Bilge Demir

• Professor
• Karabük University

This study investigates the effect of zinc alloying (0.2-2%) on the properties of biodegradable magnesium (Mg) alloys produced through powder metallurgy. Prolonged mechanical alloying, cold pressing, and sintering enhanced the hardness of Mg-Zn alloys by 9-12.5% and improved wear resistance, with Zn uniformly distributed in the Mg matrix without in...

The Ti29Nb13Ta4.6Zr (named as TNTZ) alloy is a unique candidate for biomedical applications due to super properties such as its non-toxic and non-allergenic nature, ideal Young's modulus, and excellent biocompatibility. Machining of biomaterials is a fundamental requirement of parts manufacturing and an important element of the efficiency and perfo...

The study focussed on the explosive welding of DP1000 steel and Al sheets. Secondarily, the punching of these sheets with various tips was performed, analysed and the cut surfaces were visually inspected (using electron and stereo microscopy). Moreover, a three-dimensional finite element modeling (FEM) analysis was conducted to predict the punching...

Incorporating Cu and Zn into Mg as a biomaterial offers a unique opportunity to exploit their antibacterial performance and biodegradability. The main challenge in this area is understanding the ratio and effects of these elements. To achieve this, the present work, based on two separate studies, aims to develop a regression model and apply machine...

Efforts are being made to improve material properties and reduce costs in the rapidly developing aviation industry. Composites, which are multifunctional, high-strength, cost-effective, and lightweight materials, constitute approximately 50% of the structural elements in civil aviation aircraft. Companies such as AIRBUS and BOEING, the world's larg...

Circumboreal forests covering about 30% of global forested areas are undergoing significant changes. In Siberia, global warming may reduce the dominance of summergreen larch forest inducing shifts towards evergreen forest types, specifically in the Eastern Siberian summergreen-evergreen forest transition zone. We create a Remote Sensing training da...

This study evaluated the wear behavior of multiwall carbon nanotube (MWCNT) doped non-crimp fabric carbon fiber reinforced polymer (NCF-CFRP) composites produced through vacuum infusion. Compared to 0 wt% MWCNT reinforced composite, the wear loss of 1 wt% MWCNT reinforced composite under loads of 10 N and 30 N decreased by 48.1% and 61.1%, respecti...

This study is an attempt to develop high‐quality hybrid composites via functionalization (for homogeneous distribution) of the graphene nanoplatelets (FGNP) and then doping to carbon fiber reinforced especial aviation epoxy matrix (Araldite LY5052) via vacuum bagging molding (VBM). The utilized materials were characterized by UV–Vis spectroscopy, t...

This study investigates the effect of current and duration parameters applied during the powder-mixed electrical discharge machining (PMcEDM) on dimensional accuracy, surface roughness, white layer thickness, material removal rate, and surface microstructures of TiB2 and TiB2 + nanographene-reinforced ZK60 Mg alloys produced by hot pressing powder...

In this experimental study, wear and corrosion performance of dual-phase (DP600), high-strength low-alloy (HSLA) and interstitial-free (IF) steels after severe vibratory peening-SVP (peening durations of 30 min, 1 h, 2 h, and 4 h) were investigated. SVP is a novel surface severe plastic deformation methodology, and this study emerges the performanc...

Fatigue, corrosion, and fatigue damage models are best addressed to improve and understand the service performance of materials, particularly automotive steel. This study is an attempt to experimentally and finite element investigates plain bending fatigue performance and damage model of DP 1000 sheet steel resistance spot welding (RSW) joints in 3...

Çalışmamızda kullanılan R350HT mantarı sertleştirilmiş 60E1 profil 120 cm uzunluğundaki raylara Sow5 termit kitleriyle yapılan kaynağa uygulanan eğme testleri başarılı olduğu için diğer testlere geçilmiş, Skv elite yöntemiyle yapılan kaynaklar eğme testinden geçemediği için bu yöntemle yapılan kaynaklar başarısız sayılmış, diğer testler uygulanmamı...

Bu çalışmada, kullanılmış ve hasara uğramış AISI 4140, 17CrMo5.5 kalite palet yan duvarı parçaları ve kullanılmamış AISI 4140 kalite palet yan duvarı parçaları hasar analizi yöntemleri ile incelenmiştir. Deneysel olarak; çekme, darbe ve mikroyapı görüntü analizi çalışmaları yapılmıştır. Mikroyapı incelemesinde, mikroyapıda mevcut perlit yapı miktar...

