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1
Sá da Costa, M., Fabienne Farcas, L. F. Santos, M. I. Eusébio, and António Correia Diogo. "Chemical and Thermal Characterization of Road Bitumen Ageing." Materials Science Forum 636-637 (January 2010): 273–79. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.273.
Повний текст джерелаАнотація:
Bitumen ageing stands for a number of physico-chemical modifications that occur in bitumen as a response to environmental conditions. Several tests have been proposed to simulate bitumen ageing. Two of the most common ones are: a) the Rolling Thin Film Oven Test (RTFOT), which simulates short term ageing; b) the Pressure Ageing Vessel (PAV) test, which accounts for long-term ageing and it is usually performed on the RTFOT residue. A study of the physico-chemical modifications of a 50/70 pavement grade bitumen caused by ageing is presented. Both RTFOT and PAV tests were used. A follow-up of bitumen modifications due to ageing was done by several methods. In particular: 1) Fourier transform infrared spectroscopy (FTIR), to follow bitumen oxidation by the increase of oxygenated functional groups, which were quantified by taking appropriate structural indices; 2) Iatroscan thin layer chromatography (TLC), to follow bitumen composition expressed by the generic SARA fractions (saturates, aromatics, resins and asphaltenes); 3) Gel permeation chromatography (GPC), under “ultra-fast” conditions, to follow the colloidal structure of bitumen; and 4) Differential scanning calorimetry (DSC), to evaluate the changes of the crystallized fractions (%FC) and the glass relaxation temperature (Tg). The results show that the PAV test causes more severe changes in bitumen than the RTFOT test. In particular, the evolution of the oxidation processes could be quantified by taking carbonyl and sulfoxide structural indices. Ageing also modified the SARA profile, namely, the relative contribution of aromatics, resins and asphaltenes fractions. On the other hand, DSC data remained almost unaffected after ageing tests, which may be indicative of the survival of most of the phases of the bitumen after these tests. Finally, a comparative analysis of the sensitivity and performance of all these methods is presented.
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Moustafa, Ghareeb. "Ageing of Aluminum Power Connectors Based on Current Cycle Test." European Journal of Engineering Research and Science 4, no. 1 (January 28, 2019): 110–14. http://dx.doi.org/10.24018/ejers.2019.4.1.1103.
Повний текст джерелаАнотація:
The effect of current cycle on the behavior of contact resistance of clamped connectors was investigated experimentally to characterize the thermal behavior of the used clamped connector and optimizing the installation procedure in order to reduce contact resistance and ensure a lower temperature during normal operating conditions. The thermal network method is used for calculating the temperature rise of the connector when loaded by a current. The method is based on substitution of the connector geometry by a circuit consisting of thermal resistances, capacitance and heat sources. The temperature rise is determined using the network simulation program PSPICE with the corresponding thermal model libraries. The validity of the obtained results has been checked by comparing the computed values with those measured experimentally. The agreement was found satisfactory
3
Moustafa, Ghareeb. "Ageing of Aluminum Power Connectors Based on Current Cycle Test." European Journal of Engineering and Technology Research 4, no. 1 (January 28, 2019): 110–14. http://dx.doi.org/10.24018/ejeng.2019.4.1.1103.
Повний текст джерелаАнотація:
The effect of current cycle on the behavior of contact resistance of clamped connectors was investigated experimentally to characterize the thermal behavior of the used clamped connector and optimizing the installation procedure in order to reduce contact resistance and ensure a lower temperature during normal operating conditions. The thermal network method is used for calculating the temperature rise of the connector when loaded by a current. The method is based on substitution of the connector geometry by a circuit consisting of thermal resistances, capacitance and heat sources. The temperature rise is determined using the network simulation program PSPICE with the corresponding thermal model libraries. The validity of the obtained results has been checked by comparing the computed values with those measured experimentally. The agreement was found satisfactory
4
Choi, Hyun-Jung, Hosang Ahn, Gyeong-Seok Choi, Jae-Sik Kang, and Jung-Ho Huh. "Analysis of Long-Term Change in the Thermal Resistance of Extruded Insulation Materials through Accelerated Tests." Applied Sciences 11, no. 19 (October 8, 2021): 9354. http://dx.doi.org/10.3390/app11199354.
Повний текст джерелаАнотація:
Two experiments were executed to examine the slice accelerated test method, suggested in ISO 11561 “Ageing of thermal insulation materials—Determination of the long-term change in thermal resistance of closed-cell plastics (accelerated laboratory test methods)” and to observe the changes in the thermal performance of insulation material over time by the real-time ageing process. The accelerated test method was conducted for 120 consecutive days using 10 mm thick-sliced specimens, which were sampled from a 50 mm thick plate body. The real-time ageing process was performed for 5000 consecutive days under constant temperature and relative humidity conditions as of 20 ± 5 °C and 50 ± 5% without any slicing. Degradation of thermal performance was shown to be stabilized at around 38 to 41% down from the initial values, which were correspondent with the approximately 10 days after the initial time. The real-time ageing process revealed similar degradation levels at around 130 days after the starting point. Converting the results using the scaling method specified in ISO 11561, the change was found in the range of 37 to 41% for the thermal resistance after 25 years and of 30 to 38% for the 25-year-average thermal resistance, respectively. Within the 10% error range, both the accelerated method and real-time ageing resulted in a similar level of degradation. Consequently, it was our observation that the slice accelerated test was quite enough to predict the practical degradation of insulation materials with at least 90% of accuracy under the specified time duration, temperature and thickness satisfactions.
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Roro, Kittessa T., Bonex Mwakikunga, Ngcali Tile, Brian Yalisi, and Andrew Forbes. "Effect of Accelerated Thermal Ageing on the Selective Solar Thermal Harvesting Properties of Multiwall Carbon Nanotube/Nickel Oxide Nanocomposite Coatings." International Journal of Photoenergy 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/678394.
Повний текст джерелаАнотація:
Varying amounts of dispersed multiwalled carbon nanotubes in NiO have been used to develop composites that absorb the solar energy very well but lose very little through emission. Determination of absorptance,αsol, and emissivity,εther, from such selective solar absorbers shows that the optimum efficiency of 71% can be attained when about 10 mg of MWCNTs are composited with NiO. One such absorber was subjected to thermal ageing tests. The performance criterion (PC) limit for passing the test when simulated for 25 years is(−Δα+0.25Δε)≤0.05. It was found that the typical absorber had a PC value of −0.01. This value is much better than the passing limit. Raman spectra of the typical absorber before and after the thermal ageing test showed a reduced intensity in the D and G bands of disordered and graphitic carbon, respectively but an enhancement of the NiO bands indicating loss of carbon atoms due to thermal ageing tests. Simple equations are derived determining the proportion of carbon atoms that are lost and the proportion of carbon atoms that remains in the absorber; both of these are in agreement with the original carbon composition before the thermal ageing test. It is reported that the typical absorber will retain 63% of the carbon after 25 years.
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Zhang, Hui, Tao Yu, Jian Feng Sheng, and Qiong Yu. "Thermal Class Evaluation of Glass Net Used for Transformer." Advanced Materials Research 893 (February 2014): 75–79. http://dx.doi.org/10.4028/www.scientific.net/amr.893.75.
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Zaghdoudi, Kömmling, Jaunich, and Wolff. "Scission, Cross-Linking, and Physical Relaxation during Thermal Degradation of Elastomers." Polymers 11, no. 8 (July 31, 2019): 1280. http://dx.doi.org/10.3390/polym11081280.
Повний текст джерелаАнотація:
Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined.
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Boxhammer, Jörg. "Shorter test times for thermal- and radiation-induced ageing of polymer materials." Polymer Testing 20, no. 7 (2001): 719–24. http://dx.doi.org/10.1016/s0142-9418(01)00029-0.
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Wang, Yongqiang, Changhui Feng, Ruoyu Fei, and Yu Luo. "Thermal-ageing characteristics of dry-type transformer epoxy composite insulation." High Performance Polymers 32, no. 7 (February 26, 2020): 741–52. http://dx.doi.org/10.1177/0954008320906439.
