Browsing by Author "Erman Tekkaya,A."

Now showing 1 - 3 of 3

Citation - Scopus: 1
Analysis of Damage in Metal Forming
(Hanrimwon Publishing Co., 2008) Soyarslan,C.; Erman Tekkaya,A.
Investigation of central burst formation in direct extrusion is presented with experimental and numerical studies. On the experimental side, selecting certain unfavorable die angles and reduction ratios from the Chrysler processing standard for chevron-free extrusions curve [1], a set of extrusion tests are performed. Accordingly, chevrons are produced in the first and second pass for 100Cr6 and Cf53, respectively. On the numerical side, a multiplicative finite plasticity framework is coupled with a Lemaitre variant Continuum Damage Mechanics (CDM) model giving account for the crack closure effect and implemented as ABAQUS/VUMAT subroutine. Materializing an explicit finite element scheme, the effects of main process parameters, such as friction, semi-cone angle and reduction ratio on damage accumulation zones and intensities are studied. It is shown that, for the identical geometries, with an appropriately selected crack closure parameter and an element deletion procedure, the discrete periodic cracks can be captured, which are in correlation with the conducted experimental outputs.
Efficient New Process Uses Kinematic Male Parts: Rapid Prototyping in Sheet Metal Forming;
(2009) Franzen,V.; Sebastiani,G.; Kwiatkowski,L.; Brosius,A.; Erman Tekkaya,A.; Shankar,R.
[No abstract available]
Citation - Scopus: 9
Modeling Flexforming (fluid Cell Forming) Process With Finite Element Method
(Trans Tech Publications Ltd, 2007) Ali Hatipoǧlu,H.; Polat,N.; Köksal,A.; Erman Tekkaya,A.
In this paper, the flexforming process is modeled by finite element method in order to investigate the operation window of the problem. Various models are established using explicit approach for the forming operation and implicit approach for the unloading one. In all analyses the rubber diaphragm has been modeled revealing that the modeling of this diaphragm is essential. Using the material Aluminum 2024 T3 alclad sheet alloy, three basic experiments are conducted: Bending of a straight flange specimen, bending of a contoured flange specimen and bulging of a circular specimen. By these experiments the effects of blank thickness, die bend radius, flange length and orientation of the rolling direction of the part have been investigated. Experimental results are compared with finite element results to verify the computational models.