Effect Of Natural Aging Research Articles

Weldability assessment of Al-SS dissimilar joints produced by ultrasonic spot welding route

Multiple materials are often used in the construction of modern vehicles to make them lighter and more affordable. Steel and aluminium alloys are the great building materials for these composite structures. Ultrasonic metal welding is an efficient solid-state joining technology that requires less energy and time than conventional welding methods while also eliminating the potential problems of distortion and shrinkage. In this research, stainless steel (UNS S30400) and aluminium (AA1100) sheets are ultrasonically welded with various surface treatments, including normally cleaned, electrolytically polished, and lubricated surfaces. The studies are carried out at various weld energies while maintaining constant vibrational amplitude and weld pressure parameters. The maximum lap shear and T-peel strength values are obtained as 621 N and 230 N at 2550 J of weld energy for the lubricated surface condition. According to the temperature profile, when weld energy grows, the weld interface temperature rises as well, reaching a maximum of 460 ˚C. It offers the perfect setting for the plastic flow phenomena to build strong bonds. The effects of natural aging and softening on the weld zone at each joint surface are studied through the microhardness test. Scanning electron microscopy and energy-dispersive X-ray spectroscopy investigations are also used to analyse fracture surfaces with various interface morphologies and characteristics.

Effect of Natural Aging on Cold Forming Performance of 2219 Aluminum Alloy.

To facilitate the manufacturing of the thin-walled components of 2219 aluminum alloy, the quenching-forming-aging (Q-F-A) process has been increasingly utilized. However, natural aging (NA) after quenching significantly affects the cold forming performance of this alloy. In this study, experiments are conducted to investigate the effect of NA time on the cold forming performance of 2219 aluminum alloy. The results indicate that NA can weaken the Portevin-Le Chatelier (PLC) effect, thereby reducing its influence on the cold forming performance of the alloy. The PLC effect becomes indistinct when the aging time reaches 2 years. The yield strength of 2219 aluminum alloy increases monotonically with aging time, while the elongation first increases rapidly and then decreases. After an aging time of 2 years, the yield strength increases by 28.6% from that of newly quenched alloys. The strain hardening index and hardening coefficient indicate that short-term NA (less than 4 days) increases the work hardening rate, while long-term NA reduces it. Microstructural analysis shows that the strengthening effect of NA on 2219 aluminum alloy is mainly due to the growth of G.P. zones and the precipitation of θ″ phases. The NA precipitation behavior can also cause the aggregation of solute atoms and weaken the PLC effect.

RESISTANCE OF ADDITIONAL ROOFING UNDERLAYS OF PITCHED ROOFS AGAINST ARTIFICIAL AND NATURAL AGEING

In this paper, the author deals with the resistance of light polymer foils based on microporous functional film, used as additional waterproofing layers of pitched roofs. He exposes these foils to the effects of natural ageing and the effects of artificial ageing according to the methodology of the European test standard. Subsequently, it verifies the tensile properties of the exposed foils and compares the effects of natural and artificial ageing in order to determine the possible cause of premature degradation of these materials, which often occurs in practice. He concludes that the cause of this degradation is not excessive leniency of testing standards, but the insufficient quality of materials supplied to the European market.

Genome damage accumulated in seed ageing leads to plant genome instability and growth inhibition.

Successful germination and seedling establishment are important determinants of crop yields and plant survival in natural environments. Germination potential is compromised by suboptimal environmental conditions that result in seed ageing and high levels of genome damage. However, the mutagenic and growth inhibitory potential of DNA damage accumulated in seeds on subsequent seedling growth remains largely unknown. Arabidopsis seeds deficient in the chromosomal break repair factors DNA LIGASE 4 and DNA LIGASE 6 exhibited hypersensitivity to the effects of natural ageing, with reduced germination vigour and seedling biomass relative to wild type seed. Here we identify that aged Arabidopsis seed display elevated levels of programmed cell death (PCD) in the root meristem which persists into seedling establishment, with higher levels of cell death in lines deficient in DNA double strand break repair. Reporter lines determined the effects of seed ageing on mutation levels and intrachromosomal recombination frequencies. Seed deterioration resulted in strikingly elevated levels of frameshift mutations and genome instability in germinated seedlings. Thus, elevated levels genome damage incurred in the seed stage of the plant life cycle potentially impacts significantly on subsequent plant development. Furthermore, the mutagenic effects of seed ageing has potentially long-term implications on the genome stability of plant populations and ecosystem fitness. Collectively, we identify genome damage accumulated in suboptimal quality seed impacts on subsequent plant growth and genome stability, with associated implications for crop yields and plant survival under changing climates.