Повний текст джерелаАнотація:
To study the ageing characteristics of epoxy resin composite insulation in dry-type transformers in high-temperature environments, glass fibre-reinforced epoxy resin samples were placed in a hot air ageing environment at 130°C for testing. Dielectric properties, partial discharge (PD), microscopic morphology, three-dimensional morphology and Fourier transform infrared spectroscopy of aged samples were periodically tested. The results show that during the ageing process, the change in the surface morphology of the sample leads to an overall upward trend in surface roughness, and the older the sample, the faster the surface roughness increases; changes in the surface morphology and three-dimensional morphology of the material constitute the basis for judging the condition of the insulating surface and the state of ageing development. Microcracks are the direct cause of debonding of glass fibres and epoxy matrix. Degradation of the sample during the ageing process generates many free radicals, which enhances the polarisation ability of the sample and increases both the dielectric constant and the dielectric loss factor. The real part of the complex dielectric constant is more sensitive to the ageing response of the sample. The older the sample, the greater the effect on the results of the dielectric spectrum test. Since the aged sample generates more hot electrons during the PD process and makes it easier to inject electrons into the material, the PD of the sample is rendered more intense by thermal ageing. There is a significant difference between the degradation mechanism of the thermal ageing and PD. The samples subjected to PD after thermal ageing produce new groups, and the degradation of the samples is more severe than that caused by thermal ageing, or PD, alone.
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Pellecuer, Guillaume, Jean-Jacques Huselstein, Thierry Martiré, François Forest, André Chrysochoos, and Mourad Jebli. "IGBT Wirebonds Ageing: A New Test Bench Development for Dedicated Modules Assemblies." European Journal of Electrical Engineering 24, no. 4 (August 31, 2022): 161–69. http://dx.doi.org/10.18280/ejee.240401.
Повний текст джерелаАнотація:
Wirebonds ageing in power modules used in electric vehicles is a main concern for the development of reliable inverters. The development of a specific test bench to study the evolution of their properties over time has allowed conclusions to be drawn on the possibility of accelerating or not accelerating ageing tests without distorting the mechanisms actually involved in ageing. Through the use of specifically developed test bench in terms of electrical and thermal properties the studied wirebonds samples are more easily thermally controllable, equipped with measuring devices and the energy consumption at a given cycle is divided by ten compared to a classical bench. The entire process of designing and producing the specific samples and the associated test bench and a description of the first results obtained to demonstrate the relevance of the approach is given.
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Guzmán, Manuel Alberto, Diego Hernán Giraldo-Vásquez, and Ricardo Moreno. "The Effect of Thermal Ageing on the Mechanical Properties of Natural Rubber-based Compounds Used for Rubber Bearings." Journal of Engineering and Technological Sciences 53, no. 3 (July 12, 2021): 210310. http://dx.doi.org/10.5614/j.eng.technol.sci.2021.53.3.10.
Повний текст джерелаАнотація:
Molecular changes due to high temperatures, sunlight, and oxygen, deteriorate the physical properties of rubber compounds, yielding additional crosslinks and molecular chain breakdown. Since oxidative degradation is the most important factor that determines the durability of rubber components, this study evaluated the mechanical behavior of rubber compounds exposed to accelerated thermal ageing. Therefore, three carbon black-reinforced natural rubber-based compounds typically used for rubber bearings were exposed to thermal oxidation and their mechanical properties under typical loading states were assessed through standardized tests. Significant differences were found due to thermal ageing in the compressive modulus, compression set, and creep compliance in compression, exhibiting a stiffening effect caused by additional crosslinks. However, no significant differences were observed in hardness, which is a superficial measurement and a typical test in the rubber industry to characterize rubber compounds. Therefore, the assessment of ageing in rubber bearings should not be limited to a hardness test, which is required in design standards but also addresses compressive, cyclic, and transient tests. The results obtained in this study can be considered in the design process of rubber bearings by limiting the allowable compressive stress and creep deflection due to ageing effects.
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Cheng, Yongchun, Jinglin Tao, Yubo Jiao, Qinglin Guo, and Chao Li. "Influence of Diatomite and Mineral Powder on Thermal Oxidative Ageing Properties of Asphalt." Advances in Materials Science and Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/947834.
Повний текст джерелаАнотація:
Ageing of asphalt affects the performances of asphalt pavement significantly. Therefore, effects of diatomite and mineral powder on ageing properties of asphalt were investigated systematically in order to improve the antiageing property of mixture. Thin film oven test (TFOT) was used to conduct the short term ageing in laboratory. Softening points, penetrations, force ductility, low temperature creep properties, and viscosities of asphalt mastics were tested before and after TFOT, respectively. Results indicated that percent retained penetration (PRP) increased with the increasing of fillers. Increment of softening point (ΔT), ductility retention rate (DRR), deformation energy ageing index (JAI), and viscosity ageing index (VAI) of asphalt mastics nonlinearly decreased with the increasing of fillers. Ageing of asphalt was reduced by diatomite and mineral powder. And the antiageing effect of diatomite was better than that of mineral powder as a result of its porous structure. It is suggested that the mineral powder could be reasonably replaced by diatomite in order to reduce thermal oxidative ageing of asphalt mixture. The optimal content of diatomite 12.8% is also suggested for engineering.
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Ke, Zhang, Du Miao, Hao Lei, Meng Jianping, Wang Jining, Liu Xiaopeng, Deng Zhejun, Min Jie, and Zhao Bo. "Thermal stability test and ageing mechanisms study of different solar selective absorbing coatings." Surface and Coatings Technology 323 (August 2017): 65–71. http://dx.doi.org/10.1016/j.surfcoat.2016.08.092.
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Ranga, C., A. Kumar, and R. Chandel. "Influence of electrical and thermal ageing on the mineral insulating oil performance for power transformer applications." Insight - Non-Destructive Testing and Condition Monitoring 62, no. 4 (April 1, 2020): 222–31. http://dx.doi.org/10.1784/insi.2020.62.4.222.
Повний текст джерелаАнотація:
In the present work, a new electrothermal combined stress test cell has been designed and fabricated to conduct accelerated electrothermal ageing. The fabricated test cell includes all possible real working conditions of the transformers. The effects of accelerated electrothermal ageing on the performance of power transformers with thermally upgraded Kraft (TUK), Nomex-910 and Nomex-410 solid dielectrics in conjunction with mineral oil have been investigated. The accelerated electrothermal ageing has been performed for a temperature range of 100°C to 220°C, along with 10 kV electrical stress. Subsequently, several electrical, thermal, mechanical and chemical properties of transformer oil and different paper dielectrics have been determined. It has been observed from the diagnostic test results that Nomex impregnated mineral oil samples have better electrothermal performance as well as oxidation stability when compared to the thermally upgraded Kraft oil samples. Therefore, Nomex insulating materials in conjunction with mineral oil are suggested as alternative solid dielectrics for power transformers in order to achieve better oxidation stability, improved thermal performance for long service runs and reduced operating and maintenance costs. It is envisioned that the present experimental study will be very beneficial to utility managers and end-users of power transformers.
15
Shukla, Sourabh, Awanikumar P. Patil, and Ankur Bansod. "Effect of thermal aging on IGC of cold worked Cr-Mn austenitic stainless steel." Anti-Corrosion Methods and Materials 66, no. 6 (November 4, 2019): 757–67. http://dx.doi.org/10.1108/acmm-01-2019-2053.
