Person: AYDIN, HAKAN
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AYDIN
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HAKAN
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Publication 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-9181-2023In 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.Publication Springback/springforward behaviour of dp steels used in the automotive industry(Univ Osijek, Tech Fac, 2020-01-01) Umur, Yeliz; UMUR, YELİZ; Aydin, Hakan; AYDIN, HAKAN; Yiğit, Kurtulus; YİĞİT, KURTULUŞ; Bayram, Ali; BAYRAM, ALİ; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-7364-6281; AAK-4598-2021The springback/springforward behaviour in a V-die/punch of DP600 and DP780 steels used in the automotive industry was investigated. For this study, experiments were carried out by using different combinations of parameters, including material thickness, die/punch radius, bending angle and rolling direction and the resulting measurements showed that the DP780 steel consistently exhibited greater springback values than the DP600. Augmentation of the rolling direction at an angle from 0 degrees to 90 degrees and punch radius inhibited springback formation and hastened springforward, particularly for small bending angles. The springback angle decreased with increasing material thickness and curvature radius, and increased with the bending angle, particularly for the punch tip radius of 2 mm. Increasing the ratio of curvature radius to material thickness (rt(-1)) also caused the springback to decline. In addition, a new dimensionless parameter was developed and the critical value for calculating the transition from springback to springforward was determined.Publication 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-9181-2023Effects 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.Publication A parametric study on weld zone shape of resistance spot welded 22MnB5 steel(Taylor, 2023-03-04) Tuncel, Oğuz; Aydın, Hakan; Gönül, Alişan; AYDIN, HAKAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; JQD-3823-2023The resistance spot welding of 22MnB5 with different weld currents, weld times, and quenching conditions is investigated in the current study. A Kriging Response Surface Methodology-based local sensitivity analysis is performed to investigate the effect of weld current, weld time, and quench condition on weld zone morphology and tensile shear load (TSL). When welding current, welding time, and quenching conditions are varied between the minimum and maximum values, the geometry of the weld zone was influenced by 40-60%, 20-40%, and 0-20%, respectively, according to sensitivity studies. It is also found that increasing values of welding current are the most effective welding parameter, increasing TSL by about 45%. In order to better understand the TSL variation at different welding parameters, various hardness measurements are applied for each specimen in the fusion zone and the heat-affected zone (HAZ) regions of the weld zone. Based on the location, the HAZ was divided into three regions: the inner, middle, and outer. The middle HAZ had hardness values 12% higher than the base material, while the outer HAZ had hardness values up to 36% lower than the base material. Also, macro-and microstructure images of the sample produced by combining the quenched and non-quenched materials are obtained to demonstrate how the hardness zones are identified.