Learned Irrelevance, Perseveration, and Cognitive Aging: A Cross-Sectional Study of Cognitively Unimpaired Older Adults.

The effect of natural aging on physiologic mechanisms that regulate attentional set-shifting represents an area of high interest in the study of cognitive function. In visual discrimination learning, reward contingency changes in categorization tasks impact individual performance, which is constrained by attention-shifting costs. Perseveration (PE) and learned irrelevance (LI) are viewed as two different mechanisms that shape responses to stimuli, which are predicated on the shift in stimulus form. To date, only studies examining patients with Parkinson's disease have provided some insight into the relationship between individual age and performance in PE and LI tasks. We enrolled 60 healthy individuals (mean [SD] age, 63.0 [12.6]) without a history of dementia, a cerebrovascular incident, or a neurodegenerative disease. No association was observed between crystallized intelligence or verbal fluency scores and reaction time in both PE (r = 0.074, p = 0.603; r = -0.124, p = 0.346) and LI (r = -0.076, p = 0.562; r = -0.081, p = 0.536) task conditions, respectively. In contrast, a statistically significant linear relationship was observed between age and reaction time (RT) for PE (r = 0.259, p = 0.046) but not for LI (r = 0.226, p = 0.083). No significant linear relationship was observed for changing RTs in PE and LI (r = 0.209, p = 0.110). The present study is the first report that provides a descriptive overview of age-related differences in PE and LI in a sample of cognitively unimpaired middle- to older-aged adults.

Effects of Natural Aging and Discontinuous Cyclic Loading on High Cycle Fatigue Behavior of Steels

Metallic components may not be used immediately and are stored for several months or years after fabrication in some cases, which experience long-term natural aging. Moreover, the fatigue-beared components commonly suffer discontinuous cyclic loadings in service. In this paper, the effects of natural aging and discontinuous loading on high cycle fatigue life and failure mechanism were investigated through rotating bending fatigue tests. The long-term natural aging (e.g., more than 20,000 h) reduced the fatigue life of both 25CrMo4 and 30CrMnSiA steels, and this effect was irrespective of the roughness of the specimen surface. The effect of natural aging on the failure mechanism was related to the microstructure of materials. The natural aging promoted the probability of multi-site crack initiation for 25CrMo4 steel, but had no influence on the crack initiation mode of 30CrMnSiA steel. The discontinuous cyclic loading had no harmful influence on the fatigue life of 25CrMo4 steel, and it had no influence on the failure mechanism. The specimens under continuous and discontinuous cyclic loadings both failed from single-site crack initiation or multi-site crack initiation at the specimen surface.

Effect of natural aging on selected properties of wooden facade elements made of scots pine and chestnut

Identifying wood species of each wood element of a historical wooden building and investigating the changes in wood properties due to exposed outdoors during its service life are important prerequisites for the maintenance and renovation of historical wooden buildings. In the present study, the changes in wood properties occurring during natural aging of two facade elements taken from a traditional house, which has a service life of approximately 100 years, were investigated. Destructive tests were used for the experiments. The wood species, moisture content, wood density, water absorption rate and chemical structure of both facade elements were determined. Microscopic analysis revealed that the molding was made from the wood of Scots pine (Pinus sylvestris) and the window jamb was made from chestnut (Castanea sativa). It was found that the cellulose and lignin on the outer surface of aged woods of both facade elements were degraded according to the FTIR analysis. The moisture and density values of aged wood for both facade elements were smaller than those of recent wood. The water absorption rates of aged woods of both molding and window jamb increased with natural aging.