Повний текст джерелаАнотація:
Purpose The purpose of this study is to investigate the effect of prior cold work after annealing and thermal ageing on intergranular corrosion or sensitization of Cr-Mn austenitic stainless steel (ASS) is necessary. Such a study is particularly important because ASS are mostly used and welded in mill-annealed condition, which is equivalent to fully annealed material with some cold worked (CW). Design/methodology/approach The effect of 15% CW of 202 ASS were investigated using microstructural (optical microscope), mechanical (grain size and hardness) and electrochemical methods (double loop electrochemical reactivation [DLEPR]) followed by thermal ageing (800°C, 900°C and 1000°C). Findings X-ray diffraction analysis shows the presence of martensite in CW samples. The increase in martensite formation (800°C and 900°C) can be observed with the variation of thermal ageing (TA) duration (1, 2 and 3 h). However, there was decreased in the formation of martensite at the temperature of 1000°C because of martensitic reversal. The DLEPR test result shows higher degree of sensitization (DOS) for 800°C and 900°C but for 1000°C, there was re-homogenization of samples which leads to lower DOS (thermal ageing for 1, 2 and 3 h). Originality/value For 300 series steel, there are various literature available for the effect of cold work on mechanical properties and DOS. However, no one has investigated the effect of cold work and thermal ageing on the sensitization of 202 Cr-Mn ASS.
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Bartsch, Marion, Bernd Baufeld, S. Dalkilic, Iulian Mircea, K. Lambrinou, T. Leist, J. Yan, and Anette M. Karlsson. "Time-Economic Lifetime Assessment for High Performance Thermal Barrier Coating Systems." Key Engineering Materials 333 (March 2007): 147–54. http://dx.doi.org/10.4028/www.scientific.net/kem.333.147.
Повний текст джерелаАнотація:
Strategies for time-economic lifetime assessment of thermal barrier coatings (TBC) in service are described and discussed on the basis of experimental results, achieved on material systems with coatings applied by electron beam physical vapour deposition. Service cycles for gas turbine blades have been simulated on specimens in thermo-mechanical fatigue tests, accelerating the fatigue processes by an increase of load frequency. Time dependent changes in the material system were imposed by a separate ageing, where the samples were pre-oxidized prior to the fatigue test. Results of thermo-mechanical fatigue tests on pre-aged and as-coated specimens gave evidence of interaction between fatigue and ageing processes. An alternative approach is used, which is focused on the evolution of a failure relevant damage parameter in the TBC system. The interfacial fracture toughness was selected as a damage parameter, since one important failure mode of TBCs is the spallation near the interface between the metal and the ceramic. Fracture mechanical experiments based on indentation methods have been evaluated for monitoring the evolution of the interfacial fracture toughness as a function of ageing time. It was found that the test results were influenced by both changes of the interface (which is critical in service) and changes in the surrounding material.
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Ayadi, M., O. Briat, R. Lallemand, A. Eddahech, R. German, G. Coquery, and J. M. Vinassa. "Description of supercapacitor performance degradation rate during thermal cycling under constant voltage ageing test." Microelectronics Reliability 54, no. 9-10 (September 2014): 1944–48. http://dx.doi.org/10.1016/j.microrel.2014.07.150.
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Stergiopoulos, Thomas, Athanassios G. Kontos, Nancy Jiang, Damion Milliken, Hans Desilvestro, Vlassis Likodimos, and Polycarpos Falaras. "High boiling point solvent-based dye solar cells pass a harsh thermal ageing test." Solar Energy Materials and Solar Cells 144 (January 2016): 457–66. http://dx.doi.org/10.1016/j.solmat.2015.09.052.
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Qi, Siyuan, Chris Powley, Maria Mirgkizoudi, Adele Pliscott, and Peter Collier. "Evaluation of High Temperature Joining Technologies for Semiconductor Die Attach." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2017, HiTEN (July 1, 2017): 000177–92. http://dx.doi.org/10.4071/2380-4491.2017.hiten.177.
Повний текст джерелаАнотація:
Abstract The development of novel high temperature die attach methods for semiconductor packaging enables use in harsh environments and unique opportunities for demanding industrial applications such as controls and monitoring for next generation engine and airframe platforms. Traditional die attach materials including lead solders and conductive adhesives cannot meet requirements of operation temperatures up to and exceeding 300°C due to their limited melting and glass transition temperatures [1]. The Manufacturing Technology Centre Ltd (MTC) has evaluated a range of high temperature die attach materials and processes for silicon and silicon carbide (SiC) semiconductors. Assembly processes were explored for bonding components with and without a back metallisation and with capability to support electrical back contact if required. Die attach methods evaluated include:Sinterable silver materials for back metallised semiconductor componentsSilver glass for non-back metallised semiconductor componentsGold-silicon near eutectic preforms for non-back metallised semiconductor components Two types of substrates were selected including high temperature co-fired ceramic (HTCC) packages and gold or silver plated Kovar substrates. Test assemblies were subjected to accelerated life tests consisting of thermal ageing at 400°C and thermal cycling of −40°C to 200°C. These tests enabled the evaluation of the die attach materials after accelerated conditions of use. Reliability performance of the die attach materials was assessed using visual and X-ray inspection, mechanical shear testing and microstructure analysis. For sinterable silver materials, the test assemblies constructed using HTCC packages showed no significant reduction in shear strength after 1,008 hours ageing at 400°C. However shear strengths of the test assemblies constructed using Kovar substrates reduced by 95% of the initial values after ageing at 400°C for 336 hours. All test assemblies showed no significant reduction in adhesion after thermal cycling of −40°C to 200°C for 1,000 cycles. In addition, no apparent differences in shear strengths could be detected for sintered silver interconnections for gold and silver metallised semiconductor components. Gold-silicon bonding as performed using a near eutectic preform had limited performance as aged at 400°C. Silver glass test assemblies constructed using HTCC packages showed a 50% reduction in shear strength compared to the initial values after thermal ageing at 400°C for 1,000 hours. A similar reduction in adhesion was presented after thermal cycling of −40°C to 200°C for 1,000 cycles.
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Fu, Li Jun, Wei Fang Zhang, Shuang Wang, Zong Ren Wang, and Qing Yun Tang. "Research on Analytical Procedure of Failure Mechanism Consistency in Rubber Material Accelerated Ageing Test." Applied Mechanics and Materials 184-185 (June 2012): 653–56. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.653.
Повний текст джерелаАнотація:
This paper summarizes the advantages and disadvantages of existing analytical methods of failure mechanism consistency in the accelerated aging test at first. And then according to the characteristics of the rubber material, a kind of rubber failure mechanism consistency analytical method based on failure physics is offered by analyzing the thermal analysis curves.
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Piumatti, Davide, Stefano Borlo, Matteo Quitadamo, Matteo Sonza Reorda, Eric Giacomo Armando, and Franco Fiori. "Test Solution for Heatsinks in Power Electronics Applications." Electronics 9, no. 6 (June 19, 2020): 1020. http://dx.doi.org/10.3390/electronics9061020.
Повний текст джерелаАнотація:
Power electronics technology is widely used in several areas, such as in the railways, automotive, electric vehicles, and renewable energy sectors. Some of these applications are safety critical, e.g., in the automotive domain. The heat produced by power devices must be efficiently dissipated to allow them to work within their operational thermal limits. Moreover, numerous ageing effects are due to thermal stress, which causes mechanical issues. Therefore, the reliability of a circuit depends on its dissipation system, even if it consists of a simple passive heatsink mounted on the power device. During the Printed Circuit Board (PCB) production, an incorrect assembly of the heatsink can cause a worse heat dissipation with a significant increase of the junction temperatures (Tj). In this paper, three possible test strategies are compared for testing the correct assembling of heatsinks. The considered strategies are used at the PCB end-manufacturing. The effectiveness of the different test methods considered is assessed on a case study corresponding to a Power Supply Unit (PSU).
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Boscoletto, A. Boscolo, and B. Cellarosi. "Effect of Structural Anisotropy on Thermal Ageing in Rigid PU Foams." Journal of Thermal Insulation 15, no. 4 (April 1992): 294–310. http://dx.doi.org/10.1177/174425919201500403.
