Browsing by Author "Şimşir, Caner"

Now showing 1 - 20 of 27

Citation - WoS: 0
Citation - Scopus: 2
Anisotropic Transformation Strain and Its Consequences on Distortion During Austenitization
(Amer Soc Testing Materials, 2012) Simsir, Caner; Lubben, Thomas; Hunkel, Martin; Hoffmann, Franz; Zoch, Hans-Werner; Manufacturing Engineering
The distribution of segregations, which is introduced in the continuous casting process and modified during succeeding manufacturing steps, is considered as an important "distortion potential carrier" for chemically banded steels. This article presents a recently developed mathematical model for integration of the effect of prior forming and cutting operations into heat-treatment simulations by considering "anisotropic transformation strain (ATS)." The model was justified experimentally by simulating the heating and austenitization of dilatometer specimens machined from the forged discs with distinct orientations with respect to the banded microstructure. After the verification, it is used in conjunction with former experimental work to demonstrate that the distribution of fiber flow is one of the important reasons of the dishing of carburized discs. The model provides promising results for process chain simulation to predict the heat-treatment distortion that cannot be predicted with currently available models.
Boru Sıvama Prosesinin Modellenmesi ve Analizi
(2017) Çizmeci, Kerem; Şimşir, Caner; Musıc, Ömer; Manufacturing Engineering
Bu tez çalışmasında boru sıvama prosesi incelenmiştir. İnceleme ticari sonlu elemanlar yazılımı olan Transvalor Forge ile yapılan sayısal analizler ile gerçekleştirilmiştir. İki boyutlu ve üç boyutlu sayısal modeller geliştirilmiştir. En iyi sayısal analiz parametrelerinin bulunabilmesi için değişken çalışması yapılmıştır. Sayısal model akademik literatürde bulunan verilerle karşılaştırılmıştır. Geliştirilen modeller kullanılarak, boru sıvama proses analizi gerçekleştirilmiştir.
Citation - WoS: 2
Citation - Scopus: 2
A Comprehensive Study of the Effect of Scanning Strategy on In939 Fabricated by Powder Bed Fusion-Laser Beam
(Elsevier, 2024) Dogu, Merve Nur; Ozer, Seren; Yalcin, Mustafa Alp; Davut, Kemal; Obeidi, Muhannad Ahmed; Simsir, Caner; Brabazon, Dermot; Manufacturing Engineering; Metallurgical and Materials Engineering; Department of Metallurgical and Materials Engineering
This study provides a comprehensive investigation into the effects of different scanning strategies on the material properties of IN939 fabricated using the PBF-LB process. The scanning strategies examined included alternating bi-directional scanning with rotation angles of 0 degrees, 45 degrees, 67 degrees, and 90 degrees between adjacent layers (named as shown), as well as alternating chessboard scanning with rotation angles of 67 degrees and 90 degrees (named as Q67 degrees and Q90 degrees). The results revealed that the 45 degrees and 67 degrees samples had the highest relative density, while the 0 degrees and Q67 degrees samples showed the highest average porosity. Moreover, various types of cracks, including solidification, solid-state, and oxide-induced cracks, were observed. Among the bi-directional scan samples, the 0 degrees sample displayed the most extensive cracking and the highest sigma max residual stress values in both XZ and XY planes. Conversely, the 45 degrees and 67 degrees samples exhibited fewer cracks. Notably, the lowest sigma max residual stress in the XZ planes among the bidirectional scan samples was observed in the 67 degrees sample. Additionally, microstructural analyses indicated differences in grain size and morphology, among the samples. Texture analysis indicated that the 0 degrees and 90 degrees samples exhibited strong cube textures, whereas the texture intensity weakened for the 45 degrees and 67 degrees samples. Moreover, the alternating chessboard scanning strategy led to rougher surfaces (higher Sa and Sz values) compared to the alternating bi-directional scanning strategy, regardless of the rotation angles. Furthermore, the microhardness values among the samples showed minimal variance, ranging between 321 + 14 HV and 356+ 7 HV.
