Theses supervised by Prof. Dr. Melih Bayramoğlu
12 theses · Çukurova University
The effect of process parameters on thickness and brightness of chromium plating
In many instances, the properties of the materials could be insufficient to meet some of the functional demands especially those, which arise from the environmental conditions. It could be a very corrosive atmosphere or an excessive wear condition. As the high quality materials may turn out to be too costly, designers should seek a solution, which will either protect the base material against hostile environment or improve properties of base material only at the surface. Chromium plating process is the most effective way of solving all of these problems. The aim of this study is, defining the process parameters of the chromium plating process, effects of these parameters on brightness and thickness of the chromium plating and defining the optimum process parameters which will provide the best thickness and brightness. During this study all material preparation and preliminary works before chromium plating process carried out in the plating workshop of Medikar Co. Inc. and chromium plating process done in the Mechanical Engineering Laboratory of Çukurova University. Keywords: Hard and Bright Chromium, Corrosion, Electroplating, Response Surface Methodology (RSM), Plating Thickness and Plating Brightness.
Effect of pool geometry on the quality of TIG welded joints
ABSTRACTPhD THESISEFFECT OF POOL GEOMETRY ON THE QUALITY OFTIG WELDED JOINTSUğur EŞMEDEPARTMENT OF MECHANICAL ENGINEERINGINSTITUTE OF NATURAL AND APPLIED SCIENCESUNIVERSITY OF ÇUKUROVASupervisor : Prof. Dr. Melih BAYRAMOĞLUYear: 2006, Pages: 366Jury : Prof. Dr. Melih BAYRAMOĞLU: Prof. Dr. Necdet GEREN: Assoc. Prof. Dr. Mustafa Kemal KÜLEKCİ: Assoc. Prof. Dr. Abdülkadir EKŞİ: Assist. Prof. Dr. Ali KOKANGÜLAcross the engineering spectrum, welding is an essential process in themanufacturing of components, assemblies or complete machines. Tungsten inert gas(TIG) welding is the best known and most frequently used method of weldingprocess in food industry, ships, bridges and welding of stainless steels. Basically,TIG weld quality is strongly characterized by the weld pool geometry which hasseveral quality responses such as tensile load (TL), heat affected zone (HAZ), upperwidth (UW), upper height (UH), penetration (P) and area of penetration (AP). Weldpool geometry plays an important role in determining the mechanical properties ofthe weld. Therefore, it is very important to select the welding process parameters forobtaining an optimal weld pool geometry. In this study, the effect of TIG weldingprocess parameters (welding speed, welding current, gas flow rate and gap distance)on the weld pool shape and the quality responses were investigated. Themathematical models were developed for optimization and prediction of the weldpool geometry. Also, a neural network (NN) was used to construct the relationshipsbetween welding process parameters and weld pool geometry in TIG welding.Keywords: Tungsten Inert Gas Welding (TIG), Weld Pool Geometry, CentralComposite Design (CCD), Response Surface Methodology (RSM),Neural Network (NN)
Comparisons of different methods used for improving life of hot forging dies
ABSTRACTMSc THESISCOMPARISONS OF DIFFERENT METHODS USED FOR IMPROVINGLIFE OF HOT FORGING DIESHaydar POLATDEPARTMENT of MECHANICHAL ENGINEERINGINSTITUTE of NATURAL and APPLIED SCIENCESUNIVERSITY of ÇUKUROVASupervisor : Prof. Dr. Melih BAYRAMOĞLUYear : 2006, Page: 104Jury : Prof. Dr. Melih BAYRAMOĞLUProf. Dr. Necdet GERENAssist.Prof. Dr. Ali KOKANGÜLIn this work, many of the methods used for improving life of hot forging dieswere investigated in the forging department ÇIMSATAŞ. For this aim, the surfacetreatments such as one layer surface coating AlTiN, a special multilayer coatingcalled TOKTEK (two layer coating), nitriding, and the weld overlay coating of thecontact surface of the hot forging dies were studied with same hot forging dies undersame conditions and the results were compared with the as received die material. Theas received material was hardened and tempered DIN 1.2344 (ORVAR 2M) steelwith the final hardness of 44-46 HRC.After the experiments, it was found out that all of these methods improve lifeof hot forging dies in various amounts and the best result was obtained by weldoverlay of the contact surface of the dies with CASTOLIN N9080.Key Words: hot forging, die life, nitriding, weld overlay coating
Thermally induced distortion and residual stresses in welded joints
The thermal response of materials to a welding heat source sometimes causes mechanical problems, e.g. residual stresses and distortion and changes in mechanical properties due to changes in the microstructure. Residual stresses and distortions take place in weldments due to local heating and cooling. When this residual stresses combine with the external forces, unexpected failure can be observed during service life of weldments. The distortion can effect the dimensional accuracy of the weldments. Therefore some additional straightening processes are needed after welding process.Prediction of the amount and the distribution of residual stresses and distortion before welding has been an important subject for researchers. In this thesis, SYSWELD finite element package program was used in modelling. The situation of the material after welding can be estimated by modelling, also the optimisation of welding parameters can be done.
