In order to understand and improve fracture toughness of heat affected zones (HAZs) of high-strength low alloy (HSLA) steels, complex microstructures including quasi-polygonal ferrite (QPF), acicular ...ferrite (AF), granular bainite (GB), bainitic ferrite (BF), and martensite-austenite (MA) constituent should be identified, quantified, and then correlated with critical crack tip opening displacement (CTOD). In this study, microscopic analysis methods were achieved for identification and quantitation of microstructures in the HAZs of three HSLA steels. The coarse-grained HAZ (CGHAZ) consisted of AF, GB, and BF together with a small amount of MA, while the inter-critically heated HAZ (ICHAZ) consisted of QPF, GB, and MA. In the CGHAZ, Ni promoted the formation of AF, while it prevented the formation of GB, and the addition of Ni resulted in very high critical CTOD. In the CGHAZ, both Ni and Mn promoted the formation of AF and prevented the formation of GB, while Ni was more effective than Mn. Thus, the addition of Ni resulted in very high critical CTOD. In the ICHAZ, both Ni and Mn promoted the formation MA. However, in the high-Ni-containing steel, a number of MAs were densified along Ni-segregated bands, and thus readily provided void initiation sites. This played an important role in reducing the mean free path for coalescence of voids and crack propagation, which easily led to the serious deterioration of critical CTOD.
Cross-sectional studies suggest that local ecological knowledge (LEK) helps humans cope with their environment. Among the forms of LEK, adult knowledge of wild plants has been associated with better ...child and adult health. We assess if the concurrent links between i) LEK and ii) health and nutritional status last and examine if LEK yields delayed benefits when societies face large socioeconomic and environmental changes. We use a yearly panel (2002−2010) from Tsimane’, an Indigenous Amazonian society (Bolivia). All adults (∼440) and children (∼300) measured at baseline (2003) in 13 villages were followed yearly during 2004–2010 to estimate associations between a) baseline adult knowledge and skill about uses of wild plants and b) subsequent (2004–2010) anthropometric markers of nutritional status of themselves and the children (2y ≤ age ≤ 10y) living in the household at baseline. Among children, HAZ, BMI, and sum of four skinfolds were measured; among adults, BMI, sum of four skinfolds, and percent body fat with bioelectrical impedance were measured. Some skill losses increased by a large amount the likelihood of severe childhood stunting (HAZ < -3) for girls; the complete loss of these skills increased the share of severely stunted girls from 5% to 13%–20%. These are big numbers. The effects of LEK on other anthropometric indicators of children or adults were small. For example, if all adults in a household lost all their ethnobotanical knowledge, children's and women's BMI would decrease by only 3% and 11%, respectively.
•Local ecological knowledge (LEK) is said to help people cope with the environment•Panel data from Indigenous native Amazonians (Tsimane’) is used to estimate delayed effects•More knowledge of wild plants led to large reductions in girls' growth stunting over time•Most forms of LEK were not strong predictors of later short-run anthropometric indicators
The paper presents the application of MAG welding to TMCP steels (thermo-mechanically controlled processed) grade S960MC and 3 mm thick. In the analyzed joints, the research focused on their ...mechanical properties and changes in the heat-affected zone (HAZ) that occur in this type of steels. The hardness and tensile strength tests carried out showed a significant decrease in the properties of the joint compared to the declared values of the base material and the filler material used in the tests. In the case of hardness, it was a decrease of 34% in HAZ and by 15-21% in relation to the strength limit. Changes in HAZ properties of a joint correlate with changes in its structure.
The number and size of aluminium non-monohull ships have been steadily increasing over time. This raises growing concerns regarding their structural strength, especially considering the adverse ...effects of the heat-affected-zone (HAZ) on welding connections in aluminium structures. This paper investigates the ultimate strength of welded aluminium stiffened panels under combined biaxial compressive loads and lateral pressure through the application of numerical simulations. Altogether 360 cases are simulated with varied panel lengths, welding patterns and load combinations. The results are presented and discussed with respect to force end-shortening curves, failure modes and ultimate strength. Influences of the combined loads and HAZ effects are summarized. The numerical results are compared to two commonly used design methods in the marine industry, the International Association of Classification Societies (IACS) rule and the Panel Ultimate Limit States (PULS) approach. Their applicability to welded aluminium stiffened panels is discussed, and modifications are suggested with respect to the transverse loads, lateral pressure, and HAZ effects.
•Investigating behaviour of aluminium panel under combined loads considering welding effects.•Comparing results of NLFEM simulations and predictions from design methods.•Identifying incomplete considerations of lateral loads in design methods.•Recommending potential improvements in the IACS rule to better consider transverse loads.•Proposing integration of welding effects into the IACS rule for aluminium structures.
