Hasan Sofuoğlu | Karadeniz Technical University (original) (raw)
Papers by Hasan Sofuoğlu
Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- ... more Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Bu çalışmada, yüzey pürüzlülüğünün temas basıncı, şekil değiştirme ve gerilmeler üzerindeki etkilerini araştırmak amacıyla; pürüzlü yüzey ile yarı-sonsuz ortamın temas analizi sonlu elemanlar yöntemiyle gerçekleştirilmiştir. Bu amaçla, fraktal geometri ile modellenmiş rijit pürüzlü yüzeyin homojen, elastik-tam plastik pürüzsüz yarı-sonsuz ortam ile normal teması için 2-boyutlu bir sonlu elemanlar modeli geliştirilmiştir. Mekanik yüzey yüklerinin yarısonsuz ortamda oluşan von Mises eşdeğer gerilmesi, elastik-plastik şekil değiştirmeleri ile temas basınç değerleri üzerindeki etkileri belirlenmiştir. Ayrıca, rijit pürüzlü yüzeyin yarısonsuz ortam içindeki temas derinliği miktarının (girişim) şekil değişimine etkisi de incelenmiştir. Fraktal geometri kullanarak geliştirilen ve böylece pürüz etkileşimlerinin de dikkate alındığ...
Wear, 2009
Rigid rough surface of a magnetic head and smooth surface of a hard disk are chosen to perform a ... more Rigid rough surface of a magnetic head and smooth surface of a hard disk are chosen to perform a comprehensive thermo-mechanical contact analysis at the magnetic head-disk interface, which is characterized by using the fractal geometry. The effects of mechanical and thermal surface loadings on deformation of the semi-infinite medium in normal and sliding contacts are analyzed simultaneously by developing a 2D finite element model. It is shown that frictional heating increases not only the contact area but also the contact pressure and stresses. The maximum temperature occurs at the tip of the asperities of the semi-infinite medium.
ABSTRACT Numerical analysis of powder compaction process requires multi-particle modeling approac... more ABSTRACT Numerical analysis of powder compaction process requires multi-particle modeling approach as continuum models fail to simulate the nature of process (e.g. interparticle, and particle–die interactions), accurately. This study aimed for analyzing powder compaction process utilizing 3-D finite element modeling approach along with different material models including modified Cam-Clay, Mohr–Coulomb, Shima–Oyane and von-Mises. The finite element analyses were carried out by implementing multi-particle finite element method. Moreover, continuum modeling was also performed for comparison purposes. In both cases, the compaction of spherical copper particles was analyzed at room temperature conditions. The obtained FEA results were compared in terms of equivalent stress and strain, and deformed shape. Results showed that the FE models in which von-Mises and modified Cam-clay material models were used yielded results of similar magnitude while those of Shima–Oyane and Mohr–Coulomb material models resulted in equivalent stress and strain values are in close proximity. Effect of coefficient of friction on the results was also investigated by implementing three distinct coefficients of friction (μ = 0.1, 0.25, 0.4). It was noted that increasing friction resulted in elevated level of defor-mation for the particles and harsher particle–particle, and particle–die contact interactions.
Tribology International, 2013
Tribological performances of non-grooved and micro-grooved journal bearings were studied under dy... more Tribological performances of non-grooved and micro-grooved journal bearings were studied under dynamic loading. Numerous experiments were performed using purpose-built test rig and then simulated using various numerical methods. Friction force, friction coefficient, shaft center orbit, and film thickness were determined experimentally and numerically. The experimental and numerical results were in good agreement and the friction forces progressively increased on plain and circumferential, herringbone, and transversally micro-grooved bearing. The results show that it is necessary to complete detailed investigation about the tribological properties of the micro-grooved journal bearing by taking their shape, depth and operating condition into account.
Tribology International, 2003
Design factor problems related to galling failure have become an increasing concern for deepwater... more Design factor problems related to galling failure have become an increasing concern for deepwater offshore wells. This paper presents the results of an experimental study conducted to determine friction characteristics of P-110 tubing coated with manganese phosphate and plated with tin. Six repeated tests were run to investigate the effect of lubrication type on friction characteristics of P-110 tubing by
In this study, formability of superplastic Zn-22Al alloy was investigated experimentally and nume... more In this study, formability of superplastic Zn-22Al alloy was investigated experimentally and numerically at room temperature (RT). To this goal, Zn-22Al alloy was wrought and grain size of the alloy was decreased to 200 nm by means of equal channel angular extrusion (ECAE), first. Then, Erichsen tests were conducted at 1x10 s, 1x10 s, 1x10 s strain rates. After experimental work, Ls-Dyna finite element software was used for numerical analysis of Erichsen test to compare the thickness distribution obtained both experimentallyand numerically . It was shown that Zn-22Al alloy had room temperature superplasticity and superplastic forming could be modeled accurately enough using FEA based on the good fit between numerical and experimental results.