Comparative study of the combustion and kinetic characteristics of fresh and naturally aged pine wood

Given the long-term effects of natural ageing, the wooden structure and combustion performance of ancient buildings have changed. Therefore, studying the combustion characteristics of naturally aged pine (NAP) trees may help provide a basis for the numerical simulation of fires in ancient buildings. In this study, NAP and fresh pine (FP) with a natural ageing duration of approximately 100 years were selected as samples. The morphology, thermal weight loss process, exothermic characteristics, and combustion characteristics of these two types of pine were examined through scanning electron microscopy, synchronous thermal analysis, and cone calorimetry. In addition, the thermodynamic parameters of both the samples were analysed and evaluated. The results indicated that the natural ageing effect resulted in pore enlargement and severe damage to the cell structure of pine wood. Compared with FP, the ignite of NAP decreased by 15.2 °C, and the heat dissipation of NAP during oxidative combustion decreased by 0.26 kJ/g. In addition, the average apparent activation energy of NAP during pyrolysis combustion increased by 22.03 kJ/mol compared with FP, but the overall combustion performance decreased. During the combustion process, NAP tended to form a dense carbonisation layer, resulting in a decrease in the heat release rate, total heat release rate, flue gas release rate, and CO and CO2 release rate during combustion.

Cladding and Natural Aging of Aluminium Alloy 2024 for Aircraft Application

Aluminium alloy 2024 is widely used in the manufacturing of aircraft components such as skin panels for the wing. Generally, the aluminium alloy 2024 is delivered as cold work condition i.e., 2024 T3. However, the aluminium alloy 2024 T3 does not meet the standard for aircraft wing skin. Therefore, further treatments such as cladding and heat treatment are carried out to improve its quality. Cladding was introduced to the 2024 T3 alloy at 495 °C using commercial purity aluminium. Subsequently, T42 heat treatment was introduced to the 2024 T3 alloy at 500 °C for 40 minutes, then followed by quenching and natural aging for 96 hours, yielding 2024 T42 aluminium alloy with cladding (T42 Clad). 2024 T42 aluminium alloy without cladding (T42 Bare) was also obtained by T42 heat treatment of 2024 T3. The effect of cladding and natural aging on mechanical properties is investigated by tensile test and hardness test. Conductivity meter was used to determine the electrical conductivity. Intergranular corrosion test and stress corrosion crack test were performed to investigate the effect of cladding and natural aging on corrosion resistance. Results indicate that the solution treatment and natural aging improve corrosion resistance, mechanical properties, but reduce electrical conductivity values. Cladding gives higher electrical conductivity value and elongation. Both natural aging and cladding treatment provide appropriate aluminium alloy for aircraft wing skins.

Fast aging technology of novel kiwifruit wine and dynamic changes of aroma components during storage

A novel kiwifruit wine (KW) fermented by Aspergillus niger and Aspergillus oryzae was developed with elegant flavor and poor alcoholic strength. The effects of natural aging, microwave and ultrasonic treatment on the quality of KW were investigated. A total of 61 aroma components were detected in the KW fermented by Aspergillus niger and Aspergillus oryzae. The results showed that microwave and ultrasonic treatments could promote the maturation of KW and increase the aroma components of KW. The variety of flavor components increased with a longer storage time. Combined with the taste evaluation analysis. The esters, alcohols, acids, and aldehydes in ultrasonic-aged wines were in dynamic balance and harmony with each other. The wine was soft and mellow, making the kiwi wine more typical.

Korean Ginseng Berry Extract Enhances the Male Steroidogenesis Enzymes In Vitro and In Vivo.

Testosterone hormonal replacement is the most commonly prescribed solution for men with reproductive issues; however, this treatment has various drawbacks. Hence, the identification of a natural product that promotes steroidogenesis is urgently needed. Ginseng is a popular traditional medicine. This study aimed to investigate steroidogenic effects of Korean ginseng berry extract (GBE; Panax ginseng C.A. Meyer) in vitro and in vivo. In vitro model, mouse Leydig cells were treated with varying concentrations of GBE, and the levels of steroidogenesis-related genes and proteins and testosterone were measured using western blotting, qRT-PCR, and enzyme-linked immunosorbent assay (ELISA). Similarly, in an in vivo model using lipopolysaccharide-injected C57BL/6J mice, expression of steroidogenesis-related genes and proteins and testosterone levels were analyzed. Additionally, sleep deprivation was used to simulate common life stressors related to late-onset hypogonadism (LOH) and the natural effects of aging. Mice were fed sham or GBE before being subjected to paradoxical sleep deprivation. In vitro, GBE induced steroidogenic effects by increasing the levels of enzymes associated with steroidogenesis, steroidogenic acute regulatory protein (STAR), CYP11A1, and CYP17A1. In vivo, GBE significantly increased mRNA and protein levels of steroidogenic enzymes. Furthermore, the synthetic testosterone levels in mouse Leydig cell supernatants and blood sera were increased. In the sleep deprivation study, mice fed GBE showed increased testosterone production and survival under such stressful conditions. GBE increased mRNA and protein levels of steroidogenesis-related enzymes STAR, CYP11A1, and CYP17A1. These key enzymes induced the increased production of testosterone both in vivo and in vitro. Thus, GBE might be a promising therapeutic or additive nutritional agent for improving men's health by increasing steroidogenesis or improving LOH.

Effect of Zn addition and natural aging on the microstructure and mechanical properties of secondary AlSi7Cu2 alloys

The effect of different Zn contents on the microstructure of a secondary AlSi7Cu2 alloy has been studied. The mechanical properties of the alloy during natural aging has been investigated too. The Zn additions range from 0.7 to 8 wt.%, and the tensile testing has been carried out at the as-cast condition and after 3, 7, 12 and 21 days of natural aging. Metallographic and image analysis techniques have been used to characterize the microstructural changes of the alloy. The results indicate that the alloy is strengthened as a function of the aging time and Zn addition. Both yield stress and elongation to fracture tend to stabilize over long aging times, independently of Zn level. The steady-state tensile properties are achieved earlier by increasing the Zn content. Furthermore, high Zn contents promote the formation of eutectic structure and the precipitation of needle-like Fe-rich compounds, which decrease the ductility of the material.

Influence of natural aging on the chemical composition of hemp mortars

In recent years, bio-based building materials have become increasingly popular in the field of low-carbon construction. Different bio-based solutions are being adopted because of their advantageous hygrothermal properties and low economic and environmental costs. One such bio-based solution is hemp mortar, which is used in France and other countries for various construction purposes, such as thermal or acoustic insulation for interior and exterior walls. However, the use of hemp mortars is hampered by insufficient data on their durability and risk of degradation due to natural environmental conditions. Indeed, hemp mortar is hygroscopic, heterogeneous and anisotropic, which makes it difficult to study its behaviour. Therefore, the main objective of this work is to investigate the effect of natural aging on the chemical composition of hemp mortar exposed outside in specially designed metal cage for two years. Experimentally, XRD and thermogravimetric analyses of hemp mortar samples were performed. All experimental results were compared with the results of reference samples treated under laboratory conditions. The effects of two different compositions and sample depths were also investigated. In general, the results showed a higher degree of degradation of the mineral matrix of hemp mortar during natural aging due to carbonation and hygrothermal stresses.

Color change against the natural aging effect of water-based protective layers on some etched wood materials