World class manufacturing on automobile industry and applications of autonomous maintenance in press shop
Nowadays international competency is growing fast. In this condition, to be alive the first rule is being a fast runner! To do this, we should follow dynamic structure of this age and we should open for reforms and changes in our work life. Because of that companies have to adapt themselves according to new age technologies and systems, if not, they should be ready to be passed by others. From this reality, Lean Manufacturing system was developed by Toyota. Later from all over the world, so many companies started to implement it. Lean manufacturing with a short explanation is; distinguishing of the waste and value, decreasing or if possible zeroing the waste and making the value more worthy. Autonomous Maintenance as a subject is one of the most important fundamentals of the application side of lean manufacturing.In this study, effects of Autonomous Maintenance on manufacturing productivity have been investigated. It?s applications that are the basic of the World Class Manufacturing (WCM) and Total Preventive Maintenance (TPM). So, Firstly WCM system was introduced in this study. Then it replaced by Autonomous Maintenance (AM) applications and it has been studied step by step. In application part, both the effects of the AM applications in working shop and the importance of AM in equipment improvements have been tried to emphasize with the applications realized in Press Production Shop where is from a leader of automotive sector in Turkey.Key Words: Lean Manufacturing System, Total Preventive Maintenance, Autonomous Maintenance, World Class Manufacturing.
The use of composite materials in automotive industry
The automotive industry's use of structural composite materials began in the1950s. Since those early days, it has been demonstrated that composites arelightweight, fatigue resistant and easily moulded to shape in other words, aseemingly attractive alternative to metals. However, there has been no widespreadswitch from metals to composites in the automotive sector. This is because there area number of technical issues relating to the use of composite materials that still needto be resolved including accurate material characterization, manufacturing andjoining. This paper reports composite materials determining by Ashby?s materialselection technique usage in automotive industry. Especially bus exterior and interiorcomponents manufacturing by fiber reinforced polymers (FRP) are used in thismaster thesis.Keywords: Material selection, composite materials, bus components, Ashby?stechnique, Fiber reinforced polymers
Effect of tempering temperature on the mechanical properties of hardened 1.2842 steel
Tool steels are designed to have high hardness and durability under severe service conditions. These properties are obtained with the selection of optimum conditions for the heat treatment. Generally, after quenching process some austenite is retained in tool steels. It is important to recognize that a balance must be created between the mechanical properties of a component and the optimum percentage of retained austenite for a given application.In this study, the effects of tempering temperature on the mechanical properties of hardened 1.2842 (O2) tool steel were investigated. At different tempering temperatures, volume fraction of retained austenite was estimated and effect of volume fraction of retained austenite on the hardness, impact toughness and tensile properties are discussed.X-ray Diffraction Method was used to estimate the volume fraction of retained austenite in as quenched and tempered specimens. Charpy impact test was used to determine the impact toughness and tensile test was performed to determine tensile properties of 1.2842 steel at different tempering temperatures. Then test results were interpreted and optimum tempering temperature was selected for the selected 1.2842 steel used in this work.
Effect of boronizing temperature and time on abrasion and corrosion resistance of AISI 1050 steel
In this study boronized specimens have been used that is manufactured from AISI 1050 steel and pack borozing process has been applied to this specimens at a temperature of 800-850 and 900 ºC with a time duration of 3-6 and 9 hours. Ekabor 2 has been used as a source of boron. The photographs of micro structures of boronized specimens have been taken and the layer thicknesses varied from 17 to 110 µm and the hardness values from 510 to 1890 HV have been obtained. These values have been compared with Taguchi method. Boronized and non-boronized specimens have been subjected to abrasion test under the load of 30N by using sand papers which have grain size of 220 mesh. However these specimens have been sink into the 3,5% NaCl solution for corrosion test in order to compare the strength of materials between them.
