Accelerated Degradation Process Research Articles

Towards the Standardization of Artificial Aging Protocols for Dental Composites: Evaluation of Proposed Methods

In restorative dentistry, there are no standardized in vitro accelerated aging methods to evaluate the long-term stability of dental composites. Current research aimed at extending the clinical success of restorations emphasizes the need for post-aging evaluation. This study represents the final stage of assessing three selected aging protocols that utilize a 0.1 M sodium hydroxide solution as the primary agent to accelerate degradation processes. Twelve resin-based composites, categorized into five types, were evaluated for flexural strength (FS), diametral tensile strength (DTS), hardness (HV), and fracture toughness (FT) both before and after aging. The proposed aging methods significantly degraded the mechanical properties of most materials, highlighting the effectiveness of 0.1 M NaOH as a medium for hydrolytic stability testing. Materials with a high filler content (approximately 80 wt.%) were notably prone to degradation, underscoring the importance of optimizing the filler and coupling agent. The findings suggest that incorporating thermocycling into aging protocols may enhance the development and evaluation of innovative dental composites. This work contributes to establishing a foundation for standardized aging protocols, supporting the accurate assessment of composites in vitro.

Designing a Lithium-Ion Cell for Studies of a Single Degradation Mechanism Over a Wide Temperature Range

Abstract 18650-sized cylindrical cells containing single crystal Li[Ni0.6Mn0.4Co0.0]O2, Li[Ni0.6Mn0.35Co0.05]O2, and Li[Ni0.6Mn0.3Co0.1]O2 positive electrodes along with artificial graphite negative electrodes were constructed to be balanced at 4.05 V. These cells were designed so that they would have only the single degradation mode of lithium inventory loss due to the solid-electrolyte interphase layer growth. Cells were cycled both at C/3 and C/20 over a wide temperature range from 20 to 100°C in order to accelerate degradation processes at higher temperatures and more rapidly predict low-temperature behaviour. A low upper cutoff voltage of 4.0 V was selected to avoid electrolyte oxidation, and an electrolyte composition incorporating pure lithium bis(fluorosulfonyl)imide salt was chosen based on the temperature and voltage range of operation. A thorough post-cycling analysis was performed to verify the elimination of all degradation modes except inventory loss and minor impedance growth, which enabled the application of a simple square root time model to make accurate lifetime predictions. In addition, the capacity retention of these cells at elevated temperature is incredible, with the best cells retaining 87% capacity after 1400 C/3 cycles (one year) continuously at 85°C.

A Generalized Testing Model for Interval Lifetime Analysis Based on Mixed Wiener Accelerated Degradation Process

A Generalized Testing Model for Interval Lifetime Analysis Based on Mixed Wiener Accelerated Degradation Process

Reliability modeling and statistical analysis of accelerated degradation process with memory effects and unit-to-unit variability

A reasonable description of the degradation process is essential for credible reliability assessment in accelerated degradation testing. Existing methods usually use Markovian stochastic processes to describe the degradation process. However, degradation processes of some products are non-Markovian due to the interaction with environments. Misinterpretation of the degradation pattern may lead to biased reliability evaluations. Besides, owing to the differences in materials and manufacturing processes, products from the same population exhibit diverse degradation paths, further increasing the difficulty of accurate reliability estimation. To address the above issues, this paper proposes an accelerated degradation model incorporating memory effects and unit-to-unit variability. The memory effect in the degradation process is captured by the fractional Brownian motion, which reflects the non-Markovian characteristic of degradation. The unit-to-unit variability is considered in the acceleration model to describe diverse degradation paths. Then, lifetime and reliability under normal operating conditions are presented. Furthermore, to give an accurate estimation of the memory effect, a new statistical analysis method based on the expectation maximization algorithm is devised. The effectiveness of the proposed method is verified by a simulation case and a real-world tuner reliability analysis case. The simulation case shows that the estimation of the memory effect obtained by the proposed statistical analysis method is much more accurate than the traditional one. Moreover, ignoring unit-to-unit variability can lead to a highly biased estimation of the memory effect and reliability. From the tuner reliability analysis case, the proposed model is superior in both deterministic degradation trend predictions and degradation boundary quantification compared to existing models, which can provide more credible reliability assessment.