Citation - WoS: 33
Citation - Scopus: 36
Dynamic strain aging in DP steels at forming relevant strain rates and temperatures
(Elsevier Science Sa, 2017) Bayramin, Berkay; Simsir, Caner; Efe, Mert; Manufacturing Engineering
Mechanical testing of dual phase (DP) steels at low strain rates (10(-3) s(-1)) have shown that they are susceptible to dynamic strain aging (DSA) between 100 degrees C-400 degrees C. During industrial forming processes at intermediate strain rates (1-10(2) s(-1)), the local temperatures may rise to the DSA range due to deformation heating which may disturb the exceptional formability of these steels. In this study, two grades of DP steel (DP590 and DP800) are tested at thermomechanical conditions relevant to forming and the effects of DSA on the formability are established. Test results show that the DSA controls the deformation between 200 degrees C-300 degrees C through serrations in the stress-strain curves of both grades. With increasing strain rates (up to 1 s(-1)) and temperatures, DSA intensifies and results in severe drops in uniform and total ductility with negative strain rate sensitivity, indicating poor formability at these conditions. A detailed analysis of the serrations coupled with dislocation density measurements by x-ray analysis suggests that the serrations can be linked to a periodic microstructural feature.
Citation - WoS: 6
Citation - Scopus: 6
Excessive Damage Increase in Dual Phase Steels Under High Strain Rates and Temperatures
(Sage Publications Ltd, 2021) Cobanoglu, Merve; Ertan, Rasim K.; Simsir, Caner; Efe, Mert; Manufacturing Engineering
Damage formation in dual phase steels is a complex process and it may be sensitive to the deformation conditions and mechanisms. In this study, the damage parameter is measured and compared under quasi-static and industrial forming conditions (temperatures: 25 vs 200, 300 degrees C and strain rates: 10(-3)vs 10 s(-1)) for DP590 and DP800 steels. Resonance frequency and ultrasonic sound velocity techniques are utilized for the measurements to test the effectiveness and validity of each technique. At a given strain, the damage values can be up to 700% higher at industrial forming conditions, under which dynamic strain aging (DSA) controls the deformation behavior. DSA results in lower formability and is the likely mechanism responsible from the abnormal damage evolution. Measured damage parameters are also confirmed with the void fraction characterization by microscopy, which also provided details on the void shape and distribution with respect to the deformation conditions.
Citation - Scopus: 2
Fem Modeling of the Distortion of Blank/Case Hardened Gear Blanks Due To Chemical Banding
(2012) Şimşir,C.; Hunkel,M.; Lütjens,J.; Rentsch,R.; Manufacturing Engineering
In this study, a FEM process-chain simulation model is presented for the prediction of distortion of blank and case-hardened 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. The calculated flow-net was imported into the in-house heat treatment simulation module empowered with the recently developed "Anisotropic Transformation Strain (ATS)" model which enables the inclusion of the effect of banded microstructure on distortion. Then, both blank and case-hardening processes were simulated and verified experimentally. The results indicate good predictions of the dishing directions and dishing-free cutting strategy in both cases; the dishing magnitude is predicted well in blank-hardening simulations while the quality of the prediction is reasonable in case-hardening. Copyright © 2012 ASM International® All rights reserved.
Citation - WoS: 8
Citation - Scopus: 10
A Flow Stress Model for Steel in Cold Forging Process Range and the Associated Method for Parameter Identification
(Springer London Ltd, 2018) Simsir, Caner; Duran, Deniz; Manufacturing Engineering
Detailed thermo-mechanical characterization of DIN 16MnCr5 covering the process range of cold forging applications (0.01 s(-1) 40 s(-1), 25 A degrees C Ta 400 A degrees C) by compression tests revealed flow stress instabilities associated with dynamic strain aging (DSA) which cannot be reproduced by conventional flow stress models. As a remedy, a flow stress model capable of capturing sharp changes in flow stress, strain hardening, and strain rate sensitivity is proposed. Then, a method for parameter identification is presented which can deal with inhomogeneous deformation heating of the specimen at relatively high-strain-rate tests. The presented method involves response surface-based numerical optimization of the flawed compression tests coupled with finite element (FE) simulation. The proposed flow stress model and the extracted parameters are validated in a forward rod extrusion process without using any case-specific determined parameters in FE simulation. A natural agreement is obtained between the experimental and the predicted results in terms of both the force-displacement curve and the part geometry. The authors think that the flow stress instabilities encountered in the cold forging process range may have further consequences in other inverse analysis attempts such as friction coefficient or critical damage parameter determination and that the proper treatment of material data as put forth in this study can improve the predictive capability of process modeling.
Citation - WoS: 4
Citation - Scopus: 4
A Material Perspective on Consequence of Deformation Heating During Stamping of Dp Steels
(Iop Publishing Ltd, 2017) Simsir, C.; Cetin, B.; Efe, M.; Davut, K.; Bayramin, B.; Department of Metallurgical and Materials Engineering; Manufacturing Engineering
Recent 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.