Повний текст джерелаАнотація:
The use of blowing agents as an alternative to conventional chloro-fluorocarbons (CFCs) and the quality of foaming process can lead to non-homogeneity of the foam structure with the presence of defects along the panel thickness. These defects appear as holes in cell windows or cavities. Accurate measurements of thermal conductivity were made on test specimens having different thicknesses obtained by cutting away the external faces of the panels. This type of characterization of foams blown with alternative blowing agents allowed us to understand their ageing behaviour (natural and accelerated) and the problems related to the scaling factor. Moreover this study pointed out how the effective diffusion coefficients of gases involved in the ageing process can have different values along the thickness of a sample. All these observations were related with morphological analyses. Our studies showed that sampling procedure and model design are very important for a correct analysis of ageing phenomena. Good agreement between experimental and theoretical data was found, allowing us to verify the validity of the method used to characterize non-homogeneous foams.
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Drohsler, Petra, Jaroslav Cisar, Tomas Sopik, Vladimir Sedlarik, and Martina Pummerova. "Effect of an Antioxidant Based on Red Beetroot Extract on the Abiotic Stability of Polylactide and Polycaprolactone." Molecules 26, no. 17 (August 27, 2021): 5190. http://dx.doi.org/10.3390/molecules26175190.
Повний текст джерелаАнотація:
This study investigated the effect of natural antioxidants inherent to beetroot (Beta vulgaris var. Vulgaris) on the ageing of environmentally friendly plastics. Certain properties were examined in this context, comprising thermal, mechanical, and morphological properties. A visual evaluation of relevant changes in the given polymers (polylactide and polycaprolactone) was conducted during an ageing test in a UV chamber (45 °C, 70% humidity) for 720 h. The films were prepared by a casting process, in which samples with the extract of beetroot were additionally incorporated in a common filler (bentonite), this serving as a carrier for the extract. The results showed the effect of the incorporated antioxidant, which was added to stabilize the biodegradable films. Its efficiency during the ageing test in the polymers tended to exceed or be comparable to that of the reference sample.
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Bazan, Patrycja, Dariusz Mierzwiński, Rafał Bogucki, and Stanisław Kuciel. "Bio-Based Polyethylene Composites with Natural Fiber: Mechanical, Thermal, and Ageing Properties." Materials 13, no. 11 (June 6, 2020): 2595. http://dx.doi.org/10.3390/ma13112595.
Повний текст джерелаАнотація:
The study evaluated the possibility of using natural fibers as a reinforcement of bio-polyethylene. Flax, coconut, basalt fiber, and wood flour were used in the work. Strength tests like static tensile test, three-point flexural test, or impact strength showed a positive effect of reinforcing bio-polyethylene-based composites. The effect of water and thermal ageing on the mechanical behavior of composites was assessed. In order to analyze the structure, SEM microscope images were taken and the effect of natural fibers on the change in the nature of cracking of composites was presented. Composites with natural fibers at a content of 12% by weight, resulting in increase of strength and rigidity of materials. The greatest strengthening effect for natural fibers was obtained for the composite with basalt fibers.
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Asphaug, Silje Kathrin, Berit Time, and Tore Kvande. "Moisture Accumulation in Building Façades Exposed to Accelerated Artificial Climatic Ageing—A Complementary Analysis to NT Build 495." Buildings 11, no. 12 (November 23, 2021): 568. http://dx.doi.org/10.3390/buildings11120568.
Повний текст джерелаАнотація:
Building façades must endure severe climatic exposure throughout their lifetimes. To prevent damage and expensive repairs, ageing tests are used in durability assessments. The NT Build 495 describes an artificial ageing procedure to address building material and component resistance to ultraviolet (UV) light, heat, water, and frost using a climate simulator. The test has been used for decades to investigate exterior surface materials and façade products but has only recently been adopted for multi-layered systems. This study investigates moisture accumulation in a façade system for retrofitting based on concrete and thermal insulation. Hygrothermal simulations of the façade system subjected to ageing were conducted. Moisture accumulation was considered theoretically for the current test procedure and compared to a modified setup in which the interior climate was controlled at 21 °C. Physical measurements were performed in the climate simulator to determine the boundary conditions. Results showed that moisture accumulation in the thermal insulation was largely affected by the type of concrete, that applying a water-repellent surface treatment reduced moisture accumulation, and that the current setup resulted in less moisture accumulation compared to the modified setup. The latter implicates accelerated degradation with the modified setup.
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Cao, Miao, Hailou Wang, Bohong Gu, and Baozhong Sun. "Impact damage and compression behaviours of three-dimensional angle-interlock woven composites after thermo-oxidation degradation." Journal of Composite Materials 52, no. 15 (November 7, 2017): 2085–101. http://dx.doi.org/10.1177/0021998317740199.
Повний текст джерелаАнотація:
This paper reports impact and compression behaviours of three-dimensional angle interlock woven composites after the thermal ageing degradation in both experimental and finite element analyses. The composite coupons have been aged in atmospheric environment for 4, 8, 16 and 32 days at 180℃. Barely visible impact damage was induced by low velocity impact test and the residual strength was evaluated by following compression test. The results show a substantial decline in compression after impact properties after thermal ageing. After aging at 180℃ for 32 days, the compression after impact stress and modulus retention rates of three-dimensional woven composites are 59% and 82.2%, respectively. Such degradation is attributed to interface damage and matrix degradation. The fracture morphologies observed by microscopy revealed that the failure of the original specimen was dominated by matrix crack, while for long time aged specimens interface degradation became main damage mechanism. The numerical study was used to unveil the influence of matrix crack and interface degradation on failure developments of composites. The results indicate a variation from a brittle failure mode to a progressive failure model after long time ageing.
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Balasubramanian, K. R., S. P. Sivapirakasham, and Jiss Mathew. "Analysis of Chemical Degradative Effects on Low Voltage PVC Insulation Using DSC." Applied Mechanics and Materials 592-594 (July 2014): 2475–80. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.2475.
Повний текст джерелаАнотація:
PVC insulation has extensively been used for insulating low voltage electrical cables. They offer superior insulating properties but how ageing and exposure could affect their insulation properties is a matter of concern. Chemical exposure related failure modes are known but have received only limited study. The traditional testing methods like insulation testing could only test whether the present properties are satisfactory. The application of thermal analysis methods like differential scanning calorimetry could identify the variation in thermal characteristics with respect to ageing and chemical exposure. Polluted environments may cause a direct attack upon a polymer. It has been concluded that significant changes in the behavior of insulation occurs in acidic environment that may lead to insulation failures.
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Chen, Ge, and Jia Lu Li. "Accelerated Test Design of Thermal-Oxidative Aging of Nylon 66 Airbag Material." Advanced Materials Research 332-334 (September 2011): 1202–5. http://dx.doi.org/10.4028/www.scientific.net/amr.332-334.1202.
Повний текст джерелаАнотація:
Accelerated thermal-oxidative aging tests on Nylon 66 automotive airbag material are designed and performed in this paper. After the environmental profile of airbag was analyzed, Nylon 66 airbag yarns were reasonably selected as the test samples, and its tensile strength was chosen as the significant character of their aging stability. By heat aging、humidity aging、cycle ageing and comprehensive process aging experiments, 350dtex Nylon 66 filament were sampled and the tensile strength loss of samples was measured, to determine the mechanisms and factors that influence aging stability of the Nylon 66 airbag materials. The experiment results show that Nylon 66 has excellent aging stability, and that water molecules can accelerate its degradation. The experiment data can be used to predict the airbag lifetime in a benign store environment, and as references in selecting airbag materials.
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Mazo, M. Alejandra, Isabel Padilla, Aurora López-Delgado, Aitana Tamayo, and Juan Rubio. "Silicon Oxycarbide and Silicon Oxycarbonitride Materials under Concentrated Solar Radiation." Materials 14, no. 4 (February 21, 2021): 1013. http://dx.doi.org/10.3390/ma14041013.
