 environments with modeling used to predict long-term behavior. Comparison of the 0.1 and 30 MPa 500-h cycle results did not show a significant effect of pressure on the reaction, and no significant internal carburization was observed under these conditions, even for the stainless steel, suggesting that chromia scales may be better C diffusion barriers than expected. For the Ni-based alloys, thermal cycling to simulate the solar duty cycle did not result in scale spallation after 15 kh in 10-h cycles or 4 kh in 1-h cycles at 750 °C. However, the stainless steel specimens formed an Fe-rich oxide after ~ 1500-h cumulative exposure time in both 1- and 10-h cycles. [ABSTRACT FROM AUTHOR]

In this paper a new two-parameter distribution is proposed. This new model provides more flexibility to modeling data with increasing and bathtub hazard rate function. Several statistical and reliability properties of the proposed model are also presented in this paper, such as moments, moment generating function, order statistics and stress-strength reliability. The maximum likelihood estimators for the parameters are discussed as well as a bias corrective approach based on bootstrap techniques. A numerical simulation is carried out to examine the bias and the mean square error of the proposed estimators. Finally, an application using a real data set is presented to illustrate our model. [ABSTRACT FROM AUTHOR]

Electrical machines for transportation applications need to be highly reliable, particularly if they drive safety-critical systems. At the same time, another main requirement is represented by the significant torque density, especially for aerospace, where weight constraints are extremely stringent. For achieving high peak torque, an effective strategy consists in supplying the windings with a current greater than the rated value; thus, thermally overloading the machine for limited time periods. However, if the insulation is overheated, the machine lifetime is shortened and reliability issues can arise. This paper experimentally investigates the influence of short-time thermal overload on the insulation lifetime for low voltage, random wound electrical machines. The analysis is performed on round enameled magnet wire coils, which are aged by accelerated thermal cycles. The obtained results are statistically processed through a two parameter Weibull distribution. According to the findings of the experimental data postprocessing, a lifetime prediction model is built. This model is employed for predicting the lifetime consumption of a motor embedded into an electromechanical actuator for aerospace application. [ABSTRACT FROM AUTHOR]

The main purpose of the paper is the proposal of multi-level simulation, suited for the evaluation of the lifetime of critical electronic devices (electrolytic capacitors). The aim of this issue is to imagine about the expected operation of complex and expensive power electronic systems, when the failure of the most critical component occurs. For that reason, various operational conditions and various physical influences must be considered (e.g. mechanical, humidity, electrical, heat stress), where nonlinearities are naturally introduced. Verification of the proposal is given, whereby the life-time estimation of an electrolytic capacitor operated in a DC-DC converter during various operational conditions is shown. At this point electrical and heat stress is considered for lifetime influence. First, the current state in the field of mathematical modeling of the lifetime for electrolytic capacitors, considering main phenomena is introduced. Next, individual sub-models for multi-level simulation purposes are developed, including a thermal simulation model and electrical simulation model. Several complexities of individual models are mutually compared in order to evaluate their accuracy and suitability for further use. Proper simulation tools have been mutually linked and data transfer was secured, in order to have the possibility of investigation of a lifetime depend on the changes of various variables.

Underwater long-distance high-voltage direct current transmission system can provide long-term, reliable, and sustainable energy for ocean observatories system which has higher reliability requirement than onshore or conventional underwater equipment. As the main network point for high-voltage direct current transmission system, medium-voltage converter of the primary node is at the top layer of power supply chain and its reliability will directly affect the reliability of high-voltage direct current transmission system. Based on a 2.5 kW medium-voltage converter, this study proposes a method to evaluate the reliability of medium-voltage converter with accuracy using the lifetime model of switch by analysis of component junction temperature providing theoretical foundation and technical guidance for medium-voltage converter design. Owing to the high power density of medium-voltage converter, the heat dissipation space is restricted to pressure vessel. This study proposes a thermal design method to ensure normal operation condition within appropriate temperature for medium-voltage converter and verified using ANSYS finite element analysis software.