This work is an attempt to evaluate the effect of multi-wall carbon nanotube (MWCNT) reinforcement on the properties of non-crimp fabric (NCF) carbon fiber-reinforced polymer hybrid composite (CFRP). MWCNT NCF-CFRP plates were produced by vacuum infusion. Epoxy-MWCNT mixtures were prepared by adding a surfactant, Triton-X 100, and ethanol and mixin...

This work is an attempt to evaluate the effect of multi-wall carbon nanotube (MWCNT) reinforcement on the properties of non-crimp fabric (NCF) carbon fiber-reinforced polymer hybrid composite (CFRP). MWCNT NCF-CFRP plates were produced by vacuum infusion. Epoxy-MWCNT mixtures were prepared by adding a surfactant, Triton-X 100, and ethanol and mixin...

Resistance Spot Welding (RSW) is widely used in many automotive, boiler, and ship manufacturing industries. Therefore, the optimization and effectiveness of the RSW process are very useful and cost-efficient processes in addition to improving weld quality. This study used various welding parameters to investigate the optimization of the RSW process...

z: Günümüzde ray ömrünü uzatan sıcak hadde sonrası kontrollü ve hızlı soğutmayla ray mantar sertleşmesi sağlanarak önemli ekonomik kazançlar elde edilmektedir. Ray kaynak metotlarından Aluminotermit kaynağı saha birleştirme yöntemi olarak günümüzde de önemini devam ettirmektedir. Kaliteli bir termit kaynağı yapmak için termit alaşımının sıkı deneti...

Punching is a widely used and economic manufacturing method that needs to be addressed. Especially the forces that occurred during punching and the dimensions of the parts obtained from punching are important in manufacturing processes. This study aimed to examine the cutting forces that occur in the punching process and the dimensional accuracy of...

PRODUCTION OF DUAL PHASE STEEL, EFFECT OF VOLUME FRACTION AND MORPHOLOGY OF MARTENSITE ON TENSILE PROPERTIES OF DUAL-PHASE STEEL. In this work the effect of martensite content and morphology on the tensile behaviour of dual-phase steels was examined. Ç 8620 steel containing 0.217 wt %C, 0.917 wt %Mn, 0.494 wt %Cr ve 0.437 wt %Ni was used. From thr...

In this study, two different chemical composition of steels having 0,0640 C%, 1,72 Mn%, 0,46Si%, 0,67 Ni%, and 0,0617C%, l,89Mn%, 0,363Si%, 0.85Ni% were used. The volume fraction of transformed phases from austenite were determined by intercritical annealing of steels having fine and coarse austenite dispersions at three different intercritical ann...

In this study, production of dual phase steel-Al 1100 aluminium alloy laminated composite by explosive welding and investigation the microstructural and mechanical properties especially fatigue life of the composite and its components were aimed. Finite element analysis (FEA) was used to simulate the bending fatigue tests of the Al 1100-DP steel (L...

Günümüzde ray ömrünü uzatan sıcak hadde sonrası kontrollü ve hızlı soğutmayla ray mantar sertleşmesi sağlanarak önemli ekonomik kazançlar elde edilmektedir. Ray kaynak metotlarından Aluminotermit kaynağı saha birleştirme yöntemi olarak günümüzde de önemini devam ettirmektedir. Kaliteli bir termit kaynağı yapmak için termit alaşımının sıkı denetimi...

This study investigated the manufacturability of ultra-strength steel-Al plate composite, the punch-cutting performance of these composites and base materials, and the cutting surface properties. Therefore, experimental studies included explosive welding, punching process, and materials characterisations (microstructure and sheared surface image an...

β-type Ti29Nb13Ta4.6Zr (TNTZ) alloy is a new-generation alloy that does not contain toxic/allergic elements. The alloys have low Young's modulus (⁓60 GPa) close to the cortical bone, providing excellent biocompatibility over familiar commercial CP Ti or Ti6Al4V ELI. Different macro/micro-machining methods can be used to obtain the final shape of Ti...

In this study, AZ61/15wt.%TiB2 and AZ61/15wt.%TiB2-0.5wt.%GNPs composites were manufactured by hot pressing, and the machinability of the produced samples was carried out by powder mixed electrical discharge machining (PMEDM). The influence of PMEDM parameters, namely pulse on time, current and materials, were studied by surface roughness (SR) and...

