Browsing by Author "Karadoǧan,C."

Now showing 1 - 3 of 3

Citation - Scopus: 1
Determination of Tool Motions in Stretch Forming Process for Aerospace Applications by Using Finite Element Method
(Trans Tech Publications Ltd, 2013) Hatipoǧlu,H.A.; Alkaş,C.O.; Karadoǧan,C.
Stretch forming process is commonly used in the aircraft industry for the manufacturing of large sheet panels. The success of this process is highly dependent on the tool motions during forming. These motions are determined by trial - error procedure and it is costly. This study aims to improve the design of the stretch forming process by determining the necessary tool motions with numerical analysis. For this purpose, realistic finite element model (FEM) of the process is established. Material characterization and friction tests of mostly used aluminum alloys are conducted for input to the model. In order to improve the model and validate the numerical results, experimental work is performed in which the deformation of the sheet is measured optically. Copyright © 2013 Trans Tech Publications Ltd.
Citation - Scopus: 1
Direct Evaluation of Coulomb Friction Coefficient From Sheet Strip Stretch Test on a Cylinder Surface
(Trans Tech Publications Ltd, 2014) Karadoǧan,C.; Hatipoǧlu,H.A.
Knowing the flow curve of a sheet metal, strain distribution on a sheet strip may be used to roughly but quickly evaluate the Coulomb friction coefficient. Strain distribution on the strip being stretched on a cylindrical surface of interest may be measured by an optical strain measurement system. This could be used to estimate the stresses on the specimen. The capstan equation is then used to roughly evaluate the coefficient of friction acting between the sheet strip and the cylindrical surface. Validation of the approach is done using the simulation of the process. The corresponding experiments can be performed easily on a sheet metal testing device equipped with an optical strain measurement system, which is commonly used for the experimental evaluation of FLCs. © (2014) Trans Tech Publications, Switzerland.
Citation - Scopus: 3
Flow Curve Evaluation by Optic Strain Measurements and Force Balance at the Most Critical Section in the Neck Region of a Tensile Specimen
(2011) Coruk,E.; Karadoǧan,C.
Although higher strains can be reached during a tensile test of a ductile metal, only a small portion of this Information could be extracted from this ordinary tension test: Instability In the form of necking which prevents the mathematical evaluation of stresses and strains based on the elementary measurements, Is the basic obstacle. In this study, optic strain measurements around the most strained cross section of a tensile specimen, together with the force measurements, Is used to obtain the flow curve of the material up to strains of tensile rupture. GOM-Aramis System Is utilized as the optic strain measurement system. The measured strains are assumed to be totally plastic, making It possible to compute directly the yield stresses corresponding to the strains attained at the most strained point. Obtained flow curves are compared with the flow curves from the classical tension tests done by the help of precise tangible extensometers. Further comparisons with the result of hydraulic bulge tests and simulation of the tension test shows the applicability and reliability of the approach. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.