Ahşap yapıların ve yapı malzemelerinin dayanıklılığı ve hizmet süresi, yapı kalitesi ve ekonomisinde en önemli konulardan biridir ve yapılarda ahşap yapı elemanlarının rutubet almasını engelleyen iyi bir tasarım, yapıya uzun bir hizmet ömrü sağlayacaktır. Fakat bazı yapılarda ve kullanım yerlerinde alınacak tasarım önlemleri dahi ahşabın hizmet ömrünü etkilememekte ve bu malzeme, rutubet kaynaklı mantar çürümelerine ve böcek ataklarına, yanmaya maruz kalabilmektedir. Çalışmada sodyum bikarbonat (NaHCO3) ile aşındırma işlemi (1, 2 ve 3 Atü) gerçekleştirilerek (püskürtme işlemiyle) yüzey ondüleli hale getirilmiş ve akabinde ASTM D 1413-007 (2007) standardına göre çeşitli çözelti konsantrasyonlarında (% 5, 7 ve 9) emprenye işlemine tabi tutulmuştur. En yüksek retensiyon değeri ladin odununda % 7 konsantrasyon ve 3 ATÜ’de (% 32,46), en düşük retensiyon meşe odununda % 9 konsantrasyon ve 1 ATÜ’de (% 5,22) belirlenmiştir. Ahşap malzemenin ikincil bir işlemle korunmasına yönelik su bazlı boya/vernik sistemleriyle üst yüzey işlemleri yapılmıştır. 12 aylık periyotla doğal yaşlandırma yapılarak, ahşabın dış hava etkilerine maruz kaldığı şartlar altında renk değişim değerlerinden (L*) ışıklılık değer değişimi belirlenmiştir. L* ışıklılık değeri odun türüne göre en yüksek kestane odununda (44,34), aşındırma etkisine göre en yüksek L* kontrol örneğinde, emprenye faktörüne göre L* değeri % 9 sodyum bikarbonatta (43,59), vernik/boya faktörüne göre L* en yüksek su bazlı vernikte (54,25) olarak gerçekleşirken 0,05 önem düzeyinde tüm faktörler anlamlı bulunmuştur.

Synergetic effect of natural ageing and pre-stretching on the ageing behavior in Tʹ/ηʹ phase-strengthened Al-Zn-Mg-Cu alloys

Al-Zn-Mg-Cu alloys with different major strengthening precipitates are subjected to a novel combinatorial pre-treatment, including natural ageing and pre-stretching. The evolution of hardness and microstructure during the combinatorial pre-treatment and subsequent artificial ageing has been investigated. The results reveal that the growth rate of hardness in alloy B (Zn/Mg = 10.0) is much higher than that of alloy A (Zn/Mg = 1.5) due to the fast precipitation kinetics of η′ phase compared with T′ phase. Both GP I zones and dislocations introduced by the combinatorial pre-treatment can act as heterogeneous nucleation sites for precipitation, resulting in more precipitates and higher hardness than pre-stretched alloys A and B. Dislocations distribute uniformly in combinatorial pre-treated alloys owing to the existence of GP I zones and dislocations, which promote the precipitation and refine the precipitate size. Moreover, these alloys with distinct pre-stretching (2%–10%) show similar precipitation behavior and peak hardness, and it indicates that the dislocation-induced precipitation will not be affected by the density of dislocations when plenty of GP I zones pre-exist.

Hardness increases due to (Fe, Cr)2C carbide precipitated during natural aging in high chromium cast iron

The effect of natural aging on the microstructure of carbides and martensite in high chromium cast iron subjected to a destabilizing heat treatment was investigated by correlative experimental and theoretical methods. It was observed for the first time that fine η-(Fe, Cr)2C carbides precipitated from the martensite matrix in water-quenched high chromium cast iron during natural room temperature aging, which led to a remarkable hardness increase (by 3.4 HRC). On one hand, the obvious hardness increase was attributed to the fine precipitation of M2C carbides which was observed by transmission electron microscopy. On the other hand, it is also caused by high Cr content in the η-(Fe, Cr)2C carbides, which was confirmed by first-principles calculations.

Molecular models of multiple sclerosis severity identify heterogeneity of pathogenic mechanisms

While autopsy studies identify many abnormalities in the central nervous system (CNS) of subjects dying with neurological diseases, without their quantification in living subjects across the lifespan, pathogenic processes cannot be differentiated from epiphenomena. Using machine learning (ML), we searched for likely pathogenic mechanisms of multiple sclerosis (MS). We aggregated cerebrospinal fluid (CSF) biomarkers from 1305 proteins, measured blindly in the training dataset of untreated MS patients (N = 129), into models that predict past and future speed of disability accumulation across all MS phenotypes. Healthy volunteers (N = 24) data differentiated natural aging and sex effects from MS-related mechanisms. Resulting models, validated (Rho 0.40-0.51, p < 0.0001) in an independent longitudinal cohort (N = 98), uncovered intra-individual molecular heterogeneity. While candidate pathogenic processes must be validated in successful clinical trials, measuring them in living people will enable screening drugs for desired pharmacodynamic effects. This will facilitate drug development making, it hopefully more efficient and successful.