Underwater long-distance high-voltage direct current transmission system can provide long-term, reliable, and sustainable energy for ocean observatories system which has higher reliability requirement than onshore or conventional underwater equipment. As the main network point for high-voltage direct current transmission system, medium-voltage converter of the primary node is at the top layer of power supply chain and its reliability will directly affect the reliability of high-voltage direct current transmission system. Based on a 2.5 kW medium-voltage converter, this study proposes a method to evaluate the reliability of medium-voltage converter with accuracy using the lifetime model of switch by analysis of component junction temperature providing theoretical foundation and technical guidance for medium-voltage converter design. Owing to the high power density of medium-voltage converter, the heat dissipation space is restricted to pressure vessel. This study proposes a thermal design method to ensure normal operation condition within appropriate temperature for medium-voltage converter and verified using ANSYS finite element analysis software. [ABSTRACT FROM AUTHOR]

The study of the impact of junction temperature swings (ΔTj) on degradation mechanisms during power cycling tests (PCTs) requires both a control of the applied thermal stress and a separation of degradation modes. The first requirement can be obtained by using a “constant ΔTj” power cycling strategy that allows to minimize the cross interactions between the influencing factors. The second one is made by using a dedicated power module well suited for targeting only the chips top-side degradations (metallization and bond-wire contacts). In this paper, a constant ΔTj strategy by gate voltage regulation is performed for PCTs in the dc mode. The tested modules are ideally designed for top-metal and bond-wire contacts degradation investigations. From aging indicator on the collector–emitter voltage (VCE), the results clearly show that three regimes of degradation occur systematically at the insulated gate bipolar transistor (IGBT) chips top side, whatever the stress conditions. Moreover, comparative results in “constant ΔTj” and conventional “constant ΔI” PCT strategies have shown that the feedback between stresses and damages encountered in the second strategy is more important for low ΔTj values than for high ΔTj values. In addition, results show that in case of high stresses, the “constant ΔTj” strategy with VGE regulation gives values close to a “constant ΔI” strategy but that the extrapolation toward low values of ΔTj can be questionable for the “constant ΔTj” strategy. [ABSTRACT FROM AUTHOR]

Next generation OLED displays demand high energy efficiency and high resolution, but it is a hard challenge for the OLED display industry to meet the needs for high efficiency and long lifetime simultaneously. When excitons relax to their ground state a photon is emitted; however, such excited exciton states can, on occasion, quench, leading to material degradation. In order to increase efficiency, a high concentration of excitons is needed, but this leads to more quenching events between excitons and polarons and, in turn, increased material degradation. Thus, a trade‐off exists between efficiency and lifetime, which can be alleviated by carefully optimizing the concentration and spatial distribution of excitons. In this paper, we introduce an OLED lifetime model, which we apply to overcome the aforementioned trade‐off. In order to develop the model, we first identified the key quenching factors that dominate efficiency and lifetime degradation. Based on these factors, our model can quantitatively predict device degradation. Subsequently, we can optimize the OLED stack, in terms of layer materials and thicknesses, so as to maximize efficiency, while minimizing degradation. Consequently, we demonstrate an optimized device that exhibits a 6% higher efficiency and a 2.7 times extended lifetime relative to the reference device. [ABSTRACT FROM AUTHOR]

Featured Application: A potential application for this research work is the pure electric bus with energy recovery capability. With the hybrid energy storage system based on Lithium-ion battery and Lithium-ion Capacitor, the bus will have a longer range, a higher efficiency and a lower cost in comparison to a bus with non-hybrid energy storage system or a bus with hybrid energy storage based on battery and super-capacitors. Public transportation based on electric vehicles has attracted significant attention in recent years due to the lower overall emissions it generates. However, there are some barriers to further development and commercialization. Fewer charging facilities in comparison to gas stations, limited battery lifetime, and extra costs associated with its replacement present some barriers to achieve better acceptance. A practical solution to improve the battery lifetime and driving range is to eliminate the large-magnitude pulse current flow from and to the battery during acceleration and deceleration. Hybrid energy storage systems which combine high-power (HP) and high-energy (HE) storage units can be used for this purpose. Lithium-ion capacitors (LiC) can be used as a HP storage unit, which is similar to a supercapacitor cell but with a higher rate capability, a higher energy density, and better cyclability. In this design, the LiC can provide the excess power required while the battery fails to do so. Moreover, hybridization enables a downsizing of the overall energy storage system and decreases the total cost as a consequence of lifetime, performance, and efficiency improvement. The aim of this paper is to investigate the effectiveness of the hybrid energy storage system in protecting the battery from damage due to the high-power rates during charging and discharging. The procedure followed and presented in this paper demonstrates the good performance of the evaluated hybrid storage system to reduce the negative consequences of the power peaks associated with urban driving cycles and its ability to improve the lifespan by 16%. [ABSTRACT FROM AUTHOR]

