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Friction Stir Spot Welded Joints of 409L Stainless Steels Fabricated by a Convex Shoulder Tool
Md. Abu Mowazzem Hossain,Md. Tariqul Hasan,Sung-Tae Hong,Michael Miles,Hoon-Hwe Cho,한흥남 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
Spot joints of ferritic 409L stainless steel are successfully fabricated by friction stir spot welding (FSSW) using a convex shoulder tool. The welding process, microstructure and failure of the FSSW joint are investigated experimentally. During the FSSW process, the Z-force history shows significant variations depending on the contact phenomena between the tool and the joined sheets, while the Z-torque history shows a rather steady increase without pronounced changes in the trend until the initiation of dwelling. Electron back-scatter diffraction suggests that both continuous dynamic recrystallization and recovery occurred in the stir zone during the FSSW process. Observation of the FSSW joint that failed under the given lap shear load shows that the cracks, which are the result of the interfaces between the upper and lower sheets, propagated into the weld along the interfacial surfaces, after which a necking/shear failure occurred. Finally, the rupture of the joint, which was initiated by the necking/shear failure, propagated along the circumference of the weld.
Hasan Mohammad Kamrul,Islam Md. Tariqul,Akter Rojina,Roshni Nasima Akther 한국생태학회 2022 Journal of Ecology and Environment Vol.46 No.3
Background: Increasing land demands for food production have led to biodiversity loss and land degradation in the Madhupur Sal forest. Reforestation activities such as agroforestry and woodlot plantation support the conservation of diversity, restoration of forest and prevention of soil erosion in degraded natural Sal forest. Knowing about these reforestation activities, this study is needed to compare the species composition, richness, and soil nutrients of these two plantation activities to the natural Sal forest in the degraded Madhupur Sal forest in Bangladesh. Results: The analysis showed that in between the reforestation activities, the highest Shannon- Wiener index (1.79), evenness (0.60) and Simpson’s index (0.79) were found in the agroforestry site compared to the woodlot plantation site. On the contrary, the highest species richness (n = 14), tree basal area (19.56 m2 ha−1), Margalef’s index (1.96) were recorded in woodlot plantation than in the agroforestry site. We observed that at 0–15 cm depth, soil organic matter (2.39%), total nitrogen (0.14%), available phosphorous (62.67 μg g−1) and exchangeable potassium (0.36 meq/100 g) in agroforestry plots were significantly higher compared to other forest sites. At topsoil (15–30 cm depth), soil organic matter (1.67%) and available phosphorous (21.09 μg g−1) were found to be higher in agroforestry site. Conclusions: Both reforestation approaches improved soil function, although woodlot plantation had the higher species richness. Therefore, plantation activities by the sustainable implementation of these two practices are the best alternative to restore the biodiversity, richness and conserve soil fertility in the Madhupur Sal forest of Bangladesh.
Hossain, Md. Abu Mowazzem,Hasan, Md. Tariqul,Hong, Sung-Tae,Miles, Michael,Cho, Hoon-Hwe,Han, Heung Nam Hindawi Limited 2014 Advances In Materials Science And Engineering Vol.2014 No.-
<P>Mechanical properties and failure behaviors of friction stir spot welded (FSSW) joints of two dissimilar ferrous alloys, cold-rolled carbon steel (SPCC) and 409L stainless steel (SUS 409L), are investigated under opening-dominant combined loads. The texture of dissimilar FSSW joints depends on the upper sheet material. The failure contours for the FSSW joints under combined loads are constructed in terms of the axial load and shear load by modifying existing failure criteria for resistance spot welds. The shape of the failure contour also depends on the upper sheet material. The failure contours are nearly elliptic in shape when the upper sheet is SPCC and are relatively straight lines when the upper sheet is SUS 409L.</P>
전치성,정용하,홍성태,Md. Tariqul Hasan,Huynh Ngoc Tien,Seung Hyun Hur,권용재 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2
Graphite/aluminum metal matrix composite (MMC) joints are successfully fabricated by friction stir spot welding (FSSW). Duringlap-joining processes of aluminum alloy sheets by FSSW, graphite/water colloid is applied between the tool shoulder and the upper plate. The Raman spectrum of the FSSW joint confirms that graphite/aluminum MMC is successfully induced in the stir zone. Quasi-staticshear tests and micro hardness measurements of the FSSW joint also show that the strength and toughness of the joint are significantlyimproved by inducing graphite/aluminum MMC in the stir zone. The results of the present study suggest that the mechanical propertiesof structural components joined by spot welds can be easily enhanced by adopting MMC joints by FSSW, instead of changing the materialor increasing the number of joints.