Повний текст джерелаАнотація:
The potential application of silicon oxycarbonitride (SiOCN), silicon oxycarbide (SiOC) and silicon oxycarbide–SiC (SiOC–SiC) for photothermal devices such as volumetric solar absorbers has been studied evaluating the response to thermal shock from a Fresnel lens. The accelerated ageing test comprises fast heating (32 °C min−1) and cooling rates (27 °C min−1) from 100 to 1000 °C and dwelling times of 10 min. Porous materials (SiOCNp and SiOCp) failed the thermal shock tests; they were massively degraded by the formation of a large depression in the focus of solar radiation. Dense materials (SiOCd and SiOC–SiCd) withstood 100 cycles of thermal shock ageing tests due to the formation of a protective silica layer. The absorptance values for dense materials remained fairly constant before and after thermal shock tests: from 94.5 to 94.3% for SiOCd and from 93.3 to 93.3% for SiOC–SiCd. These preliminary studies indicate their potential for high-temperature solar receiver applications.
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Pang, Yuan-Jin, Wen-Shuai Xu, Ben-Tengzi Yang, Hai-Ying Ni, and Jun Chen. "Influence of early thermal-oxidative ageing on the structure and properties of polyoxymethylene copolymer." Royal Society Open Science 8, no. 6 (June 2021): 210034. http://dx.doi.org/10.1098/rsos.210034.
Повний текст джерелаАнотація:
Thermal-oxidative ageing of polyoxymethylene (POM) copolymer in the oven at 100°C for 1, 2, 3, 5, 7, 10, 14 and 21 days and the influence of early thermal-oxidative ageing on POM structure and properties were studied by means of wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry and tensile test. Based on the results, we found that the early thermal-oxidative ageing of POM copolymer can be divided into three regions. The region I is the initial 3 days. In this region, some molecular chains rearranged, resulting in internal stress relaxation, increase of crystallinity degree and grain size due to the perfection of crystal structure; both extended chain crystal (ECC) and folded chain crystal (FCC) increased and ECC grew faster than FCC. The region II is from 3 days to 10 days, and in this region, chain scission took place in amorphous region and led to chemi-crystallization. The region III is after 10 days. In this region, the structure and performance of POM copolymer reached a stable situation at this stage. In this work, the difference between skin and core were also analysed.
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Lin, Zhen, Li Fen Cao, Miao Miao Liu, Jun Xie, Dao Yan Feng, Zhi Qin Peng, and Zhi Wen Hu. "Physical and Chemical Changes of Wool Fabrics after Artificial Ageing." Key Engineering Materials 671 (November 2015): 59–64. http://dx.doi.org/10.4028/www.scientific.net/kem.671.59.
Повний текст джерелаАнотація:
The exposure of wool fabrics to light, humidity and heat are inevitable, which will accelerate their ageing, as time goes on. The exact influences of these factors were not being parallel compared and studied previously, but are very important for preparing suitable storage or display environment for wool fabrics, especially for those excavated old wools in history. Hereby, wool fabrics were treated by heat ageing, hydrothermal ageing, UV ageing and UV & ozone ageing to figure out the effects of light, humidity and heat on their physical and chemical changes resulted in the degradation of wool. The performances of the wool fabrics with different treatments were investigated by thermogravimetric analysis (TGA), angle contact test, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD), etc. It has been found that thermal ageing resulted in the maximum yellowness of the wool fabrics. Hydrothermal ageing was most functional in decreasing the breaking strength and crystallinity of the wool fabrics. UV lighting induced significant hydrophilicity increase on the surfaces of the wools. The addition of ozone on UV lighting did not facilitate the further ageing of wool fabrics much.
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Celauro, Clara, Rosalia Teresi, and Nadka Tz Dintcheva. "Effect of Short-Term and UV Irradiation Aging on the Behaviour of SBS-Modified Bitumen." Sustainability 14, no. 11 (June 6, 2022): 6915. http://dx.doi.org/10.3390/su14116915.
Повний текст джерелаАнотація:
To obtain road bitumen with improved temperature and fatigue resistance, polymers and/or rubbers could be added to it. A particularly suitable polymer for bitumen modification is styrene-butadiene-styrene (SBS) copolymer but limited information is available about the ageing behaviour of modified binders. In this work, two neat bitumens, with different penetration grades, and two SBS-modified bitumens, containing different SBS amounts, were selected, and their short-term and UVB ageing behaviour were investigated considering dynamic shear rheometry and Attenuated Total Reflectance-Fourier Transformation InfraRed spectroscopy (ATR-FTIR). Short-time ageing behaviour was investigated performing the rolling thin film oven test (RTFOT), while artificial UV ageing was examined/investigated using UVB lamps. The structural changes in bitumen were monitored at different UV exposure times. All the results suggest that the bitumen having higher penetration grade is more stable than the one with a lower penetration grade in the RTFOT ageing condition, and SBS addition exerts a beneficial effect on thermal stability during processing. Further, SBS addition also has a beneficial effect on the UV ageing resistance of bitumen, reducing its oxidation tendency.
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Renaud, Alexis, Victor Pommier, Jérémy Garnier, Simon Frappart, Laure Florimond, Marion Koch, Anne-Marie Grolleau, Céline Puente-Lelièvre, and Touzain Sebastien. "Aggressiveness of Different Ageing Conditions for Three Thick Marine Epoxy Systems." Corrosion and Materials Degradation 2, no. 4 (December 3, 2021): 721–42. http://dx.doi.org/10.3390/cmd2040039.
Повний текст джерелаАнотація:
Three different coated steel systems were aged in natural or artificial seawater, in neutral salt spray (NSS), and using alternate immersion tests in order to evaluate the aggressiveness of the different ageing conditions. Commercial epoxy coatings were applied onto steel (S355NL), hot-galvanized steel (HDG), and Zn-Al15 thermal spraying coated steel. The defect-free systems were immersed in artificial seawater at 35 °C for 1085 days and in natural seawater for 1200 days and were characterized by electrochemical impedance spectroscopy (EIS). Panels with artificial defects were immersed for 180 days in artificial seawater and, regarding adhesion, were evaluated according to ISO 16276-2. In parallel, the three coated systems were submitted to cyclic neutral salt spray (NSS) for 1440 h: defect-free panels were regularly evaluated by EIS, while the degree or corrosion was measured onto panels with artificial defect. After NSS, defect-free panels were immersed in artificial seawater at 35 °C for further EIS investigations. Finally, alternate immersion tests were performed for 860 days for the three defect-free coated systems and for 84 days for panels with a defect. The results showed that, for defect-free panels, immersions in natural or artificial seawater and NSS did not allowed us to distinguish the three different systems that show excellent anticorrosion properties. However, during the alternate immersion test, the organic coating system applied onto HDG presented blisters, showing a greater sensitivity to this test than the two other systems. For panels with a defect, NSS allowed to age the coatings more rapidly than monotone conditions, and the coating system applied onto steel presented the highest degree of corrosion. Meanwhile, the coating systems applied onto HDG and the thermal spray metallic coating showed similar behavior. During the alternate immersion test, the three coated systems with a defect showed clearly different behaviors, therefore it was possible to rank the three systems. Finally, it appeared that the alternate immersion test was the most aggressive condition. It was then proposed that a realistic thermal cycling and an artificial defect are needed when performing ageing tests of thick marine organic coating systems in order to properly rank/evaluate the different systems.
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Zhang, Zou, Jia, Wang, Li, and Shi. "Effect of Thermo-Oxidative Ageing on Nano-Morphology of Bitumen." Applied Sciences 9, no. 15 (July 26, 2019): 3027. http://dx.doi.org/10.3390/app9153027.
Повний текст джерелаАнотація:
In recent years, the research on bitumen has reached the nanometer level, but there are still some problems in the study of the relationship between the atomic force microscope (AFM) nano-morphology and ageing of bitumen. The purpose of this paper is to find out the effect of thermal oxygen ageing on the nano-morphology of bitumen. Atomic force microscope (AFM) test sample of bitumen was prepared in this paper. Area ratio of bee-like structure, roughness, and maximum amplitude were selected as the nano-morphological parameters of the bitumen. The calculation method of nano-parameters was also proposed. Bitumen with different ageing degrees was prepared by thin film oven test (TFOT). Nano-morphological parameters of bitumen with different ageing degrees were obtained by AFM and analyzed with NanoScope Analysis, and the relationships between nano-morphological parameters and bitumen technical indexes after ageing, such as penetration, ductility, softening point, and viscosity were analyzed. The test results show that the wave crests and wave troughs of the bee-like structure on the surface of the bitumen alternate, while the other areas are relatively flat. The bee-like structure continues to develop as the ageing time prolongs, and the number of bee-like structures decreases, but the volume and the undulation degree increase. With the ageing time prolonging, the nano-parameters of bitumen, such as the area ratio of bee-like structure, roughness, and maximum amplitude, show a trend of increasing gradually, but the increasing rates become smaller and smaller. During the ageing process of bitumen, with the increase of nano-morphological parameters (area ratio of bee-like structure, roughness, and maximum amplitude), penetration at 25 °C and ductility at 15 °C of the bitumen decrease, and softening point and viscosity at 60 °C increase. AFM testing technology and image analysis method in this paper can be used for a reference in the nano-scale study of bitumen.
