Funda KAHRAMAN - Academia.edu (original) (raw)

Papers by Funda KAHRAMAN

Ohs academy, Sep 2, 2023

Makale Tarihçesi Öz-Mevcut piyasanın ağır rekabet koşulları, şirketlerin sahip olduğu kaynakların... more Makale Tarihçesi Öz-Mevcut piyasanın ağır rekabet koşulları, şirketlerin sahip olduğu kaynaklarını daha verimli kullanması yönünde iyileştirmeler yapmaya mecbur bırakmaktadır. Bu durumun, şirketlerin iş sağlığı ve güvenliği alanındaki planlama ve aktivitelerine de yansıması olağandır. Belirlenen risklere dair ; hangi riske, hangi derecede önem verilerek, risklerin giderilmesi işlemine nereden başlanması gerekliliği, risklerin giderilmesi için hazırlanacak planlamanın belirlenmesi açısından kıymetli bir veri olacaktır. Bu sayede şirket hem gereksiz zaman ve para kaybından uzaklaşmış olacaktır hem de doğru riskleri doğru zamanda gidererek, olası iş kazalarının önüne geçmek adına uygun bir adım atmış olacaktır. Aksi durumda nispeten düşük önem sahip risklere yüksek önemler atfedilerek giderilmesi daha öncelikli olan risklerin giderilmesinin ötelenmesine yol açılarak iş kazalarının yaşanmasına sebep olunabilir. Yapılan bu çalışma, elektrik yapım işi sektöründeki bir şirketin, klasik Fine Kinney yöntemiyle hazırlanan risk değerlendirme raporunu baz alarak, Analitik Hiyerarşi Süreci, Analitik Ağ Süreci ve Bulanık Fine Kinney yöntemleriyle riskler önceliklendirilmeye çalışılmıştır. Analitik Hiyerarşi Süreci ve Analitik Ağ Süreci yöntemleri için SuperDesicion yazılımı, Bulanık Fine Kinney metodu için ise MATLAB programında bulunan Fuzzy Logic Toolbox yazılımı kullanılmıştır. Risklerin önceliklendirilmesi işleminde firmanın risk değerlendirme raporunun da hazırlanmasında rol alan firma çalışanlarından iş güvenliği uzmanları, iş yeri hekimi ve proje yöneticilerinin oluşturduğu on kişilik bir ekip görev almıştır. Bu seçimin yapılmasında iş sağlığı ve güvenliği konusunda yetkin olmaları ve firmanın faaliyetlerine hâkim olmaları dikkate alınmıştır. Kullanılan yöntemlerin tümü bir arada değerlendirilerek, karar vericiye mevcut tehlikelerin giderilmesinde; hangilerine, ne ölçüde önem atfederek öncelik verilmesi konusunda önerilerde bulunulmuştur. Sonuçlar karşılaştırıldığında bulanık Fine Kinney yönteminin en uygun sonuç ürettiği görülmüş ve Elektrik kategorisindeki tehlikelerin öncelikli olarak ele alınarak giderilmesi gerektiği önerilmiştir.

Çukurova Üniversitesi Mühendislik Fakültesi Dergisi

Elektrik yapım işi temel olarak; üretilen ve dağıtıma hazır elektriğin, hane ve işletmelere dağıt... more Elektrik yapım işi temel olarak; üretilen ve dağıtıma hazır elektriğin, hane ve işletmelere dağıtılması için gerekli olan alt yapının inşasını ve bu konuda önceden tesis edilmiş altyapıların modernizasyonunu ve büyütülmesini konu edinmiş bir alandır. Dolayısı ile ülkenin tüm büyüme ve kalkınma planlarında elektrik yapım işi sektörü ve üreteceği hizmet, stratejik bir öneme sahiptir. Elektrik yapım işi sektörü, ülkemiz mevzuatına göre çok tehlikeli işler sınıfında yer almaktadır. Her yıl pek çok ölümlü ve ağır yaralanmalı iş kazası meydana gelmektedir. Bu sebeple sektör içinde yer alan firmaların oluşturacakları risk değerlendirmeleri ve bu doğrultuda tehlikelerin giderilmesi oldukça önemlidir. Bu sürecin belirli bir plan dahilinde işletilmesi, hem firmanın zaman, iş gücü ve para gibi kısıtlı kaynaklarının verimli kullanılmasına hem de aciliyet arz eden tehlikelerin daha hızlı giderilmesine olanak sağlayacaktır. Bu çalışmada; sektörde referans alınmış bir firmanın Fine-Kinney metodu k...

Burnishing is a plastic deformation process, and it has become more popular as a finishing proces... more Burnishing is a plastic deformation process, and it has become more popular as a finishing process. Thus, it is especially crucial to select the burnishing parameters to reduce the surface roughness. In the present study, a surface roughness prediction model using artificial neural network (ANN) is developed to investigate the effects of burnishing conditions during machining of AA 7075 aluminum material. The ANN model of surface roughness parameters (Ra) is developed considering the conditions as burnishing force, number of tool passes, feed rate and burnishing speed. The experimental results were trained in an ANN program and the results were compared with experimental values. It is observed that the experimental results coincided with ANN results.