State of health prediction of lithium-ion batteries under early partial data based on IWOA-BiLSTM with single feature

The safe and stable operation of electric vehicles relies on fast and accurate predictions of the state of health (SOH) of the battery. To address challenges such as limited availability of extensive battery aging data or data with informative missingness, the novel SOH prediction method based on the improved method whale optimization algorithm (IWOA)-Bi-directional Long Short-Term Memory (BiLSTM) with strong correlated single aging feature is proposed. Firstly, to accurately predict the accelerated degradation process of the battery capacity, the knee-point in the capacity degradation curve is identified as a starting point for SOH prediction by Bacon-Watts model. Next, a small number of early partial aging features of the battery cycle are extracted, such as time of charging or discharging, and various correlation analysis methods are used to select the single feature with the highest correlation with capacity degradation to reduce the computational complexity of multiple feature factors. Finally, BiLSTM model is established to predict battery SOH. In addition, in order to improve the efficiency of the adjustment for hyperparameters, IWOA is proposed to optimize the BiLSTM’s hyperparameters. Compared to the traditional Whale Optimization Algorithm (WOA), IWOA has better global search capability, robustness, and efficiency through enhancements in search strategy, mutation operation, adaptive parameter adjustment, and performance optimization. The proposed method is validated using battery datasets from NASA and CALCE. Compared with BiLSTM and WOA-BiLSTM, the simulation results indicate that the MSE of SOH prediction based on IWOA-BiLSTM method mostly remains below 0.05, and index of agreement (IA) basically maintains higher than 99%.

Consideration of Moisture Factor during Material Selection in Plastic Product Design

This research paper aims to investigate the significance of considering the humidity factor during material selection in plastic product design. Humidity is a crucial environmental parameter that can profoundly influence the properties and performance of plastic materials. To ensure the long-term performance and dependability of plastic products, it is essential to comprehend and take into consideration the impacts of moisture on plastics. Humidity plays a fundamental role in the degradation and functional changes of plastic materials. Moisture absorption can lead to reduced mechanical strength and accelerated degradation processes. The selection of appropriate materials that can withstand humid conditions becomes paramount in product design. For this reason it is important to evaluate the moisture absorption properties of plastic materials. Different polymers exhibit varying degrees of moisture diffusion rates that directly affect their performance in humid environments. Evaluation of moisture measurement results allows designers to make informed decisions during material selection. For this reason, we designed an experiment to investigate which material retains less moisture. In our research, we determined 2 different experimental groups. The first of these groups (type A) was kept under normal conditions by adding glass fiber additive at different rates to the PA66 material, and each product with 3 different additives was tested for moisture for 10 days and the results were recorded. In the second experimental group, type B, the products produced with the same material and additives at the same rate were kept in water for 24 hours, then they were removed from the water and moisture tests were performed. It is aimed to make material selection by interpreting the test results and thus to facilitate the making of designs suitable for use.

Ionic Liquid Bridge Assisting Bifacial Defect Passivation for Efficient All-Inorganic Perovskite Cells with High Open-Circuit Voltage.

Serious open-circuit voltage (Voc) loss originating from nonradiative recombination and mismatch energy level at TiO2/perovskite buried interface dramatically limits the photovoltaic performance of all-inorganic CsPbIxBr3-x (x = 1, 2) perovskite solar cells (PSCs) fabricated through low-temperature methods. Here, an ionic liquid (IL) bridge is constructed by introducing 1-butyl-3-methylimidazolium acetate (BMIMAc) IL to treat the TiO2/perovskite buried interface, bilaterally passivate defects and modulate energy alignment. Therefore, the Voc of all-inorganic CsPbIBr2 PSCs modified by BMIMAc (Target-1) significantly increases by 148 mV (from 1.213 to 1.361 V), resulting in the efficiency increasing to 10.30% from 7.87%. Unsealed Target-1 PSCs show outstanding long-term and thermal stability. During the accelerated degradation process (85 °C, RH: 50∼60%), the Target-1 PSCs achieve a champion PCE of 11.94% with a remarkable Voc of 1.403 V, while the control PSC yields a promising PCE of 10.18% with a Voc of 1.319 V. In particular, the Voc of 1.403 V is the highest Voc reported so far in carbon-electrode-based CsPbIBr2 PSCs. Moreover, this strategy enables the modified all-inorganic CsPbI2Br PSCs to achieve a Voc of 1.295 V and a champion efficiency of 15.20%, which is close to the reported highest PCE of 15.48% for all-inorganic CsPbI2Br PSCs prepared by a low-temperature process. This study provides a simple BMIMAc IL bridge to assist bifacial defect passivation and elevate the photovoltaic performance of all-inorganic CsPbIxBr3-x (x = 1, 2) PSCs.

