Department of Modeling and Design Engineering Systems
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Browsing Department of Modeling and Design Engineering Systems by Subject "manufacturing engineering"
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Item DESIGN AND IMPLEMENTATION OF A PARALLEL BOUNDARY ELEMENT METHOD SOLUTION FOR 3D PARTICLE FLOW PROBLEMS IN MICROCHANNELS(2015-01-30) KARAKAYA, Ziya; BARANOĞLU, Besim; YAZICI, AliA new formulation for tracking multiple particles in slow viscous flow for microflu idic applications is presented. The method employs the manipulation of the boundary element matrices so that a system of equations is obtained relating to the rigid body velocities of the particle to the forces applied on the particle. The formulation is spe cially designed for particle trajectory tracking and involves successive matrix multi plications for which Symmetric Multiprocessing (SMP) parallelisation is applied. It is observed that the present formulation offers an efficient numerical model to be used for particle tracking and can easily be extended for multiphysics simulations in which several physics are involved.Item EXPERIMENTAL AND NUMERICAL INVESTIGATION OF STRETCH FORMING PROCESS FOR AEROSPACE APPLICATIONS(2015-10-25) HATİPOĞLU, Hasan Ali; KARADOĞAN, CelalettinStretch forming process is commonly used in the aerospace industry for forming large sheet panels. In this process, a flat sheet is stretched over a form-block that acts by hydraulic power. During this action, the sheet is gripped from the sides by jaws which are also hydraulically moved. Process parameters like die-jaw movements and lubrication conditions have to be determined properly in order to produce good quality parts. In the present situation, those parameters are determined by production experience and traditional methods which slow down the process and increase the scrap risk. This study aims to optimize the stretch forming process by establishing a finite element model which provides numerical tryouts instead of physical ones. The success of the numerical analysis is highly dependent upon proper modeling of material behavior and friction. In order to capture the correct material behavior, tensile tests, bulge tests and forming limit diagram tests of commonly used sheet alloys were conducted. The results were then used for defining the hardening curves, yield loci, anisotropic constants and forming limit curves. In another study, the friction coefficients for various conditions between the tool and the sheet surfaces were determined by doing distinctive tests. Experiments were conducted by forming marked aluminum alloy sheets on a semi-circular form-die and measuring the deformation optically. They were used for the validation of the established numerical model. Finally, a method was proposed to determine the tool movements and applied successfully on a real aircraft part.Item INVESTIGATION OF FRICTION IN SHEET METAL FORMING(2022-02-28) Kalkan, Hakan; KAFTANOĞLU, BilginInvestigation of friction is carried out in the radial drawing region between the die and blank holder and also in the stretching zone over the punch in deep drawing. Two methods are developed to calculate the coefficient of friction in each zone using the experimentally determined data such as punch force diagrams and strain distributions obtained by an optical scanning system. The current methods differ from the existing techniques which are obtained in simulative tests. The proposed methods can be applied at room temperature and at elevated temperatures. In deep drawing tests, EN 10268 steel is used with dry and graphite lubrication and hot deep drawing tests are performed at . Deep drawing tests are performed at different lubrication and temperature conditions. Blank holder load is another parameter which changes the punch loads. 9 different stretch forming tests are performed to determine the coefficient of friction in this zone. Three different materials are used with dry and paraffin lubricated conditions. Comparisons of friction coefficients are made with those obtained by other techniques.Item SUSTAINABLE MACHINING Of DIFFICULT-TO-CUT MATERIALS USING MQL TECHNIQUE(2022-02-15) Osman, Khaled Ali; Kılıç, Sadık Engin; Ünver, Hakkı ÖzgürGlobal industrial trends are leaning towards making machining processes eco-friendly and acceptable for sustainable manufacturing. In this regard, reduction strategies for cutting fluid (CF) consumption have been widely discussed in the literature as a highly challenging issue. Numerous effective strategies have been proposed as an alternative to the use of cutting fluids. Minimum quantity lubrication (MQL) is one of them which promises to be both economical and environmentally friendly. Despite the high expectations from MQL applications in machining processes, there is still a number of limitations to MQL application especially in machining difficult-to-cut materials such as titanium alloys (Ti-6Al-4V). Insufficiency of MQL under such extreme conditions has led to other works focusing on exploring different methods to improve the properties of MQL applications of the cutting fluids. In this respect, much effort has been devoted in recent years to achieving an improvement in MQL by adopting nanotechnology. This study proposes a novel approach to an eco-friendly lubrication/cooling strategy by integrating MQL with hexagonal boron nitride (hBN) for use in slot milling of Ti-6Al-4V. The novelty here lies in increasing the lubrication/cooling effect and enhancing the thermal conductivity of the MQL technique by means of nanofluids to improve Ti-6Al-4V machinability. For this purpose, the research specifically focuses on the effects of dispersed hBN into a fatty oil (cutting fluid). Therefore, to build a comprehensive understanding of the effect of using MQL with hBN on responses during the slot milling of Ti-6Al-4V, all results were compared with dry, flood and MQL conditions. Based upon the response surface method (RSM), the central composite design (CCD) has been utilized to create the design of experiments using 5 levels and 5 factors for cutting force (Fc) and surface roughness (Ra) measurements according to combinations of control parameters, i.e., cutting speed (v), feed per tooth (ft), axial depth (ap), flow rate of cutting fluid (Q) and concentrations of hBN (NPs). The study was then focused on a Multi-Objective Particle Swarm Optimization (MOPSO) utilizing RSM models in terms of Ra and the specific cutting energy (SEC). The results reveal that all responses are sensitive to changes in the feed per tooth, axial depth of cut and cutting fluid flow rate. However, these responses are not sensitive to changes in the cutting speed. In addition, utilizing MQL with hBN nanoparticles can reduce Fc and Ra. In conclusion, MQL with hBN nanoparticles is found to be an effective alternative technique for conventional flood lubrication when machining Ti-6Al-4V.Item THE DEVELOPMENT OF A METHOD TO IMPROVE THE LIMIT DRAWING RATIO OF BLANKS USING PREFERENTIAL HEATING(2015-01-30) KAYHAN, Erdem; KAFTANOĞLU, Bilgin; KONCA, ErkanThe method developed in the current thesis can shortly be described as the application of nonisothermal local heating in the flange region of the blank to improve the formability of sheet metals in deep drawing. The use of elevated temperature gives the possibility of significantly increasing the ductility of the material and the associated forming capability. It also drastically reduces the yield point and hence the forming forces and required pressures. One of the advanced high strength sheet steels (AHSS), DP600, widely used in the automotive industry due to enabling the reduction in car weigth and increasing the crash safety is chosen as a work material in this reasearch. Using AHSS steels also reduce the material thickness and lower fuel consumption. The three different types of steels, two HSLA and one IF steels, are additionally examined to observe the validity of the developed method. As a result of the experiments conducted within the temperature limits 180oC to 275oC in flange region, the Limiting Drawing Ratio in deep drawing (LDR) is increased up to 25.58 %. Since the temperature range stays in the warm region, material properties are not influenced; but the strength remains the same while the required forming forces are reduced.