Browsing by Author "Simsir, C."
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Conference Object Citation Count: 4A Material Perspective on Consequence of Deformation Heating During Stamping of DP Steels(Iop Publishing Ltd, 2017) Davut, Kemal; Cetin, B.; Şimşir, Caner; Davut, K.; Bayramin, B.; Department of Metallurgical and Materials Engineering; Manufacturing EngineeringRecent studies showed that, during stamping of high strength steels at industrially relevant production rates, local temperature in the blank may rise up to 200 degrees C - 300 degrees C due to deformation heating. Moreover, die temperature may also rise up to 100 degrees C - 150 degrees C for progressive stamping dies. Based on the common assumption that the blank softens as the temperature increases, thermal softening creates a margin in Forming Limit Diagram (FLD) and therefore the FLD determined at room temperature can safely be used for those cases. In this article, the validity of this assumption on DP590 steel is questioned by high temperature tensile tests (RT - 300 degrees C) at various strain rates (10(-3) s(-1) - 1 s(-1)). The results indicated a decrease both in uniform and total elongation in 200 degrees C - 300 degrees C range together with several other symptoms of Dynamic Strain Aging (DSA) at all strain rates. Concurrent with the DSA, the simulated FLD confirms the lower formability at high temperature and strain rates. Thus, it is concluded FLD determined at RT may not be valid for the investigated steels.Article Citation Count: 35Multiscale modeling of tempering of AISI H13 hot-work tool steel - Part 1: Prediction of microstructure evolution and coupling with mechanical properties(Elsevier, 2016) Şimşir, Caner; Broeckmann, C.; Simsir, C.; Manufacturing EngineeringIn the first part of this two part study, the mechanical properties necessary for the simulation of tempering of an AISI H13 (DIN 1.2344, X40CrMoV5-1) tool steel was derived using physically based precipitation simulations and microstructure-property relationships. For this purpose, the precipitation of fine carbides were simulated using a thermo-kinetic software which allows prediction of the evolution of precipitation/dissolution reactions and the particle sizes. Then, those microstructural findings were coupled with physically based microstructure-property models to predict the yield stress, flow curve and creep properties. The predicted mechanical properties were verified with corresponding experiments and a good agreement was found. In the second part of this study, those properties were coupled with a Finite Element (FE) model in order to predict the relaxation of internal stresses and the evolution of deformations at the macroscopic scale. (C) 2015 Elsevier B.V. All rights reserved.Article Citation Count: 13Multiscale modeling of tempering of AISI H13 hot-work tool steel - Part 2: Coupling predicted mechanical properties with FEM simulations(Elsevier Science Bv, 2016) Şimşir, Caner; Broeckmann, C.; Simsir, C.; Manufacturing EngineeringSimulation of austenitization and quenching of steel using the Finite Element Method (FEM) is nowadays a common tool to predict residual stresses and deformations during these processes. However the simulation of tempering, which determines the final residual stresses and distortions has been often neglected or performed in a purely phenomenological and highly simplified way. The objective of this study is to precisely predict the relaxation of internal stresses during tempering, taking explicitly into account the evolution of the microstructure. Mechanical properties which determine the relaxation of stress; namely the drop of the yield stress and the creep mechanism are the key factors for the success of the simulation. These mechanical parameters can be determined experimentally for a specific tempering temperature. However tempering temperature for most steels varies for each industrial application in order to adjust the desired hardness-toughness relation. Consequently, experimentally measurement of decisive mechanical properties which determine the amount of stress relaxation for each tempering temperature is very costly. Therefore, these material parameters were simulated from physically based material models with coupled microstructural simulations in the first part of this two-part investigation. In this part of the study, the simulated mechanical properties will be coupled with the FEM simulations using "Abaqus (R)", in order to simulate the stress relaxation during the tempering process of a thick-walled workpiece made of hot-work tool steel AISI H13 (DIN 1.2344, X40CrMoV5-1). Utilizing this methodology, different tempering conditions (soaking time, tempering temperature) can be considered in the model to predict the stress relaxation in macroscopic scale. (C) 2015 Elsevier B.V. All rights reserved.Conference Object