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Öğe Decomposition of process damping ratios and verification of process damping model for chatter vibration(ELSEVIER SCI LTD, 2012) Turkes, Erol; Orak, Sezan; Neseli, Suleyman; Yaldiz, SuleymanIn the previous study, by the same authors, titled "A new process damping model (PDM) for chatter vibration (Measurement, 44 (8) (2011) 1342-1348)", a new approach has been presented for obtaining process damping ratios (PDRs). This PDM has been constituted on the basis of the shear angle (phi) oscillations of the cutting tool and the alteration of the penetration forces when they penetrate into the wavy surface. Variation and quantity of PDR are predicted by reverse running analytical calculation procedure of traditional Stability Lobe Diagrams (SLDs). In this study, firstly, how the PDM in previous study results with different materials such as AISI-1050 and Al-7075 are examined. Then, two problems are solved: how much of the total PDR of cutting system is caused by the tool penetration and how much is caused by (phi) oscillation? Finally, verification of PDR values and PDM are performed by energy equations. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Design and applications of a pneumatic accelerator for high speed punching(ELSEVIER SCI LTD, 2007) Yaldiz, Suleyman; Saglam, Haci; Unsacar, Faruk; Isik, HakanHigh speed forming is an important production method that requires specially designed HERF (high energy rate forming) machines. Most of the HERF machines are devices that consist of a system in which energy is stored and a differential piston mechanism is used to release the energy at high rate. In order to eliminate the usage of specially designed HERF machines and to obtain the high speed forming benefits, the accelerator which can be adapted easily onto conventional presses has been designed and manufactured in this study. The designed energy accelerator can be incorporated into mechanical press to convert the low speed operation into high-speed operation of a hammer. Expectations from this work are reduced distortion rates, increased surface quality and precise dimensions in metal forming operations. From the performance test, the accelerator is able to achieve high speed and energy which require for high speed blanking of thick sheet metals. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Design, development and testing of a four-component milling dynamometer for the measurement of cutting force and torque(ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD, 2007) Yaldiz, Suleyman; Unsacar, Faruk; Saglam, Haci; Isik, HakanThe cutting forces generated in metal cutting have a direct influence on generation heat, tool wear or failure, quality of machined surface and accuracy of the work piece. In this study, a milling dynamometer that can measure static and dynamic cutting forces, and torque by using strain gauge and piezo-clectric accelerometer has been designed and constructed. The orientation of octagonal rings and strain gauge locations has been determined to maximise sensitivity and to minimise cross-sensitivity. The force and torque signals were captured and processed using proper data acquisition system. The dynamometer has been subjected to a series of tests to determine its static and dynamic characteristics. The results obtained showed that the dynamometer could be used reliably to measure static and dynamic cutting forces and torque. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Designing Mobile Applications for Teaching Manufacturing Technologies Course(BUCHAREST UNIVERSITY PRESS, 2015) Koklu, Nigmet; Andreescu, Nicoleta A.; Yaldiz, SuleymanRapid developments in technology supply the equipment that can be used in teaching learning environments and they can provide diversification about it. These new technologies facilitate learning by improving the quality of learning and this increasing students' performance. Benefiting from the technological tools in education has also triggered productivity in education and training during many educational activities. Rapidly advancing technology in recent years has demonstrated its impact on the mobile applications field as well. Mobile devices have entered into every area of daily life. Nowadays, the most common system used in mobile devices is the android operating system. Despite having hundreds of thousands applications in the Android operating system, the number of applications that will be used in education and teaching is not so much as expected. However, day by day, the number of applications that can be used in education is expected to increase. A mobile application in android operating system that is designed to be used in education has been developed. This application has been prepared in order to be used in manufacturing courses which is taught in machinery engineering department. In this practice course on manufacturing technology, course documents have been gathered under one roof in Android app. Thereby, it has been simplified for the manufacturing technology students to have access to information and documents related to the lesson.Öğe The effect of tool geometry and cutting speed on main cutting force and tool tip temperature(ELSEVIER SCI LTD, 2007) Saglam, Haci; Yaldiz, Suleyman; Unsacar, FarukIn this paper, the effects of rake angle and entering angle in tool geometry and cutting speed on cutting force components and the temperature generated on the tool tip in turning were investigated. The data used for the investigation derived from experiments conducted on a CNC lathe according to the full factorial design to observe the effect of each factor level on the process performance. As the experiments were designed using an orthogonal arrays, the estimates of the average effects will not be biased. During the tests, the depth of cut and feedrate were kept constant and each test was conducted with a sharp uncoated tool insert. For a comparison, the main cutting force and the temperature generated in secondary shear zone for different cutting parameters and tool geometries were calculated by Kienzle approach and with based on orthogonal cutting mechanism, respectively. The average deviation between measured and calculated force results were found as 0.26%. For statistical analyze the orthogonal arrays as L-16 was used with a total of 16 tests. Finally, it was found that rake angle was effective on all the cutting force components, while cutting speed was effective on the tool tip temperature. The cutting force signals and temperature values provided extensive data to analyse the orthogonal cutting process. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Linear analysis of chatter vibration and stability for orthogonal cutting in turning(ELSEVIER SCI LTD, 2011) Turkes, Erol; Orak, Sezan; Neseli, Suleyman; Yaldiz, SuleymanThe productivity of high speed milling operations is limited by the onset of self-excited vibrations known as chatter. Unless avoided, chatter vibrations may cause large dynamic loads damaging the machine spindle, cutting tool, or workpiece and leave behind a poor surface finish. The cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. Many researchers focused on the development of analytical and numerical methods for the prediction of chatter. However, the applicability of these methods in industrial conditions is limited, since they require accurate modelling of machining system dynamics and of cutting forces. In this study, chatter prediction was investigated for orthogonal cutting in turning operations. Therefore, the linear analysis of the single degree of freedom (SDOF) model was performed by applying oriented transfer function (OTF) and \tau decomposition form to Nyquist criteria. Machine chatter frequency predictions obtained from both forms were compared with modal analysis and cutting tests. (C) 2010 Elsevier Ltd. All rights reserved.Öğe A new process damping model for chatter vibration(ELSEVIER SCI LTD, 2011) Turkes, Erol; Orak, Sezan; Neseli, Suleyman; Yaldiz, SuleymanThis paper presents a new analytical process damping model (PDM) and calculation of Process Damping Ratios (PDR) for chatter vibration for low cutting speeds in turning operations. In this study a two degree of freedom complex dynamic model of turning with orthogonal cutting system is considered. The complex dynamic system consists of dynamic cutting system force model which is based on the shear angle (phi) oscillations and the penetration forces which are caused by the tool flank contact with the wavy surface. Depending on PDR, the dynamic equations of the cutting system are described by a new mathematical model. Variation and quantity of PDR are predicted by reverse running analytical calculation procedure of traditional Stability Lobe Diagrams (SLD). Developed mathematical model is performed theoretically for turning operations in this study and simulation results are verified experimentally by cutting tests. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Optimization of tool geometry parameters for turning operations based on the response surface methodology(ELSEVIER SCI LTD, 2011) Neseli, Suleyman; Yaldiz, Suleyman; Turkes, ErolThis investigation focuses on the influence of tool geometry on the surface finish obtained in turning of AISI 1040 steel. In order to find out the effect of tool geometry parameters on the surface roughness during turning, response surface methodology (RSM) was used and a prediction model was developed related to average surface roughness (Ra) using experimental data. The results indicated that the tool nose radius was the dominant factor on the surface roughness. In addition, a good agreement between the predicted and measured surface roughness was observed. Therefore, the developed model can be effectively used to predict the surface roughness on the machining of AISI 1040 steel with in 95% confidence intervals ranges of parameters studied. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Three-dimensional finite element modeling of effect on the cutting forces of rake angle and approach angle in milling(SAGE PUBLICATIONS LTD, 2017) Gok, Kadir; Sari, Huseyin; Gok, Arif; Neseli, Suleyman; Turkes, Erol; Yaldiz, SuleymanIn this study, milling operations were carried out using AISI 1040 specimens steel in dry cutting conditions. The cutting tools used in the experiment include P20 tool steel and they also have three different approach angles (45 degrees, 60 degrees, 75 degrees) and rake angles (0 degrees, -6 degrees, -12 degrees). In milling experiments, cutting parameters with a depth of cut of 1.5mm, cutting speed of 193m/min, and feed rate of 313mm/min were selected. A comparison was presented between the force values which were obtained by measured value and predicted with numerical simulations, and then a good agreement was found between measured and predicted force values. As result of, it was observed that the rake and approach angles were effective in milling operations.Öğe Virtual Training Centre For CNC: a Sample Virtual Training Environment(BUCHAREST UNIVERSITY PRESS, 2007) Sahin, Mehmet; Yaldiz, Suleyman; Unsacar, Faruk; Yaldiz, Y. Burak; Bilalis, Nikolaos; Maravelakis, Emmanuel; Antoniadis, AristomenisIt is a fact that virtual training has been a scope of interest for vocational training for a very long time. However, it needs more time to be more common in all specific training fields. This paper presents the development of a Virtual Training Centre (VTC) to promote and reinforce Vocational Training in Computer Numerical Control (CNC) Machines. "Virtual Training Centre for CNC" is a multilateral LdV project and of high importance in terms of virtual teaching and learning in vocational education and training. This virtual training environment is based on a common curriculum developed by the project partners. Since it is an interactive training tool, accessibility is the most important advantage over other training tools in VET.Öğe Virtual Training Centre for CNC: An Accomplished Cooperation Case(BUCHAREST UNIVERSITY PRESS, 2010) Yaldiz, SuleymanRecently cooperation among educational organizations has been a key for the internationalization of universities. Furthermore, one of the objectives of the innovative VET systems is regarded as transparency and distribution of information. This function concerns the potential and actual use of information. There may be different systems and structures of information distribution among the various actors, and in the public. Moreover, there are preconditions for creating transparency in the VET system. To improve quality there must be systems for distributing information and certain mechanisms to ensure the circulated information can be used by the various actors in the policy process. The more widespread the distribution, the better the potential use of the data will be and as a reversal effect, better quality data can be expected, as the actors are able to check the information against their experience and will provide feedback to the systems for gathering data. This article aims to promote a cooperation of developing a training tool with the cooperation of universities in Turkey, Greece and Romania under LdV projects. The training tool (http://www.vtcforcnc.com) is a virtual environment set up to teach CNC use based on a common curriculum developed by the partners in English, Turkish, Greek and Romanian.Öğe WEB-BASED LEARNING IN MECHANICAL DESIGN(BUCHAREST UNIVERSITY PRESS, 2007) Yaldiz, Suleyman; Neseli, SuleymanNowadays virtual learning is regarded as one of the most important approaches in VET as well as in other educational fields. This paper is based on an experimental period in which a virtual training envionment (www.autocadokulu.com/portal/index.php) was used to train the students virtually in machine designing. After the training period, the successes rate of the previews year and this experimental period were compared. In addition, the students were interviewed regarding the advantages of virtual learning. The results obtained from both the tests and the interview show that students are much more interested in virtual learning and they mostly find it useful. However, it seems that both the trainees and the trainers should be encouraged and technically supported to make full use of virtual learning environment.