International Journal of Scientific and Technological Research, 2018

In this study, the effect of cutting parameters on the various performance characteristics in the... more In this study, the effect of cutting parameters on the various performance characteristics in the drilling process (hole enlargement) of AA 5754 Aluminium alloy were experimentally investigated. Rotational speed, feed and depth of cut were considered as control factors, arithmetic average roughness, material removal rate and machining time were considered as response factors. Experiments were designed according to Taguchi L9 orthogonal array. Multi-response signal to noise ratio was calculated for the response variables simultaneously. Analysis of variance was performed to find out the effective cutting parameters on the surface roughnes, material removal rate and machining time. Furthermore, confirmation test was conducted for the obtained optimum combination level of factors. The obtained results indicate that the rotational speed was found to be the dominant factor among controllable factors, followed by the feed and the depth of cut. Optimal performance parameters were obtained ...

Modification of Al-Si cast alloys can be achieved in two different ways, namely by additions of c... more Modification of Al-Si cast alloys can be achieved in two different ways, namely by additions of certain eleinents or with rapid cooling rate. Modifications of the Al-Si al1oys are carried out extensivcly in industry to improve the mechanical properties, particularly ductility. In this study, the effects of antiinony addition.s and growth rate on the inicrostructure and eutectic morphology on the directionally solidified Al- 1 2.5°/o Si cutectic all oy has been investigated. The results showed that antimony can be identified as a grain refiner. Over modification occurs in Al- 12.5 °/oSi alloy when modifier is present in the amount of 1 %Sb results in AISb compound.

Industrial Lubrication and Tribology, 2018

Purpose This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sinteri... more Purpose This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sintering temperature (T) on the transverse rupture strength (TRS), hardness and density of fly ash reinforced bronze-based composite materials by using multi-objective Taguchi technique, analysis of variance (ANOVA) and regression analysis. Design/methodology/approach The bronze-based composite materials containing 5, 10 and 15 Wt.% fly ashes were prepared by using spark plasma sintering carried out under a pressure of 35 MPa, at 750, 800 and 850 °C for 3 min. Sintering temperature and fly ash reinforcement ratio were considered as input parameters; the TRS, hardness and density were considered as output parameters. Experiments were designed according to Taguchi L9 orthogonal array. Multi signal-to-noise ratio (MSNR) was computed to define the optimal process parameters. ANOVA was conducted to detect the importance of the input parameters for the process performance. Moreover, the linear model...

Materiali in tehnologije, 2016

In this research, the heat-treatment effect on the mechanical properties of free-cutting steels w... more In this research, the heat-treatment effect on the mechanical properties of free-cutting steels was investigated. Free-cutting steels (FCSs) are used where high degrees of machining are required as they increase the machining speed and reduce the tool wear. The effect of heat treatment on mechanical properties was identified using tensile and fatigue tests, and microstructure images taken with a scanning electron microscope (SEM). The studied material included commercially available AISI 12L14 cylindrical bars of free-cutting steel. FCS was heated to 900°C and held at this temperature for different time spans. The degradation of the mechanical properties of free-cutting steel due to the elevated temperature was assessed. At a microscopic level, more mechanical damage was observed between the steel matrix and the second phase of the heat-affected specimens. Keywords: fatigue, tensile strength, free-cutting steel, heat treatment V prispevku je bil raziskan vpliv toplotne obdelave na mehanske lastnosti avtomatnih jekel. Avtomatna jekla (FCS) se uporabljajo v primerih, ko so zahtevane velike stopnje obdelave, saj dopu{~ajo ve~je hitrosti rezanja ob manj{i obrabi orodja. Vpliv toplotne obdelave na mehanske lastnosti je bil dolo~en z rezultati nateznega preizkusa in preizkusa utrujenosti. Z vrsti~nim elektronskim mikroskopom (SEM) so bili narejeni posnetki mikrostrukture. Preiskovane so bile komercialno dosegljive palice iz avtomatnega jekla AISI 12L14. FCS je bil segret na 900°C in razli~no dolgo zadr`an na tej temperaturi. Dolo~eno je bilo zmanj{anje mehanskih lastnosti avtomatnega jekla zaradi povi{ane temperature. V toplotno obdelanih vzorcih je bilo z mikroskopom opa`enih ve~mehanskih po{kodb. Klju~ne besede: utrujenost, nateg, avtomatna jekla, toplotna obdelava

Materials Testing, 2016

In this study, a detailed analysis of hybrid weld manufacturing technologies that can significant... more In this study, a detailed analysis of hybrid weld manufacturing technologies that can significantly contribute to the joining of materials has been carried out. Past, present and future projection, advantages, dis advantages, technological barriers and drawbacks of the processes are given. Detailed explanations of the recent developments of hybrid weld manufacturing technologies and main components are given. Potential industrial applications are assessed and evaluated using economic and technological results. The developments in hybrid welding manufacturing technologies generally improved metallurgical and mechanical properties of weld joints. Hybrid processes usually combine the benefits of each individual process. Due to low heat input, hybrid welds create fine grain structures, minimize base material dilution and achieve high toughness and mechanical properties. These processes are especially appropriate for high performance alloys and dissimilar metal joining. The results of th...

