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    Effect of the blank holder force on drawing of aluminum alloy square cup: Theoretical and experimental investigation
    (2008) Demirci, Halil.I.; Esner, C.; Yasar, M.
    In this study, the influence of AA5754-O material, an aluminum alloy, in forming the blank holder force (BHF) in deep drawing process has been investigated. For this purpose, a new experimental system has been prepared. By means of this system, deep drawing process can be implemented through applying variable forces in computer-controlled manner on the blank holder and sheet plate. The numerical model of forming with deep drawing process has been built up and analyzed via the LS-DYNA software. Cup depths, tearing and wall thickness variations of the experimental and numerical results have been compared. It has been observed that no earing and wrinkling have occurred in BHF's between 1.3 and 8 MPa in square deep drawing process, and that tears have occurred in forces exceeding 18 MPa. It has further been observed that the best forming has occurred at 5 MPa, and that the numerical and experimental model developed is in harmony with one another at a rate of 85%. © 2007 Elsevier B.V. All rights reserved.
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    An experimental study on a pure detonation engine about its reaction in water
    (2006) Yasar, M.; Kadi, I.
    Reaction force developed by the detonation pressure is used in various fields in the world. It is being used under control where advanced technology is needed such as; supersonic or hypersonic planes, rockets, ceramic coating of metals, surface hardening, welding of thin film metals, plastic formation of metals. This experimental study was made to investigate; how much a reaction force by the detonation pressure can be developed in water, which has a higher density than air, whether this reaction force can be used in industry or not, and the usability of this force to propel a detonation apparatus in water. LPG and O 2 gases were used in this experimental study. A specially designed prototype detonation engine was put in a water pool and then gases sent into the engine and ignited. Detonation pressure, detonation velocity and the reaction force were measured during combustion. As a result, the Detonation Engine (DE), which was developed by us, with a 120 mm diameter nozzle and flow rate 1.2 m 3/h for LPG and 4.2 m 3/h for O 2 output that push force was approximately 5000 N. During this measurement, flowing reactant rate was 20 times more volume of DE and 0,001665 m 3 for LPG and 0.0058335 m 3 for O 2,.
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    High velocity forming of aluminum cylindrical cups-experiments and numerical simulations
    (2007) Yasar, M.; Kadi, I.
    A new two stage detonation forming machine was developed and cylindrical aluminum cups were formed by using gas detonation forming technology. The forming process was analyzed with the explicit finite element method with various parameters and ANSYS/LS-DYNA software. Defects of wrinkling and rupture were predicted for some forming conditions. The strain and the thickness distribution results were in good agreement with the experimental results. It was seen that thinning and forming mainly take place during the one fourth of the time. The effects of detonation pressure and blank holding force on the deformation of the work pieces were discussed. The numerical results were compared with those obtained in the experiments.
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    Investigation on wear mechanisms of boronized AISI 4140 steel
    (Scibulcom Ltd., 2017) Bozali, U.; Yasar, M.; Cetin, M.; Veli, Cay, V.; Gunen, A.
    In this study, AISI 4140 steel was subjected to box boronizing treatment at 1123 K, 1173 K and 1223 K for 2h, 4h, and 6h with commercially EKabor 2 powders. Friction and wear behaviour of the boronized and following worn AISI 4140 have been examined. After the wear tests, surface profilometer image analysis and EDS analysis were done. Also wear track area, wear track volume and wear rate were calculated based on the surface of the worn materials. In the AISI 4140 steel and in the boronized samples for 2 h severely plastic deformation wear mechanism were determined whereas in the samples boronized for 4h and 6h micro-ploughing wear mechanism were determined. Properties of boride layers have an effect on the type of wear mechanism. The boronized samples showed up to 27.3 times higher wear resistance than non-boronized AISI 4140 steel. © 2017, Scibulcom Ltd. All rights reserved.