Tribology International
Abstract A comparative numerical and experimental analysis of metal powder compaction processes w... more Abstract A comparative numerical and experimental analysis of metal powder compaction processes was presented. Closed-die compaction of spherical copper particles with a nominal diameter of 200 μm was analyzed using Multi Particle Finite Element Method (MPFEM). The von Mises material model associated with contact sensing algorithms was employed to investigate variation of coefficient of friction, and contact interactions between powder particles as well as particles with the die walls. Three different friction models (Amonton-Coulomb, Wanheim-Bay, and Levanov) were used to provide a better insight and the latter two were integrated into the commercial finite element package via user-subroutines. To verify the established model, some compaction experiments were carried out. Optical, and scanning electron microscopy analyses were performed, and images obtained were compared with the numerical results. The values of the coefficient of friction obtained using Wanheim-Bay and Levanov friction models fall into the range of 0.04–0.07. From the stress distribution perspective, it was observed that the results obtained with Wanheim-Bay friction model were more conforming to experimental cases where high relative density compaction takes place while Levanov friction model was found to be preferable at low relative density compaction process.
3.4 Finite Element Analysis of Ring Compr ession Test 3.4.1 The Results of FE Analysis of Ring Co... more 3.4 Finite Element Analysis of Ring Compr ession Test 3.4.1 The Results of FE Analysis of Ring Compression Test 71 3.5 The FE Analysis of Compression Test 3.5.1 The Results of FE Analysis of Compression Test 3.5.2 The Effect of Mesh Sensitivity 3.5.3 The Effect of the Coefficient of Friction 3.6 FE Analysis of Open-die Backward Extrusion Test 121 3.6.1 The Results of FE Analysis of Open-die Backward Extrusion IV. EXPERIMENTAL PROCEDURE 131 4.1 Introduction 131 4.2 Procedure for Physical Modeling 131 4.3 Strain-Rate Sensitivity Test of Plasticine 4.3.1 Effect of Strain-Rate on Plasticine 4.4 Compression Test 4.4.1 Specimen Preparation 4.4.2 Test Procedure 4.4.3 Compression Test Results 4.5 Ring Compression Test 4.5.1 Specimen Preparation and Test Procedure 163 4.5.2 Experimental Ring Compression Test Results 165 4.6 Open-Die Backward Extrusion Test 165 4.6.1 Test Procedure and Results 168 V. COMPARISON AND DISCUSSION 171 VI. CONCLUSION AND RECOMMENDATION 186 6.1 Conclusion 186 6.2 Recommendation 189 REFERENCES 191 APPENDIX A. THE RUNNING PROCEDURE OF ABAQUS 199 IV f B. ABAQUS FINITE ELEMENT PROGRAM FOR THE ANALYSIS OF RING COMPRESSION TEST 201
Academic Perspective Procedia, 2018
Bu çalışmada, süperplastik Zn-22Al alaşımının oda sıcaklığındaki şekillendirilebilirl... more Bu çalışmada, süperplastik Zn-22Al alaşımının oda sıcaklığındaki şekillendirilebilirliği deneysel ve sayısal olarak incelenmiştir. İlk olarak, Zn-22Al alaşımı döküm yoluyla üretilmiş ve eş kanallı açısal ekstrüzyon (EKAE) yöntemi uygulanarak tane boyutu 200 nm düşürülmüştür. Erichsen testleri 1x10-1 , 1x10-2 ve 1x10-3 s-1 deformasyon hızlarında gerçekleştirilmiştir. Deneysel çalışma sonrası, Ls-Dyna sonlu elemanlar yazılımı kullanılarak Erichsen testinin sonlu elemanlar analizleri yapılmış, deneysel ve sayısal olarak elde edilen kalınlık değişimleri karşılaştırılmıştır. Zn-22Al alaşımının oda sıcaklığında süperplastik şekillendirilebildiği gösterilmiş, ve bu malzeme için elde edilen deneysel ve sayısal sonuçlar arasındaki uyum göz önüne alındığında süperplastik şekillendirmenin sonlu elemanlar yöntemi ile yeterince hassas olarak modellenebildiği gö...