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Zhumadilova, Zhanar O., Vladimir P. Selyaev, Ruslan E. Nurlybayev, Yelzhan S. Orynbekov, Indira B. Sangulova, and Erzhan I. Kuldeyev. "Prediction of Durability of Thermal Insulating Epoxy Coatings with Regard to Climatic Ageing." Polymers 14, no. 9 (April 19, 2022): 1650. http://dx.doi.org/10.3390/polym14091650.
Повний текст джерелаАнотація:
It is generally accepted that the color and performance characteristics of liquid thermal insulation coatings are affected by the combined effect of various climatic factors such as solar radiation, temperature fluctuations, moisture, precipitation and others. This work presents the results of a scientific study of the full-scale exposure of coatings with regard to climatic ageing. Methods have been carried out, such as: spectrophotometry and direct scanning; determining adhesion, determining the adhesion strength of facing and protective coatings; and thermal conductivity and thermal resistance. As the results of the research work have shown, only in situ climatic tests, accompanied by the obligatory recording of the aggressive factors affecting the coating, make it possible to assess changes in the properties of epoxy coatings in full-scale conditions and, consequently, their climatic resistance by the methods of spectrophotometry and direct scanning. The ageing of polymer composites is known to be accompanied by a change not only in elasticity but also in color. Of the epoxy coatings tested, Etal-45M showed the greatest color variation during the in situ climate test. The most decorative resistant coatings are obtained using epoxy resin ED-20 + modified epoxy resin Etal-1440N.
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Sekunowo, O. I., G. I. Lawal, and S. O. Adeosun. "Mechanical Response of Al-1.09Mg2Si Alloy under Varying Mould and Thermal Ageing Conditions." Journal of Metallurgy 2012 (December 11, 2012): 1–7. http://dx.doi.org/10.1155/2012/921235.
Повний текст джерелаАнотація:
Samples of the 6063 (Al-1.09Mg2Si) alloy ingot were melted in a crucible furnace and cast in metal and sand moulds, respectively. Standard tensile, hardness, and microstructural test specimens were prepared from cast samples, solution treated at 520∘C, soaked for 6 hrs, and immediately quenched at ambient temperature in a trough containing water to assume a supersaturated structure. The quenched specimens were then thermally aged at 175∘C for 3–7 hrs. Results show that at different ageing time, varied fractions of precipitates and intermetallics evolved in the specimens’ matrices which affect the resulting mechanical properties. The metal mould specimens aged for four hours (MTA-4) exhibited superior ultimate tensile strength of 247.8 MPa; microhardness, 68.5 HV; elongation, 28.2% . It is concluded that the extent of improvement in mechanical properties depends on the fractions, coherence, and distribution of precipitates along with the type of intermetallics developed in the alloy during ageing process.
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Mokhtar, Noor Zaimah Mohd, Mohd Arif Anuar Mohd Salleh, Andrei Victor Sandu, Muhammad Mahyiddin Ramli, Jitrin Chaiprapa, Petrica Vizureanu, and Mohd Izrul Izwan Ramli. "Effect of Electromigration and Thermal Ageing on the Tin Whiskers’ Formation in Thin Sn–0.7Cu–0.05Ga Lead (Pb)-Free Solder Joints." Coatings 11, no. 8 (August 4, 2021): 935. http://dx.doi.org/10.3390/coatings11080935.
Повний текст джерелаАнотація:
The investigation on tin (Sn) whiskers formation has been widely applied in the field of lead-free electronic packaging. This is due to the fact that use of the Sn–Pb finishes has converted to Pb-free finishes in the electronic industry. Sn whiskers can grow long enough to cause a short circuit, which affects electronic devices’ reliability. This study investigates Sn whiskers’ formation in the thin Sn–0.7Cu–0.05Ga Pb-free solder under the influence of electromigration and thermal ageing for surface finish applications. The samples were stored in ambient conditions for 1000 h before being exposed to electromigration and thermal ageing to study the corresponding whiskers’ growth. A scanning electron microscope (SEM) was used to study the Sn whiskers’ microstructure, while an optical microscope (OM) was utilized to investigate the IMC layers in the samples. The results show that the addition of 0.05 wt.% gallium (Ga) decreased the Sn whisker’s length and growth density while simultaneously refining the IMC layers. Synchrotron micro-XRF (µ-XRF) shows the existence and distribution of Ga addition in both electromigration and thermal ageing samples. The shear test was used to determine the solder alloys’ mechanical properties. As a result, the addition of Ga to the Sn–0.7Cu solder improved the fracture morphology of solder joints. In conclusion, Ga’s addition resulted in decreasing Sn whisker formation and refining of the IMCs while also increasing the shear strength of the Sn–0.7Cu solder by ~14%.
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Sokolar, Radomir, and Martin Nguyen. "The Effect of Class C Fly Ash on the Plasticity and Ageing of Ceramic Mixtures Based on Kaolin." Materials 14, no. 11 (May 23, 2021): 2761. http://dx.doi.org/10.3390/ma14112761.
Повний текст джерелаАнотація:
The main aim of the presented article is to describe the behavior of class C fly ash—kaolin plastic doughs during the ageing process. Class C fly ash (CCFA) from the fluidized technology of fuel combustion in a thermal power plant was used as a non-plastic admixture to modify the plasticity in a kaolin–quartz sand mixture (for example, the base of a porcelain mixture). The ageing of plastic ceramic dough determined the effect of the CCFA admixture (0–10–20 wt. %) on the initial water content, plasticity (according to the Pfefferkorn test) and bulk density of a dried green body. The main feature of the CCFA admixture in the kaolin–quartz sand mixture is a solidifying effect. Fly ash increases the initial (mixing) water for the preparation of ceramic dough with constant plasticity (30 mm height of deformed cone Hf, according to the Pfefferkorn test), and Hf increases as the dough ages (the dough solidifies faster and loses its plasticity) with the addition of class C fly ash. The effect of CCFA addition on the plasticity and ageing of kaolin–quartz sand dough is documented on Bigot curves: higher content of fly ash decreases the drying shrinkage of the plastic dough, especially when drying samples that have been aged for 24 h in a plastic wrap (without the possibility of drying). The plastic dough’s ageing increases the porosity of the dried green body with increased content of CCFA in the raw materials mixture and increased ageing time.
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Radeef, H. R., N. A. Hassan, A. R. Z. Abidin, M. Z. H. Mahmud, C. R. Ismail, H. F. Abbas, Z. H. Al-Saffar, and S. Redha. "Impact of Ageing and Moisture Damage on the Fracture Properties of Plastic Waste Modified Asphalt." IOP Conference Series: Earth and Environmental Science 971, no. 1 (January 1, 2022): 012009. http://dx.doi.org/10.1088/1755-1315/971/1/012009.
Повний текст джерелаАнотація:
Abstract The utilisation of plastic waste as a modifier in asphalt mixtures has inflicted significant impacts on the cracking resistance of the produced mixtures. Whilst many studies have evaluated the cracking resistance of asphalt mixtures incorporating plastic waste using wet method, limited studies have used the dry method are available. The current study aims to evaluate the effect of plastic waste incorporation on the fracture properties of conventional asphalt mixture. In addition, the impact of ageing and moisture damage on the fracture properties of modified asphalt was also investigated. Indirect tensile strength test was carried out to assess the CT-index, tensile strength, and fracture energy of the asphalt mixtures before and after exposure to ageing and moisture conditioning. The finding revealed that the asphalt mixture incorporating plastic waste demonstrated superior resistance to thermal and fatigue cracking compared to the control mixture, thus proving the capability of plastic waste in increasing the resistance of asphalt against ageing and moisture damage.