Millerin Sementasyon İşleminin Deney Tasarımı Kullanılarak İncelenmesi
(2017) Yılmaz, Hasan; Şimşir, Caner; Davut, Kemal; Manufacturing Engineering
Sementasyon işlemi, mil imalatında yaygın olarak termokimyasal bir ısıl işlemdir. Sementasyon sonrası yetersiz sertlik derinliği, uygunsuz yüzey ve çekirdek sertliği ve çarpılma yaygın hurda ürün sebepleridir. Bundan sebeple, sementasyon sırasında süreç parametrelerinin etkilerinin anlaşılması, kontrolü ve optimizasyonu kayıpların önlenmesi için hayati önem taşımaktadır. Bu çalışmada semenyastasyon parametreleri Taguchi yöntemiyle Deney Tasarımı (DoE) aracılığıyla incelenmiş ve iyileştirilmiştir. İyileştirmenin temel hedefi imalatta değişik fırınların kullanılmasından kaynaklı değişkenliğin azaltılmasıdır. Deneyler iki değişik endüstriyel gaz sementasyon fırınında, iki değişik çelikten (16MnCr5,20NiCrMo2-2) tornalarak üretilmiş düz ve basamaklı millerde gerçekleştirilmiştir. Sementasyon deneylerinden sonar, millerin boyutları Koordinat Ölçüm Makinesi (CMM) ile ölçülürken, karbon ve sertlik dağılımları Optik Yayınım Spektrometresi (OES) ve Vickers sertlik ölçümleriyle belirlenmiştir. Sonuçlar sementasyon gazının karbon potansiyelinin sertlik derinliğindeki ve değişikliğindeki gerek değişkenliği gerek ortalama değeri en çok etkileyen parametre olduğunu göstermektedir. Anahtar Kelimeler: Mil, Sementasyon, Taguchi Yöntemi, Optimizasyon
Citation - WoS: 40
Citation - Scopus: 46
Multiscale modeling of tempering of AISI H13 hot-work tool steel - Part 1: Prediction of microstructure evolution and coupling with mechanical properties
(Elsevier, 2016) Eser, A.; Broeckmann, C.; Simsir, C.; Manufacturing Engineering
In 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.
Citation - WoS: 13
Citation - Scopus: 18
Multiscale Modeling of Tempering of Aisi H13 Hot-Work Tool Steel - Part 2: Coupling Predicted Mechanical Properties With Fem Simulations
(Elsevier Science Bv, 2016) Eser, A.; Broeckmann, C.; Simsir, C.; Manufacturing Engineering
Simulation 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.
Citation - WoS: 7
Citation - Scopus: 9
Parameter Identification for an Armstrong-Frederick Hardening Law for Supercooled Austenite of Sae 52100 Steel
(Elsevier, 2010) Wolff, Michael; Suhr, Bettina; Simsir, Caner; Manufacturing Engineering
The mechanical properties of the supercooled austenite phase are sensitive parameters for the prediction of distortion of the components during heat treatments as the inelastic deformation occurs mostly on the soft austenite phase. Recent studies clarified that one of the overlooked issues related with the thermomechanical behavior of supercooled austenite during heat treatment and welding is its complicated cyclic hardening behavior (cf. Simsir et al., Acta Materialia, 2010). Based on those concerns, this article presents an optimization method for determination of temperature-dependent parameters for an Armstrong-Frederick model with combined non-linear kinematic and isotropic hardening, which can potentially pull the quality of simulations through. The results indicate that the proposed approach yields satisfactory results for simulation of heat treatments and welding even with a small and imperfect experimental data pool. (C) 2010 Elsevier B.V. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
A Potential Solution To Mystical Materials in Indentation Test
(Elsevier Science Bv, 2017) Billur, E.; Cetin, B.; Music, O.; Simsir, C.; Davut, K.; Department of Metallurgical and Materials Engineering; Automotive Engineering; Manufacturing Engineering
Various 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.
Citation - Scopus: 10
The Prediction of the Distortion of Blank-Hardened Gear Blanks by Considering the Effect of Prior Manufacturing Operations
(2011) Şimşir,C.; Eisbrecher,I.; Hunkel,M.; Lübben,T.; Hoffmann,F.; Manufacturing Engineering
This article presents a recently developed mathematical model for Integration of the effects of prior manufacturing steps into heat treatment simulations by considering the modification of the banded microstructure in forming and machining processes. The model was justified by simulating the heating, austenitizatlon and quenching of dilatometer specimens machined from the forged discs with distinct orientations to the banded microstructure. Then, It Is tested In prediction of dishing of blank-hardened gear blanks, which cannot be reproduced by previously available models. The model provides promising results for process chain simulation and development of system-oriented measures for the solution of heat treatment distortion problem. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
Citation - WoS: 15
Citation - Scopus: 25
Process-Chain Simulation for Prediction of the Distortion of Case-Hardened Gear Blanks
(Wiley-v C H verlag Gmbh, 2012) Simsir, C.; Hunkel, M.; Luetjens, J.; Rentsch, R.; Manufacturing Engineering
In 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.