In this study, ZK60 magnesium matrix composites were produced with different content of CeO 2 (0.25, 0.5 and 1 wt%) by hot pressing. The wear behaviour of the samples was investigated under loads of 5 N, 10 N, 20 N and 30 N, at sliding speeds of 75 mm/s, 110 mm/s and 145 mm/s. The worn surfaces, wear debris, and counterface material was analysed to...

z Bu çalışmada, kriyojenik işlemin HSLA kalite ticari otomotiv sac kaynaklı birleştirmelerinin sertlik ve aşınma özelliklerine etkisi incelenmiştir. Lazer kaynak işlemleri; katı hal lazer kaynağı olarak, 1 kW lazer ışın gücünde ve 250 mm.s-1 ilerleme hızında uygulanmıştır. Bu kaynak işlemi alın (butt) pozisyonunda ve dolgu metalsiz olarak çift tara...

his study theoretically and experimentally investigates blanking/piercing operations of explosively welded commercial DP600 advanced steel sheets, Al1100 aluminium sheets, and DP600-Al1100 composite plates, in which punches with different tip shapes are used. The experimental studies included several methods, such as explosive welding, punching, te...

In this study, ZK60 alloy, ZK60/15 wt.% TiB2, and ZK60/15 wt.% TiB2 − 0.5 GNPs composites were prepared by hot pressing. The density, microstructure, hardness, and tribological and compression behavior of the samples were investigated. Microstructure investigations showed that TiB2 particles were generally homogeneously dispersed, but GNPs particle...

Piercing/blanking-cutting sheet metals with a punch are still the industry's most preferred process. This study previously aimed to fabricate the Ultra Strength DP1200 Steel-AA1100 sheet composite and then research punch shearing performance and surface characterization of this plate composite and original materials. Experimental studies include va...

This study focused on optimization of different electrode tip types (Conical round, Flat R3, Flat R6, Flat conical) and welding current parameters to obtain the ideal tensile shear strength of resistance spot welded DP600 steel. Welding processes were carried out at 5 and 7 kA welding currents for each of the 4 different tip types. Experimental res...

Bu çalışmada, nokta direnç kaynak yöntemi ile birleştirilen geliştirilmiş yüksek mukavemetli çeliğin kaynak çekirdek çapı, çekme makaslama dayanımı ve mikrosertlik özellikleri üzerinde farklı elektrot uç tiplerinin etkisi incelenmiştir. Bu amaçla, özellikle otomotiv sektöründe tercih edilen konik yuvarlak, düz R3, düz R6 ve düz konik elektrot uç...

Multi-walled carbon nanotubes (MWCNTs) have many unique features that improve composite material properties, including a large surface area, thermal and chemical stability, and thermal and electrical conductivity. Our study aimed to examine the influence of MWCNT weight percentage on the fatigue characteristics of a polymer matrix composite strengt...

Drilling with utilization of twist drills is the most regularly applied for finishing process of metal matrix composites for purposes of structure fastening. Delamination is typically considered as the primary failure mode in drilling of metal matrix composites. This paper presents an optimization of the drilling parameters with application of Tagu...

In this study, an attempt was made to manufacture an AZ31–Al5005 laminated composite by explosive welding. A mixture of ammonium nitrate (90%), fuel oil (5%), and TNT (5%) was used as the explosive. The detonation velocity of the explosive material was approximately 3100 m•s⁻¹. The microstructure and mechanical and corrosion properties of the joint...

Resistance spot welding (RSW) of magnesium alloys is very attractive due to not require filler metal. AZ31 Mg alloy sheets were exposed to RSW by constant weld electrode pressure, constant weld times, and numerous weld currents. The potentiodynamic polarization technique was used for the investigation of the corrosion behavior of the alloys. Result...

Abstract Resistance spot welded joints were realized for 5 different electrode pressures in constant welding current and constant welding time of DP600 steel, the effects of electrode pressure on microstructure and hardness were investigated in the present study. Microstructure and hardness change depending on material properties and welding parame...

In this study, resistance spot welding (RSW) process has been used on DP600 automotive steel at pressures of 2, 3, 4, 5 and 6 bar at a welding current of 7 kA. Microstructure, hardness and residual stress were examined to evaluate the effect of the welding pressure. An experiment at 5 kA and 6 bar was also conducted to investigate the effect of wel...

In this study, resistance spot welding (RSW) process has been used on DP600 automotive steel at pressures of 2, 3, 4, 5 and 6 bar at a welding current of 7 kA. Microstructure, hardness and residual stress were examined to evaluate the effect of the welding pressure. An experiment at 5 kA and 6 bar was also conducted to investigate the effect of wel...

surface excellence of machined areas is the surface roughness (Ra). In this study, the influence of the cryogenic cooling during the turning process of Al 6082 alloys on the surface roughness was investigated. The cutting tool geometry (tool nose radius and rake angle), cutting speed and feed rate factors were utilized as the main parameters. Refri...