Impact of Natural Degradation on the Aged Lignocellulose Fibers of Moroccan Cedar Softwood: Structural Elucidation by Infrared Spectroscopy (ATR-FTIR) and X-ray Diffraction (XRD)

The aims of this study are to investigate the structure of four historical Moroccan cedar softwood samples of different aging time duration (16th, 17th, 19th, 21st centuries) and compare among these four samples, using two analytical methods, FTIR and XRD, in order to confirm some structural changes and determine the degree of deterioration. The pronounced hemicellulose deterioration was highlighted by a breakdown of IR acetyl groups at 1738 cm−1 from the 19th century sample until aged ones. The cellulose XRD crystallinity index showed an important decrease from recent to oldest samples (51.8 to 20.2%) justifying the damages mainly in the two oldest samples (17th and 16th centuries), also confirmed by FTIR. The alteration of lignin was manifested in the case of the two ancient samples (16th and 17th centuries), proven by the decrease in IR bands related to aromatic nuclei (1595, 1500, 1230 cm−1) evolving towards a new diconjugate C=O formers at 1647 cm−1 (quinone, Ar-CO-Ar, Ar-CO-C=C). For accurate elucidation, the data of two combined techniques were compared and correlated. The obtained results depended on the part of the wood exposed to weathering effects (internal or external) and were influenced by both extended time of aging and effects of natural deterioration agents. The effects of natural aging were investigated in four historical Moroccan cedar softwood samples (16th, 17th, 19th, 21st centuries) using two analytical tools: FTIR and XRD. The pronounced hemicellulose deterioration was highlighted by a breakdown of IR acetyl groups at 1738 cm−1 and declines in the absorption signal at 1268 cm−1 from the 19th century sample until aged ones. The cellulose XRD crystallinity index (CrI) estimation showed an important decrease from recent to oldest samples (51.8 to 20.2%) justifying the damages mainly in the two oldest samples (17th and 16th centuries). These data were also confirmed by FTIR showing a significant reduction in both area profiles of C-O-C (1150–1000 cm−1) and C-H crystalline cellulosic bands (1375, 1318, and 1268 cm−1), respectively. The lignin alteration in both old samples (16th and 17th centuries) was proven by the decrease in IR aromatic skeleton (1595, 1500, and 1230 cm−1) evolving towards a new diconjugate C=O formers at 1647 cm−1 (quinone, Ar-CO-Ar, Ar-CO-C=C). To determine the structural difference and the degree of deterioration, the IR area of C=O band intensities ranging from 1550 to 1800 cm−1 was exploited. For accurate elucidation, the data of two combined techniques were compared and correlated. The obtained results depended on the part of the wood (internal or external) exposed to weathering effects and were influenced by both extended time of aging and effects of natural deterioration agents.

Effect of Natural and Artificial Aging on Steel Mechanical Properties and Fracture Toughness

Effect of Natural and Artificial Aging on Steel Mechanical Properties and Fracture Toughness

Assess the effect of natural ageing and storage containers on seed quality of tomato seeds

The present study entitled "Seed quality assessment in the naturally aged seed of tomato was conducted during rabi 2020-2021 and 2021-2022 at the Department of Seed Science and Technology, CCS Haryana Agricultural University, Hisar. The freshly stored seed was observed to be highest in seed quality parameters i.e., germination per cent, seedling length, seedling dry weight and seed vigour indices as compared to when seeds were stored in different containers during 18 months storage period. As the storage period increase, the seed quality parameter goes on decreasing. Among the containers, 18-month seeds stored in a polythene bag (&gt; 700 gauge) recorded significantly higher seed germination (60.67%), seedling length (8.77cm), seedling dry weight (11.42 mg), vigour index -I (532) and seed vigour index-II (793) as compared to a cloth bag. Standard germination percentage was maintained up to 15 months of storage in a polythene bag. In both containers, polythene bags performed better than cloth bags throughout the storage period.