Mustafa Bakkal

Istanbul Technical University · Department of Mechanical Engineering

Hybrid composites produced by the addition of metal alloys to carbon fiber reinforced composites (CFRP) have superior mechanical and physical properties, excellent specific strength and high resistance to corrosion. The most commonly used machining processes in the use of hybrid materials in industry is the drilling process. After the drilling proc...

In this study, fatigue properties of a novel continuous glass fiber reinforced composite with an acrylic-based thermoplastic matrix Elium®, have been investigated and S-N curves were obtained. The effect of various fiber orientations of the plies with glass fibers of 0°/90°/±45°, 0°/90°, and ±45° alignment has been evaluated. The highest fatigue st...

Tube spinning is a continuous bulk forming technique used to produce seamless tubes. In the last six decades, tube spinning process has been applied to a wide range of engineering products; especially in automotive, aerospace and nuclear industry. However, understanding of the process mechanics is limited. Key references were published about 60 yea...

KEYWORDS The paper reports, the effect of water sorption on the microstructural and flexural properties of the flax fiber/ polylactic acid (PLA) biocomposites compared to the composites with maleic anhydride (MAH) as coupling agents and alkali treatment. In the current study, five different biocomposites which are 15 % wt. flax/PLA, 25 % wt. flax/P...

Tube spinning is a bulk deformation process used to produce seamless, cylindrical, conical, and contoured tubes. Over the last six decades, tube spinning process has been applied in a wide range of engineering applications; especially in automotive, aerospace, and nuclear industry. However, the process has seen little change, and despite a large vo...

This study presents an investigation on the effectiveness, automation characteristics, and mechanics of joints between different material types namely glass fiber reinforced plastics (GFRPs) and SS304 stainless steel using an industrial Nd: YAG continuous-wave laser welder and a 2-axis custom design jig. The custom design jig includes computer-contr...

Carbon fiber reinforced composites (CFRP) have superior mechanical properties such as high strength/density ratio, and good damping ability. CFRP which is frequently used in parts in the aviation industry can also be single or stacked together with titanium and aluminum alloys. However, delamination could occur on the CFRP surfaces after drilling w...

In this work, various stabilizers have been introduced to prevent or delay degradation due to ultraviolet (UV) light exposure to prolong the service life of cotton fiber-reinforced composites. The effect of various additives like hindered amine light stabilizer, UV absorber (UVA), and antioxidant as photostabilizers of CF/low-density polyethylene (...

In the study, elastic modulus estimation methods of natural fiber reinforced composites considered as alternatives to synthetic fiber reinforced composites have been investigated. Finite element analysis (FEA) and some mathematical models which are used for synthetic fiber reinforced composites were preferred. During the study, randomly oriented co...

This chapter discusses some of the most common metallic glass sheets, ribbons, and bulk metallic glasses (BMGs) rod, bar, and plate manufacturing methods. The discussed methods include: rapid quenching methods, water‐quenching method, arc melting drop/suction casting method, high‐pressure die casting method, copper mold casting method, cap casting...

In the production of composites, due to the amount of plastic waste, some stringent policies have been forced on the industries to use more biodegradable, less harmful reinforcements. Reinforcements such as natural fibers have been encouraged instead of traditional inorganic reinforcements to manufacture composite material. Due to this, in the rece...

A two-dimensional analytical model to calculate the temperature distribution in orthogonal cutting with dual-zone contact on the rake face is presented. The study considers heat generation in the primary shear zone and on the rake face. The material behavior in the primary shear zone is represented by Johnson-Cook constitutive equation while the co...

This research studies the sustainable and high-throughput drilling of compacted graphite iron (CGI), a high strength, lightweight material for automotive powertrain applications. CGI drilling experiments were conducted using a 4 mm diameter coated carbide drill at 26.5 mm/s feed rate. In two repeated tests under three lubrication conditions: dry, d...

Turn-milling is a relatively new machining technology which is performed for cutting of symmetrical or non-symmetrical rotational parts. To improve productivity, determination of cutting parameters in turn-milling is crucial. However, experimental approach is costly, hence it is important to develop predictive models, especially analytical models,...

