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High Voltage Cables
Published in N. H. Malik, A. A. Al-Arainy, M. I. Qureshi, Electrical Insulation in Power Systems, 2018
N. H. Malik, A. A. Al-Arainy, M. I. Qureshi
Cables are usually subjected to electrical, thermal, mechanical, radiation, environmental and chemical stress aging simultaneously. With one aging stress at a time, the lifetime results are quite different from those obtained when several aging parameters are applied simultaneously. Therefore, considerable research effort is being exerted in understanding multifactor stress aging [39]. However, so far, no general quantitative model capable of predicting the aging behavior and life expectancy under multifactor stress aging of insulation exists. At present most of the accelerated aging studies concentrate on simultaneous voltage, temperature and environmental (water and chemicals) effects. Figure 9.14 shows a voltage-life curve for XLPE and PE cables with accelerated aging tests along with cables removed from service [40]. This figure shows that due to water treeing, the life of a cable is shortened considerably. However, without treeing, the cable’s life points lie on the characteristic aging curve of the respective material as given by equation (9.10).
More about the New Thermal Transfer Adhesives
Published in Ralph D. Hermansen, Polymeric Thermosetting Compounds, 2017
Tom Sutherland conducted a study of how the two new thermal transfer adhesives would fare in space over a spacecraft’s lifetime. Tom actually ran this project, while my role was one of advising and assisting him. Our study was done through a technique called accelerated aging, that is, using testing of samples at elevated temperatures to simulate longer times at lower temperatures. Design engineering wanted the answers as soon as possible, not after dozens of spacecraft were in orbit with potential unknown problems caused by unforeseen problems with a new adhesive.
Making big things happen
Published in James P Trevelyan, Learning Engineering Practice, 2021
One option is to incorporate what is known as accelerated ageing into the test specification. An artefact intended for outdoor application in a coastal environment could be subjected to alternating high and low temperatures, high and low humidity, intense ultraviolet radiation, salt spray, and vibration, perhaps simultaneously. The degradation that might take a decade or more in the actual location might be reproduced with 2 months of testing by using accelerated ageing.
Research on the Aging Effects of Adhesive and Composites on the Degradation Mechanism of Composite Adhesive Joints in Thermal-Humidity-Cycles for Automobiles
Published in The Journal of Adhesion, 2023
Guofeng Qin, Yunli Zhang, Peiwen Mi, Yongjian Zhu, Ming Li, Jingxin Na
Due to the lack of regularity of weather variations in the natural environment and long research period, the accelerated aging method of increasing temperature or humidity is generally used. The common accelerated aging environments are humid environments, high-temperature environments and hygrothermal environments.[6] Galvez et al.[7] analyzed the suitability of carbon fiber/steel adhesive joints in 60°C and 99% RH and found that temperature had a greater influence in the initial phase. Meanwhile, moisture was mainly absorbed in the form of bound water and caused expansion and plasticization. In addition, the degradation process of adhesive joints was accelerated because the moisture penetrated through the adhesive-substrate interface. Zhang et al.[8] studied the performance variations of adhesive joints of two commonly used adhesives of SY14 M and SY24C in the water conditions at room and high temperature. Results show that the hydrolysis reaction accelerated the moisture absorption and reduced the plasticity, especially for tough adhesives at high temperature. Tan et al.[9] studied the degradation of aluminum alloy adhesive joints using a modified Arcan device in the condition of high temperature with different humidity levels and there was a sharp decline by about 40% in the failure strengths. Therefore, Existing studies have shown that the aging process of bonded joints can be significantly accelerated by increasing the temperature or humidity to a relatively large degree, thus helping to reveal the degradation mechanism of bonded joints.
Destructive and non-destructive evaluation of reinforced concrete dry casks affected by alkali-silica reactivity damage
Published in Structure and Infrastructure Engineering, 2019
Mohammad Hanifehzadeh, Majid Ebad Sichani, Bora Gencturk, Jamie E. Padgett
The aging process usually occurs very slowly and simulating the potential 60-year life span of the cask is not possible in the laboratory without accelerated methods. In the accelerated aging procedure, it is assumed that the material properties are altered by the same physical and chemical processes as would be observed in the normal service life of the structure but over a much shorter period of time. One of the well-known methods of accelerating the ASR process frequently used is adding alkali hydroxide to the mixing water of concrete and keeping the specimens in controlled high humidity and temperature conditions. An alternative method is the outdoor storage of the specimens in variable temperature and moisture conditions (Diamond & Ong, 1994; Gao, Multon, Cyr, & Sellier, 2013; Smaoui et al., 2004). This method is more convenient for large-scale specimens as is the case in this study. Considering the methods available in the literature, to achieve a high rate of degradation in a short period of time, 0.8% NaOH by weight of cement was added to the concrete mixing water to increase the alkalinity of the concrete pore solution.
Bond behavior degradation between FRP and masonry under aggressive environmental conditions
Published in Mechanics of Advanced Materials and Structures, 2018
Rafael Ramirez, Hamid Maljaee, Bahman Ghiassi, Paulo B. Lourenço, Daniel V. Oliveira
Experimental investigations on durability and long-term performance of materials are usually studied through real exposure or accelerated ageing tests. Accelerated ageing involves exposure of representative specimens to aggressive environments, that is, an experimental setting with more severe conditions than the ones expected during the usual service life of the structure. It must be noted that the severity of the conditions is therefore dependent on the type of structure and material. Within the scope of this work, aggressive environmental conditioning makes reference to the accelerated ageing of the specimens in the context of moisture and hygrothermal exposure, which are known to cause premature degradation and decay in FRP-masonry elements. Real exposure tests require longer time to produce meaningful results but provide a full understanding of the actual degradation phenomena. In comparison, accelerated ageing tests are performed over a shorter time span, but special care should be taken for interpretation of the obtained results, as the degradation mechanisms may change with respect to real conditions. In this case, the challenge lies in correlating the results to real exposure data.