Optimization of GMAW process parameters for improving mechanical properties of DP1000 steel joint
Euro-6 norms for reduction of CO2 emissions and ECE-R66-01 regulation for safer passenger transportation became legislative obligations for bus builders. These two adaptations increase the weight of a bus as nearly 600kg which also increases the fuel consumption nearly 1.5-3%. Dual phase (DP) steels can compensate these increases by decreasing the thickness of the components. Because, ferrite provides the steel with good formability and martensite increases the hardness and ultimate tensile strength (UTS) in DP steels. But, the literature reviews showed that increase in heat input of Gas Metal Arc Welding (GMAW) can decompose the martensite islands and increase the ferrite grain size. As a result, hardness and UTS of the welded joint can decrease critically. Thus, this study focused on the optimization of GMAW process parameters for improving mechanical properties of DP1000 steel joint. In this aim, visual and microstructural inspections, Vickers hardness measurements and tensile tests were applied. As a result of the tensile tests, 100% of welded DP1000 samples fractured in subcritical (SC) region. The minimum decrease in UTS was calculated as 21,85% and the maximum decrease in UTS was defined as 26,55%. Increase in heat input (HI) also increased the martensite tempering effect and decreased the hardness and UTS. Welding speed, wire feed rate and voltage had 30.41%, 26.58% and 18,30% weightiness respectively on UTS. As a result, the optimum butt welding parameter combination of 1.20mm DP1000 steel was defined as 17.5V arc voltage, 380mm/min welding speed and 2.2m/min WFR and 45A arc current to provide the highest mechanical properties.
The effect of bending temperature, holding time, thickness and bending angle on spring back of dual phased high strength steel sheets
It is very important to have a predictable spring back in metals to get accurate dimensions after bending. Especially in the last years, various studies were made about the spring back to eliminate or at least to minimize it. In addition to process parameters, the work piece material properties are also important in spring back. High strength DP1000 steel which is widely used in many different fields in recent years due to its unique properties, was preferred as a specimen in this work. The aim of this study was to find the effect of temperature, bending angle, thickness and holding time on spring back. In experimental work, 1 mm and 2 mm thickness of sheets were bent by using 90° and 135° bending angles at temperature levels of room temperature (RT), 100°C, 200°C, 300°C, 400°C and 500°C. Effect of punch holding time was tested for 40 seconds. Effects of all factors and their interactions were analyzed in Design Expert. ANOVA and Regression Analyses were executed. It was seen that the spring back decreased when the temperature, holding time and thickness were increased. On the other hand, increasing bending angle caused an increase in spring back. The smallest spring back was achieved with the interaction effect of the temperature and the holding time.
Effect of surface treatments and stacking sequences on the mechanical properties of fiber metal laminates
In this study, the effect of surface treatments and stacking sequences on the mechanical properties of fiber metal laminates (FMLs) were investigated. Aluminum 8006 alloys and very thin stainless steel wire meshes were used as metal in FML composites. The surface treatments such as anodizing, and etching were applied on Aluminum 8006 to improve the adhesive bonding capability. Also, FML composites were manufactured with different stacking sequences to investigate the effect of the hybridization. To determine the mechanical properties of FML composites several tests were carried out such as three-point bending, lap shear, Charpy impact tests. By this means, it is aimed to study comprehensively the effect of type of metals, surface treatments, and the stacking sequence on the mechanical properties of FMLs. To figure out the effect of design parameters on experimental results, a two-way Analysis of variance (ANOVA) was applied. It has been seen that a significant improvement in flexural, shear strength and impact resistance of FML composites could be obtained by optimum hybridization.
Effect of process parameters on interlaminar fracture toughness of fiber metal laminate (FML) composites
Fiber metal laminate (FML) composites were created primarily to improve the fatigue strength of modern civil aviation industry. And further studies show that, it provides additional advantages such as, excellent impact and damage tolerance, fire resistance and impact resistance with the aid of different configurations, while having a low weight. However, the production of a FML composite is a significant challenge, due to poor bonding at the fiber-metal interface. In this study, the interfacial bond behavior at the fiber-metal interface was investigated by determining their interlaminar fracture toughness values and determining the effect of process parameters on interlaminar fracture toughness of fiber metal laminate (FML) composites.