This paper presents the effect of tool path on machining of thin walled thermoplastic polymer, ABS. The effects of cutting speed, feed rate and tool path are studied to evaluate surface quality on thin walled parts. Four different cutting pattern (“zig”, “zig-zag”, “follow periphery” and “trochoidal”) with uncoated WC tool were investigated in the...

This study investigates the temperature distribution of a compacted graphite iron (CGI) workpiece in minimum quantity lubrication (MQL) deep-hole drilling. The temperature distribution in the workpiece is predicted using the finite element method, in which the heat flux loads on the chisel and the cutting lip applied to the finite element model are...

In this study, the hybridization effect on the mechanical properties of the natural fiber reinforced composites was investigated. For this purpose, glass fibers in different ratios of 2.5, 5 and 10 wt% were added in the polymer composites with cotton fibers at the ratios of 12.5 and 25 wt%. In order to have better interfacial bonding and increase t...

The effect of photostabilizers on the mechanical, thermal, and physical properties of textile fiber reinforced polymer (T-FRP) composites was investigated. In the first phase of this study, the effect of different concentrations of ultra violet absorber (UVA), hindered amine light stabilizers (HALS) and antioxidants (AOs) into T-FRP composites for...

This study deals with the effect of water absorption on the physical and mechanical properties of the glass fiber/waste cotton fabric hybrid composites compared to the samples with maleic anhydride (MA) as coupling agent. Water absorption studies were performed for four different soaking times of 100, 250, 500, and 1000 h at room temperature. To cl...

Vorwort Technische Kunststoffe, faserverstärkte Verbundwerkstoffe sowie multifunktionale Kunststoff-Verbunde unterstützen heute nachhaltig den modernen Automobilbau. Multifunktionswerkzeuge und automatisierte Verarbeitungsprozesse ermöglichen in vielen Fällen besonders wirtschaftliche Systemlösungen. Die additive Fertigung in Verbindung mit Kunstst...

Improving performance during fine turn-milling operations including accuracy and productivity requires controlling of the cutting forces and the thermally induced displacement of the cutting edge. The objective of this investigation is to determine the thermally induced displacement of TCP during turn-milling and to reduce this displacement by usin...

Milling is the one of most common cutting operations in industry. Interrupted nature of the milling process allows use of higher speeds which in turn improves productivity. Cutting temperature is one of the key factors to be investigated in process optimization. In milling, cutting temperature analysis is harder compared to turning due to experimen...

This research investigates the high-throughput drilling of the compacted graphite iron (CGI), a high strength, lightweight material for automotive powertrain applications, at 26.5mm/s feed rate using 4mm diameter coated carbide drill. The CGI drilling experiments show that maximum 1740, 3150 and 2948 holes were drilled in two repeated tests under t...

In this work, the effect of hybridization on the mechanical and rheological properties of the glass fiber/waste cotton fabric-reinforced hybrid composites was investigated. For this purpose, glass fibers in different ratios of 2.5, 5, and 10 wt.% were added to the polymer composites with cotton fibers at the ratios of 12.5 and 25 wt.%. In order to...

Residual stress is an inevitable phenomenon that affects the final part performance. High strain rate and thermal gradient cause microstructural deformations which generate residual stress at machined surface and subsurface of the machine part. It is crucial to measure the machining induced residual stress to prevent the undesired part failures. Th...

In this study, weathering effect on untreated textile fiber-reinforced polymer composites and the effect of different chemical treatments for better interfacial adhesion on the outdoor performance were investigated. Degradation of physical, mechanical, and chemical properties of textile fiber-reinforced polymer composites was evaluated through comm...

The drill temperature distribution in CO2 assisted CGI drilling is studied in this paper. Finite element method is conducted to predict tool temperature during cutting process. The amount of heat transfer to drill due to the friction between tool and chip is estimated based on the predicted friction force and the chip velocity. Cutting force compon...

Frezeyle tornalama esasen bir tornalama işlemi olup işlem sırasında sabit bir takım yerine freze takımı kullanılmaktadır. Bu nedenle işlem kesintili bir işlem halini almaktadır. Sonuç olarak bir takımın bir dönüşü ısınma ve soğuma döngülerini içermektedir. Bu da kesme sıcaklığının sürekli kesmenin olduğu tornalama işlemine göre daha düşük olmasına...