Effect the Surfactant on the Dispersion and Mechanical Properties of Multi-Walled Carbon (MWCNT) Reinforced Polymer Composites, International Symposium on light Alloys and Composite Materials, ISLAC18, Karabük

Bu çalışmada DP600 otomotiv sac çeliğinin sabit kaynak akımı ve sabit kaynak süresinde, 5 farklı elektrot basıncı için nokta direnç kaynaklı birleştirmeleri gerçekleştirilmiş, elektrod basıncının mikroyapı ve sertliğe olan etkileri araştırılmıştır. Mikroyapı ve sertlik, malzeme özelliklerine ve başta ısı girdisi olmak üzere kaynak parametrelerine b...

Based on this study, the effects of the different types of welding currents and electrode pressures on the tensile shear properties of the resistance spot welding (RSW) which are the joints of the commercial DP600 sheet steel are now been investigated. In addition to the fact that the electrode pressure is not much of a popular piece or topic of di...

In this study, the maximum tensile shear load bearing capacity of the resistance spot welded DP1000 steel was measured and the tensile shear properties of the joints were evaluated. The effects of different welding parameters on microstructure, microhardness and tensile shear properties were investigated. Weld processes were performed by using 5kA...

The machinability of graphene-reinforced magnesium-based hybrid nanocomposites produced through the application of powder metallurgy method has not been completely reported. This article presents an experimental investigation on the thrust force, the surface roughness (Ra), and drilled surfaces characteristics in the drilling process of a Mg/SiC/GN...

LŞGHT ALLOYS AND COMPOSİTE MATERİALS

Purpose: This study aims to determine the effect of the coexistence of multiple risk factors on prevalence of pulmonary embolism (PE), which has a high mortality. Method: We conscripted 220 patients who submitted to the emergency department of Turgut Özal Medical Center (TOTM) between January 2013 and January 2014. Of these, 110 patients were diagn...

Abstract: In this study, two advanced strength sheet steel which have the same strength level have been used. These two sheet steel sample have been welded as over lope by using resistance spot welding. Welding processes have important effect on advanced sheet properties, due to heat generation. Because of, their origin also are dependent on heat t...

Abstract:Due to high demands for energy saving, lightweight materials attract a large amount of research interest. Magnesium is lightweight structural metal. Magnesium and its alloys are used in automotive, aerospace and chemical applications in wide scale that is because of their low density. However, their applications are restricted by their low...

zet: Bu çalışmada 7114 kalite IF çeliğinin nokta direnç kaynak birleştirmelerinde kaynak süresinin ve çekirdek çapının dayanıma etkisi incelenmiştir. Nokta direnç kaynak işlemleri sabit basma kuvveti (6 bar) ve kaynak akımı (7kA) ile değişen kaynak sürelerinde (5-10-15-20-25 ve 30 çevrim) gerçekleştirilmiştir. Birleştirilmiş numunelerin mikroyapı i...

In this study, commercial dual-phase steel production methods have been investigated. Manufacturers, in area’s of industries which use materials, would like to use advanced materials having light weight, higher strength, formable and higher strength after forming. This situation also valid for user. Particularly in automotive industry, to decrease...

In this study, commercial dual-phase steel production methods have been investigated. Manufacturers, in area’s of industries which use materials, would like to use advanced materials having light weight, higher strength, formable and higher strength after forming. This situation also valid for user. Particularly in automotive industry, to decrease...

In this study, butt welding of commercial AZ31 magnesium alloy sheets has been investigated by using the tungsten inert gas welding process with alternating and pulsed current. Magnesium alloy welding, although well developed and understood, can present some problems, such as porosity, hot cracking, oxide formation, etc.. Samples of the welded part...

In this study, low carbon Mn-Ni steel having 0,0640 C%, 1,72 Mn%, 0,46Si%, 0,67 Ni%, was used. The volume fractionsof transformed phases from austenite were determined by intercritical annealing of steels having fine and coarse austenite dispersions at three different intercritical annealing temperatures (ICAT) and then cooling at various rates. By...

In this study, AZ31 Mg alloy sheets were welded by resistant spot welding (RSW) with using constant weld pressure, several weld times and various weld current conditions. The aim of this study is to investigate the effect of the weld current on tensile shear properties of welded samples. Etching, measurement of nugget size, microhardness, tensile s...

