Browsing by Author "Tutar, Mumin"

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Effect of rotational speed and dwell time on mechanical properties of dissimilar AA1050-AA3105 friction stir spot welded joints
(Walter De Gruyter Gmbh, 2014) Tunçel, Oğuz; Aydın, Hakan; Yüce, Celalettin; Tutar, Mumin; Yavuz, Nurettin; Bayram, Ali; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; 0000-0003-1387-907X; 0000-0002-6886-6367; J-2753-2016; R-3733-2017; 16312009400; 56400829400; 56237466100; 54406234300; 6701698986; 7004197848
Friction stir spot welding is a newly developed joining technology which is expected to be used in the automotive industry for joining body parts made of aluminum sheets. The effect of the rotational speed and dwell time on the mechanical properties of dissimilar friction stir spot welded aluminum sheet alloys was investigated in this study. In the experimental studies, macro-structural characterization, micro-hardness tests and tensile shear tests were conducted. The experimental results showed that the tensile shear load and tensile deformation of the friction stir spot welded joints decreased roughly by 20 % and 25 %, respectively, when the rotational speed increased from 1000 rpm to 2000 rpm. On the other hand, when the dwell time increased from 3 s to 11 s, the tensile shear load increased roughly by 7 %, while the tensile deformation decreased roughly by 19 %, respectively.
Effect of the microstructure on the notched tensile strength of as-cast and austempered ductile cast irons
(Sage Publications, 2012) Durmuş, Ali; Aydın, Hakan; Tutar, Mumin; Bayram, Ali; Yiğit, Kurtuluş; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; J-2753-2016; 55964532400; 16312009400; 54406234300; 7004197848; 56490995600
In this study, the effect of microstructure on the mechanical properties of four types of ductile cast irons with different morphologies was investigated using circumferentially notched cylindrical specimens with different notch root radii. These cast irons were also austempered using the same austempering heat treatment to make a comparison with the as-cast samples. Characterization of the specimens has been carried out by means of microstructure, hardness, tensile properties, notch tensile strength, notch sensitivity, fracture toughness, and fractography. A mixture of ferrite and pearlite in the microstructure of cast irons gives rise to a material of the highest tensile strength, notch tensile strength, and fracture toughness properties with the intermediate ductility and notch sensitivity. A higher pearlite in the matrix of cast irons gives very important mechanical properties such as hardness and strength, but brittleness of the matrix and notch sensitivity are greatly increased. Austempering significantly increased the mechanical properties and also reduced the difference between the mechanical properties of the cast irons. Austempered ferritic ductile irons exhibited the highest notch tensile strength and fracture toughness, and the high tensile strength and the intermediate ductility properties with the lowest notch sensitivity, whereas austempered pearlitic ductile irons had the lowest tensile strength, ductility, notch tensile strength, fracture toughness, and the intermediate notch sensitivity properties. The mechanical properties of the as-cast and austempered ductile irons have increased almost linearly with increase in the notch root radius.
Effect of welding parameters on microstructure and mechanical properties of aluminum alloy AA6082-T6 friction stir spot welds
(Natl Inst Science Communication-Niscair, 2017-06) Aydın, Hakan; Tuncel, Oğuz; Umur, Yeliz; Tutar, Mumin; Bayram, Ali; Uludağ Üniversitesi/Mühendislik Mimarlık Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; J-2753-2016; GXG-5601-2022; AAK-4598-2021; 16312009400; 56400829400; 57191961457; 54406234300; 7004197848
Friction stir spot welding is an alternative joining technique for lightweight materials such as aluminum alloys. In this study, the influence of welding parameters, namely rotational speed, plunge depth, dwell time and travel speed, on weld microstructure and weld strength of friction stir spot welded AA6082-T6 aluminum alloy have been investigated. The joined samples were investigated by the methods of microstructural observations, microhardness tests, tensile shear tests and fractography. The hardness values of weld zone decreased significantly after FSSW process. Among the weld zones, HAZ showed the lowest hardness values. Higher rotational speed and lower travel speed led to the lower hardness values in the weld zone. The plunge depth and dwell time did not significantly affect the hardness values in the weld zone, except the SZ near TMAZ. Larger plunge depth and higher dwell time promoted higher hardness values in the SZ near TMAZ. The tensile test results showed that tensile shear load increased with increasing plunge depth and dwell time and with decreasing tool rotational speed and travel speed. The most effective welding parameter was found as dwell time. Higher rotational speed, higher plunge depth, higher dwell time and lower travel speed resulted in relatively ductile fracture.
