Yazar "Gemi, Lokman" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • Küçük Resim Yok
    Öğe
    Change in Porosity of A356 by Holding Time and Its Effect on Mechanical Properties
    (Springer, 2018) Uludağ, Muhammet; Cetin, Remzi; Gemi, Lokman; Dispinar, Derya
    In most of the practical casting operations, it is important to be able to cast large number of part with one single melt. Therefore, when quantity of the charge and melting crucible is increased, during casting process, the liquid is led to settle for a long period of time. In this work, 10kg charge of A356 was melted at 750 degrees C and held for 240min. A sand mold with different thickness was cast at 30, 60, 120, and 240min of holding time of the liquid, before and after degassing conditions. Melt quality was measured by reduced pressure test, and pore size and number were measured at each cast part. A correlation between bifilm index and tensile properties was established. It was found that melt quality was decreased with increased holding time and pore formation was enhanced linearly. Additionally, mechanical properties of the alloy were decreased with decreased melt quality and increased pore formation due to holding time of the liquid.
  • Küçük Resim Yok
    Öğe
    Experimental and statistical analysis of low velocity impact response of filament wound composite pipes
    (Elsevier Sci Ltd, 2018) Gemi, Lokman; Kayrici, Mehmet; Uludağ, Muhammet; Gemi, Dilek Soylu; Sahin, Omer Sinan
    Nowadays, filament wound composite pipes (GRP) are used as a structural element in many applications such as natural gas and oil transmission lines, and portable bridge constructions for military purposes. GRP pipes can expose to impact loading from various causes. This loading can cause an invisible level of damage. Thus, the detection and evaluation of such damages are of great importance. In this study, the low velocity impact response of (+/- 55 degrees)(3) filament wound E-glass/epoxy composite pipes has been studied. The pipes have been subjected to drop weight impact loading with various impact energies. The force-time and force-displacement relations have been examined. The impact damage formation was also evaluated. It is concluded that the damage development in the pipes is controlled by displacement trough radial direction. The obtained results were evaluated statistically by means of Weibull approach. Microscopy analysis of impacted region revealed that debonding, radial cracks, transfer cracks and delamination damage modes are the main observed damage modes.
  • Küçük Resim Yok
    Öğe
    Relationship Between Machinability, Microstructure, and Mechanical Properties of Al-7Si Alloy
    (Amer Soc Testing Materials, 2018) Uludağ, Muhammet; Yazman, Sakir; Gemi, Lokman; Bakircioglu, Baris; Erzi, Eray; Dispinar, Derya
    In this work, commercially available Al-7Si alloy was used, and the microstructure was modified by the additions of AlSr15, AlTi5B1, and Al3B. Cylindrical samples were cast into a sand mold and the machinability of the alloys was characterized by means of surface roughness, chip morphology, and buildup edge of the chips. Tool life and surface finish can be improved by decreased chip size by lowering the energy required for machining. The surface finish is an indicator of the quality of the material during the machining process. Therefore, in addition, melt quality was measured by means of reduced pressure test and the calculation of the bifilm index was used to compare the melt quality with machinability. It was found that there is a good correlation between bifilm index and surface roughness of the machined parts. Thus, for a better surface finish, melt quality, which can be quantified by bifilm index, has to be high. AlSr15 modified alloy exhibits the lowest built-up edge with the lowest surface roughness, because strontium modification causes coarse silicon crystals to transform to fine fibrous structure, which enhances machinability.