Non‐periodic inspection and replacement policy of system subject to non‐homogeneous gamma degradation process

AbstractThe non‐homogeneous gamma process can exhibit a convex average trend with a non‐linear shape parameter, providing significant flexibility in fitting an accelerated degradation process. However, few studies have been conducted on the maintenance modeling of systems undergoing a non‐homogeneous gamma degradation process despite its versatility. Meanwhile, most maintenance studies adopt a periodic inspection policy to reveal the degradation level. However, it is reasonable to inspect less frequently when the degradation level of the system is low and to perform inspections more frequently when the degradation level increases. Therefore, we conduct a study on the inspection/replacement policy of systems undergoing a non‐homogeneous gamma degradation process, where three non‐periodic inspection policies are investigated. We formulate the problem as a SMDP framework and present a value iteration algorithm to obtain the optimal action at each decision epoch that minimizes the long‐term average cost. A comprehensive numerical study is provided to illustrate the effectiveness of our proposed model.

Evaluation of the characteristics of the electric bus battery

This article provides battery parameters that should be considered when choosing a battery for a specific application. The correct choice of battery is very important at the stage of vehicle development, because batteries that are not selected properly can cause operational problems associated with a lack of power, energy and accelerated degradation processes. The battery selection method should take into account the aforementioned features and performance characteristics of the vehicle. The article describes methods for obtaining such characteristics with their assessment using the example of selecting a battery for a vehicle. Keywords: climate control, vehicle, electric heating, heat balance

Research on imperfect condition-based maintenance strategy based on accelerated degradation process

To address the situation that the degraded system cannot be repaired as new and the degradation is accelerated after repair in engineering practice, an imperfect condition-based maintenance model is proposed based on the Gamma process by introducing the maintenance improvement factor and the accelerated degradation factor. The maintenance improvement factor describes the recovery degree of the degradation amount after imperfect maintenance, then gives a quantitative representation method of the system maintenance improvement effect and the determination method of the maximum number of imperfect maintenance. The accelerated degradation factor is combined with the geometric process to describe the accelerated degradation process of the system after imperfect maintenance. The Monte Carlo method is used to determine the optimal number of imperfect preventive maintenance decisions. Through the demonstration of calculation examples, the influence of accelerated degradation factor and maintenance improvement factor on the long-term operation maintenance rate and the optimal number of imperfect maintenance is analyzed. The results show that the model can more comprehensively describe the degradation and maintenance process of degraded systems, and it can effectively reduce maintenance cost ratio under long-term operation. It provides a certain theoretical support for formulating an economical and reasonable maintenance strategy that is more in line with the actual degradation and maintenance process in engineering practice.

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Numerical simulation analysis of a large-scale experiment

The complex process of thermal-hydro-mechanical-biochemical (THMBC) coupled degradation in high food waste content (HFWC) municipal solid waste (MSW) is the main cause of intense heat, gas, and leachate generation in the landfills, which could lead to environmental disasters. A large-scale indoor experiment on HFWC MSW has been done with operations of loading, heated mature leachate recharging to study the rules of degradation. A THMBC coupled degradation model is used to analyze the results in the first 400 days drawn from the experiments, to explain how recharge of heated mature leachate accelerated degradation process and how was the portion of settlement led by intraparticle water release. The numerical simulation also calculated the landfill gas that was not collected in the experiment due to operational defects. The results show that recharging the heated mature leachate allows the stabilization process to occur at least six months earlier and settlement due to intraparticle water release accounts for half of the settlement in the first 60 days. The research indicates highly coupled THMBC model can be used to analyze the complex process in MSW degradation, make up for the shortcomings of physical experiments, and provide theoretical support for the design, construction, and management of landfills.