Şaftların sementasyon sonrası su-verme işleminin bilgisayar simülasyonlarıyla incelenmesi
(2017) Terzi, Büşra Yazır; Şimşir, Caner; Davut, Kemal; Manufacturing Engineering
Sementasyon ve sonrasında su verme ısıl işlemleri çelik şaftların özelliklerini ve performanslarını geliştirmek için yaygın şekilde kullanılan endüstriyel işlemlerdir. Bu işlemlerle ilişkili olan kabuk derinliğindeki farklılıklar ürün geri gönderimindeki en sık rastlanan sorunlardandır. Bu sebeple, bu çalışmanın başlıca amacı, sementasyon sonrası su verilmiş DIN 16MnCr5 (1.7131) çelik şaftlarının uygun etkin ve kontrol parametrelerinin belirlenmesidir. Diğer bir amaç kaçınılmaz deneysel varyasyonlarını tahmin etmek ve bilgisayar simülasyonlarının doğruluğuna deneysel belirsizlikler ile karar vermektir. Bu çalışma hem deneyler hem de simülasyonlar üzerinden yürütülmüştür. Deneysel çalışma simülasyonları doğrulamak için kullanılmıştır. Sistemin kontrol parametrelerine karar vermek amacıyla, yerel hassasiyet analizi bilgisayar simülasyonlarında her bir kontrol parametresi kendi referans değeri çevresinde sarsıma uğratılarak yapılmıştır. Sertlik, kalıntı gerilme ve boyutsal değişimler bu sarsımlarla boyutsuz hassasiyet indeksi ve toplam belirsizlik yardımıyla ilişkilendirilmiştir. Bunlara ek olarak, etkin parametrelerin tanımlanması amacı doğrultusunda sanal bir deney tasarımı sonlu elemanlar yöntemi yazılımı olan SYSWELD® kullanılarak gerçekleştirilmiştir. Anahtar Kelimeler: Sementasyon, sanal deney tasarımı, DIN 16MnCr5, hesaba dayalı hassasiyet analizi
Citation - WoS: 2
Citation - Scopus: 2
Simulation and Optimization in Materials Technology
(Hindawi Ltd, 2014) Guerrero, Martha; Simsir, Caner; Deus, Augusto; Sarler, Bozidar; Manufacturing Engineering
[No Abstract Available]
Citation - Scopus: 0
Simulation and Optimization in Quenching Technology for Automotive Components
(ASM International, 2013) Felde,I.; Simsir,C.; Manufacturing Engineering
Heat treatment is widely used in automotive industry from a simple immersion quenching of gears upto the complex production technology of press hardening. The selection of process parameters to develop the desired properties is challenging due to the complexity of the physical phenomena occuring during the manufacturing clycle. In the last decades several compuational methods have been applied successful to optimize the heat treatment processes. The paper is focusing on some examples demonstrating the state of the art of the simulation tools including the physical phenomena of quenching, the theoretical background of the coupled modek used for estimation the microstructure, mechanical propertis and deformation of automotive components heat treated.
Citation - WoS: 9
Citation - Scopus: 14
Simulation of Quenching: a Review
(Amer Soc Testing Materials, 2012) Gur, C. Hakan; Simsir, Caner; Manufacturing Engineering
Quenching is an important part of the production chain of steel components. The final properties of the product are largely determined during this stage, and this renders quenching as one of the most critical stages of production, requiring design and optimization specific to the product. The simulation of quenching requires the solution of a multi-scale/multi-physics problem with complex boundary conditions because of the simultaneously occurring heat transfer, phase transformation, and mechanical interactions. The aim of this paper is to provide an updated review of research studies on the simulation of quenching. The subject is covered from the pioneering work up to very recent advances in the field, with special emphasis on future research needs for improving the industrial usage of heat treatment simulations.
Citation - WoS: 8
Citation - Scopus: 10
Simulation of Through-Hardening of Sae 52100 Steel Bearings - Part I: Determination of Material Properties
(Wiley-v C H verlag Gmbh, 2016) Mustak, O.; Evcil, G. E.; Simsir, C.; Manufacturing Engineering
A 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.