Bu çalışmada kompakt grafitli dökme demirin (KGDD) minimum miktarda yağlama sistemi kullanılarak derin delinmesi sırasındaki iş parçasındaki sıcaklıkların dağılımı incelenmiştir. Çalışmada kesme kuvveti ve tork matkabın radyal çapı ve kesici kenarı küçük elemanlara ayrılarak hesaplanmıştır. İş parçasına geçen ısı miktarını tahmin etmek için adveksi...

There are limited studies in the literature about machinability of bulk metallic glass (BMG). As a novel and promising structural material, BMG material machining characteristics need to be verified before its utilization. In this paper, the effects of cutting speed, feed rate, depth of cut, abrasive particle size/type on the BMG grinding in dry co...

Unique mechanical properties of the compacted graphite iron (CGI) attracted attention of manufacturers and suppliers mainly in automotive industry in last decades. However due to the low machinability of the CGI material, more efficient machining strategies need to be implemented. Improvement in the cost-effective and environmentally sensitive proc...

The main objective of this research is to study the effect of recycled low density polyethylene (r-LDPE) matrix on the tensile, impact, and flexural properties of the novel textile waste cotton fiber reinforced (T-FRP) composites. For this purpose, the T-FRP composites were manufactured by using two different matrix types; namely, virgin LPDE (v-LD...

This paper presents a validated temperature distribution model that allows the prediction of temperature increase on a compacted graphite iron (CGI) workpiece during the drilling process. The thermal modeling procedure begins with the geometric modeling of inclination, rake, helix, and effective rake angles. Then, force models are evaluated for the...

Investigation of cutting temperature is one of the most important research areas in metal cutting since it is a significant factor that affects the tool life and the quality of the machined part. It is known that cutting temperatures in continuous cutting are higher than those in interrupted cutting. Including cutting and non-cutting periods provid...

Due to the increasing importance of natural fiber reinforced polymer composites, a large number of papers published about fabrication of these materials, but yet the secondary manufacturing performance knowledge of such materials is rather limited. Understanding cutting performance of a novel natural fiber (cotton) reinforced polymer composite is t...

Frezeyle tornalama, geleneksel tornalama ve frezeleme işlemlerini birleştiren görece yeni bir talaşlı imalat işlemidir. İşlemin frezelemede olduğu gibi kesintili karakteristiği, düşük kesme sıcaklıkları ve yüksek üretkenlik sağlamaktadır. Ek olarak, frezeyle tornalama işlemi geleneksel işlemlerde olmayan ve takım ile iş parçası ekseni arasındaki me...

Bu makalede kompakt grafitli dökme demirin (CGI) delik delme işleminde iş parçasında oluşan sıcaklığın dağılımı incelenmiştir. Delik delme takımının (matkabın), kesme kenarları değişen kesme açılarına sahip olduğundan, kesme kenarı küçük elemanlara ayrılmış ve her bir elemana elemanter kesici takım (EKT) adı verilmiştir. Çalışmada kesme kenarı ve m...

This paper investigates the compacted graphite iron (CGI) workpiece temperature distribution in drilling process. The cutting forces and torque values have been obtained using segregated cutting edge method at the very beginning of the study. Each segregated cutting edges were named as elementary cutting tool (ECT) due to the different cutting angl...

Recently, Minimum Quantity Lubrication (MQL) became drastically demanding method due to its cost wise efficiency and eco-friendly aspect in machining. Moreover, MQL also enhances the friction behavior on tool-chip contact zone on rake face of tool. This study presents an experimental approach to analyze the seizure and sliding mechanism at the tool...

Compacted graphite cast iron (CGI) is one alternative engine material to gray cast iron. However the machining of CGI is cumbersome and increases the overall manufacturing costs. This paper investigates the tool life effect of minimum quantity lubrication (MQL) on CGI turning by using ceramic cutting tool. Cutting tests were performed under 200 m/m...

This paper presents two separate methods to improve the tensile strength (TS) of textile waste cotton reinforced polymer composites (T-FRP) as prospective functional materials with respect to environmental concerns. Two very different methods were designed in order to improve the TS of the composite. In the first method, maleated anhydride polyethy...