Tubav Bilim Dergisi, 2009

Galetaj prosesi, taĢlama, lepleme ve honlama gibi talaĢ kaldırma prosesleri ile karĢılaĢtırıldığı... more Galetaj prosesi, taĢlama, lepleme ve honlama gibi talaĢ kaldırma prosesleri ile karĢılaĢtırıldığında birçok avantaja sahiptir. Galetaj prosesi ile, yüzey sertliği, korozyon ve aĢınma direnci artırmakta, iĢ parçasının yüzeyinde basma tarzı kalıntı gerilmelerin oluĢması nedeniyle yorulma dayanımı iyileĢmektedir. Bu çalıĢmada, AISI 4140 çelik malzemenin galetaj prosesinde, Taguchi deneysel tasarım metodu uygulanmıĢ ve yüzey pürüzlülüğü için optimum proses parametrelerini belirlenmiĢtir. Proses karakteristiklerini incelemek için ortogonal dizi, sinyal gürültü oranı (S/N) ve varyans analizi kullanılmıĢtır. Optimum galetaj parametreleri kullanılarak, malzemenin yüzey pürüzlülüğü % 74 oranında azaltılmıĢtır.

In this paper, a quadratic model was developed for the prediction of surface roughness in turning... more In this paper, a quadratic model was developed for the prediction of surface roughness in turning process of AISI 4140 steel using Response Surface Methodology (RSM) with rotatable Central Composite Design (CCD). The relationship between the surface roughness and cutting conditions was analyzed. In the development of predictive models, cutting speed, feed rate and depth of cut were considered as model variables and surface roughness was considered as a response variable. The results showed that, cutting speed and feed rate have the most significant effect on surface roughness.

Journal of Materials Science: Materials in Electronics, 2014

Bi 2 Sr 2 Co 1.8 O x ceramics have been synthesized through solid-state reaction methods and dire... more Bi 2 Sr 2 Co 1.8 O x ceramics have been synthesized through solid-state reaction methods and directionally grown from the melt by laser floating zone technique. Mechanical and thermoelectric characteristics of this material were determined by three point bending tests and the four probe technique, respectively. The mechanical and thermoelectric properties of Bi 2 Sr 2 Co 1.8 O x were determined as a function of the environmental conditions, air and water. Flexural strength data show that textured materials possess a high degradation resistance due to the low porosity of the external part of the rods (∼ 65µm), which avoids water infiltration and, as a consequence, the internal degradation. Moreover, power factor values are maintained practically unchanged for the samples immersed in water for 24h.

Journal of the European Ceramic Society, 2015

Ca 3 Co 4 O 9 + x wt% Ag (x=0, 1, 3, 5, and 10) polycrystalline thermoelectric ceramics have been... more Ca 3 Co 4 O 9 + x wt% Ag (x=0, 1, 3, 5, and 10) polycrystalline thermoelectric ceramics have been prepared by a sol-gel route via nitrates followed by high temperature treatment before sintering. Out-of-plane XRD data have shown that major phase is the Ca 3 Co 4 O 9 one, accompanied by metallic Ag. SEM observations have agreed with the XRD data. Apparent density measurements have revealed that all samples possess densities ranging between 80 and 90 % when Ag content is raised. Mechanical properties have shown a drastic increase of bending stress when Ag is added to the samples. Electrical resistivity decreases with the Ag content, compared with the pure ones, while Seebeck coefficient slightly decreases. Maximum power factor values around 0.43 mW/K 2 m at 800 ºC have been achieved for the 10 wt% Ag samples which is much higher than the measured in the pure Ca 3 Co 4 O 9 samples.

In this study, abrasive wear behaviour of poly oxy methylenes (POM) under various testing conditi... more In this study, abrasive wear behaviour of poly oxy methylenes (POM) under various testing conditions was investigated. A central composite design (CCD) was used to describe response and to estimate the parameters in the model. Response surface methodology (RSM) was adopted to obtain an empirical model of wear loss as a function of applied load and sliding distance. Also, a neural network (NN) model was developed for the prediction and testing of the results. Finally, a comparison was made between the results obtained from RSM and NN.