Effect of welding parameters on tensile properties and fatigue behavior of friction stir welded 2014-T6 aluminum alloy
(Springer India, 2012-02) Sayaca, Tayfun; Aydın, Hakan; Tutar, Mumin; Durmuş, Ali; Bayram, Ali; Uludağ Üniversitesi/Mühendislik-Mimarlık Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; J-2753-2016; 16312009400; 54406234300; 55964532400; 7004197848
The present work describes the effect of welding parameters on the tensile properties and fatigue behaviour of 2014-T6 aluminum alloy joints produced by friction stir welding (FSW). Characterization of the samples has been carried out by means of microstructure, microhardness, tensile properties and fatigue behaviors. The hardness in the softened weld region decreases with decreasing the welding speed. Irrespective of the tool rotation speeds, the best tensile and fatigue properties were obtained in the joints with the welding speed of 80 mm/min. The joint welded with a rotating speed of 1520 rpm at 80 mm/min has given a highest tensile and fatigue properties. The fatigue behaviors of the joints are almost consistent with the tensile properties, especially elongations. Higher ductility in FSW joints made the material less sensitive to fatigue. The location of tensile fractures of the joints is dependent on the welding parameters. On the other hand, the fatigue fracture locations change depending on the welding parameters and stress range. In addition, a considerable correlation could not be established in between heat indexes and mechanical properties of FSW 2014-T6 joints under the investigated welding parameters.
The hydro-abrasive erosion wear behavior of duplex-treated surfaces of AISI H13 tool steel
(Sciense Press, 2014-12-23) Tutar, Mumin; Aydın, Hakan; Durmuş, Ali; Bayram, Ali; Yiǧit, Kurtuluş; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; J-2753-2016; 54406234300; 16312009400; 55964532400; 7004197848; 56490995600
The influence of duplex surface treatments consisting of a DC-pulsed plasma nitriding process and subsequent coatings of CrN and TiAlN deposited by physical vapor deposition (PVD) on AISI H13 tool steel was studied in this article. The treated samples were characterized using metallographic techniques, SEM, EDS, and microhardness methods. Hydro-abrasive erosion wear tests were performed in a specifically designed wear tester in which the samples were rotated in a wear tank containing a mixture of distilled water and ceramic abrasive chips with a fixed rotational speed. The wear rates caused by the abrasive particle impacts were assessed based on accumulated weight loss measurements. The worn surfaces were also characterized using optical microscopy, SEM, and EDS. Microhardness measurements indicated a significant increase in the surface hardness of the duplex-treated samples. The surfaces of the samples with the TiAlN coating were approximately 15 times harder than that of the untreated samples and 3 times that of the plasma nitrided samples. Hydro-abrasive erosion wear results showed that the duplex surface treatments, especially the CrN coating, displayed the highest erosion wear resistance.
The effect of duplex surface treatment on erosion performance of qro 90 supreme steel
(Springer India, 2019-04-01) Tutar, Mumin; TUTAR, MÜMİN; Aydın, Hakan; Durmus, Ali; DURMUŞ, ALİ; AYDIN, HAKAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7286-3433; 0000-0001-7364-6281; 0000-0002-5037-1120; J-2753-2016
In this study, CrN and TiAlN thin films were deposited on plasma-nitrided QRO 90 Supreme hot work tool steel by physical vapor deposition process and analysed with regard to their erosion performance under hydro-abrasive erosion conditions. The as-received specimens were quenched to room temperature from 1050A degrees C and tempered gradually at 605A degrees C for 2 h and at 560A degrees C for 4 h. These specimens were plasma-nitrided for 10 h at 500A degrees C at a pressure of 250 Pa in a gas mixture of 80% N-2 + 20% H-2 and then coated with TiAlN or CrN coatings by cathode arc evaporation. The specimens were characterized by metallographic techniques, SEM, EDS and micro-hardness test. Plasma nitriding and duplex surface treatments significantly increased the hardness of the specimens and thus significantly reduced the erosion of the specimens. The hardnesses on the surface of plasma-nitrided, CrN-deposited and TiAlN-deposited QRO 90 steels were 1092 HV0.025, 2436 HV0.025 and 3578 HV0.025, respectively. TiAlN-coated specimens were about 17-fold harder than the as-received specimens and over 3-fold harder than the plasma-nitrided specimens. The erosion resistance of CrN-coated specimens was increased by a factor of 3.6 and 1.5 compared with that of the as-received and plasma-nitrided specimens, respectively. A brittle fracture phenomenon was observed on the eroded surface of the duplex-treated specimens while a ductile material removal was observed on the as-received and the tempered specimens. The plasma-nitrided specimens showed a mixed behaviour of ductility and brittleness.