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RISS 인기검색어
- 검색키워드
- 저자 : B. V. Feujofack Kemda (검색결과 2 건)
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B. V. Feujofack Kemda,N. Barka,M. Jahazi,D. Osmani 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2
Industry is constantly moving towards an increasing of production speed while minimizing production costs. This paperpresents an efficient method for minimizing production times and energies through optimization of process parameters inresistance spot welding (RSW). Two grades of steel were used in this study, ASTM A36 steel and A653 hot dipped galvanizedsteel. Welding was done in overlap configuration, grade for grade, while following complete factorial plans. Micrographicanalysis revealed welds microstructure while micro-indentation hardness tests enabled to establish hardness profiles alongweld nuggets. Tensile-shear tests have been carried out in order to quantify the mechanical strength of welds. Analysis ofvariance showed that welding current is the most significant parameter and contributes for about 70% to welds mechanicalstrength. The ratio of hardness in the fusion zone to nugget surface area was found to be correlated with the failure modeof welded specimens. On that basis, a multi-objective optimization of the process parameters, through the non-dominatedsorting genetic algorithm was performed. This optimization resulted in a reduction of current, electrode pressing force andwelding time of 10.58%, 13.59% and 32.61% respectively. Optimized parameters were then assessed trough tensile-sheartesting of welded specimens, all specimens passed the validation tests by experiencing failure in the base metal.
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B. V. Feujofack Kemda,N. Barka,M. Jahazi,D. Osmani 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
In recent years, the usage of dual phase (DP) steels, transformation induced plasticity (TRIP) steels and boron steels in someauto body parts has become a necessity because of their strength and lightweight. Resistance spot welding (RSW) being aprocess were steel is heated and cooled in a very short period of time, the resulting weld nugget is generally fully martensitic,especially in the case of DP, TRIP and boron steels but that also holds for plain carbon steels as AISI 1010 grade whichis extensively used in auto body inner parts. Martensite in is turn must be avoided as much as possible when welding steelbecause it is the principal source of brittleness. Thus, this work aims in finding a mean to reduce martensite fraction andincrease phase diversity in weld nugget. The prediction of phase transformation during RSW has been done. Simulationshave been performed for 2 mm AISI 1010 sheets and results show that the application of post weld heat treatment leads tothe reduction of martensite fraction, and formation of ferrite and bainite in the nugget. Welding experiments have been donein parallel and experimental weld nugget geometry is in good agreement with simulation results.
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