Materials Testing, 2015

In the present study, Grey based fuzzy algorithm was used for the optimization of complex multipl... more In the present study, Grey based fuzzy algorithm was used for the optimization of complex multiple performance characteristics of the ball burnishing process. Experiments have been planned according to Taguchi's L16 orthogonal design matrix. Burnishing force, number of passes, feed rate and burnishing speed were selected as input parameters, whereas surface roughness and microhardness were selected as output responses. Using Grey relation analysis (GRA), Grey relational coefficient (GRC) and Grey relation grade (GRG) were obtained. Then, Grey-based fuzzy algorithm was applied to obtain Grey fuzzy reasoning grade (GFRG). Analysis of variance (ANOVA) was carried out to find the significance and contribution of parameters on multiple performance characteristics. Finally, a confirmation test was applied at the optimum level of GFRG to validate the results. The results also show the feasibility of the Grey-based fuzzy algorithm for continuous improvement in product quality in complex...

Wire-electrical-discharge machining (WEDM) is a modification of electro-discharge machining (EDM)... more Wire-electrical-discharge machining (WEDM) is a modification of electro-discharge machining (EDM) and has been widely used for a long time for cutting punches and dies, shaped pockets and other machine parts on conductive materials. WEDM erodes workpiece materials by a series of discrete electrical sparks between the workpiece and an electrode flushed or immersed in a dielectric fluid. The WEDM process is particularly suitable for machining hard materials as well as complex shapes. In this paper, a neural network and the Taguchi design method have been implemented for minimizing the surface roughness in a WEDM process. A back-propagation neural network (BPNN) was developed to predict the surface roughness. In the development of a predictive model, machining parameters of open-circuit voltage, pulse duration, wire speed and dielectric flushing pressure were considered as the input model variables of the AISI 4340 steel. An analysis of variance (ANOVA) was used to determine the signif...

Materials Testing, 2015

A forming limit diagram (FLD) illustrates the behavior of sheet metal under different levels of s... more A forming limit diagram (FLD) illustrates the behavior of sheet metal under different levels of strain. The line describing the behavior of the metal is called forming limit curve (FLC). Forming limit diagram provides information on the maximum stress the metal can undergo before fracturing or necking. The diagrams are constructed by using forming limit test of sheet metal and measuring the deformation. In this study, formability of AISI 1020 sheet metal with different thickness were investigated using experimental data obtained from forming limit test. Forming limit diagram, strain hardening exponent (n) and height of cup values have been obtained for evaluating formability of the studied material. After each test, deformation of the grid was measured by using Mylar band and the true major and true minor strains were computed. Same formability results have been found from the FLD, strain hardening exponent and height of the cup for studied materials.

Ceramics International, 2015

The effect of environmental conditions on the microstructural, mechanical and thermoelectric prop... more The effect of environmental conditions on the microstructural, mechanical and thermoelectric properties of highly textured Bi 2 Ca 2 Co 1.7 O x thermoelectric materials was investigated by powder x-ray diffraction, scanning electron microscopy, three point bending test, electrical resistivity, and thermopower measurements. Textured thin rods were directionally grown from the melt through a laser floating zone melting technique. The mechanical and thermoelectric properties of Bi 2 Ca 2 Co 1.7 O x were determined as a function of two different environmental conditions, air and water. Flexural strength data showed that these oxide materials possess an unsuspected degradation resistance. These good results have been related to the presence of a very thin (∼250µm) low porosity region and relatively small grain sizes, which avoids the internal degration by water infiltration through the porosity. Moreover, thermoelectric performances, evaluated through the power factor are maintained practically unchanged, independently of the environmental conditions.

Materials Testing, 2012

Abstract Process capability indices are effective tools for both, process capability analysis and... more Abstract Process capability indices are effective tools for both, process capability analysis and quality assurance. In quality assurance programs, process capability indices reflect the performance of key quality characteristics for a control process. Quality assurance in mass production is enabled by using statistical process control techniques. In this study, various statistical process control techniques were carried out using the measured values taken from the workpieces that represent the whole process in the medium sized company. The chances for using statistical techniques for quality estimation processes have been discussed. For this purpose, normal probability plots and histograms were prepared and the process capability indices were calculated. As a result of this study, it turned out that the process capability for the whole process was inadequate and the mass production was unstable. Some actions must be taken by engineers to improve the quality level by shifting the process mean to target value and reducing the process variation.

Materials Testing, 2012

The present paper focuses on two techniques, namely regression and neural network, for predicting... more The present paper focuses on two techniques, namely regression and neural network, for predicting tool wear. Predicted values of tool wear by both techniques were compared with experimental values. Also, the effects of the main machining variables on tool wear have been determined. The metal volume removed (MVR) was taken as response (output) variable and cutting speed, feed rate, depth of cut and hardness were taken as input parameters, respectively. The relationship between tool wear and machining parameters was found out by direct measurement of the tool wear by MVR. The results showed the ability of regression and neural network models to predict the tool wear, accurately.