Micro fabrication techniques used for the production of dental implants offer different surface s... more Micro fabrication techniques used for the production of dental implants offer different surface shaping options particularly effective on the quality of osseointegration. However, to obtain osseointegration with current implant surface roughening techniques bring about various problems. These are mainly operating and maintenance costs of systems used in roughening process, high cost of powder used in blasting, being an imported material, health risk due to blasting powder, high noise at production area and adverse effects of chemicals used. The purpose of this study is to determine the stress values of dental implants with micro-scale hemispherical pockets on the surface produced at CNC machines under various loading conditions after osseointegration. In the study, solid modelling programs were used to design dental implant. Hemispherical cavities in the diameter of 150 and 300 µm are opened on the surface of dental implants excluding the grooved surfaces. Loadings were carried out ...
Turkish Journal of Engineering and Environmental Sciences, 1998
The friction coefficient and the galling process in metal to metal parts depend on many variables... more The friction coefficient and the galling process in metal to metal parts depend on many variables such as normal load, lubricant, roughness and design of the friction surfaces. Since developing a mathematical model is very difficult for friction pheenomena and the galling process, these tribological events can be explained with studies taking some parameters as constant. In this study, an experimental system was established in order to investigate the friction coefficient versus the normal load with respect to time. Moreover, yield stress and rotational speed for different materials were determined with the Up and Down Technique. In all the experiments, L80 and J55 tubing materials were used.
Dental deficiency problems on the damaged mandibles can be solved by applying implant abutment wi... more Dental deficiency problems on the damaged mandibles can be solved by applying implant abutment with different lengths, artificial chin material and using prosthesis filling materials. The purpose of this study to investigate the stresses occurred on hard and soft bones after recovering the deficiency caused by totally edentulous and damaged mandible by using abutments with different lengths and prosthesis filling material. At the first step of this study, prosthesis data were obtained by optical scanning method. The data were then used to design an implant model suited to prosthesis using Solidwork programs. Later, 3-D model of assembly with abutment and mandible (soft bone, hard bone and mucosa) was created. Two different damaged parts of 2.5 and 4.5 mm in depth were created with the aid of Solidwork program on the right hand side of the mandible. Implants were then applied between the foremen channels. Later, the damaged models were recovered by abutment with different lengths as ...
The purpose of this study is to investigate the stresses occurred onhard and soft bones after rec... more The purpose of this study is to investigate the stresses occurred onhard and soft bones after recovering the deficiency caused by totally edentulousand damaged mandible by using abutments with different lengths andprosthesis filling material. Two different damaged parts of 2.5 and 4.5 mm indepth were created with the aid of Solidworks program on the right hand sideof the mandible. Implants were then applied between the foremen channels.Later, the damaged models were recovered by abutment with different lengthsas for the first method. Two models using abutment were, therefore, obtainedfor the damaged parts of 2.5 and 4.5 mm in depth. In the second method, for thesame damaged cases, prosthesis filling material was used to recover deficiencykeeping the abutment length constant. Finally, there were totally obtained 4different damaged models of two fixed with abutment and two fixed with fillingmaterial and 1 undamaged model. At the second step of this study, the stressvalues were obtaine...
Journal of Engineering Materials and Technology
This study aimed to investigate the micro deep drawability of Zn-22Al alloy at room temperature i... more This study aimed to investigate the micro deep drawability of Zn-22Al alloy at room temperature in which it shows superplastic properties. To this goal, two-step equal channel angular extrusion (ECAE) process was carried out to obtain an ultra-fine grained structure (UFG), first. Upon achieving the grain size of 200 nm, the formability of the alloy at room temperature and at a high strain rate was investigated both experimentally and numerically. Micro deep drawing experiments were performed at different deep drawing ratios (1.66, 1.84, 2.0 and 2.25) and for different sheet thicknesses (0.2, 0.4 and 0.6 mm). Finite element model of the micro deep drawing was also established to assess and compare the thickness variation in deep drawn parts. Results showed that the superplastic Zn-22Al alloy has a great potential in microforming applications. It was also noted that the limiting drawing ratio can be obtained as high as 2.25 in room temperature condition.
