Yazar "Halkaci, H. Selcuk" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim Yok
    Öğe
    Detailed Investigation of Forming Limit Determination Standards for Aluminum Alloys
    (AMER SOC TESTING MATERIALS, 2013) Dilmec, Murat; Halkaci, H. Selcuk; Ozturk, Fahrettin; Turkoz, Mevlut
    In this study, experimental studies were conducted to evaluate the differences between the ASTM E2218-02 and ISO 12004-2 standards that are used for construction of the forming limit curve (FLC) and that made various assumptions, which create dissimilar FLCs for the same material. The comparison was made for two materials which have moderate brittle and ductile characteristics, AA2024-T4 and AA5754-O alloys, respectively. The effects of a specimen's geometry, lubrication condition, and determination methods of limit strains on FLCs were considered and compared. Because the same strain evaluation method should be used for the standards, so as to be able to investigate the effect of only standards, a simple method in the computer grid analysis system was used. To test the validity and the reliability of the method, limit strains on the same specimens were also determined with using a real-time measurement method for the ISO experiments, and the results reveal that the method is reliable. Failure mechanisms were inspected for further investigation. The Nakajima specimens formed with the two standards showed different failure mechanisms. Finally, conducting the case studies, it was concluded that ISO 12004-2 yields more reliable and reproducible results than the ASTM standard.
  • Küçük Resim Yok
    Öğe
    Effects of sheet thickness and anisotropy on forming limit curves of AA2024-T4
    (SPRINGER LONDON LTD, 2013) Dilmec, Murat; Halkaci, H. Selcuk; Ozturk, Fahrettin; Livatyali, Haydar; Yigit, Osman
    In this study, the effects of sheet thickness and anisotropy of AA2024-T4 on forming limit curve (FLC) are experimentally investigated according to ISO 12004-2 standard. A new limit strain measurement method is proposed by using the grid analysis method so as to determine limit strains conveniently and reliably. In addition to the regular test specimens, various widths are added to enhance the FLC's accuracy at the plane strain condition (PSC). The accuracy and reliability of the proposed method are verified for different materials. Results illustrate that an increase in the sheet thickness increases the FLC level. The additional experiments for additional widths improve the accuracy of the FLC at the PSC, and the position of the lowest major strain value differs from the literature. However, the effect of anisotropy on the FLC is found to be insignificant. Finally, experimental and numerical case studies are carried out for conventional deep drawing, stretch drawing, and hydraulic bulge processes. Results reveal that different FLCs are necessary for different thicknesses for accurate predictions.