Abstract: An accurate lifetime model is needed in power electronic systems as a cost‐effective means of improving reliability and performance assessment, which have long been highly desired to reduce the maintenance cost and to make the product more competitive in the market. Die‐attach solder layer fatigue has been identified as one of the root causes of failure of power electronic modules. This paper presents “physics‐of‐failure lifetime model”, which takes fatigue accumulative effect into consideration and can quantify the effect of long‐term small‐temperature cycling to device fatigue life cycle to estimate the lifetime of the power module. First, small ΔTj power cycling tests were designed to obtain the effects of ΔTj on aged and un‐aged modules. They indicated that the traditional lifetime models were not accurate in predicting the lifetime of power modules. Therefore, a new time‐domain crack propagation model based on the cumulative damage in the die‐attach solder layer is proposed, which includes time‐dependent material properties and temperature profiles. Moreover, power cycling experiments and simulations are conducted to demonstrate the method by comparing the number of cycles to failure. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Translation abstract Hot work tools are subjected to complex thermal and mechanical loads during hot forming processes. Locally, the stresses can exceed the material's yield strength in highly loaded areas. During mass production, this leads to cyclic plastic deformations and thermomechanical fatigue of the tools, which can be a major lifetime limiting factor. However, established concepts for thermomechanical fatigue life assessment of hot work tools do not exist, since this aspect first reached attention in the last years with the needs for higher resource and energy efficiency as well as optimized manufacturing processes (e. g. in the frame of Industrie 4.0). Hence, in this paper, the contemporary industrially used concepts for dimensioning hot forming tools regarding the tooling fatigue life are presented. Furthermore an overview of existing plasticity and lifetime models is given. The models are divided in phenomenological and mechanism based models. The review shows that further research is essential in this field. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are the key material of components used in elevated temperature of gas turbines, and their mechanism of delamination and failure under service conditions has been the hot spot of research for a long time. The influences of strain ranges and phase angles on the thermomechanical fatigue (TMF) properties of samples with TBCs were investigated. It is shown that under the same phase angles, the TMF lifetime decreases with the increase of strain ranges. Under the same strain range, the in-phase tests have longer TMF lifetime than out-of-phase tests. In both samples, cracks are initiated in thermally grown oxide (TGO) layer, and then propagate along the bond coat/ceramic top coat, forming the delamination cracks. When the delamination cracks connect with the segmentation cracks initiated in ceramic coat, the TBCs spall. A TMF lifetime model concerning strain ranges and phase angles is established, and an exponential law exists between TMF lifetime and the maximum stress. [ABSTRACT FROM AUTHOR]

Understanding the impact of process variability on TDDB is crucial for assuring robust reliability for current and future technology nodes. This work introduces a lifetime prediction model that considers local field enhancement to assess the combined impact of die-to-die spacing variability and line edge roughness. The model is applied to 16 nm half-pitch BEOL interconnects assuming either the power law or the root-E as field acceleration model and the impact on lifetime reduction is discussed. In comparison with the ideal case of a straight line with a nominal spacing of 16 nm, a 1-sigma spacing variation of 0.6 nm and 1-sigma LER of 1 nm leads to ~ 3 orders of magnitude lifetime reduction when assuming power-law whereas this value is ~ 1 order of magnitude when assuming root-E. [ABSTRACT FROM AUTHOR]

This paper presents the development of a semi-empirical combined lifetime model for a Nickel Manganese Cobalt Oxide (NMC) cathode and a graphite anode based cell, considered as one of the most promising candidates for the automotive industry. The development of this model was based on a thorough understanding of the degradation behavior of a 20-A h NMC cell, based on the analysis of the results of an extensive test-matrix using 146 cells. This test-matrix was designed around four impact factors: temperature (25–45 °C), Depth-of-Discharge (100–20% DoD), middle State-of-Charge (80–20% Mid-SoC) and current rates (C/3 to 2C). Gathering sufficient data for a mathematical model requires a huge time-investment, and the measurements gathered over the course of 2.5 years offer a unique insight in the aging behavior of the NMC cells used in this study. Experimental results for cycling aging indicated that the capacity loss was strongly affected by the Depth-of-Discharge and temperature. For calendar aging, an initial increase in capacity was observed when stored at low State-of-Charges, due to electrochemical milling, while the deterioration of the capacity was affected most by high storage State-Of-Charges and storage temperatures. The developed combined lifetime model showed an error of less than 5% RMS compared to the measurement results after a Worldwide harmonized Light vehicles Test (WLTC) was applied for 18 months. [ABSTRACT FROM AUTHOR]