The International Journal of Advanced Manufacturing Technology
Thin-walled tubes are widely used as energy absorbers due to their high crashworthiness performan... more Thin-walled tubes are widely used as energy absorbers due to their high crashworthiness performance. This study aims to evaluate the effect of plastic forming history carried out for thickness optimization on crashworthiness performance of thin-walled square tube (TWST). Within the scope of the study, a series of numerical analyzes were conducted for the TWST using commercial finite element (FE) software. In order to determine the individual effect of optimization, the FG thickness of TWST was first obtained using LS-OPT software. Later, thickness gradient was achieved by performing a rolling process to consider individual plastic forming effects. Afterwards, a deep drawing process was carried out to shape TWST by considering springback and trimming effects. Finally, crash responses were obtained under axial high-velocity impact loading to determine the coupled effect of optimization and plastic forming on the crashworthiness performance of the TWST. It was determined that the coupled effect, which takes plastic forming and optimization effects into account, reduced the peak crush force of the TWST by 24% and increased the absorbed energy value by 39%. The results obtained from this study showed that coupled effect of optimization and plastic forming processes has a significant effect on the crashworthiness performance of the TWST, and otherwise, either overestimated or underestimated results are obtained.
Biomedical Engineering / Biomedizinische Technik, 2015
The aim of this work was to study how the stress distributions of the hip joint&a... more The aim of this work was to study how the stress distributions of the hip joint's components were changed if the activity was switched from walking to stair climbing for three different prostheses types subjected to either concentrated or distributed load. In the scope of the study, three different cemented prostheses, namely, Charnley, Muller, and Hipokrat were used for cemented total hip arthroplasty (THA) reconstruction. The finite element modeling of the hip joint with prosthesis was developed for both hip contact and muscle forces during walking and stair climbing activities. The finite element analyses were then pursued for both concentrated and distributed loading conditions applied statically on these models. Maximum von Mises stresses and strains occurred on the cortical and trabecular layers of bones; prosthesis and cement mantle were determined in order to investigate the mechanical failure of cemented THA reconstruction subjected to the different femoral loading and the activity conditions. This study showed that prosthesis, loading, and activity types had a significant effect on the stresses of components of the hip joint utilized for predicting mechanical failure of the cemented THA reconstruction.
SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012
SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012
Tribology International, 2016
Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- ... more Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Bu çalışmada, yüzey pürüzlülüğünün temas basıncı, şekil değiştirme ve gerilmeler üzerindeki etkilerini araştırmak amacıyla; pürüzlü yüzey ile yarı-sonsuz ortamın temas analizi sonlu elemanlar yöntemiyle gerçekleştirilmiştir. Bu amaçla, fraktal geometri ile modellenmiş rijit pürüzlü yüzeyin homojen, elastik-tam plastik pürüzsüz yarı-sonsuz ortam ile normal teması için 2-boyutlu bir sonlu elemanlar modeli geliştirilmiştir. Mekanik yüzey yüklerinin yarısonsuz ortamda oluşan von Mises eşdeğer gerilmesi, elastik-plastik şekil değiştirmeleri ile temas basınç değerleri üzerindeki etkileri belirlenmiştir. Ayrıca, rijit pürüzlü yüzeyin yarısonsuz ortam içindeki temas derinliği miktarının (girişim) şekil değişimine etkisi de incelenmiştir. Fraktal geometri kullanarak geliştirilen ve böylece pürüz etkileşimlerinin de dikkate alındığ...
Wear, 2009
Rigid rough surface of a magnetic head and smooth surface of a hard disk are chosen to perform a ... more Rigid rough surface of a magnetic head and smooth surface of a hard disk are chosen to perform a comprehensive thermo-mechanical contact analysis at the magnetic head-disk interface, which is characterized by using the fractal geometry. The effects of mechanical and thermal surface loadings on deformation of the semi-infinite medium in normal and sliding contacts are analyzed simultaneously by developing a 2D finite element model. It is shown that frictional heating increases not only the contact area but also the contact pressure and stresses. The maximum temperature occurs at the tip of the asperities of the semi-infinite medium.