Reuse of end—of—life membranes through accelerated polyamide degradation

End—of—life (EoL) thin—film composite (TFC) reverse osmosis membranes were converted into ultrafiltration—like (UF) membranes in an accelerated degradation process of the polyamide (PA) using an oxidant (NaOCl) in the presence of either MgCl2 or CaCl2. The PA degradation was evaluated by measuring pure water permeability (PWP), MgSO4 passage and molecular weight cut—off; the more PWP increased, and the less MgSO4 was retained after treatment, the more the PA was degraded. By adding 10 mM of metal ions, PWP increased 2.1 (MgCl2) and 3.1 (CaCl2) times compared to the increase achieved with hypochlorite alone (2560 ppm∙h of free chlorine). Changes in the membranes after treatment were analyzed by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE—SEM), and by measuring their surface charge and contact angle. FTIR and FE—SEM confirmed the PA layer degradation. FE—SEM micrographs showed that full removal of the PA layer can be achieved by using an oxidation dose of 12,700 ppm∙h when Ca2+ is used but doses as high as 300,000 ppm*h are needed without catalyst. The results proved that by controlling the oxidation process it was possible to control the cut—off (MWCO) value of the membrane from 16,100 g∙mol—1 to 27,100 g∙mol—1. Before treatment, EoL membranes showed a MWCO of approximately 1200 g∙mol—1, meaning that molecules with that size could be retained in a 90%. In summary, the presented method enables reducing waste by the conversion EoL membranes into tailored UF—like membranes and by decreasing the amount of oxidant used in the conversion process.

Analysis of the impact of green urban areas in historic fortified cities using Landsat historical series and Normalized Difference Indices

Urban green areas minimize the negative effects of climatic change and improve the sustainability of historic cities. Despite this, green areas have traditionally been considered a threat to heritage buildings because they cause humidity changes, that accelerate degradation processes. Within this context, this study evaluates the trends in the inclusion of green areas in historic cities and the effects it causes on humidity and conservation of earthen fortifications. To achieve this goal, vegetative and humidity information has been obtained since 1985 from Landsat satellite images. The historical series of images has been statistically analysed in Google Earth Engine to obtain maps that show the means, 25th, and 75th percentiles of the variations registered in the last 35 years. The results allow visualizing spatial patterns and plotting the seasonal and monthly variations. In the decision-making process, the proposed method allows to monitor whether the presence of vegetation is an environmental degradation agent in the nearby earthen fortifications.The analysis of the historic fortified cities of Seville and Niebla (Spain) shows a gradual increase in green areas and an interest in locating them near the earthen fortifications. The impact on the fortifications is specific to each type of vegetation and can be positive or negative. In general, the low humidity registered indicates low danger, and the presence of green areas favours drying after heavy rains. This study suggests that increasing green spaces to historic cities does not necessarily endanger the preservation of earthen fortifications. Instead, managing both heritage sites and urban green areas together can encourage outdoor cultural activities, reduce the impacts of climate change, and enhance the sustainability of historic cities.

Missing data interpolation and multi‐sensors integration and its application in accelerated degradation data

AbstractMultiple sensors are commonly used for accelerated degradation monitoring. Since different sensors may be sensitive at different stages of the accelerated degradation process and each sensor dataset may contain only partial information of the unit degradation, then integration approaches of the accelerated degradation data from multiple sensors can effectively improve degradation modeling and life prediction accuracy. We present a non‐parametric approach that assigns weights to each sensor based on the dynamic clustering of the sensors' observations. Missing data are common in degradation data acquisition, especially when multiple sensors are used. We provide two approaches for data interpolation: the nonlinear Brownian bridge and the inverse Gaussian bridge when the underlying degradation paths follow the Brownian motion process and inverse Gaussian process, respectively. The stochastic bridges capture the nonlinearity and uncertainties of the degradation processes. The data integration model and stochastic bridge models are validated with real accelerated fatigue crack growth data monitored with multiple NDT sensors. The proposed models provide an accurate accelerated degradation path and reliability prediction.

Critical Current Degradation in HTS Tapes for Superconducting Fault Current Limiter under Repeated Overcurrent

Superconducting fault current limiters (SFCL) can be an alternative to conventional devices limiting short-circuit currents in power systems. SFCL use high-temperature superconducting tapes of the second generation (HTS 2G) in SFCL, which, after reaching the characteristic critical current of the tape, go into the resistive state (quenching), limiting the short-circuit current. The critical current determines the moment of activation of the SFCL. Therefore, its value should not change during the operation of the device due to repeated limitation of short-circuit currents. The constancy of the critical current is a prerequisite for proper cooperation with the power system protection devices. Multiple quenching can cause microdamage in the superconducting layers responsible for lowering of the value of the critical current of the HTS tapes. The article presents the research results on the degradation processes of 2G HTS tapes intended for the construction of SFCL due to the action of prospective short-circuit currents with values exceeding the critical current of the tested tapes. The decrease in the value of the critical current of the HTS tape as a result of multiple transitions to the resistive state was investigated. The amount of energy emitted during the test current pulse of 0.2 s duration was determined. The limitation values of the voltage drop on the tape, which does not cause accelerated degradation processes, were defined. The microstructural tests of cross-sections of new HTS tapes subjected to prospective short-circuit currents were performed.