Ohs academy, Sep 2, 2023

Makale Tarihçesi Öz-Mevcut piyasanın ağır rekabet koşulları, şirketlerin sahip olduğu kaynakların... more Makale Tarihçesi Öz-Mevcut piyasanın ağır rekabet koşulları, şirketlerin sahip olduğu kaynaklarını daha verimli kullanması yönünde iyileştirmeler yapmaya mecbur bırakmaktadır. Bu durumun, şirketlerin iş sağlığı ve güvenliği alanındaki planlama ve aktivitelerine de yansıması olağandır. Belirlenen risklere dair ; hangi riske, hangi derecede önem verilerek, risklerin giderilmesi işlemine nereden başlanması gerekliliği, risklerin giderilmesi için hazırlanacak planlamanın belirlenmesi açısından kıymetli bir veri olacaktır. Bu sayede şirket hem gereksiz zaman ve para kaybından uzaklaşmış olacaktır hem de doğru riskleri doğru zamanda gidererek, olası iş kazalarının önüne geçmek adına uygun bir adım atmış olacaktır. Aksi durumda nispeten düşük önem sahip risklere yüksek önemler atfedilerek giderilmesi daha öncelikli olan risklerin giderilmesinin ötelenmesine yol açılarak iş kazalarının yaşanmasına sebep olunabilir. Yapılan bu çalışma, elektrik yapım işi sektöründeki bir şirketin, klasik Fine Kinney yöntemiyle hazırlanan risk değerlendirme raporunu baz alarak, Analitik Hiyerarşi Süreci, Analitik Ağ Süreci ve Bulanık Fine Kinney yöntemleriyle riskler önceliklendirilmeye çalışılmıştır. Analitik Hiyerarşi Süreci ve Analitik Ağ Süreci yöntemleri için SuperDesicion yazılımı, Bulanık Fine Kinney metodu için ise MATLAB programında bulunan Fuzzy Logic Toolbox yazılımı kullanılmıştır. Risklerin önceliklendirilmesi işleminde firmanın risk değerlendirme raporunun da hazırlanmasında rol alan firma çalışanlarından iş güvenliği uzmanları, iş yeri hekimi ve proje yöneticilerinin oluşturduğu on kişilik bir ekip görev almıştır. Bu seçimin yapılmasında iş sağlığı ve güvenliği konusunda yetkin olmaları ve firmanın faaliyetlerine hâkim olmaları dikkate alınmıştır. Kullanılan yöntemlerin tümü bir arada değerlendirilerek, karar vericiye mevcut tehlikelerin giderilmesinde; hangilerine, ne ölçüde önem atfederek öncelik verilmesi konusunda önerilerde bulunulmuştur. Sonuçlar karşılaştırıldığında bulanık Fine Kinney yönteminin en uygun sonuç ürettiği görülmüş ve Elektrik kategorisindeki tehlikelerin öncelikli olarak ele alınarak giderilmesi gerektiği önerilmiştir.

Çukurova Üniversitesi Mühendislik Fakültesi Dergisi

Elektrik yapım işi temel olarak; üretilen ve dağıtıma hazır elektriğin, hane ve işletmelere dağıt... more Elektrik yapım işi temel olarak; üretilen ve dağıtıma hazır elektriğin, hane ve işletmelere dağıtılması için gerekli olan alt yapının inşasını ve bu konuda önceden tesis edilmiş altyapıların modernizasyonunu ve büyütülmesini konu edinmiş bir alandır. Dolayısı ile ülkenin tüm büyüme ve kalkınma planlarında elektrik yapım işi sektörü ve üreteceği hizmet, stratejik bir öneme sahiptir. Elektrik yapım işi sektörü, ülkemiz mevzuatına göre çok tehlikeli işler sınıfında yer almaktadır. Her yıl pek çok ölümlü ve ağır yaralanmalı iş kazası meydana gelmektedir. Bu sebeple sektör içinde yer alan firmaların oluşturacakları risk değerlendirmeleri ve bu doğrultuda tehlikelerin giderilmesi oldukça önemlidir. Bu sürecin belirli bir plan dahilinde işletilmesi, hem firmanın zaman, iş gücü ve para gibi kısıtlı kaynaklarının verimli kullanılmasına hem de aciliyet arz eden tehlikelerin daha hızlı giderilmesine olanak sağlayacaktır. Bu çalışmada; sektörde referans alınmış bir firmanın Fine-Kinney metodu k...

Burnishing is a plastic deformation process, and it has become more popular as a finishing proces... more Burnishing is a plastic deformation process, and it has become more popular as a finishing process. Thus, it is especially crucial to select the burnishing parameters to reduce the surface roughness. In the present study, a surface roughness prediction model using artificial neural network (ANN) is developed to investigate the effects of burnishing conditions during machining of AA 7075 aluminum material. The ANN model of surface roughness parameters (Ra) is developed considering the conditions as burnishing force, number of tool passes, feed rate and burnishing speed. The experimental results were trained in an ANN program and the results were compared with experimental values. It is observed that the experimental results coincided with ANN results.

