Explore the vast range of titles available.

The degradation and stability of biodegradable films determine the service length of mulch films in actual use. Most biodegradable polymers degrade too fast to meet the required durability of mulch films. The objective of this work is to investigate the degradation behaviors of poly(butylene adipate-co-terephthalate) (PBAT)/polyhydroxyalkanoate (PHA) blend mulch films. Several different types of stabilizers were incorporated in the biodegradable blends to provide protection for the PHA/PBAT films during thermal processing and aging on agricultural fields. The degradation process of the films was systematically studied under an Accelerated aging test (AAT) and a Soil aging test (SAT). Adding a UV stabilizer, or antioxidant to the mulch films led to significant improvement in the retention of mechanical properties of the films under both AAT and SAT. Morphological evolution of the films with or without a UV stabilizer as a function of aging times was studied by Scanning electron microscopy. The results of thermal properties and crystallinity revealed damage of crystalline structure of the films during AAT. Spectrocopic results indicated that the films underwent both hydrolysis and photodegradative chain scissions (Norrish Type I/II reactions and photo-oxidation). Two degradation mechanisms of the PBAT/PHA biodegradable mulch films were proposed.

Based on the rate-dependent non-aging constitutive model and the rate-independent aging constitutive model, a rate-dependent aging constitutive model is proposed to explain the changes in mechanical properties of ethylene propylene diene monomer (EPDM) rubber under different strain rates and aging states. In order to simulate the actual use state of rubber, accelerated aging tests are conducted on the samples in a hot air aging environment. The grey wolf algorithm is utilized to accurately fit the engineering stress–strain curve obtained from the experiment, obtaining specific coefficient values that represent the effects of strain rate, aging time, and aging temperature in the constitutive model. The results confirm the effectiveness of the proposed rate-dependent aging constitutive model in accurately predicting the mechanical property changes of EPDM rubber under different strain rates and aging states. The consistency between the experimental data and the calculated results is within the acceptable error range. It is worth noting that the stress in the model shows the dependence on strain rate, aging time and aging temperature, emphasizing the mechanical property changes of EPDM rubber at high temperatures and low strain rates simulated in the uniaxial tensile state.

Compared with the constant stress accelerated aging test, the step stress accelerated aging test reduces the accelerated aging test time by increasing the aging temperature step by step to obtain the aging failure life of rubber in a shorter time, but its data processing method is not mature enough. In this paper, a simplified step is proposed to process the step stress accelerated aging data. The identification of the acceleration factor is transformed into an optimization problem to avoid the error accumulation problem caused by fitting the data at each temperature. Considering the non-Arrhenius phenomenon in the rubber aging process, a modified Arrhenius equation was used to extrapolate the acceleration factor at low temperatures to calculate the prediction curves for the degradation of polyurethane rubber properties at low temperatures. The life prediction results of the constant stress accelerated aging test and step stress accelerated aging test were compared, and the dispersion coefficient between the two results was between 0.9 and 1. The results obtained by the two methods were in good agreement, which proved the correctness and feasibility of the method used in this paper.

In the lining of water conveyance tunnels, the expansion joint is susceptible to leakage issues, significantly impacting the long-term safety of tunnel operations. Polyurea is a type of protective coating commonly used on concrete surfaces, offering multiple advantages such as resistance to seepage, erosion, and wear. Polyurea coatings are applied by spraying them onto the surfaces of concrete linings in water conveyance tunnels to seal the expansion joint. These coatings endure prolonged exposure to environmental elements such as water flow erosion, internal and external water pressure, and temperature variations. However, the mechanism of polyurea coating’s long-term leakage prevention failure in tunnel operations remains unclear. This study is a field investigation to assess the anti-seepage performance of polyurea coating in a water conveyance tunnel project located in Henan Province, China. The testing apparatus can replicate the anti-seepage conditions experienced in water conveyance tunnels. An indoor accelerated aging test plan was formulated to investigate the degradation regular pattern of the cohesive strength between polyurea coating and concrete substrates. This study specifically examines the combined impacts of temperature, water flow, and water pressure on the performance of cohesive strength. The cohesive strength serves as the metric for predicting the service lifetime based on laboratory aging test data. This analysis aims to evaluate the polyurea coating’s cohesive strength on the tunnel lining surface after five years of operation.

Lightweight Cellular Concrete (LCC) embankments endure significant operational loads throughout the service life of expressways. This study explores the fatigue characteristics of LCC embankments under cyclic loading through experimental analysis and numerical simulation. Based on vehicular dynamic loads and other related factors, a simplified method for complex vehicular dynamic loads is proposed, and an in-depth analysis is conducted in conjunction with indoor accelerated aging tests. Under cyclic loading, the longitudinal strain of LCC undergoes three stages: rapid growth, slow growth, and rapid growth again, while the elastic modulus gradually decreases with increasing cycles. At the same cyclic life ratio, a smaller stress ratio results in a more pronounced strength reduction. An optimized formula is proposed based on the inverse power law model to predict the decay of LCC compressive strength. Furthermore, using the LCC embankment on the Guangdong-Fojiang Expressway as a case study, numerical analysis was performed to determine the stability and residual strength characteristics under various vehicular dynamic loads. The results indicate that a bearing capacity of 100 kPa and a frequency of 15 Hz represent not only the limit where the safety factor falls below 1 but also where the residual strength reaches 65% of the original strength. These parameters can be recommended as reference values for the maximum load-bearing capacity and traffic flow for LCC embankments on expressways.

