Browsing by Author "Bilici, Abdullah Yasin"

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    Investigation of microstructure and mechanical properties of dissimilar electrical resistance spot welded tbf/dp600 steel sheets
    (Gazi Üniversitesi, 2022-01-01) Aydın, Hakan; Yılmaz, İmren Öztürk; Bilici, Abdullah Yasin; AYDIN, HAKAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-7364-6281; JQB-9181-2023
    Effects of welding parameters on microstructure and mechanical properties of spot-welded TBF/DP600 sheets were investigated. TBF was welded with and without electro-galvanizing. Microhardness and tensile tests were carried out, and microstructure characterized by optical microscopy. Nugget size was determined by image processing, indentation was measured by ultrasonic technique. Steels were not completely mixed with each other in FZ. Increasing in welding current and time expanded HAZ and increased mixing-ratio in FZ, nugget size, indentation and load capacity. TBF was more affected by thermal cycle than DP600. LME-based microcracks in HAZ of galvanized TBF at high heat input were observed, while corrosion started rapidly in weld zone of ungalvanized TBF. Highest hardness was observed in HAZ on TBF side. However, significant softening occurred in transition zone between HAZ and base metal on TBF side. The nugget size, indentation and load capacity were higher in galvanized TBF group. In dissimilar spot-welded TBF/DP600 sheets, DP600 has determined weld strength. Fractures are of fusion zone button type with higher weld strength in high heat input, while fractures are of partial fusion zone button type with lower weld strength in low heat input. In galvanized TBF, higher weld strength was obtained in lower heat input.
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    Microstructure and mechanical properties of dissimilar resistance spot welded DP1000-QP1180 steel sheets
    (Journal of Central South Univ, 2019-01-01) Öztürk Yılmaz, İmren; Bilici, Abdullah Yasin; Aydın, Hakan; AYDIN, HAKAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0001-7364-6281; JQB-9181-2023
    In this study, the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000-QP1180 joints was investigated. Heat affected zone (HAZ) width of QP1180 side was smaller than that of DP1000 side. HAZ width and indentation depth increased with increasing welding current and welding time. The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time. The lowest hardness was on the DP1000 side. On the QP1180 side, the center of HAZ had the peak hardness. With increasing welding current, hardness values throughout the weld zone decreased and the tensile shear load increased. At lower welding currents, the welding time did not affect the tensile shear load. Tensile elongation decreased with the increase of welding time, whereas there is no relationship between the welding current and elongation. The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.