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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.
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>
Superplasticity of 5083 Aluminum Alloys during Microforming
Md. Abu Mowazzem Hossain,홍성태(Sung-Tae Hong),박규열(Kyu Yeol Park),나영상(Young-Sang Na) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4
The mechanical behavior of superplastic Al5083 alloy during microforming process is investigated by finite element analysis. A micro V-groove die is modeled to analyze the effects of forming time, load, and temperature on the microformability of the Al5083 alloy. First, the microformability of the Al5083 alloy is estimated using a microformability index. The simulation results suggest that the microformability increases as the forming load, time, and temperature increase. Superplasticity of the Al5083 alloy during microforming using the V-groove die is also investigated in terms of the effective strain rate. The results show that the superplasticity of the Al5083 alloy occurs in a specific part of the material for a specific period during microforming process, depending on the forming conditions and on the microformability index.
Effects of Friction Stir Processing on the Thermal Conductivity of a Strain-Hardened Al-Mg Alloy
정용하,Md. Abu Mowazzem Hossain,홍성태,한경식,이광진,박주원,한흥남 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.9
Strain-hardened aluminum-magnesium alloy (aluminum 5052-H112 alloy) plates are successfully friction stir processed. The thermal conductivity of the FSPed aluminum alloy is consistently measured to be higher than that of the base metal, even though the amount of grain boundaries significantly increases in the FSPed zone due to grain size refinement by FSP as observed by electron back-scatter diffraction (EBSD) analysis. In terms of thermal conductivity of the selected strain-hardened aluminum alloy, the result suggests that the effect of reduced dislocation by recrystallization, which is confirmed by X-ray diffraction analysis, surpasses the effect of increased grain boundaries due to grain size refinement. As the tool rotation speed increases, the thermal conductivity of the FSPed aluminum alloy increases even more, since the dislocation density in FSPed zone decreases further while the effect of grain size refinement is diminished by a slight grain growth.
Das Riton Kumer,Hossain Md. Abu Mowazzem,Islam Md. Tazul,Banik Sajal Chandra 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5
An experimental investigation was conducted in this study to assess the effect of the front toe angle and tire pressure on the fuel efficiency of light-duty vehicles. According to the investigations, increasing the toe angle results in an increase in rolling resistance, which has an impact on the fuel efficiency of the vehicle. It was observed that due to misalignment of the front toe-in angle (0.00° to 5.06°) and front toe-out angle (0.00° to -5.06°), the car had traveled approximately 7.38 km and 7.63 km less for the same amount of fuel. The rate of increase in fuel consumption was found to be about 74 % and 79.31 %, respectively. Also, it was shown that under steady-state conditions, the rolling resistance varies nonlinearly with tire inflation pressure while the fuel consumption varies nearly linearly. As the tire pressure lowered (under-inflation, 22 psi), it was observed that the vehicle’s rolling resistance rose at a rate of nearly 85.10 % and fuel consumption increased at a rate of nearly 40.29 %. In contrast, the rolling resistance and fuel consumption were considerably reduced as the tire pressure increased from 33 psi to 42 psi (over-inflation). Finally, a regression model was proposed using test data. Such a model would be useful to explain the relationship between the related factors and determine the rate of fuel consumption.