Browsing by Author "Soyarslan, C."

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Citation - WoS: 15
Finite deformation plasticity coupled with isotropic damage: Formulation in principal axes and applications
(Elsevier Science Bv, 2010) Soyarslan, C.; Tekkaya, A. E.; Manufacturing Engineering; Department of Mechatronics Engineering; 06. School Of Engineering; 01. Atılım University
A local, isotropic damage coupled hyperelastic-plastic framework is formulated in principal axes. It is shown that, in a functional setting, treatment of many damage growth models, including those originated from phenomenological models (with formal thermodynamical derivations), micromechanics or fracture criteria, proposed in the literature, is possible. As a model problem, a Lemaitre-variant damage model with quasi-unilateral damage evolutionary forms is given with special emphasis on the feasibility of formulations in principal axes. To this end, closed form expression for the inelastic tangent moduli, consistent with the linearization of the closest point projection algorithm, is derived. It is shown that, generally, even in the absence of quasi-unilateral damage evolutionary conditions, the consistent tangent moduli are unsymmetric. The model is implemented as a user defined material subroutine (UMAT) for ABAQUS/Standard. The predictive capability of the selected model problem is studied through axi-symmetric application problems involving forward extrusion of a cylindrical billet, upsetting of a tapered specimen and tension of a notched specimen, in which characteristic failure mechanisms are observed. (C) 2010 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 2
Finite Element Analysis of Stress Distribution on Modified Retentive Tips of Bar Clasp
(Taylor & Francis Ltd, 2012) Oyar, P.; Soyarslan, C.; Can, G.; Demirci, E.; Department of Mechatronics Engineering; 01. Atılım University
This study used finite element analysis to evaluate the retentive tips of bar clasps made from different alloys and using different designs in order to determine whether or not different materials and tip forms are suitable for bar clasp applications. Co-Cr, Ti and Type IV Au alloys were selected based on their physical and mechanical properties. The 3D finite element models of three different bar clasp retentive tip geometries prepared from Co-Cr, Ti and Type IV Au alloys were constructed using the finite element software package MSC. Marc. Analysis of a concentrated load of 5N applied to the removable partial denture approach arms in an occlusal direction was performed. Although stress distribution and localisation within bar clasps with different retentive tips were observed to be similar and were concentrated in the approach arm, stress intensities differed in all models.
Citation - WoS: 16
Citation - Scopus: 19
Prevention of Internal Cracks in Forward Extrusion by Means of Counter Pressure: a Numerical Treatise
(verlag Stahleisen Mbh, 2009) Soyarslan, C.; Tekkaya, A. E.; Manufacturing Engineering; Department of Mechatronics Engineering; 06. School Of Engineering; 01. Atılım University
In the context of forward bulk extrusion, where product defects are frequently observed, the effect of counter pressure on damage accumulation materializing a Continuum Damage Mechanics (CDM) approach is presented. A Lemaitre variant damage model accounting for unilateral damage evolution coupled with a multiplicative finite plasticity is utilized for this purpose. After a presentation of the crack governing mechanism, it is demonstrated that application of counter pressure introduces a marked decrease in the central damage accumulation, which in turn increases the formability of the material through keeping the tensile triaxiality in tolerable limits. It is also shown that, for a crack involving process, through systematic increase of the counter pressure, the crack sizes diminish; and at a certain level of counter pressure chevron cracks can be completely avoided.
Soğuk Dövmede Sürekli Ortamlar Hasar Mekaniği (sohm) Uygulamaları: Bölüm Iı-ekstrüzyonda V-şeklindeki Merkezi Kırık Oluşumunun Önlenmesi
(2008) Soyarslan, C.; Tekkaya, A.e.; Akyüz, U.; Department of Mechatronics Engineering; 01. Atılım University
Çalışmanın bu kısmında, soğuk ileriye çubuk akıtma işleminde görülen merkezi kırıkların, uygun işlem parametrelerinin belirlenmesi ile önlenmesine yönelik, SOHM'ne dayanan sayısal çalışmalara yer verilmiştir. Kırık kapanma katsayısı, pekleşme üstel fonksiyon katsayısı, sürtünme, kalıp açısı ve alan indirim oranı, uygulanan ters basınç değeri gibi parametrelerin merkezi hasar birikimine tesiri, kapsamlı \"bir biçimde incelenmiştir. Gösterilmiştir ki, kalıp açısı-alan indirim oranı uzayını tarayan bir grup sayısal analizle, işlemin hatasız gerçekleşeceği sınır geometri değerlerinin ekonomik olarak temini mümkündür. Önerilen sayısal yöntemin çekici yönlerinden biri de, farklı işlem koşullarını aynı sistematik içerisinde kapsayabilecek genellikte olmasıdır. Buna örnek olarak işlem tasarımına eklenen ters basınç uygulamalarının hasar birikimine etkisi sayısal olarak modellenmiş, uygun karşı basınç değerlerinde iç kırıkların engellenebileceği gösterilmiştir.