Browsing by Author "Durmus, Ali"

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Stress-constrained infill optimization in additive manufacturing for the armrest of an office chair
(Gazi Üniversitesi, 2021-01-01) Kuş, Süleyman; Durmus, Ali; DURMUŞ, ALİ; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-5037-1120
In this research; an armrest of an office chair is studied by Fused Deposition Modeling, while ensuring requirements of TS EN 1335 are met in each one of design, analysis, optimization and testing phase. The effect of two different optimization studies for the interior volume of the armchair model was investigated. In the first optimization study, an appropriate outer section thickness and cellular size change when the inner filling of the armrest shows a homogeneous distribution. In another optimization study, a regional density optimizations evaluated wherein regions having a high tension on the armrest model are defined with a homogeneous low density, relative to other regions with a fuller density. According to the finite element analysis results of the homogeneous density models with 50% occupancy; In armrest models with close weight, reductions in von-Mises stresses ranging from 29% to 36% have occurred for various load conditions. However, a suitable alternative that did not exceed the safe limit stress values established by reference to tensile and bending tests could not be obtained. In the regional density optimization study, the von-Mises stress value is obtained approximately 20% lower over four test loads than the best alternative with homogeneous density, and a suitable result is obtained according to the safe limit stress values with this model. This armrest model with the appropriate result has been produced and subjected to validation tests. As a result of the tests, it has been determined that the model fulfills the required requirements.
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.