International Journal of Scientific and Technological Research, 2018

In this study, the effect of cutting parameters on the various performance characteristics in the... more In this study, the effect of cutting parameters on the various performance characteristics in the drilling process (hole enlargement) of AA 5754 Aluminium alloy were experimentally investigated. Rotational speed, feed and depth of cut were considered as control factors, arithmetic average roughness, material removal rate and machining time were considered as response factors. Experiments were designed according to Taguchi L9 orthogonal array. Multi-response signal to noise ratio was calculated for the response variables simultaneously. Analysis of variance was performed to find out the effective cutting parameters on the surface roughnes, material removal rate and machining time. Furthermore, confirmation test was conducted for the obtained optimum combination level of factors. The obtained results indicate that the rotational speed was found to be the dominant factor among controllable factors, followed by the feed and the depth of cut. Optimal performance parameters were obtained ...

Modification of Al-Si cast alloys can be achieved in two different ways, namely by additions of c... more Modification of Al-Si cast alloys can be achieved in two different ways, namely by additions of certain eleinents or with rapid cooling rate. Modifications of the Al-Si al1oys are carried out extensivcly in industry to improve the mechanical properties, particularly ductility. In this study, the effects of antiinony addition.s and growth rate on the inicrostructure and eutectic morphology on the directionally solidified Al- 1 2.5°/o Si cutectic all oy has been investigated. The results showed that antimony can be identified as a grain refiner. Over modification occurs in Al- 12.5 °/oSi alloy when modifier is present in the amount of 1 %Sb results in AISb compound.

Industrial Lubrication and Tribology, 2018

Purpose This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sinteri... more Purpose This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sintering temperature (T) on the transverse rupture strength (TRS), hardness and density of fly ash reinforced bronze-based composite materials by using multi-objective Taguchi technique, analysis of variance (ANOVA) and regression analysis. Design/methodology/approach The bronze-based composite materials containing 5, 10 and 15 Wt.% fly ashes were prepared by using spark plasma sintering carried out under a pressure of 35 MPa, at 750, 800 and 850 °C for 3 min. Sintering temperature and fly ash reinforcement ratio were considered as input parameters; the TRS, hardness and density were considered as output parameters. Experiments were designed according to Taguchi L9 orthogonal array. Multi signal-to-noise ratio (MSNR) was computed to define the optimal process parameters. ANOVA was conducted to detect the importance of the input parameters for the process performance. Moreover, the linear model...

Materiali in tehnologije, 2016

In this research, the heat-treatment effect on the mechanical properties of free-cutting steels w... more In this research, the heat-treatment effect on the mechanical properties of free-cutting steels was investigated. Free-cutting steels (FCSs) are used where high degrees of machining are required as they increase the machining speed and reduce the tool wear. The effect of heat treatment on mechanical properties was identified using tensile and fatigue tests, and microstructure images taken with a scanning electron microscope (SEM). The studied material included commercially available AISI 12L14 cylindrical bars of free-cutting steel. FCS was heated to 900°C and held at this temperature for different time spans. The degradation of the mechanical properties of free-cutting steel due to the elevated temperature was assessed. At a microscopic level, more mechanical damage was observed between the steel matrix and the second phase of the heat-affected specimens. Keywords: fatigue, tensile strength, free-cutting steel, heat treatment V prispevku je bil raziskan vpliv toplotne obdelave na mehanske lastnosti avtomatnih jekel. Avtomatna jekla (FCS) se uporabljajo v primerih, ko so zahtevane velike stopnje obdelave, saj dopu{~ajo ve~je hitrosti rezanja ob manj{i obrabi orodja. Vpliv toplotne obdelave na mehanske lastnosti je bil dolo~en z rezultati nateznega preizkusa in preizkusa utrujenosti. Z vrsti~nim elektronskim mikroskopom (SEM) so bili narejeni posnetki mikrostrukture. Preiskovane so bile komercialno dosegljive palice iz avtomatnega jekla AISI 12L14. FCS je bil segret na 900°C in razli~no dolgo zadr`an na tej temperaturi. Dolo~eno je bilo zmanj{anje mehanskih lastnosti avtomatnega jekla zaradi povi{ane temperature. V toplotno obdelanih vzorcih je bilo z mikroskopom opa`enih ve~mehanskih po{kodb. Klju~ne besede: utrujenost, nateg, avtomatna jekla, toplotna obdelava

Materials Testing, 2016

In this study, a detailed analysis of hybrid weld manufacturing technologies that can significant... more In this study, a detailed analysis of hybrid weld manufacturing technologies that can significantly contribute to the joining of materials has been carried out. Past, present and future projection, advantages, dis advantages, technological barriers and drawbacks of the processes are given. Detailed explanations of the recent developments of hybrid weld manufacturing technologies and main components are given. Potential industrial applications are assessed and evaluated using economic and technological results. The developments in hybrid welding manufacturing technologies generally improved metallurgical and mechanical properties of weld joints. Hybrid processes usually combine the benefits of each individual process. Due to low heat input, hybrid welds create fine grain structures, minimize base material dilution and achieve high toughness and mechanical properties. These processes are especially appropriate for high performance alloys and dissimilar metal joining. The results of th...