ABSTRACT Numerical analysis of powder compaction process requires multi-particle modeling approac... more ABSTRACT Numerical analysis of powder compaction process requires multi-particle modeling approach as continuum models fail to simulate the nature of process (e.g. interparticle, and particle–die interactions), accurately. This study aimed for analyzing powder compaction process utilizing 3-D finite element modeling approach along with different material models including modified Cam-Clay, Mohr–Coulomb, Shima–Oyane and von-Mises. The finite element analyses were carried out by implementing multi-particle finite element method. Moreover, continuum modeling was also performed for comparison purposes. In both cases, the compaction of spherical copper particles was analyzed at room temperature conditions. The obtained FEA results were compared in terms of equivalent stress and strain, and deformed shape. Results showed that the FE models in which von-Mises and modified Cam-clay material models were used yielded results of similar magnitude while those of Shima–Oyane and Mohr–Coulomb material models resulted in equivalent stress and strain values are in close proximity. Effect of coefficient of friction on the results was also investigated by implementing three distinct coefficients of friction (μ = 0.1, 0.25, 0.4). It was noted that increasing friction resulted in elevated level of defor-mation for the particles and harsher particle–particle, and particle–die contact interactions.
Tribology International, 2013
Tribological performances of non-grooved and micro-grooved journal bearings were studied under dy... more Tribological performances of non-grooved and micro-grooved journal bearings were studied under dynamic loading. Numerous experiments were performed using purpose-built test rig and then simulated using various numerical methods. Friction force, friction coefficient, shaft center orbit, and film thickness were determined experimentally and numerically. The experimental and numerical results were in good agreement and the friction forces progressively increased on plain and circumferential, herringbone, and transversally micro-grooved bearing. The results show that it is necessary to complete detailed investigation about the tribological properties of the micro-grooved journal bearing by taking their shape, depth and operating condition into account.
Tribology International, 2003
Design factor problems related to galling failure have become an increasing concern for deepwater... more Design factor problems related to galling failure have become an increasing concern for deepwater offshore wells. This paper presents the results of an experimental study conducted to determine friction characteristics of P-110 tubing coated with manganese phosphate and plated with tin. Six repeated tests were run to investigate the effect of lubrication type on friction characteristics of P-110 tubing by
In this study, formability of superplastic Zn-22Al alloy was investigated experimentally and nume... more In this study, formability of superplastic Zn-22Al alloy was investigated experimentally and numerically at room temperature (RT). To this goal, Zn-22Al alloy was wrought and grain size of the alloy was decreased to 200 nm by means of equal channel angular extrusion (ECAE), first. Then, Erichsen tests were conducted at 1x10 s, 1x10 s, 1x10 s strain rates. After experimental work, Ls-Dyna finite element software was used for numerical analysis of Erichsen test to compare the thickness distribution obtained both experimentallyand numerically . It was shown that Zn-22Al alloy had room temperature superplasticity and superplastic forming could be modeled accurately enough using FEA based on the good fit between numerical and experimental results.
Tribology International
Abstract A comparative numerical and experimental analysis of metal powder compaction processes w... more Abstract A comparative numerical and experimental analysis of metal powder compaction processes was presented. Closed-die compaction of spherical copper particles with a nominal diameter of 200 μm was analyzed using Multi Particle Finite Element Method (MPFEM). The von Mises material model associated with contact sensing algorithms was employed to investigate variation of coefficient of friction, and contact interactions between powder particles as well as particles with the die walls. Three different friction models (Amonton-Coulomb, Wanheim-Bay, and Levanov) were used to provide a better insight and the latter two were integrated into the commercial finite element package via user-subroutines. To verify the established model, some compaction experiments were carried out. Optical, and scanning electron microscopy analyses were performed, and images obtained were compared with the numerical results. The values of the coefficient of friction obtained using Wanheim-Bay and Levanov friction models fall into the range of 0.04–0.07. From the stress distribution perspective, it was observed that the results obtained with Wanheim-Bay friction model were more conforming to experimental cases where high relative density compaction takes place while Levanov friction model was found to be preferable at low relative density compaction process.