In this study, the effect of adhesive bonding on strength and strength-ductility behaviour of welding joint in electrical resistance spot welding of 7315 grade IF steel sheets was investigated. 7315 grade (DIN EN 10130-1999) IF steels were adhesively bonded and different welding current and welding cycle conditions were performed in welding process...

Bu çalışmada, sıcak haddelenmiş Ç 5140 çeliğine uygulanan tam tavlama ve normalleştirme ısıl işlemleri ile mikroyapıları ve mekanik özellikleri değiştirilmiştir. Mikroyapı ve mekanik özellik değişikliklerinin yüzey pürüzlülüğü ve kesme kuvvetlerine etkisini incelemek amacıyla tornalama yöntemiyle işleme deneyleri yapılmıştır. Deneyler, kuru kesme ş...

In the present work, the transformation characteristics of ductile iron austempered from intercritical austenitization temperature ranges were investigated. For this purpose, an unalloyed ductile cast iron containing 3.50wt% C, 2.63wt% Si and 0.318wt% Mn were intercritically austenitized (partially austenitized) at various temperatures and then rap...

In this study, the effects of weld current and weld time on the tensile peel strength and tensile-shear strength of 7114 grade IF (Interstitial Free) steel sheets joined by spot welding were investigated. Weld processes were performed by using 3, 5, 7, 9 kA weld current and 5, 10, 15, 20, 25, 30 weld cycles. The microstructure of the welded materia...

In this investigation, two steels with different chemical compositions were used to study the hardenability of austenite with different alloy content and dispersion in dual-phase steel. The results showed that ferrite carbide aggregate did not form and considerable amount of the austenite present at the intercritical annealing temperatures transfor...

The aim of this paper is investigation of microstructure and property relationship in aluminum–HSLA steel and aluminum–dual phase steel bimetals fabricated by explosive welding technique. Dual phase steel was produced by intercritical annealing and water quenching from 1.45Mn–0.2Si–0.186C HSLA steel. Hardness, tensile shear strength, tensile streng...

In the present work, an unalloyed ductile cast iron containing 3.50 C wt.%, 2.63 Si wt.%, 0.318 Mn wt.% and 0.047 Mg wt.% was austempered for various times at both the conventional austenitizing temperature (single phase austenitic region) and the different intercritical austenitizing (partially austenitizing) temperature ranges to investigate the...

A study has been made of the cold deformation aging susceptibility of dual phase steel with 14 and 22% martensite by volume. It was found that yield strength (YS) and ultimate tensile strength (UTS) increased with increasing testing temperature up to 200°C and then decreased at 250°C which indicated that static strain aging is dominant up to 200°C....

Tensile shear, microstructural properties of resistance spot-welded dual-phase steels having different martensite volume fractions (MVF) of 14, 17, 19 and 25% are investigated. These steels are produced from low-carbon Mn-Ni steel by air and water quenching after intercritical annealing. Joining of these steels by the resistance-spot welding method...

In this study, production of dual-phase steel from AISI 4140 steel having 0.44% C, 0.35% Si, 0.71% Mn, 1.13% Cr, 0.17% Mo and its impact strength at different martensite volume fractions (MVF) are determined. Dual-phase steel production is accomplished by intercritically annealing at intercritical temperatures (alpha + gamma region, between 740 deg...

In this study, the effects of cutting parameters such as cutting speed, feed rate and cutting depth over cutting forces have been investigated. For this purpose, nickel based super alloy Inconel 718 has been processed with ceramic cutting tool having 1.2 mm insert radia on a digitally controlled turning lathe (CNC) without using cooling water. Diff...

Tensile shear stresses and microstructure of dual steels with different volume fractions of martensite are studied after spot resistance welding. A Mn-Ni low-carbon steel heated in the intercritical temperature range and cooled in water and in air is studied. Spot resistance welding of test pieces is performed for different times at constant weldin...

Bu çalışmada, %0,0640C, %1,72Mn, %0,46Si, %0,67Ni ve %0,0617C, %1,89Mn, %0,363Si, %0.85Ni olmak üzere iki farklı kimyasal kompozisyona sahip çelik tipi kullanılmıştır. İnce ve kaba olmak üzere iki farklı östenit dağılımı oluşturularak ve üç farlı kritik tavlama sıcaklıklarından (KTS) (ferrit+östenit bölgesi, A1-A3 arası) farklı soğutma hızlarında ö...