Tubav Bilim Dergisi, 2009

Galetaj prosesi, taĢlama, lepleme ve honlama gibi talaĢ kaldırma prosesleri ile karĢılaĢtırıldığı... more Galetaj prosesi, taĢlama, lepleme ve honlama gibi talaĢ kaldırma prosesleri ile karĢılaĢtırıldığında birçok avantaja sahiptir. Galetaj prosesi ile, yüzey sertliği, korozyon ve aĢınma direnci artırmakta, iĢ parçasının yüzeyinde basma tarzı kalıntı gerilmelerin oluĢması nedeniyle yorulma dayanımı iyileĢmektedir. Bu çalıĢmada, AISI 4140 çelik malzemenin galetaj prosesinde, Taguchi deneysel tasarım metodu uygulanmıĢ ve yüzey pürüzlülüğü için optimum proses parametrelerini belirlenmiĢtir. Proses karakteristiklerini incelemek için ortogonal dizi, sinyal gürültü oranı (S/N) ve varyans analizi kullanılmıĢtır. Optimum galetaj parametreleri kullanılarak, malzemenin yüzey pürüzlülüğü % 74 oranında azaltılmıĢtır.

In this paper, a quadratic model was developed for the prediction of surface roughness in turning... more In this paper, a quadratic model was developed for the prediction of surface roughness in turning process of AISI 4140 steel using Response Surface Methodology (RSM) with rotatable Central Composite Design (CCD). The relationship between the surface roughness and cutting conditions was analyzed. In the development of predictive models, cutting speed, feed rate and depth of cut were considered as model variables and surface roughness was considered as a response variable. The results showed that, cutting speed and feed rate have the most significant effect on surface roughness.

Journal of Materials Science: Materials in Electronics, 2014

Bi 2 Sr 2 Co 1.8 O x ceramics have been synthesized through solid-state reaction methods and dire... more Bi 2 Sr 2 Co 1.8 O x ceramics have been synthesized through solid-state reaction methods and directionally grown from the melt by laser floating zone technique. Mechanical and thermoelectric characteristics of this material were determined by three point bending tests and the four probe technique, respectively. The mechanical and thermoelectric properties of Bi 2 Sr 2 Co 1.8 O x were determined as a function of the environmental conditions, air and water. Flexural strength data show that textured materials possess a high degradation resistance due to the low porosity of the external part of the rods (∼ 65µm), which avoids water infiltration and, as a consequence, the internal degradation. Moreover, power factor values are maintained practically unchanged for the samples immersed in water for 24h.

Journal of the European Ceramic Society, 2015

Ca 3 Co 4 O 9 + x wt% Ag (x=0, 1, 3, 5, and 10) polycrystalline thermoelectric ceramics have been... more Ca 3 Co 4 O 9 + x wt% Ag (x=0, 1, 3, 5, and 10) polycrystalline thermoelectric ceramics have been prepared by a sol-gel route via nitrates followed by high temperature treatment before sintering. Out-of-plane XRD data have shown that major phase is the Ca 3 Co 4 O 9 one, accompanied by metallic Ag. SEM observations have agreed with the XRD data. Apparent density measurements have revealed that all samples possess densities ranging between 80 and 90 % when Ag content is raised. Mechanical properties have shown a drastic increase of bending stress when Ag is added to the samples. Electrical resistivity decreases with the Ag content, compared with the pure ones, while Seebeck coefficient slightly decreases. Maximum power factor values around 0.43 mW/K 2 m at 800 ºC have been achieved for the 10 wt% Ag samples which is much higher than the measured in the pure Ca 3 Co 4 O 9 samples.

In this study, abrasive wear behaviour of poly oxy methylenes (POM) under various testing conditi... more In this study, abrasive wear behaviour of poly oxy methylenes (POM) under various testing conditions was investigated. A central composite design (CCD) was used to describe response and to estimate the parameters in the model. Response surface methodology (RSM) was adopted to obtain an empirical model of wear loss as a function of applied load and sliding distance. Also, a neural network (NN) model was developed for the prediction and testing of the results. Finally, a comparison was made between the results obtained from RSM and NN.

