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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.

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.

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. ***

An important factor having a negative impact on the technical condition of aircraft structure elements is the adverse effect of the atmosphere, which causes formation of corrosion in aircraft structures, especially in riveted lap joints. The electric potential difference between the sheet material and the rivet, in the presence of humid air, may cause electrochemical corrosion. The paper presents specimens that imitate the repair on the Mi-24 helicopter with the use of blind rivets in places where solid double-sided rivets could not be used. The aim of the research was to assess the corrosion resistance of lap joints with the use of single-sided and double-sided rivets. The analysis of corrosion resistance was carried out based on accelerated aging tests in a salt spray chamber. The salt chamber tests were aimed at determining the changes taking place in the specimens exposed to the marine environment. In the course of periodic observations changes in the mass of the specimens and in the form of corrosion losses were recorded. These activities were aimed at determining whether the exposure of specimens in the salt chamber causes electrochemical corrosion or pillowing. In addition, the specimens were subjected to static strength tests to assess the effect of corrosion on the strength properties of riveted joints.

The high power conversion efficiencies of small-area perovskite solar cells (PSCs) have driven interest in the development of commercial devices. Rong et al. review recent progress in addressing stability, how to allow mass production, and how to maintain uniformity of large-area films. They note that lifetimes exceeding 10,000 hours under 1 sun (1 kW/m 2 ) illumination have been reported for printable triple mesoscopic PSCs. Science , this issue p. eaat8235 Perovskite solar cells (PSCs) have witnessed rapidly rising power conversion efficiencies, together with advances in stability and upscaling. Despite these advances, their limited stability and need to prove upscaling remain crucial hurdles on the path to commercialization. We summarize recent advances toward commercially viable PSCs and discuss challenges that remain. We expound the development of standardized protocols to distinguish intrinsic and extrinsic degradation factors in perovskites. We review accelerated aging tests in both cells and modules and discuss the prediction of lifetimes on the basis of degradation kinetics. Mature photovoltaic solutions, which have demonstrated excellent long-term stability in field applications, offer the perovskite community valuable insights into clearing the hurdles to commercialization.

Currently, there is a lack of adequate standards for evaluating the integrity inspection cycle of polyethylene (PE) gas pipelines. In this study, a series of photo-oxidation accelerated-aging experimental tests for PE80 gas pipe samples were performed. The attenuation laws of several critical performance parameters, such as micro-morphology, tensile strength, and thermal stability tests, were established. These parameters were determined at different aging times. A novel comprehensive performance evaluation method for pipeline integrity was developed using the analytic hierarchy process, and a reasonable inspection period for pipeline integrity was identified. The results showed that the samples experienced two stages of aging: rapid aging stage and aging platform stage. During the rapid aging stage, the comprehensive evaluation index for the aging performance decreased rapidly. However, the comprehensive evaluation index for the aging performance remained almost unchanged during the aging platform stage.