In this paper, the effect of junction temperature swing duration on lifetime of transfer molded power insulated gate bipolar transistor (IGBT) modules is studied and a relevant lifetime factor is modeled. This study is based on 39 accelerated power cycling test results under six different conditions by an advanced power cycling test setup, which allows tested modules to be operated under more realistic electrical conditions during the power cycling test. The analysis of the test results and the temperature swing duration dependent lifetime factor under different definitions and confidence levels are presented. This study enables to include the t△ Tj effect on lifetime model of IGBT modules for its lifetime estimation and it may result in improved lifetime prediction of IGBT modules under given mission profiles of converters. A postfailure analysis of the tested IGBT modules is also performed. [ABSTRACT FROM AUTHOR]

The endurance degradation mechanisms of p-channel floating gate flash memory device with two-transistor (2T) structure are investigated in detail in this work. With the help of charge pumping (CP) measurements and Sentaurus TCAD simulations, the damages in the drain overlap region along the tunnel oxide interface caused by band-to-band (BTB) tunneling programming and the damages in the channel region resulted from Fowler-Nordheim (FN) tunneling erasure are verified respectively. Furthermore, the lifetime model of endurance characteristic is extracted, which can extrapolate the endurance degradation tendency and predict the lifetime of the device. [ABSTRACT FROM AUTHOR]

Despite advantages of organic light-emitting diode (OLED) displays over liquid crystal displays, reliability concerns persist. These concerns must be addressed before OLED displays are widely adopted. In particular, existing methods are unable to reliably estimate the lifetime of large OLED displays (i.e., displays of 55 in or larger). This study proposes a novel model that incorporates physical and statistical uncertainty to estimate the lifetime of large OLED panels under normal usage conditions. A likelihood-ratio-based validation method is presented to determine the validity of the calculated model parameters. A bivariate acceleration model with two critical factors—temperature and luminance—is presented. The lifespan predicted by the proposed lifetime model shows a good agreement with the experimental results. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to identify promising indicators for prognosis of electrical treeing. Both phase-resolved partial discharge analysis (PRPDA) and pulse sequence analysis (PSA) are utilized. The prognostic properties of the features are evaluated in terms of monotonicity, prognosability, and trendability. The investigation reveals that PSA has a higher prognostic suitability index than PRPDA. An exponential fit is applied to the feature with the highest suitability index, in order to demonstrate its use for prognostic modeling and prediction of time until breakdown. [ABSTRACT FROM AUTHOR]

The employment of sintered silver (SAG) as die attach material is one of the most promising solutions to utilize the advantages of wide bandgap semiconductors in modern power electronic packaging. Its electrical, thermal and mechanical – i.e. reliability correlated – properties are far superior to those of time honored eutectic solders. To master the challenges of a high-quality production on an industrial level in accordance with the ever increasing application-driven reliability requirements, SAG die attach technology has to be developed, tested and lifetime-modelled in the context of a design for reliability approach, in order to be understood and thus savely put into application in the field. This requires the use of modern physics-of-failure paradigms, as today's mostly used empirical lifetime models are meeting their limits with power electronics becoming more diverse in all relevant determinants such as materials, packaging technologies, geometric dimensions and reliability requirements. Introduced will be an isothermal bending test (ITBT) as highly accelerated, simple but very insightful test mimicking the power cycling load regime. This test will be combined with a physics of failure based approach, which will be presented including material characterization, modelling, simulation and definition of a failure parameter. This test method has the potential to produce reliability results much faster than non-mechanical tests, while the physical failure parameter still allows transferability of the resulting model. We show for the first time a physics-of-failure based lifetime model for SAG using isothermal bending in comparison with thermal shock test. For this we used the total inelastic strain (including plastic, primary and secondary creep) as local failure parameter for die attach degradation by fatigue crack growth. • State of the art of material characterization and reliability of sintered silver • A concept for mechanical acceleration of physics of failure based lifetime modeling • Advantages of the physics of failure paradigm and the limits of empirical models • Mechanical material data for used sinter silver layers are shown and discussed • Mechanical fatigue test benchmarked by passive thermal cycling test • Concept of defining a universal failure parameter for reliability modelling [ABSTRACT FROM AUTHOR]