Materials Testing, 2015

In the present study, Grey based fuzzy algorithm was used for the optimization of complex multipl... more In the present study, Grey based fuzzy algorithm was used for the optimization of complex multiple performance characteristics of the ball burnishing process. Experiments have been planned according to Taguchi's L16 orthogonal design matrix. Burnishing force, number of passes, feed rate and burnishing speed were selected as input parameters, whereas surface roughness and microhardness were selected as output responses. Using Grey relation analysis (GRA), Grey relational coefficient (GRC) and Grey relation grade (GRG) were obtained. Then, Grey-based fuzzy algorithm was applied to obtain Grey fuzzy reasoning grade (GFRG). Analysis of variance (ANOVA) was carried out to find the significance and contribution of parameters on multiple performance characteristics. Finally, a confirmation test was applied at the optimum level of GFRG to validate the results. The results also show the feasibility of the Grey-based fuzzy algorithm for continuous improvement in product quality in complex...

Wire-electrical-discharge machining (WEDM) is a modification of electro-discharge machining (EDM)... more Wire-electrical-discharge machining (WEDM) is a modification of electro-discharge machining (EDM) and has been widely used for a long time for cutting punches and dies, shaped pockets and other machine parts on conductive materials. WEDM erodes workpiece materials by a series of discrete electrical sparks between the workpiece and an electrode flushed or immersed in a dielectric fluid. The WEDM process is particularly suitable for machining hard materials as well as complex shapes. In this paper, a neural network and the Taguchi design method have been implemented for minimizing the surface roughness in a WEDM process. A back-propagation neural network (BPNN) was developed to predict the surface roughness. In the development of a predictive model, machining parameters of open-circuit voltage, pulse duration, wire speed and dielectric flushing pressure were considered as the input model variables of the AISI 4340 steel. An analysis of variance (ANOVA) was used to determine the signif...

Materials Testing, 2015

A forming limit diagram (FLD) illustrates the behavior of sheet metal under different levels of s... more A forming limit diagram (FLD) illustrates the behavior of sheet metal under different levels of strain. The line describing the behavior of the metal is called forming limit curve (FLC). Forming limit diagram provides information on the maximum stress the metal can undergo before fracturing or necking. The diagrams are constructed by using forming limit test of sheet metal and measuring the deformation. In this study, formability of AISI 1020 sheet metal with different thickness were investigated using experimental data obtained from forming limit test. Forming limit diagram, strain hardening exponent (n) and height of cup values have been obtained for evaluating formability of the studied material. After each test, deformation of the grid was measured by using Mylar band and the true major and true minor strains were computed. Same formability results have been found from the FLD, strain hardening exponent and height of the cup for studied materials.

Ceramics International, 2015

The effect of environmental conditions on the microstructural, mechanical and thermoelectric prop... more The effect of environmental conditions on the microstructural, mechanical and thermoelectric properties of highly textured Bi 2 Ca 2 Co 1.7 O x thermoelectric materials was investigated by powder x-ray diffraction, scanning electron microscopy, three point bending test, electrical resistivity, and thermopower measurements. Textured thin rods were directionally grown from the melt through a laser floating zone melting technique. The mechanical and thermoelectric properties of Bi 2 Ca 2 Co 1.7 O x were determined as a function of two different environmental conditions, air and water. Flexural strength data showed that these oxide materials possess an unsuspected degradation resistance. These good results have been related to the presence of a very thin (∼250µm) low porosity region and relatively small grain sizes, which avoids the internal degration by water infiltration through the porosity. Moreover, thermoelectric performances, evaluated through the power factor are maintained practically unchanged, independently of the environmental conditions.

Materials Testing, 2012

Abstract Process capability indices are effective tools for both, process capability analysis and... more Abstract Process capability indices are effective tools for both, process capability analysis and quality assurance. In quality assurance programs, process capability indices reflect the performance of key quality characteristics for a control process. Quality assurance in mass production is enabled by using statistical process control techniques. In this study, various statistical process control techniques were carried out using the measured values taken from the workpieces that represent the whole process in the medium sized company. The chances for using statistical techniques for quality estimation processes have been discussed. For this purpose, normal probability plots and histograms were prepared and the process capability indices were calculated. As a result of this study, it turned out that the process capability for the whole process was inadequate and the mass production was unstable. Some actions must be taken by engineers to improve the quality level by shifting the process mean to target value and reducing the process variation.

Materials Testing, 2012

The present paper focuses on two techniques, namely regression and neural network, for predicting... more The present paper focuses on two techniques, namely regression and neural network, for predicting tool wear. Predicted values of tool wear by both techniques were compared with experimental values. Also, the effects of the main machining variables on tool wear have been determined. The metal volume removed (MVR) was taken as response (output) variable and cutting speed, feed rate, depth of cut and hardness were taken as input parameters, respectively. The relationship between tool wear and machining parameters was found out by direct measurement of the tool wear by MVR. The results showed the ability of regression and neural network models to predict the tool wear, accurately.