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Pan, Pan, Yi Kuang, Xiaodi Hu, and Xiao Zhang. "A Comprehensive Evaluation of Rejuvenator on Mechanical Properties, Durability, and Dynamic Characteristics of Artificially Aged Asphalt Mixture." Materials 11, no. 9 (August 29, 2018): 1554. http://dx.doi.org/10.3390/ma11091554.
Повний текст джерелаАнотація:
In this study, the aged asphalt binder and mixture were laboratory prepared through short-term ageing testing and long-term ageing testing. Firstly, the effect of rejuvenator on physical properties of aged asphalt binders was investigated. In addition, a series of laboratory tests were performed to evaluate the influence of ageing and rejuvenator content on the mechanical properties, durability and dynamic characteristics of asphalt mixtures. Physical test results of asphalt binder testified that rejuvenator used can efficiently recover the aged asphalt binder. However, the effect of ageing and rejuvenator content exhibits different trends depending on the physical property tests conducted. Moreover, artificially aged asphalt mixture with rejuvenator has better ability to resist moisture damage and ravelling. In addition, the ITSR value is more suitable to evaluate the moisture susceptibility for asphalt recycling. Although rejuvenator improves the thermal cracking resistance and fatigue property of aged asphalt mixture, rejuvenated mixture shows greater modulus and inferior ability to resist reflective cracking than the unaged mixture. Moreover, rejuvenated mixture shows less dependence on frequency at high temperature regions and stronger dependence at low temperature regions compared to unaged and long-term aged mixtures.
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Oliveira, Fernando A. Costa. "Damage Assessment of Mullite Ceramic Foams in Radiant Gas Burners." Materials Science Forum 587-588 (June 2008): 99–103. http://dx.doi.org/10.4028/www.scientific.net/msf.587-588.99.
Повний текст джерелаАнотація:
The damage imposed on open-cell mullite ceramic foams was evaluated in pre-mixed radiant gas burners. After exposure to the prevailing combustion environment, foams suffered moderate strength degradation as a result of thermal stresses being imposed on the material during service. There was evidence of chemical attack during combustion although thermal shock measurements suggest that damage sustained by the foams results mainly from thermal shock rather than chemical degradation. Indeed, samples from burners subjected to ageing tests did not show additional damage compared to those subjected to short ageing tests indicating that most of damage occurred during start-up. For comparison purposes, a set of ceramic foam samples were subjected to a water quench test so that the extent to which the foams were damage by exposure to the combustion environment, under well controlled conditions, could be established. The strength retained after thermal shock by open-cell mullite foams decreased gradually with increasing quench temperatures. This suggests a cumulative damage mechanism reflecting an increase in damage throughout the material rather than sudden failure owing to propagation of pre-existing cracks along a plane. Damage in mullite foams was mainly localised at the top layer of the burners where higher temperatures and steeper thermal gradients were imposed on the material. Surprisingly, needle-like mullite crystals with a large aspect ratio were also found to have grown at the surface of the burners via a vapour feed gas-liquid catalyst-solid needle-like growth (VLS) mechanism.
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Barretta, Chiara, Gernot Oreski, Sonja Feldbacher, Katharina Resch-Fauster, and Roberto Pantani. "Comparison of Degradation Behavior of Newly Developed Encapsulation Materials for Photovoltaic Applications under Different Artificial Ageing Tests." Polymers 13, no. 2 (January 15, 2021): 271. http://dx.doi.org/10.3390/polym13020271.
Повний текст джерелаАнотація:
The main focus of this work is to investigate the degradation behavior of two newly developed encapsulants for photovoltaic applications (thermoplastic polyolefin (TPO) and polyolefin elastomer (POE)), compared to the most widely used Ethylene Vinyl Acetate (EVA) upon exposure to two different artificial ageing tests (with and without ultraviolet (UV) irradiation). Additive composition, optical and thermal properties and chemical structure (investigated by means of Thermal Desorption Gas Chromatography coupled to Mass Spectrometry, UV-Visible-Near Infrared spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis and Fourier Transform-Infrared spectroscopy, respectively) of the analyzed polymers were monitored throughout the exposure to artificial ageing tests. Relevant signs of photo-oxidation were detectable for TPO after the UV test, as well as a depletion of material’s stabilizers. Signs of degradation for EVA and POE were detected when the UV dose applied was equal to 200 kW h m−2. A novel approach is presented to derive information of oxidation induction time/dose from thermogravimetric measurements that correlate well with results obtained by using oxidation indices.
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Berardone, Irene, and Marco Paggi. "Nondestructive monitoring of damage caused by accelerated ageing in photovoltaic modules." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 23-24 (November 28, 2019): 7565–72. http://dx.doi.org/10.1177/0954406219889382.
Повний текст джерелаАнотація:
Accelerated ageing tests of photovoltaic laminates are requested by the IEC standards for quality control, which require the assessment of the electrical power losses after a prescribed amount of temperature and/or humidity cycles inside a climatic chamber (thermal cycling, humidity freeze, and damp heat tests). Since electric damage is measured only at the end of such tests, its kinetics induced by thermo-elastic stresses and the related degradation phenomena are reported in few cases. The aim of this study is to investigate the progress of damage, reporting the results of an unprecedented experimental campaign on a photovoltaic mini-module composed of nine multi-crystalline silicon solar cells, one of them containing a cracked cell, subject to a revised thermal cycling test including moisture. Every 40 cycles, and up to 460 (corresponding to 1840 h of testing), the progress of electric damage is assessed by monitoring the evolution of the overall electric resistance of the module. Moreover, electroluminescence images are taken with the same time interval, to assess local damage phenomena responsible for electric power-losses. Cracks are found to significantly accelerate the progress of damage as compared to what happens in intact solar cells, inducing progressive gridline failure and the spread of electrically inactive zones.
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Passilly, Bruno, and Romain Delannoy. "Characterization of the ageing of an epoxy resin using high temperature nanoindentation." Matériaux & Techniques 107, no. 2 (2019): 206. http://dx.doi.org/10.1051/mattech/2019004.
Повний текст джерелаАнотація:
This article aims to understand better the mechanical properties and behavior of organic matrix composite materials under elevated temperature conditions. Two specific specimens of cured RTM6 epoxy resin are tested with DMA analysis: one being unaged and the other one aged for 5000 h at 130 °C under ambient air. Anti-plasticization effects seem to occur on aged resin. Series of nano-indentation tests are carried out from the surface to the core of the sample so as to measure gradient properties of the resin, at temperatures up to 150 °C using a high temperature indentation machine prototype. Thermo-oxidation phenomena involve oxidized layer formation during thermal ageing of the epoxy resin which is characterized through measurements of indentation Young’s modulus. After aged treatment, the variation of Young’s modulus of the oxidized layer at the surface of the sample is not clearly affected by the increasing test temperature whereas Young’s modulus of the core of the sample is decreasing significantly with the temperature test as on unaged epoxy resin. Thus, asymptotic growing of the oxidized layer is then confirmed.
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Kong, Byeong Seo, Jiho Shin, Gokul Obulan Subramanian, Junjie Chen, Changheui Jang, Ye-eun Na, Dongchan Jang, Ho Jung Lee та Jun-Seog Yang. "Evaluation of thermal ageing activation energy of δ-ferrite in an austenitic stainless steel weld using nanopillar compression test". Scripta Materialia 186 (вересень 2020): 236–41. http://dx.doi.org/10.1016/j.scriptamat.2020.05.046.