As automotive industry tries to meet the expectations of the user demands for a long time, they also try to respond the scope of expanding environmental protection laws. Because of the low emission laws, engine designers are forced to improve technology in order to have more effective combustion process in engines. For this purpose CGI is used inst...

This paper presents mathematical models and experimental data for the turn milling process which combines conventional turning and milling. Turning with a milling tool offers the advantage of intermittent cutting which allows higher productivity by increased cutting speeds and improved tool life. In this paper, models for turn milling process geome...

Waste cotton fiber reinforced (WCF-R) composites are manufactured by using virgin low density polyethylene (v-LDPE) and recycled low density polyethylene (r-LDPE) which is supplied from the industry. The effects of cotton fiber loading, recycled LDPE matrix and coupling agent ratio on the mechanical properties of composites was investigated by tens...

Manufacturing of parts made out of difficult-to-cut materials presents many challenges. Reduced productivity and increased cost due to low machinability and tool life are main problems in these applications. Turn-milling may offer important advantages in solving these problems. Turn-milling combines conventional turning and milling processes provid...

This paper introduces a technique which evaluate performance of hole quality after drilling process. Hole making is one of the most time consuming process in industry. For some applications the quality of holes are very crucial and be expected of tight tolerance from manufacturer. One of the most common device used by manufacturers to investigate t...

Machining of difficult-to-cut materials such as high-temperature metals is challenging due to their low machinability resulting in reduced productivity and high manufacturing cost. Turning is a common operation used for production of these parts where cutting speed, and thus the material removal rate, is limited due to high tool wear rate. Therefor...

Abstract This paper presents an analytical approach for modeling of turn-milling which is a promising cutting process combining two conventional machining operations; turning and milling. This relatively new technology could be an alternative to turning for improved productivity in many applications but especially in cases involving hard-to-machine...

In this study, an analytical model is developed in order to calculate the temperature distribution in orthogonal cutting with dual-zone contact at the rake face. The study focuses on heat generation at the primary shear zone and at the rake face. The material behavior at the primary shear zone is represented by Johnson-Cook constitutive equation wh...

This paper investigates the temperature distribution on the work piece in milling process by inverse heat transfer method. To best of our knowledge, neither a complete analytical solution nor an empirical formula has been derived before for heat generation by machining process. Variation of the temperature on milling surfaces cannot be measured suf...

In this study, various forms of non-woven waste were recycled for the manufacture of composites by the extrusion technique. The performance of the composites, as well as the effect of the reprocessing steps, was investigated with regards to the mechanical and thermal properties. A reinforcement material of polyester non-woven waste in differing for...

Demands of aerospace industry for high performance alloys have been increasing due to their superior thermal and mechanical properties. These properties, on the other hand, decrease the machinability resulting in lower productivity. Conventional machining techniques can be insufficient to provide higher productivity for these cases. Special process...

Turn-milling is relatively a new cutting process which combines two conventional manufacturing processes; turning and milling. This promising technology becomes an alternative to turning due to its advantages such as higher productivity and lower cutting temperatures, which provide longer tool life. Intermittent characteristics of turn-milling help...

In this study, mechanical properties of composite laminates reinforced with various forms of glass fibers have been investigated. Tensile testing, impact testing and optical microscopy and SEM analysis results were discussed. The results of glass fiber reinforced novel composite material have been compared with the results of a commercial car front...

This paper presents a procedure for developing a finite element model of random chopped cotton fiber reinforced polyethylene composites to determine their mechanical properties. In experimental studies, composite plates with polymer (polyethylene) matrix and waste cotton fabrics reinforcements were manufactured in two different volume fractions (7....

In this study, waste cotton fabric reinforced polymer matrix composite plate has been processed by a-custom-made recycling extruder. Two different (12.5% and 25% fibers by weight) waste fabric reinforced composite plates were produced and reprocessed six times to assess repetition effect of processing on the mechanical and rheological properties on...

Kesme sırasında ortaya çıkan yüksek sıcaklıklar, takım malzemesinin dayanımını düşürerek takım aşınmasına neden olur ve sonuç olarak takım ömrü düşer. Özellikle torna gibi temasın sürekli olduğu kesme durumlarında sürtünme nedeniyle oluşan sıcaklıklar yüksektir. Bu nedenle son zamanlarda tornalama-frezeleme işlemi giderek yaygınlaşmaktadır. Frezeyl...

