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  • Küçük Resim
    Öğe
    A Giant Unilateral Pulmonary Artery Aneurysm: Case Report
    (1996) Cin, Veli Gökhan; Özer, Faruk; Deveci, Ahmet; Yaşar, Savaş
    A 65-year-old man presented with a left-sided pulmonary artery aneurysm with a fusiform shape. He was considered to be inoperable. Pulmonary hypertension is common with right heart enlargement, as in the present case. Posttraumatic aneurysms have also been reported. Differential diagnosis must distinguish between these two conditions. If 2D echo and CT have failed to distinguish the condition then right heart catheterization and pulmonary angiography are the methods of choice.
  • Küçük Resim
    Öğe
    Yüksek hızlı demiryollarında tekerlek-ray temas analizi
    (Selçuk Üniversitesi, 25.06.2018) Deveci, Ahmet; Kalyoncu, Mete
    Wheel-rail contact area, determines the dynamic performance together with the loads of the railway vehicle. Because of the high stresses in this contact area, plastic deformations occur on the wheel and rail profile. Nowadays, if high speed trains reaching operating speeds up to 320 km are considered, plastic deformations on the wheel and rail profile will cause both lost of transport comfort and economic. For this reason, A better understanding of the wheel-rail contact area and stresses it are a necessity to state a proper damage analysis. In the first and second part of this thesis, information is given about high speed railway lines and high-speed trains in our country and in the world.The studies about the forces, contact, pressure, stress etc. between the wheel and rail are mentioned. In the third part, information about profiles and mechanical properties of rail and wheels used in international railways are given. In curve occurring superelevation (height difference of the right and left rail ars) calculation are indicated. In the fourth part, between which is formed by TCDD on the UIC60E1 rail used in the high speed railways and the S1002 profiled wheel with 850 mm rolling radius used in high speed train, the static and dynamic vertical wheel load calculated, alignment (straight line) and the narrowest curve on the Ankara-Istanbul YHD separately. According to the calculated maximum dynamic vertical wheel loads, the contact area at contact points where the lateral slide distance of the wheel on the rail is 0 and 6 mm and the maximum contact pressure are calculated according to the Hertz theory. Sub-surface principal shear and von-Mises stresses were determined using methods provided by Johnson. Finally, analyses were done by the finite element method using ANSYS Workbench simulation program. The analytical calculations made by analysing the results of the finite element method are compared. Analytical calculations and FEM results are found to be close to each other. The contact area found by the finite element method is similar to the elliptical shape and the maximum contact pressure is almost formed at the centre of the contact area. Both methods, the maximum contact pressure on the corner of the rail head and on the flange of the wheel (resulting from a 6 mm lateral slip) were found to be greater than two times greater than the maximum contact pressure on the top of the rail head and on the conical surface of the wheel (where lateral slip is zero). The maximum stresses at both contact points were above the general strength of the many rail and wheel steels. Also, as the wheel rolling diameter increased, the maximum contact pressure decreased.