Kimlik, benlik, haz ve tüketim arasındaki ilişki literatürde çeşitli alanlarda sıklıkla tartışılmaktadır. Teknolojinin gelişmesi ile birlikte gündelik yaşama dâhil olan birçok yenilik insanın ...kendisini yeniden tanımlamasına olanak sağlamış, kimlik, benlik ve tüketim gibi unsurların da yeni boyutlar kazanmasına neden olmuştur. Teknolojinin sağladığı en son yenilik olan ve Mark Zuckerberg’in 2021 yılında duyurusunu yapmış olduğu metaverse evreninin erişilmez olana görece daha kolay erişme imkânını beraberinde getirmesi beklenmektedir. Bununla birlikte gündelik hayatta yaşanan birçok teknolojik yeniliğin insan hayatına dâhil olmasından önce filmler, diziler ve internet gibi kanallar aracılığıyla gelecek olan teknolojiye dair bilgiler topluma aktarılarak, toplum sürece hazırlanmaktadır. Çalışmada, kimlik, benlik, haz ve metaverse arasındaki ilişki Ready Player One filmiyle ele alınmış ve Ferdinand de Saussure’ün göstergebilimsel çözümlemesi uygulanmıştır. Çalışmada Mark Zuckerberg’in 2021 yılında duyurduğu metaverse evreninden 3 yıl önce 2018 yılında Ready Player One filmiyle metaverse evrenine dair imgelemeler yapıldığı sonucuna ulaşılmıştır. Bunun yanı sıra bireylerin kimliklerini ve benliklerini yeniden tanımlama imkânının sanal âlemde daha fazla mümkün olduğu ve bu tanımlama sürecinde imkânların sınırının kişinin hayalleriyle sınırlı olduğu sonucuna varılmıştır. Diğer taraftan ise metaverse evreninin insana yeni tüketim alanları sunduğu ve bu kapsamda yeni olanakların doğduğunu ifade etmek mümkündür.
The present work investigated the effects of Al, Si, and N content on the impact toughness of the coarse-grained heat-affected zone (CGHAZ) of Ti-containing low-carbon steel. Simulated CGHAZ of ...differing Al, Si, and N contents were prepared, and Charpy impact toughness was determined. The results were interpreted in terms of microstructure, especially martensite-austenite (M-A) constituent. All elements accelerated ferrite transformation in CGHAZ but at the same time increased the amount of M-A constituent, thereby deteriorating CGHAZ toughness. It is believed that Al, Si, and free N that is uncombined with Ti retard the decomposition of austenite into pearlite and increase the carbon content in the last transforming austenite, thus increasing the amount of M-A constituent. Regardless of the amount of ferrite in CGHAZ, its toughness decreased linearly with an increase of M-A constituent in this experiment, indicating that HAZ toughness is predominantly affected by the presence of M-A constituent. When a comparison of the effectiveness is made between Al and Si, it showed that a decrease in Si content is more effective in reducing M-A constituents.
Alumina is widely used in the automotive, electrical component and aircraft industries due to its low thermal conductivity and high hardness. However, alumina is notoriously difficult to machine due ...to its extreme hardness. According to some researchers, laser machining offers a cost-effective machining technique for alumina. Even though many works on laser machining of alumina have been published, most have focused on thin alumina plates. This study determined the effect of a CO2 laser machining method on hole quality in terms of the heat-affected zone (HAZ) and taper angle for 3 mm alumina thickness. Design of Experiment (DOE) was performed to identify the effect of laser power and frequency on the output findings. The HAZ and the taper angle were measured using a Scanning Electron Microscopy image. Based on the ANOVA analysis, HAZ and taper angles were influenced by the laser power input. The HAZ thickness increased as laser power and frequency decreased, but the taper angle decreased as frequency decreased. Low laser power (50 W) resulted in a small inlet diameter (0.236 mm), while high laser power (150 W) resulted in a larger inlet diameter (0.272 mm). Multi-response optimization analysis for both HAZ and taper angle showed that 149 W and 2956 Hz frequency were the optimum process parameters which yielded the best output conditions.
Laser cutting is a promising alternative to the traditional methods in CFRP cutting. However, laser cutting is based on thermal interaction that results in thermal damages of both matrix and fibres. ...The heat affected zone (HAZ) extension is strictly dependent on the adopted laser source and the working parameters. The paper presents an experimental study on the laser cutting of CFRP plate, 1 mm in thickness by means of 150 W Nd:YAG pulsed laser. The cutting region and the influence of process parameters, pulse energy, pulse duration and overlapping, on the kerf geometry and the HAZ were analyzed. Experimental results showed that the adopted laser is able to cut the CFRP plate, up to 10.8 mm/s. However, an accurate selection of the process parameters is necessary in order to obtain the maximum cutting speed and a narrow HAZ. Moreover, a relation between the HAZ extension and the process parameters (average power, cutting speed, pulse frequency and pulse duration) was found.
In the present work, laser cutting of Carbon Fibre Reinforced Plastics (CFRP) is investigated by means of a Quasi Continuous Wave (QCW) fibre laser. The adoption of high pulse power (up to 4.5 kW) ...and short pulse duration (0.05 ms) may reduce the HAZ formation and allows high cutting speed. For the aforementioned reasons, the improvement of the laser cutting parameters is industrially relevant, especially on materials that are difficult to cut with the standard modes. To assess the influence of the process parameters on kerf geometry and Heat Affected Zone, experimental tests were carried out fixing the average power at 450W and changing the pulse power, the pulse duration, and the overlapping factor. The tests were performed adopting a full factorial design 33 according to the DoE methodology. ANalysis Of VAriance was used to determine which and how the process parameters affect the kerf geometry and HAZ extension. Results show that the laser allows cutting 1.3 mm-thick CFRP sheets with cutting speed up to 2700 mm/min. Also, by an appropriate selection of the process parameters, it is possible to obtain narrow kerfs (smaller than 200 μm) and a limited HAZ (about 0.5 mm). Besides, the correlation between the inner and the outer HAZ was found: the HAZ measured on the bottom surface can be usefully adopted as a damage index to understand the overall thermal damage since it can be correlated to section HAZ. The latter is the reference damage parameter according to UNI EN ISO 12584 standard.
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