Citation Count: 3A Potential Solution to Mystical Materials in Indentation Test(Elsevier Science Bv, 2017) Billur, Eren; Davut, Kemal; Music, O.; Simsir, C.; Şimşir, Caner; Music, Ömer; Department of Metallurgical and Materials Engineering; Automotive Engineering; Manufacturing EngineeringVarious methods have been designed to determine the elasto-plastic properties of metals. Instrumented indentation test (IIT) is considered to be a good candidate to determine local properties after manufacturing operations. In order to acquire elastoplastic properties from IIT, either dimensional analysis or inverse analysis of the force-displacement curve is performed. However, the major drawback of those methods is the uniqueness of the solution. Some materials may exhibit almost identical force-depth curves, although they have different elastoplastic properties. Those materials are referred as "mystical materials". In this contribution, topological features of the indentation surfaces, i.e. indent size, pile-up and sink-in behaviour, are investigated to find a differentiating property. According to the results, indent size, pile-up and sink-in behaviour may help to find the unique solution to the inverse problem. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.Article Citation Count: 14Process-chain simulation for prediction of the distortion of case-hardened gear blanks(Wiley-v C H verlag Gmbh, 2012) Şimşir, Caner; Hunkel, M.; Luetjens, J.; Rentsch, R.; Manufacturing EngineeringIn this study, a process-chain simulation model is presented for the prediction of distortion of low-pressure gas carburised SAE 5120 (EN 20MnCr5) steel gear blanks. For this purpose, the evolution of the banded microstructure stemming from the continuous casting process was traced by computer simulations of subsequent shape rolling, forging and machining steps. Then, the simulated local orientation angles of the deformed banded microstructure are transferred to heat treatment simulation module as an input for the recently developed material model that exploits the Anisotropic Transformation Strain (ATS) concept to reproduce the dishing behaviour which cannot be reproduced by former models. The results indicate that the suggested procedure provides quite good predictions of the dishing directions and dishing-free cutting strategy, whereas; the dishing magnitude is predicted fairly reasonably considering large scatters in the experiments.Article Citation Count: 8Simulation of through-hardening of SAE 52100 steel bearings - Part I: Determination of material properties(Wiley-v C H verlag Gmbh, 2016) Şimşir, Caner; Evcil, G. E.; Simsir, C.; Manufacturing EngineeringA complete material dataset for the simulation of through-hardening of SAE 52100 (DIN/EN 100Cr6, JIS SUJ2) steel was derived by a combination of experimental and theoretical/computational methods. In the experimental part, alpha/quenching and deformation dilatometry techniques are combined with density measurements, X-Ray diffraction, optical and scanning electron microscopy to determine temperature and phase dependent transformation kinetics parameters, thermal and transformation strains, flow curves and the transformation plasticity parameter. Thermal properties such as thermal conductivity, specific heat and enthalpy and elastic properties are acquired by thermodynamics based material property calculation method using a commercial software. For most of the material properties, the results were in good agreement with the literature, while the minor discrepancies are discussed considering the raw material, equipment used, testing and evaluation procedure. In Part II of this article, compiled material data is validated successfully in an industrial oil and salt-bath quenching of bearing races.Article Citation Count: 4Simulation of through-hardening of SAE 52100 steel bearings - Part II: Validation at industrial scale(Wiley-v C H verlag Gmbh, 2016) Şimşir, Caner; Mustak, O.; Simsir, C.; Manufacturing EngineeringIn this study, the material dataset presented in part I of this article is validated at industrial scale in batch through-hardening of bearing races. The material dataset acquired is implemented in a commercial heat treatment simulation software. Heat transfer coefficients for the oil and salt bath are determined by using a commercial standard quench probe. Zone temperatures and transfer times of the roller-belt furnace are measured directly from the system. Through-hardening of inner ring (IR) of 6813 bearing in oil and salt bath is simulated considering most of the industrial details. Finally, predicted dimensional changes are compared with the coordinate measurement results and a good agreement is achieved. It is concluded that determined material and process data, idealizations and simulation procedure can be considered "validated" for further improvement of the industrial process.