It has been a challenge to quantify the credibility of the accelerated storage model until now. This paper introduces a quantitative measurement named the CMADT (Creditability Metric of Accelerated Degradation Test), which quantifies the credibility of the accelerated aging model based on available data. The relevant criterion data are obtained from the natural storage test. CMADT is a credibility metric obtained by measuring the difference in the metric area between the probability distribution of the accelerated storage model and its criterion data. In addition, the accelerated aging model might include multiple parameters resulting in several single-parameter CMADTs. This paper proposes a method that integrates several single-parameter CMADT metrics into a single metric to assess the overall credibility of the accelerated storage model. Moreover, CMADT is universal for different scales of sample data. The cases addressed in this paper show that CMADT helps designers and decision-makers judge the credibility of the result obtained by the accelerated storage model intuitively and makes it easier to compare various products horizontally.

To investigate the aging behavior of HTPB composite solid propellant under constant strain conditions, this study analyzed the aging patterns of the propellant’s maximum elongation at four temperatures (323.15 K–343.15 K) and five strain levels (0–18%) using thermal–mechanical coupled accelerated aging tests. The results show that the maximum elongation initially increases, then decreases under constant strain conditions. To measure the mechanical work-induced decrease in the activation motor, we created a modified Arrhenius model with a strain correction factor based on empirical observations. The acceleration coefficient of a solid motor grain at the accelerated aging temperature (323.15 K) in comparison to the long-term storage temperature (293.15 K) was found to be 20.08 through finite element analysis. This means 206.80 days at the accelerated aging temperature is equivalent to 10 years at the long-term storage temperature.

Ternary lithium-ion batteries are commonly used in electrical power systems. It is necessary to accurately estimate the life characteristics of the battery cell/pack under specific cycle conditions. In this article, the empirical model of the capacity attenuation value is improved, and a mathematical model of the capacity attenuation rate is established. The cell capacity value based on the entire state of charge (SOC) interval and the divided SOC intervals are identified. The difference between them is calculated and analyzed. A multiple regression model is presented to describe the linear relationship between the health state parameters and the capacity value of a ternary lithium-on battery. Finally, an accelerated aging test is introduced, and a fast cycle life evaluation method is proposed. The proposed method is validated with experimental data under different charge/discharge currents. The obtained results show that the new model and the algorithms trained by divided SOC intervals are effective. They also show that the cycle life estimation error can be ranged within 3%. In addition, the cycle time of the aging test can be reduced to about one fifth of that with the traditional method.

Calcined ginger nuts admixed by fly ash and quartz sand (CGN-(F+S)) has been validated to be basically compatible to earthen sites as an anchor grout. Accelerated ageing tests including water stability test, temperature and humidity cycling test, soundness test and alkali resistance test are conducted with the objective to further research the property changes of CGN-(F+S) grout. Density, surface hardness, water penetration capacity, water permeability capacity, soluble salt, scanning electron microscopy (SEM) images and energy dispersive spectrometry (EDS) spectrum of these samples have been tested after accelerated ageing tests. The results show that densities of samples decrease, surface hardness, water penetration capacity and water permeability capacity of samples increase generally. Besides, soluble salt analysis, SEM and EDS results well corroborate the changes. Based on the results it can be concluded that property changes are most serious after temperature and humidity cycling test, followed by water stability, soundness and alkali resistance test in sequence. But in general, CGN-(F+S) still has good durability.

This work was carried out to estimate field and controlled room seedling emergence potential through seed vigour tests in cress (Lepidium sativum L.) seeds. Early radicle emergence percentages after 12 (RE12h), 24 (RE24h) and 36 (RE36h) hours of germination test, mean germination time, accelerated aging (45 °C, 100% RH, 24 h), electrical conductivity (EC) of soaking water (40 ml, 50 seeds, 20 °C), after 16 hours (EC16h) and 24 hours (EC24h), and EC16h and EC24h after accelerated ageing (AA, 45 °C, 100% RH, 24h) were tested as vigour tests in ten commercial seed lots of cress. Standard laboratory germination ranged between 88 and 93%. Seeds were sown on two occasions in field and controlled room conditions, and seedling emergence percentages were determined after 30 days in the soil and 14 days in the controlled room. Seedling emergence ranged between 67 and 85% and 59 and 83% in the first and second sowings in the field. These values were 75 and 92% in controlled room sowing. Vigour tests were correlated to seedling emergence potential at various significance levels but RE24h and EC16h showed the highest correlation coefficient values (p < 0.001) in all three sowing conditions as r = 0.879-0.988 in RE24h, and r = 0.902-0.962 in EC16h. Results indicated that early radicle emergence percentages after 24 hours (RE24h) and electrical conductivity value after 16 hours (EC16h) can be successfully used to estimate the seedling emergence potential of cress seeds in field and controlled room conditions.   *** In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. ***