This chapter covers the series of machinability evaluation test result and discussions of Zr52.5Ti5Cu17.9Ni14.6Al10 bulk metallic glass (BMG). These tests are lathe turning, drilling, milling and preliminary level grinding tests. In the continuous machining methods such as turning, drilling and grinding of BMG, above a threshold cutting speed, the...

This paper aims to evaluate the machinability of a novel composite material which is textile fabric reinforced composite. In this study, four different cutting tools with different geometries were used due to the lack of information on tool selection for thermoplastic matrix composites. During machining of this novel composite, the fixture design i...

In this study, effect of feed rate on cutting forces on turning of Zr-based bulk metallic glass (BMG) material was investigated under orthogonal cutting conditions. Four different feed rates were used in the experiments at a constant spindle speed. Specific cutting and edge coefficients for BMG-WC workpiece-tool pair were identified by using mechan...

Zr based bulk metallic glasses have unique properties due to their amorphous microstructure such as high resistance to corrosion and high tensile strength. It is important to investigate whether the BMG will endure or not its amorphous structure during machining. This investigation is usually carried out by costly experiments that is why finite ele...

In this paper, the effects of the cutting speed in metallic glass grinding were investigated in dry conditions. The results showed that grinding forces decrease as grinding energy increase with the increasing cutting speeds. The present investigations on ground surface and grinding chips morphologies -shows that material removal and surface formati...

In this study, waste cotton fabric reinforced polymer matrix composite material has been manufactured by a custom made recycling extruder. Composites with different reinforcement ratios as 12,5%wt ( 12,5%wtRPE ) and 25%wt ( 25%wtRPE ) were tested for their mechanical properties such as tensile strength and young’s modulus. The material was then gra...

This paper presents the effect of lubricant, SAE EP 90, on tribological properties of Zr-based bulk metallic glass. The coefficient of friction and wear rate values were evaluated for the wide range of applied normal loads (5–40 N) and contact sliding speeds (0.15–1.60 m/s). Wear and friction properties of tribolayers were strongly affected by both...

In this study, effect of feed rate on cutting force, burr formation, and surface roughness on milling of Zr-based bulk metallic glass (BMG) material was investigated at constant spindle speed, 5000 rpm. Uncoated 1 mm diameter solid-WC tools with two cutting edges were used for all tests. Cutting mechanics of helical endmill was examined. Specific c...

In this study, machinability of Zr-based bulk metallic glass (Zr52.5Ti5Cu17.9Ni14.6Al10) (BMG) material was investigated by conducting a set of milling and drilling experiments. In milling, two different tool paths, spiral and slot milling, were used. To investigate the behavior of BMG in drilling by two different tools at different feed rates, two...

Machined Zr52.5Ti5Cu17.9Ni14.6Al10 bulk metallic glass (BMG) chips were characterized using high resolution electron microscopy. Compared to conventional processing techniques, machining produces very high heating/cooling, and deformation rates. It is therefore of interest to compare structural changes in machining chips with those produced by conv...

The aim of this work is to manufacture fabric waste reinforced polymer composites in order to re-evaluate textile wastes. Three plain woven fabrics from 100% polyester and 100% cotton are used as the reinforcement, and unsaturated polyester resin is used as the matrix material. Fabrics that are used as the reinforcement are continuously oriented at...

In this study, the effects of different heat treatments on titanium alloys’ machinability were observed. Annealed Ti6Al4V alloy’s machinability was compared to other two different microstructure which occurred after well-known heat treatments; quenching and age hardening. Beside microstructure also the effects of cutting speed and feed rate were ob...

Wear and friction characteristics of Zr-based bulk metallic glass under dry sliding conditions are investigated. This study demonstrates that load and sliding speed significantly affect the wear characteristics of bulk metallic glass material and sliding distance is less effective on wear. Critical sliding speed and normal force limits, 1 m/s and 1...

A shear punch test technique was used for characterization of the mechanical properties of Zr–5Ti–17.9Cu–14.6Ni–10Al bulk metallic glass. The ultimate shear stress values matched very closely with values derived from uniaxial compression tests reported in the literature. This is consistent with a lack of pressure sensitivity in compression reported...