Formability analysis of sheet metals by cruciform testing

Güler, Baran
Alkan, K.
Efe, Mert
Cruciform biaxial tests are increasingly becoming popular for testing the formability of sheet metals as they achieve frictionless, in-plane, multi-axial stress states with a single sample geometry. However, premature fracture of the samples during testing prevents large strain deformation necessary for the formability analysis. In this work, we introduce a miniature cruciform sample design (few mm test region) and a test setup to achieve centre fracture and large uniform strains. With its excellent surface finish and optimized geometry, the sample deforms with diagonal strain bands intersecting at the test region. These bands prevent local necking and concentrate the strains at the sample centre. Imaging and strain analysis during testing confirm the uniform strain distributions and the centre fracture are possible for various strain paths ranging from plane-strain to equibiaxial tension. Moreover, the sample deforms without deviating from the predetermined strain ratio at all test conditions, allowing formability analysis under large strains. We demonstrate these features of the cruciform test for three sample materials: Aluminium 6061-T6 alloy, DC-04 steel and Magnesium AZ31 alloy, and investigate their formability at both the millimetre scale and the microstructure scale.


Grain boundary grooving induced by the anisotropic surface drift diffusion driven by the capillary and electromigration forces: Simulations
Akyildiz, Oncu; Ogurtani, Tarik Omer (AIP Publishing, 2011-08-15)
The morphological evolution kinetics of a bicrystal thin film induced by anisotropic surface drift diffusion and driven by the applied electrostatic field is investigated via self consistent dynamical computer simulations. The physico-mathematical model, which is based upon the irreversible thermodynamic treatment of surfaces and interfaces with singularities [T. O. Ogurtani, J. Chem. Phys. 124, 144706 (2006)], provided us with auto-control on the otherwise free-motion of the triple junction at the intersec...
Progressive changes in surface structure and electronic properties on Si(001) surface by CaF2 adsorption
Alzahrani, A. Z.; Usanmaz, D. (AIP Publishing, 2011-06-15)
Ab initio calculations, based on pseudopotentials and density functional theory, have been performed to investigate the atomic geometry and electronic structures of calcium fluoride (CaF2) on the Si(001) surface. We have considered the experimentally observed (2 x 1) and (3 x 1) reconstructions with different bonding configurations of the CaF2 molecule on the Si(001) surface. Our total energy calculations suggest that the (3 x 1) structure is slightly more preferable than the (2 x 1). The key structural par...
Structural and optical properties of porous nanocrystalline Ge
Kartopu, G.; Sapelkin, A. V.; Karavanskii, V. A.; Serincan, U.; Turan, Raşit (AIP Publishing, 2008-06-01)
Nanocrystalline Ge films were prepared by isotropic chemical etching on single-crystalline Ge substrates with 100 and 111 orientations. The structural and optical properties have been investigated by transmission electron microscopy (TEM), electron diffraction (ED), Raman photoluminescence (PL), and infrared spectroscopy. The average size of nanocrystals (NCs) was estimated by fitting of the Raman spectra using a phonon-confinement model developed for spherical semiconductor NCs. Considered collectively TEM...
Ion-matrix sheaths related to planar targets with semicylindrical grooves
Demokan, O; Filiz, Y (AIP Publishing, 2003-01-01)
In this work, the ion-matrix sheaths near planar targets with infinitely long, semicylindrical grooves are studied analytically to optimize ion implantation, concerning a broad range of industrial products. The potential profiles inside and outside the groove are derived and the velocity components inside the groove are estimated. The variation of the angle of incidence on the surface of the groove and the constant potential contours outside the groove are obtained. Results are observed to be in good agreem...
Surface morphological evolution on single crystal films by strong anisotropic drift diffusion under capillary and electromigration forces
Ogurtani, Tarik Omer; Celik, Aytac (AIP Publishing, 2006-08-15)
The morphological evolution of voids at unpassivated surfaces and the sidewalls of single crystal metallic films is investigated via computer simulations by using a mathematical model based on fundamental postulates of irreversible thermodynamics. The effect of drift-diffusion anisotropy on the development of surface morphological scenarios is explored under the action of electromigration (EM) and capillary forces, utilizing numerous combinations of the surface texture and the direction of the applied elect...
Citation Formats
B. Güler, K. Alkan, and M. Efe, “Formability analysis of sheet metals by cruciform testing,” 2017, vol. 896, Accessed: 00, 2020. [Online]. Available: