Department of Manufacturing Engineering
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Item ULTRASONIC ASSISTED DRILLING OF PRECIPITATION HARDENED MARTENSITIC STAINLESS STEEL(2023-01-03) ENİS, Metin Berk; KILIÇ, Sadık Engin; LOTFI, Bahram17PH4 Stainless Steel is widely used in sectors such as the nuclear industry, aerospace, and defence industry, thanks to its significant corrosion resistance, high fatigue and tensile strength, toughness, and high hardness. Drilling is one of the most used methods in these sectors and general machining processes, but it reduces the drilling performance considerably due to the high wear resistance, hardness, and thermal conductivity of this material. Ultrasonic Assisted Drilling (UAD) is a hybrid method that makes the metal removal process more accessible by using low amplitude vibrations and high frequency. For the first time, the UAD method was used to increase the efficiency of a drilling operation in 17-PH-4 stainless steel in this study. The experimental design was prepared to compare the conventional drilling (CD) method and UAD, as well as to see the effect of UAD on pecking and direct drilling. The experimental results showed that UAD reduces cutting forces, burr formation at the exit hole, built-up edge (BUE), and continuous chip formation, increases dimensional accuracy, and improves surface quality compared to the conventional drilling method. The test results show that the increase in cutting speed significant effect on the reduction of cutting forces, BUE, surface roughness, and continuous chip formation. When the surface roughness, cutting forces, and burr formation results are examined, the positive effect of UAD is higher in direct drilling than in pecking.Item A COMBINED EXPERIMENTAL-NUMERICAL INVESTIGATION ON ALUMINIUM EXTRUSION(2011-04-27) KALKAN, Hakan; ÖZDEMİR, İzzet; BARANOĞLU, BesimThis study focuses on an industrial size aluminum extrusion process and consists of both experimental and computational parts. On the basis of process parameters and die geometry supplied by ASAŞ Aluminum Company, full scale computational models of the process have been constructed by using different commercial Finite Element and Finite Volume software packages. The necessary material characterization has been done by compression tests for which a new uni-axial compression test set-up suitable for high temperatures has been designed and manufactured. The measured load-displacement diagrams and exit temperatures are compared with the computational results. In addition to that, Finite Element and Finite Volume results are also compared. These results indicate that reasonable good agreement between the measured data and computational results can be achieved provided that the Finite Element Method is used and proper material characterization is conducted.Item THERMOELASTIC ANALYSIS OF HEAT GENERATING MULTI-LAYERED COMPOSITE CYLINDERS AND TUBES(2012-04-18) YILDIRIM, Murat; ARGEŞO, HakanA computational method is developed for the thermoelastic analysis of internally heat generating multi-layered composite cylinders and tubes having temperature dependent physical properties. The composite assembly is considered to be infinitely long and have axially constrained ends. In the formulations, small deformation theory is used. The layers that form the composite assembly are isotropic and have uniform heat generation. The thermal and mechanical problems are uncoupled and axisymmetric. The thermal problem is steady state and the mechanical problem is a plane strain problem. The computational model is based shooting algorithm. Both the thermal and mechanical problems are solved with the use of shooting algorithm. The computational model is first verified through the use of some benchmark problems that have analytical solutions in which the physical properties are considered to be temperature independent. The computational method is then used to solve some composite cylinder/tube assemblies that have temperature dependent physical properties.Item EXPERIMENTAL INVESTIGATION OF INFLUENCE PARAMETERS ON FORMING LIMIT DIAGRAMS OF ALUMINUM ALLOY-AL 2024(2013-04-22) ÇELİK, Gökhan; KAFTANOĞLU, Bilgin; KARADOĞAN, CelalettinSheet metal forming is the key word for aerospace, automobile and aeronautics industry. To fulfill the customer expectations, safety requirements and market competitions, sheet metal forming processes must be well analyzed before production. At this stage, importance of material characterization and finite element (FE) simulations arise. This study is focused on combination of material characterization and FEA (Finite Element Analyses) of sheet metals to be able to make improvements of sheet metal while considering cost and quality. On the material characterization parts of the study, simple tension tests, hydraulic bulge tests (HBT) and forming limit diagrams are determined for Al2024 aluminum alloy. HBT is obtained using a new specialized code and compared to the simple tension tests. High accuracy mechanical extensometers are used to obtain instantaneous deformation during tensile test and similarly high accuracy CCD cameras are used to obtain material deformation during determination of FLDs and flow curves from HBT. FE studies are performed to validate experimental studies and to determine coefficient of frictions of different lubricants. Analyses are carried out using a commercial FE package, Marc Mentat 2007® . Material inputs are supplied from experimental uniaxial and hydraulic bulge tests. Flow curve validations are performed comparing HBT and uniaxial tensile tests up to 0.15 strains. Experiments revealed that initial material thickness and lubrication has a significant effect on formability window of aluminum sheets and speed of punch has no great effect on limits of aluminum formability since Al2024 is a strain rate independent material. Beside these, higher strains than uniaxial tensile test are obtained in HBT with new developed code.Item EXPERIMENTAL AND NUMERICAL STUDY ON STRETCH FORMING PROCESS(2013-06-20) ALKAŞ, Celal Onur; KARADOĞAN, Celalettin; ŞİMŞİR, CanerStretch forming process is commonly used in the aircraft industry for the manufacturing of large sheet panels. The success of this process is highly dependent on the process parameters like mechanical properties of sheet material, the friction condition between tools-part interfaces and relative motions between tool and jaws. Determining the best parameters by trial - error procedure is quite difficult and costly, so that finite element analysis is needed. The scope of this study is to establish finite element model (FEM) for stretch forming process. For this purpose, accurate material and reliable friction modeling are required. Material characterization tests of mostly used aluminum alloys are conducted to prepare input to the model. Standard tensile, stack compression, hydraulic bulge test (HBT) and forming limit diagram (FLD) tests are performed in order to identify deformation behavior and anisotropy properties of aluminum sheet materials. High accuracy CCD cameras are used to obtain material deformation during determination of FLDs and flow curves from HBT. Also, friction coefficients are determined for various lubrication conditions encountered in stretch forming processes using inverse based analysis. Using these inputs, numerical model of the process is established by FEM for three basic stretching tool motions, which are; stretching the sheet by jaw, stretching the sheet by form die and finally stretching the sheet material by synchronized motion of both tools. In order to improve the model and validate the analyses results, experimental work is also performed in which the deformation of the sheet is measured optically using GOM-Argus® 3- D deformation measurement device. Then, three selected aerospace sheet parts were analyzed and success of the model for industrial applications is proved.Item PERFORMANCE EVALUATION OF BORON NITRIDE COATED CUTTING TOOLS(2022-06-15) Doğan, BerkayIn this study, boron nitride coatings are made by physical vapor deposition (PVD) technique. The coated substrates are D2 steel, carbide end mills and silicon wafer. Characterizations are performed for each substrate coated with BN. Apart from characterization measurements, cutting tests of carbide end mills are performed. Single crystal hexagonal BN (h-BN) target is used for BN formation in coating experiments. Radio frequency (RF) and Inductively Coupled Plasma (ICP) are used as power supplies. BN coatings in different parameters are made and the results are revealed. As a result of BN coating experiments, coating thickness, nano hardness, friction coefficient, crystal structure analysis and scratch behavior are measured. Force and moment measurements of carbide end mills coated with BN are made on CNC milling machine using dynamometer. According to the results of the studies, it is seen that carbide end mills with BN coating in different parameters can reduce the cutting forces and moments when machining the work piece. The positive results of the use of the ICP power supply on nano hardness, coating thickness and coefficient of friction are observed.Item A COMBINED NUMERICAL-EXPERIMENTAL INVESTIGATION ON MICRO-EXTRUSION(2013-06-14) MURAT, Levent; ÖZDEMİR, İzzet; ŞENGÖNÜL, MerihIn this work, to develop an understanding on micro forming processes, a combined experimental-numerical investigation on micro forming is presented. On the experi mental side, in order to demonstrate the statistical size effect, an experimental set-up for micro-extrusion has been designed and micro-extrusion test with copper billets of different average grain size, has been conducted successfully. On the modelling side, due to large displacement and large strains developing during the forming process, a geometrically non-linear continuum mechanics description is preferred. Since a grain level description is necessary for micro forming operations, crystal plasticity is used to model the mechanical response of each grain. To this end, the crystal plasticity framework has been coded as a user defined material model and integrated into the commercial FE software Abaqus as a UMAT subroutine. With this tool, a numerical investigation on the influence of grain orientations on frictional response at small scales is carried out.Item ENHANCED CHARACTERIZATION and DIE DESIGN for SHEET METAL FORMING in AUTOMOTIVE INDUSTRY(2014-03-10) GÜRBÜZ, İsmail; KARADOĞAN, CelalettinLast several decades, existing global competition are going on among automotive companies because of increasing customer expectations, safety requirements, the manufacturing time and cost. These requirements play most significant role for automotive companies to continue one’s existence in automotive market. Many automotive companies manage to develop their capabilities and techniques as mechanically, trial-error and virtually to manufacture high quality car components. Since the trial-error method is quite difficult and costly, finite element method (FEM) must be used. Tryout is the validation process of dies for a robust mass production. Each company has its own tryout strategy and the crucial know-how is usually not publicised. Being the major player in automotive industry in Turkey, TOFAŞ aims to catch up with the global actors, and hence intends to further develop its own tryout strategy utilizing virtual tools. In this study, one of the major milestones towards this success is introduced. Concerning the material properties, friction coefficients, elastic properties of dies and compensation strategies, the basic know-how and necessary information is created for further automatization of the virtual tryout practice. Material characterization plays most significant role in order to prepare input the virtual model. In this study, several material characterization tests are performed. Standard tensile tests are performed to obtain early stage of the yield curves and anisotropy parameters of sheet materials. The plastic behavior of the sheet metal under biaxial stress state is usually obtained by HBT. Hydraulic Bulge Test (HBT) is performed using high quality optical measurement system (GOM Aramis). Nakajima test is used to obtain Forming Limit Curve (FLC). The optical measurement system GOM Aramis is used to obtain sheet metal deformation during prediction of FLC and yield loci and flow curves from HBT. Furthermore, friction coefficient is an important parameter in order to obtain accurate results from virtual model. Basically there are two approaches in determining the friction coefficient: direct approaches provide the friction coefficient without inverse analysis through simulations and indirect ones requires inverse simulative evaluation. Elastic modulus, which is also a significant parameter to get accurate results from virtual models, is determined using several testing methods such as, tensile testing, ultrasonic measurement, Resonant Frequency and Damping Analysis (RFDA). Moreover, several testing method (Three Point Bending, Four Point Bending and Frictionless Stretch Drawing) and finite element method are used to verify obtained elastic modulus values. Finally, a new approach is proposed for the compensation of die and press deflection.Item INVESTIGATION OF BORON NITRIDE COATINGS(2014-06-09) DÖKMETAŞ, Nihan; KAFTANOĞLU, Bilgin; ŞİMŞİR, CanerThis thesis presents detailed characterization studies on Boron Nitride (BN) coatings. In this study, BN coatings are obtained with the method of Radio Frequency (RF) magnetron sputtering technique, in a Physical Vapor Deposition (PVD) system, from target to substrate. BN coating formation on different substrates are investigated on varies substrates such as AISI D2 Steel, 316 L steel, optical glasses, Ti implants. Also, using different deposition parameters, the effect of parameters are researched. All coating results are investigated by using XRD, SEM, CaloTest®, Filmetrics F20 Thin-Film Analyzer Device ®, step profilometer, Scratch tester, Tribometer tester, Nanoindentation tester, FTIR, AFM and profilometer. Compositional, structural and mechanical measurements and analysis are performed for the characterization of BN coating. According to our investigations, it is observed that BN coatings obtained in different phases such as a--BN, e-BN, r-BN, w-BN, t-BN and h-BN structures besides c-BN structures. The effects of chemical and microstructural constitution on the tribological properties were investigated. Generally, it is found that there is good adhesion and lower friction because of more than one structure. In some cases hardness is found to increase. On the other hand, some difficulties are encountered in measurements because the coating thickness is generally 1 μm or lower. A statistically significant change could not be determined in roughness for 3 and 6 hours coating compared to substrate roughness.Item ANALYSIS OF COLD EXTRUSION(2014-06-09) DURAN, Deniz; KARADOĞAN, Celalettin; ÖZDEMİR, İzzetCold extrusion is a cold forging process where product of smaller cross sectional area is obtained by compressing a billet through an aperture in the die. In this study, different facets of cold extrusion processes are investigated experimentally and numerically to a certain extent that seem to be overlooked in the existing studies. Proper material characterization that is necessary to analyse cold extrusion processes is addressed. A method for reconstruction of isothermal flow curves based on the flawed test data is proposed. An unexpected instability is observed for 16MnCr5 steel in the process range of 200-400°C, where material exhibits negative strain rate sensitivity. This instability is associated with dynamic strain aging phenomenon. The importance of the proposed method is presented for a forward rod extrusion case. The pitfall existing for a common friction identification test, namely, the double cup extrusion test, is emphasized when insufficient material data is used in the inverse analysis. Treatment of surface enlargement, a crucial tribological parameter, within FEA framework under arbitrary deformations is discussed and an alternative calculation scheme is developed. An experimental method for surface enlargement measurement is developed to verify the numerical predictions. A recently proposed, surface evolution based friction model is investigated and possible improvements are addressed. Forward rod extrusion process with multiple area reductions is examined as the proof of concept study. Following, the simulated surface roughness predictions are compared with the experimental surface topography measurements for a forward rod extrusion process.Item ENHANCED CHARACTERIZATION and DIE DESIGN for SHEET METAL FORMING in AUTOMOTIVE INDUSTRY(2015-01-30) GÜRBÜZ, İsmail; KARADOĞAN, CelalettinLast several decades, existing global competition are going on among automotive companies because of increasing customer expectations, safety requirements, the manufacturing time and cost. These requirements play most significant role for automotive companies to continue one’s existence in automotive market. Many automotive companies manage to develop their capabilities and techniques as mechanically, trial-error and virtually to manufacture high quality car components. Since the trial-error method is quite difficult and costly, finite element method (FEM) must be used. Tryout is the validation process of dies for a robust mass production. Each company has its own tryout strategy and the crucial know-how is usually not publicised. Being the major player in automotive industry in Turkey, TOFAŞ aims to catch up with the global actors, and hence intends to further develop its own tryout strategy utilizing virtual tools. In this study, one of the major milestones towards this success is introduced. Concerning the material properties, friction coefficients, elastic properties of dies and compensation strategies, the basic know-how and necessary information is created for further automatization of the virtual tryout practice. Material characterization plays most significant role in order to prepare input the virtual model. In this study, several material characterization tests are performed. Standard tensile tests are performed to obtain early stage of the yield curves and anisotropy parameters of sheet materials. The plastic behavior of the sheet metal under biaxial stress state is usually obtained by HBT. Hydraulic Bulge Test (HBT) is performed using high quality optical measurement system (GOM Aramis). Nakajima test is used to obtain Forming Limit Curve (FLC). The optical measurement system GOM Aramis is used to obtain sheet metal deformation during prediction of FLC and yield loci and flow curves from HBT. Furthermore, friction coefficient is an important parameter in order to obtain accurate results from virtual model. Basically there are two approaches in determining the friction coefficient: direct approaches provide the friction coefficient without inverse analysis through simulations and indirect ones requires inverse simulative evaluation. Elastic modulus, which is also a significant parameter to get accurate results from virtual models, is determined using several testing methods such as, tensile testing, ultrasonic measurement, Resonant Frequency and Damping Analysis (RFDA). Moreover, several testing method (Three Point Bending, Four Point Bending and Frictionless Stretch Drawing) and finite element method are used to verify obtained elastic modulus values. Finally, a new approach is proposed for the compensation of die and press deflection.Item ANALYSIS OF ELASTIC-PLASTIC INTERFERENCE FIT JOINTS(2015-10-23) IŞIK, Hatice Hava; MUSIC, Omer; KARADOĞAN, CelalettinIn automotive industry, increasing product complexity has driven the development of new joining processes for mechanical parts. Typical examples are welding, adhesive bonding and mechanical fastening used to join components in a product assembly. Joining by interference fits belongs to a wider group of mechanical joining processes, some examples of which are self-pierce rivets, mechanical clinches, pin joints and threaded connections. In interference-fit joints, interference of two mating parts leads to contact pressure at the interface. This contact pressure holds the two parts together through friction, providing a mechanical joint. Strength of this joint depends mainly on the coefficient of friction, contact pressure and contact area. Such joints are used in a wide variety of applications, ranging from automobile to aerospace industry. This study focuses on analysis of elastic-plastic interference fit joints formed by fitting the filter pin into the cylindrical hole in the injector body. This process has been studied in detail, however a review of literature reveals that analytical and numerical models have been developed for relatively simple geometries, and the number of publications for complex, asymmetric, three-dimensional geometries is limited. This study presents a detailed examination of the elastic-plastic interference fit joints for both simple and complex geometries. The mechanics of the process is studied in detail through physical trials, analytical and numerical models. Both trials and modelling are done for two-dimensional and three-dimensional geometries. The effects of geometrical properties, material properties and cylinder-tube, grooved geometry and actual process are investigated. Developed numerical models are applied to an industrial problem; analysis of an asymmetric, three-dimensional interference fit joints used in high pressure diesel injection systems, specifically the joint between the fuel filter and the injector body of an injection system. Strength of this joint is one of the key parameters determining the performance of the fuel injection system as a whole and as such is studied in detail. A detailed investigation of the joining process shows that the joint strength can be improved through careful selection of filter and body materials, geometry and other parameters that affect the joining process.Item MODELLING AND ANALYSIS OF TUBE SPINNING(2017-04-02) Çizmeci, Kerem; Şimşir, CanerThis thesis investigates the process of tube spinning. The investigation is based on numerical simulations by commercial finite element software Transvalor Forge. Two dimensional and three dimensional numerical analysis models have been developed. Parameter optimization has been performed to find the variables of numerical analysis. The proposed numerical model was compared with the related works in the literature. Using the developed models, analysis of tube spinning process has been performed.Item INVESTIGATION OF CARBURIZED QUENCHING PROCESS OF SHAFTS USING DESIGN OF EXPERIMENTS(2022-03-01) Yılmaz, Hasan; Şimşir, Caner; Davut, KemalCarburizing is a widely-used thermochemical heat treatment process in shaft manufacturing. Insufficient case-depth, inadequate surface/core hardness, and distortion are the common reasons for scrapped products after carburizing. Thus, understanding, control and optimization of the process parameters in carburizing is crucial to avoid losses. In this study, carburizing parameters were investigated and optimized by Design of Experiments (DoE) using the Taguchi method. The target of the optimization is the minimization of the variability in the production due to the use of different furnaces for the process. Experiments were carried out on as-turned shafts (plain and stepped) made of two different grades of steel (16MnCr5 and 20NiCrMo2-2) using two different industrial gas carburizing furnaces. After the carburizing experiments, dimensional changes were measured using a Coordinate Measurement Machine (CMM), while carbon and hardness profiles were determined using Optical Emission Spectroscopy (OES) and Vickers indentation techniques. The results indicated that carbon potential of the carburizing gas is the most important parameter associated both with the variability and the mean effect for the case-depth and the diameter change.Item IMPLEMENTATION OF EXPERT SYSTEMS IN CAPP FOR PREDICTIVEMAINTENANCE IN DISCRETE MANUFACTURING SYSTEMS(2022-03-01) Al-Humairi, Elaf Riyadh Resen; LOTFISADIGH, Bahram; AMİNBAKHSH, SamanStrict global market competition and continuously changing customer demands, push manufacturing enterprises towards flexible manufacturing systems. In this way, pro cess planning and scheduling steps are truly crucial for manufacturers. Especially in the case of flexible job shops with volume and product type flexibility, these pro cesses become even more critical. A new industrial revolution called “Industry 4.0” brings new technological possibilities by integrating computer and information tech nologies with manufacturing systems to support enterprises to face this overwhelming competition pressure and enhance the efficiency of process planning and scheduling processes. Some of these technologies like agent-based systems, virtualization of manufacturing systems, system simulation by the creation of cyber-physical layers, digital twins and others can be named as some of them were studied and developed in several types of research in literature. In this research, a new methodology by in tegrating the ontology modelling of manufacturing domain and reasoning rules as a solution for the process planning phase, with the Lekin scheduling program is pro posed. In this thesis, first, the ontology domain model developed for metal cutting processes is described, then designed and added reasoning rules and SPARQL queries are explained in detail. Finally, the scheduling results obtained from Lekin program built-in heuristics are explained.Item INVESTIGATION OF CARBURIZED QUENCHING PROCESS OF SHAFTS USING COMPUTER SIMULATIONS(2022-02-28) Yazır Terzi, Büşra; Şimşir, Caner; Davut, KemalCarburizing and subsequent quenching heat treatments are commonly used industrial processes to improve the properties and performance of steel shafts. Variation of the case depth related to these treatments are the most frequent reason for product rejection. Therefore, the major aim of this study is to identify the suitable control parameters for subsequent optimization of carburized quenching DIN 16MnCr5 (1.7131) steel shafts. Another aim is to estimate inevitable experimental variations and determine the accuracy of computer simulations in presence of experimental uncertainties in the process parameters. This study is performed on both experiments and simulations. Experimental study is used to verify the simulations. In order to determine the control parameters of the process, a local sensitivity analysis is conducted using computer simulations in which each control parameter is perturbed around its reference state and the associated dimensional changes were correlated to those perturbations by a dimensionless sensitivity index. Additionally, for the purpose of identifying the effective parameters, a virtual design of experiments is performed on finite element method software SYSWELD®.Item DESIGN AND IMPLEMENTATION OF AN INCREMENTAL SHEET FORMING PROCESS FOR BENDING OF HIGH STRENGTH THICK STEEL SHEETS(2022-02-24) Çetin, Barış; Billur, Eren; Baranoğlu, BesimAs a specific section of armored combat vehichle industry, hull production, for many case, has a production step for bending of ultra high strength steels (UHSS). This bending operation is generally performed by means of high tonnage press brakes in air bending condition. The steels in hull production have very high tensile strengtht values compared to conventional mild steel such as 1250 MPa or even higher. These strength levels absolutely require high bending forces, undoubtfully. On the other hand, incremental sheet forming process has been recently implemented in metal forming industry which is mainly based on the gradual and local excitation of plastic deformation. This new generation technique has some advantages such as increasing the formability, eliminating the complex tool requirements and reducing the form ing forces reasonably. In this study, basically the potential of incremental forming process in force reduction is investigated. A new incremental bending process is pro posed, simulated and experimentally verified within the scope of the study. Through the wide range of data obtained from the simulation and experimental efforts, some optimization could also be conducted on the process parameters. Briefly, the results of the incremental bending of UHSS plates are compared with the conventional air bending operation.Item DETERMINATION OF PROCESS MAP FOR HOT FORMING OF Ti-6Al-4V(2022-02-24) Demirkol, Yasin; Şimşir, CanerTitanium alloys are used in the field of aviation, turbine blades, gas turbines and engine parts, propellers and many other parts because of their resistance to corrosion as well as their high strength to weight ratio. However, in order to take advantage of these properties, titanium alloys having low ductility at room temperature require high temperature forming techniques which have inherent disadvantages. Hot forging is the most common method for manufacturing these components. Titanium hot forging is more complicated than conventional steel forging due to many reasons: flow instabilities that may occur during forging, macro-micro cracks, static and dynamic strength loss due to melting at grain boundaries and heterogeneous microstructure and alpha layer formation due to air interaction are most common problems. More important than these, the microstructure formed during the titanium alloys forging cannot be repaired by the post-forging heat treatment as opposed to many steels. For this reason, titanium forging must be designed as a "thermo mechanical-metallurgical process", not only as a forming process. In this work, the material data required for designing the hot forging process of the Ti 6Al-4V alloy to satisfy the above conditions was obtained by experimental methods. A wide range of temperature and strain rate controlled compression tests was performed to find the material law parameters that determine the behavior of the material in the plastic region. A "Process Map" was generated which restricts the amount of temperature, deformation amount and speed to obtain forged products without any problems and desired microstructure.Item PREDICTION OF TENSILE MECHANICAL PROPERTIES OF TIN-BISMUTH ALLOYS BY VICKERS HARDNESS TEST(2022-02-22) Alkilani, Nuri Aburodess Alssid; Şengönül, Cemal Merih; Şimşir, CanerMechanical properties under tensile are the most fundamentally used ones to predict the mechanical behavior of materials. However, the tensile test can be a cumbersome method concerning its bulky equipment, detailed sample preparation protocols and considerably high cost. Since there is a strong relation between hardness and tensile strength of the materials, there are some research studies aimed to establish a correlation between the tensile properties and hardness values of a material. In fact, hardness measurement is mostly a trivial process which can be performed without complicated protocols to get information about a material in an apparently cheap and fast way by using small-scale benchtop instruments. In this research work, we adopted similar approach to attain an analytical relationship between mechanical properties like tensile strength, yield strength, strain hardening exponent and strength coefficient of a low melting point alloy system, tin-bismuth (Sn-Bi) and their Vickers hardness numbers. This thesis covers a comparative analysis of data from hardness and tensile tests to develop a mathematical relationship that will predict the stress-strain behavior of these alloys, particularly eutectic. Hence four different compositions of the Sn-Bi alloys are used with Bi percentages such as 30%, 40%, 50% and 57% in this work. Tensile tests were performed at room temperature and their plastic regions up to UTS were analyzed to determine the aforementioned mechanical properties of the given alloy compositions. Concurrently hardness measurements were performed to obtain their Vickers hardness numbers. As a result, we determine a strong relationship between the tensile mechanical properties and the hardness of the Sn-Bi alloy and the established numeric model predicted most of the mechanical properties with a high statistical significance.Item FINITE ELEMENT MODELING OF MACHINING PARTICLE REINFORCED ALUMINUM METAL MATRIX COMPOSITES(2022-02-22) Rake, Nakka Lotfy; Kılıç, Sadık Engin; Oliaei, Samad Nadimi BavilMetal matrix composites (MMCs) have become key materials in many technical fields, including automotive, aerospace and nuclear power plants. In most of these applications, machining processes are required to achieve the desired characteristics of the final product. Therefore, it is important to study the machining of MMCs and develop process models to understand their behavior during machining operations. Based on process models, machining quality and cost can be improved by optimizing the cutting conditions for specific MMCs. As a step towards this goal, finite element modeling (FEM) is used to study the machining of particulate aluminum metal matrix composites (p-Al-MMCs). The selected matrix material was aluminum alloy A359 reinforced with silicon carbide (SiC) particles having a diameter of 20 μm with a volume fraction of 20%. Orthogonal cutting of p-Al-MMC has been studied by three different approaches. In the first approach attempt has been made to implement an equivalent homogeneous material model (EHM), while in the second and third approaches p-Al-MMC is modeled as a two-phase heterogeneous material. The second and third approaches rely on periodic square and periodic hexagonal distributions of reinforcement particles, respectively. The interaction between matrix/cutting tool, matrix/reinforcement and reinforcement/ cutting tool has been considered. The results of FE simulations are compared with the experimental data available in the literature. The results revealed that, EHM models calibrated using high strain rate tests may not be able to give good predictions of cutting forces and they should be re-calibrated for machining simulations. The results also revealed that, by modeling p-MMCs as a heterogeneous material the accuracy of cutting force predictions can be improved significantly.