3.4 Finite Element Analysis of Ring Compr ession Test 3.4.1 The Results of FE Analysis of Ring Co... more 3.4 Finite Element Analysis of Ring Compr ession Test 3.4.1 The Results of FE Analysis of Ring Compression Test 71 3.5 The FE Analysis of Compression Test 3.5.1 The Results of FE Analysis of Compression Test 3.5.2 The Effect of Mesh Sensitivity 3.5.3 The Effect of the Coefficient of Friction 3.6 FE Analysis of Open-die Backward Extrusion Test 121 3.6.1 The Results of FE Analysis of Open-die Backward Extrusion IV. EXPERIMENTAL PROCEDURE 131 4.1 Introduction 131 4.2 Procedure for Physical Modeling 131 4.3 Strain-Rate Sensitivity Test of Plasticine 4.3.1 Effect of Strain-Rate on Plasticine 4.4 Compression Test 4.4.1 Specimen Preparation 4.4.2 Test Procedure 4.4.3 Compression Test Results 4.5 Ring Compression Test 4.5.1 Specimen Preparation and Test Procedure 163 4.5.2 Experimental Ring Compression Test Results 165 4.6 Open-Die Backward Extrusion Test 165 4.6.1 Test Procedure and Results 168 V. COMPARISON AND DISCUSSION 171 VI. CONCLUSION AND RECOMMENDATION 186 6.1 Conclusion 186 6.2 Recommendation 189 REFERENCES 191 APPENDIX A. THE RUNNING PROCEDURE OF ABAQUS 199 IV f B. ABAQUS FINITE ELEMENT PROGRAM FOR THE ANALYSIS OF RING COMPRESSION TEST 201
Academic Perspective Procedia, 2018
Bu çalışmada, süperplastik Zn-22Al alaşımının oda sıcaklığındaki şekillendirilebilirl... more Bu çalışmada, süperplastik Zn-22Al alaşımının oda sıcaklığındaki şekillendirilebilirliği deneysel ve sayısal olarak incelenmiştir. İlk olarak, Zn-22Al alaşımı döküm yoluyla üretilmiş ve eş kanallı açısal ekstrüzyon (EKAE) yöntemi uygulanarak tane boyutu 200 nm düşürülmüştür. Erichsen testleri 1x10-1 , 1x10-2 ve 1x10-3 s-1 deformasyon hızlarında gerçekleştirilmiştir. Deneysel çalışma sonrası, Ls-Dyna sonlu elemanlar yazılımı kullanılarak Erichsen testinin sonlu elemanlar analizleri yapılmış, deneysel ve sayısal olarak elde edilen kalınlık değişimleri karşılaştırılmıştır. Zn-22Al alaşımının oda sıcaklığında süperplastik şekillendirilebildiği gösterilmiş, ve bu malzeme için elde edilen deneysel ve sayısal sonuçlar arasındaki uyum göz önüne alındığında süperplastik şekillendirmenin sonlu elemanlar yöntemi ile yeterince hassas olarak modellenebildiği gö...
Micro fabrication techniques used for the production of dental implants offer different surface s... more Micro fabrication techniques used for the production of dental implants offer different surface shaping options particularly effective on the quality of osseointegration. However, to obtain osseointegration with current implant surface roughening techniques bring about various problems. These are mainly operating and maintenance costs of systems used in roughening process, high cost of powder used in blasting, being an imported material, health risk due to blasting powder, high noise at production area and adverse effects of chemicals used. The purpose of this study is to determine the stress values of dental implants with micro-scale hemispherical pockets on the surface produced at CNC machines under various loading conditions after osseointegration. In the study, solid modelling programs were used to design dental implant. Hemispherical cavities in the diameter of 150 and 300 µm are opened on the surface of dental implants excluding the grooved surfaces. Loadings were carried out ...
Turkish Journal of Engineering and Environmental Sciences, 1998
The friction coefficient and the galling process in metal to metal parts depend on many variables... more The friction coefficient and the galling process in metal to metal parts depend on many variables such as normal load, lubricant, roughness and design of the friction surfaces. Since developing a mathematical model is very difficult for friction pheenomena and the galling process, these tribological events can be explained with studies taking some parameters as constant. In this study, an experimental system was established in order to investigate the friction coefficient versus the normal load with respect to time. Moreover, yield stress and rotational speed for different materials were determined with the Up and Down Technique. In all the experiments, L80 and J55 tubing materials were used.
Dental deficiency problems on the damaged mandibles can be solved by applying implant abutment wi... more Dental deficiency problems on the damaged mandibles can be solved by applying implant abutment with different lengths, artificial chin material and using prosthesis filling materials. The purpose of this study to investigate the stresses occurred on hard and soft bones after recovering the deficiency caused by totally edentulous and damaged mandible by using abutments with different lengths and prosthesis filling material. At the first step of this study, prosthesis data were obtained by optical scanning method. The data were then used to design an implant model suited to prosthesis using Solidwork programs. Later, 3-D model of assembly with abutment and mandible (soft bone, hard bone and mucosa) was created. Two different damaged parts of 2.5 and 4.5 mm in depth were created with the aid of Solidwork program on the right hand side of the mandible. Implants were then applied between the foremen channels. Later, the damaged models were recovered by abutment with different lengths as ...
The purpose of this study is to investigate the stresses occurred onhard and soft bones after rec... more The purpose of this study is to investigate the stresses occurred onhard and soft bones after recovering the deficiency caused by totally edentulousand damaged mandible by using abutments with different lengths andprosthesis filling material. Two different damaged parts of 2.5 and 4.5 mm indepth were created with the aid of Solidworks program on the right hand sideof the mandible. Implants were then applied between the foremen channels.Later, the damaged models were recovered by abutment with different lengthsas for the first method. Two models using abutment were, therefore, obtainedfor the damaged parts of 2.5 and 4.5 mm in depth. In the second method, for thesame damaged cases, prosthesis filling material was used to recover deficiencykeeping the abutment length constant. Finally, there were totally obtained 4different damaged models of two fixed with abutment and two fixed with fillingmaterial and 1 undamaged model. At the second step of this study, the stressvalues were obtaine...
Journal of Engineering Materials and Technology
This study aimed to investigate the micro deep drawability of Zn-22Al alloy at room temperature i... more This study aimed to investigate the micro deep drawability of Zn-22Al alloy at room temperature in which it shows superplastic properties. To this goal, two-step equal channel angular extrusion (ECAE) process was carried out to obtain an ultra-fine grained structure (UFG), first. Upon achieving the grain size of 200 nm, the formability of the alloy at room temperature and at a high strain rate was investigated both experimentally and numerically. Micro deep drawing experiments were performed at different deep drawing ratios (1.66, 1.84, 2.0 and 2.25) and for different sheet thicknesses (0.2, 0.4 and 0.6 mm). Finite element model of the micro deep drawing was also established to assess and compare the thickness variation in deep drawn parts. Results showed that the superplastic Zn-22Al alloy has a great potential in microforming applications. It was also noted that the limiting drawing ratio can be obtained as high as 2.25 in room temperature condition.
The International Journal of Advanced Manufacturing Technology
Thin-walled tubes are widely used as energy absorbers due to their high crashworthiness performan... more Thin-walled tubes are widely used as energy absorbers due to their high crashworthiness performance. This study aims to evaluate the effect of plastic forming history carried out for thickness optimization on crashworthiness performance of thin-walled square tube (TWST). Within the scope of the study, a series of numerical analyzes were conducted for the TWST using commercial finite element (FE) software. In order to determine the individual effect of optimization, the FG thickness of TWST was first obtained using LS-OPT software. Later, thickness gradient was achieved by performing a rolling process to consider individual plastic forming effects. Afterwards, a deep drawing process was carried out to shape TWST by considering springback and trimming effects. Finally, crash responses were obtained under axial high-velocity impact loading to determine the coupled effect of optimization and plastic forming on the crashworthiness performance of the TWST. It was determined that the coupled effect, which takes plastic forming and optimization effects into account, reduced the peak crush force of the TWST by 24% and increased the absorbed energy value by 39%. The results obtained from this study showed that coupled effect of optimization and plastic forming processes has a significant effect on the crashworthiness performance of the TWST, and otherwise, either overestimated or underestimated results are obtained.
Biomedical Engineering / Biomedizinische Technik, 2015
The aim of this work was to study how the stress distributions of the hip joint&a... more The aim of this work was to study how the stress distributions of the hip joint's components were changed if the activity was switched from walking to stair climbing for three different prostheses types subjected to either concentrated or distributed load. In the scope of the study, three different cemented prostheses, namely, Charnley, Muller, and Hipokrat were used for cemented total hip arthroplasty (THA) reconstruction. The finite element modeling of the hip joint with prosthesis was developed for both hip contact and muscle forces during walking and stair climbing activities. The finite element analyses were then pursued for both concentrated and distributed loading conditions applied statically on these models. Maximum von Mises stresses and strains occurred on the cortical and trabecular layers of bones; prosthesis and cement mantle were determined in order to investigate the mechanical failure of cemented THA reconstruction subjected to the different femoral loading and the activity conditions. This study showed that prosthesis, loading, and activity types had a significant effect on the stresses of components of the hip joint utilized for predicting mechanical failure of the cemented THA reconstruction.
SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012
SAÜ Fen Bilimleri Enstitüsü Dergisi, 2012
Tribology International, 2016