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Shih, Tsai-Chin, Che-Tong Lin, Sheng-Yang Lee, Wei-Jen Chang, Nai-Chia Teng, Keng-Liang Ou, and How Tseng. "EFFECT OF STEREOCOMPLEX FORMATION IN D-LACTIDE-CONTAINING PLLA ON THERMAL BEHAVIORS AND MECHANICAL PROPERTY CHANGES USING THE AGEING DEGRADATION TEST." Biomedical Engineering: Applications, Basis and Communications 25, no. 05 (October 2013): 1340003. http://dx.doi.org/10.4015/s1016237213400036.
Повний текст джерелаАнотація:
Introduction: The formation of a stereocomplex between PLLA and PDLA has been studied intensively because it increases the mechanical performance and thermal/hydrolytic resistance of polylactide-based materials; however, few studies have investigated the stereocomplex formation between PLLA and the (D-lactide)-containing PLLA copolymer. To investigate the effect of the D-lactide content of PLLA on the thermal behaviors and mechanical properties, (5D/95L) polylactide [(5D/95L)PLA], which contains a molar ratio of 5% of the D-form and 95% of the L-form of the monomer, and (15D/85L) polylactide [(15D/85L)PLA], which contains a molar ratio of 15% of the D-form and 85% of the L-form of the monomer, were used in a series of specimens. For the hydrolytic degradation test, the specimens were placed in 20-mL vials, which were filled with phosphate-buffered solution; the vials were allowed to stand at 57°C for 91 days in accordance with the ASTM F1635-95 (2000) standard test method for in vitro studies. The mechanical properties, thermal properties and crystallization behaviors were investigated using DSC and MTS, respectively. Results: The initial bending strength of the (5D/95L)PLA and (15D/85L)PLA were 35.4 and 31.1 N, respectively. After 1 week, the binding strength of the (5D/95L)PLA increased by 9.8%, and the binding strength of the (15D/85L)PLA decreased by 26%. In addition, the DSC curve of the (5D/95L)PLA demonstrated a higher melting temperature in the 1st week, and this Tc was observed in the DSC curve of the (5D/95L)PLA only during this time. The DSC curve of the (15D/85L)PLA was irregular. Discussion & Conclusions: In the (5D/95L)PLA, the recrystallization that occurred during the hydrolysis process was confirmed by the Tc and the increase in the bending strength. The stereocomplex crystallites may be formed in the (15D/85L)PLA during the degradation process. Because of the increase in the D-form monomer, the stereocomplexes were generated more easily and acted as nucleation sites. The PLLA crystal near the stereocomplex crystallites exhibited an incomplete structure, which led to a faster decrease in the bending strength. The low D-lactide content in the matrix of the PLLA did not form a stereocomplex crystallite because the surface area was not large enough to act as a nucleation site. However, the higher D-lactide-containing fraction formed a large stereocomplex crystallite. The (5D/95L)PLA demonstrated better thermal/hydrolytic resistance and mechanical stability than the (15D/85L)PLA.
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De Smet, David, Madeleine Wéry, Willem Uyttendaele, and Myriam Vanneste. "Bio-Based Waterborne PU for Durable Textile Coatings." Polymers 13, no. 23 (December 2, 2021): 4229. http://dx.doi.org/10.3390/polym13234229.
Повний текст джерелаАнотація:
Polyurethane (PU) coatings are often applied on high added value technical textiles. Key factor to success of PU coatings is its versatility and durability. Up to today most PU textile coatings are solvent-based or water-based. Recent advances are made in applying bio-based PU on textiles. Currently, polymers made from renewable raw materials are experiencing a renaissance, owing to the trend to reduce CO2 emissions, the switch to CO2-neutral renewable products and the depletion of fossil resources. However, the application of bio-based coatings on textiles is limited. The present paper discusses the potential of a bio-based anionic PU dispersion as an environment friendly alternative for petroleum-based PU in textile coating. Coatings were applied on textile via knife over roll. The chemical, thermal and mechanical properties of the bio-based PU coating were characterised via FT-IR, thermogravimetric analysis, differential scanning calorimetry and tensile test. The performance of the coating was studied by evaluating antimicrobial properties, fire retardancy, the resistance to hydrostatic pressure initially and after washing, QUV ageing and hydrolysis test. The developed bio-based PUD coating complied to the fire retardancy test ISO 15025 and exhibited excellent hydrostatic pressure, QUV ageing resistance, hydrolysis resistance, wash fastness at 40 °C.
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Talhi, Fatima Zohra, Mohamed Tahar Benaniba, Naima Belhaneche-Bensemra, and Valérie Massardier. "Comparison of material properties in butt welds of used and unused polyethylene pipes for natural gas distribution." Journal of Polymer Engineering 37, no. 3 (March 1, 2017): 279–85. http://dx.doi.org/10.1515/polyeng-2016-0015.
Повний текст джерелаАнотація:
Abstract The main purpose of this work was to evaluate the long term performance of butt welded polyethylene (PE) pipes in comparison to non-welded counterparts. Therefore, old welded PE pipes with different ages that had been used in Algerian gas distribution systems for up to 30 years were investigated. Samples prepared by butt welding of unaged pipes were used as reference. Crystallinity, melt rheology and thermal stability of pipes materials were examined at the weld zone and at the pipe wall. In order to assess the mechanical strength of welds, tensile test was conducted on both welded and unwelded specimens and the results of the strain to failure were considered for the determination of the weld factor. Compared to the reference, the results revealed that the crystallinity of PE materials at the weld zone was not affected by ageing as at the pipe wall. However, a slight decrease of the melt viscosity was observed for both welded and non-welded samples. The welds were found to be more sensitive to thermal and oxidative degradation than the parent pipes while the remaining amount of antioxidants was sufficient for service continuation. The tensile results indicate that welds strength were almost unaffected by ageing.
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Cruz González, Celso Eduardo, Mauricio Torres Arellano, Saúl Ledesma Ledesma, and Perla Itzel Alcántara Llanas. "Thermomechanical evaluation of a glass-epoxy composite for astronomical optical devices." Materials Testing 64, no. 9 (September 1, 2022): 1313–24. http://dx.doi.org/10.1515/mt-2022-0005.
Повний текст джерелаАнотація:
Abstract Astronomical devices, such as optical benches, carry high precision instrumentation work at low temperatures (−150 °C). To fulfill engineering requirements, glass-epoxy composite trusses are proposed. To evaluate the performance of this solution, thermomechanical characterization is carried out by means of dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), flammability tests, and tensile test and Scanning Electron Microscopy (SEM) observations. Two family of coupons are tested; first one environmentally aged for 10 years and second one recently fabricated, both at 20, 0 and −20 °C. Ageing influence is more noticeable on thermal behavior as Tg and self-extinguish capacity are lower. Ultimate tensile strength and maximum strain are lower for the aged coupons (16–25%), but there is not a remarkable difference in terms of stiffness. Also, coupons mechanically tested at −20 °C show a slight increment in strength. These results show that ageing of glass-epoxy composites must be considered when high performance devices are conceived to be fabricated with.
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Lopes, Carla MV, Luís Silva, Pedro Sequeira, and Francisco Q. de Melo. "Assessing the thermal degradation of bonded joints in flat ceramic tiles of building facades by numerical and experimental dynamic analysis." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 234, no. 8 (June 2, 2020): 1129–41. http://dx.doi.org/10.1177/1464420720928569.
Повний текст джерелаАнотація:
Flat ceramic tiles are widely used as protective and aesthetic construction elements in urban building facades. Under the effect of extreme temperatures from the weather seasonality, bonded joints of these tiles undergo thermal cycle’s loads. In this work, a dynamic technique based on vibration metrology is implemented. This procedure consists in the analysis of accelerograms obtained in bonded ceramic tiles from low-intensity impact loads. A corresponding study carried out with finite element modelling allowed an accurate calibration of mechanical parameters of the tile/adhesive pair as well as the estimation of a vibration dissipation factor. Several test specimens subjected to a defined period of thermal cycles stressing were also analysed for the mentioned accelerogram and an expression for the ageing estimation of the mechanical properties of the bonded joints in the tiles was obtained.