Description of the status of supply of hums and nutrient elements of desert pasture soils based on geoinformation systems

It is vitally important to increase the productivity of the degraded and low-fertility sandy desert soils in the world. In particular, special attention is being paid to the use of modern technologies aimed at quickly and qualitatively identifying the changes occurring in sandy desert soils, eliminating the negative effects of desert soils, and preventing the accelerated degradation processes in pastures through a comprehensive study of soil properties. In this research, GIS software was used to map humus and nutrient elements of desert pasture soils. The results showed that the amount of mobile phosphorus in sandy desert soils fluctuated in the range of 10-40 mg/kg in Nurota district, while in Konimekh district this indicator changed in the range of 17-40 mg/kg.

An optimal condition based maintenance model for accelerated degrading products

Condition-based maintenance (CBM) is an effective method to guarantee product availability and minimze the cost in the operation period. Degradation modeling is important in CBM decision-making. For some products such as mechanical systems, the degradation process is accelerated. The main purpose of this paper is to investigate optimizing the CBM strategy for accelerated degrading products. The maintenance process of accelerated degradation process is illustrated and an accelerated degradation model based on the Inverse-Gaussian process is built. On the constraint of availability, the optimal CBM strategy is obtained by minimizing cost. Finally, a numerical example is introduced to illustrate the proposed model.

Reliability assessment for micro inertial measurement unit based on accelerated degradation data and copula theory

With its extensive use in industry, assessing the reliability of the micro inertial measurment unit (MIMU) has become a pressing need. Unfortunately, the MIMU is made up of several components, and the degradation processes of each are intertwined, making it difficult to assess the MIMU’s reliability and remaining useful life. In this research, we offer a reliability assessment approach for the MIMU, which has long-lifetime and multiple performance characteristics (PCs), based on accelerated degradation data and copula theory.Each PC model of MIMU is constructed utilizing drift Brownian motion to depict accelerated degradation process. The copula function is used to model the multivariate dependent accelerated degradation test data and to describe the dependency between multiple MIMU performance parameters. The particle swarm optimization algorithm is used to estimate the unknown parameters in the multi-dependent ADT model. Finally, the storage test and simulation example on MIMU’s accelerated degradation data verify the feasibility and effectiveness of the proposed method.

A closed-loop recycling process for carbon fiber reinforced vinyl ester resin composite

Carbon fiber reinforced thermosetting polymer composites have been widely used in industrial fields, such as wind blades, aerospace and automobiles. However, it is extremely hard to degrade their waste due to the insoluble and infusible crosslinked networks. A solvothermal method is proposed to degrade carbon fiber reinforced vinyl ester resin composite (CF/VER) in this paper. The degradation reaction was conducted in a teflon-lined autoclave at 160 ℃ to 240 ℃ for 60 min to 180 min using isopropanol and acetone as solvents. NaOH or KOH were added to efficiently accelerate degradation process. Degradation ratio up to 99.96% was achieved. Furthermore, a multi-step degradation mechanism was put forward based on FT-IR and GC/MS analysis of degradation products. SEM, FT-IR, and XPS analysis of recycled carbon fibers (RFs) revealed that resin was nearly completely removed. Furthermore, contact angle measurement showed surface wettability of RFs was enhanced. XRD and Raman spectra further verified microstructure of RFs was not damaged drastically. Besides, reusing of degradation products and RFs was explored. Epoxy resin cured with degradation products exhibited excellent performances. Meanwhile, flexural strength tests and SEM images of fracture surfaces showed RFs reinforced epoxy resin composites had superior mechanical strength due to stronger interfaces between fibers and resin. Therefore, an efficient and closed-loop recycling process demonstrated in this manuscript provides a new pathway for degradation and reuse of CF/VER.

Degradation process of Ag/AgCl chloride-sensing electrode in cement extract with low chloride concentration

The accelerated degradation process of Ag/AgCl chloride-sensing electrode was investigated in cement extract by electrochemical behaviors monitoring and surface analysis. The results showed that the potential of Ag/AgCl chloride-sensing electrode was negatively shifted in cement extract, accompanied by the continuous dissolution and exfoliation of AgCl film; however, no Ag2O formed on the electrode surface. The adhesive strength of AgCl to Ag substrate maintained the equilibrium potential of Ag/AgCl chloride-sensing electrode during early stage, but the negative potential shift was pronounced during late stage, which was related to the adsorption of OH- at Ag/AgCl interface, suppressing cathodic reaction on the electrode.