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    A process control method for the electric current-activated/assisted sintering system based on the container-consumed power and temperature estimation
    (Springer, 2018) Yener, Şuayb Çağrı; Yener, Tuba; Mutlu, Reşat
    In this paper, the current, voltage and temperature of the container of an electric current-activated/assisted sintering (ECAS) system are measured and recorded with respect to time during the sintering process. By post-processing of the recorded data, the power and thermal energy of the system container are calculated. Interpretation of the measured and post-processed data has provided a criterion: It has been found that the dissipated electrical power in quasi-steady state is almost equal to the power conducted from the container to the copper bars throughout the stiffs and the convection and radiation powers are negligible compared to the conducted power. Therefore, the container-stored thermal energy or the container surface temperature can be estimated from the dissipated electrical power with the values of the container heat capacitance and the stiff thermal resistances without the need for a temperature measurement equipment. If the thermal energy or the temperature required to make the samples has a known/required minimum value and if this amount of the thermal energy is provided to the sample, the sample production process can be stopped. In this study, for an actual implemented design, we suggest that ECAS current and voltages should be continuously measured in real time and the process is automatically terminated when the calculated steady-state container temperature becomes equal to the required container temperature. Therefore, a standard procedure for material production in ECAS system is provided to automate sample production and the performance of the produced samples is guaranteed.
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    Capacitive voltage effect at a resistive sintering system container and its electrical model
    (Walter De Gruyter Gmbh, 2024) Yener, Suayb Cagri; Mutlu, Resat; Yener, Tuba; Akbulut, Hatem
    The electric current activated/assisted sintering (ECAS) method enables various kinds of materials to be produced much faster and environmentally friendly compared to conventional sample production systems. The main handicap of this system is that the heating regime varies according to the material type even the chemical composition of the same type of material and causes partial melting due to the sudden current flow. Previously, the ECAS output equivalent circuit is modeled as a temperature-dependent resistor in the literature. This study shows that it is insufficient to model the ECAS output consisting of a container and two stiffs as a resistor considering experimental waveforms. We report the discovery of a capacitive effect at the output of the ECAS system that has not been reported before. We have given an equivalent electrical circuit for the ECAS system output and examined the effect's temperature dependence. The circuit model, which consists of a parallel resistor-capacitor (Rp-C) circuit in series with another resistor (Rs), is suggested for the container and the stiffs. By using the experimental data, the equivalent circuit parameters are calculated by curve-fitting. The temperature dependence of the equivalent circuit parameters is also examined. Possible explanations for the capacitive effect are given. Such a model and further examining the effect may help design better ECAS systems.
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    Computer Aided Design of PID Control of Pulse DC Sintering System
    (Institute of Electrical and Electronics Engineers Inc., 2019) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, Reşat
    Pulse DC sintering (PDCS) systems, an effective way of producing sintered materials, are complex systems. They need to be modelled both electrically and thermally. Such a system can be controlled manually or automatically. To the best of our knowledge, a closed loop control of the PDCS system is not available in the literature yet. In this study, simplified model of a PDCS system is performed and a PID controller is designed to control the container temperature using Simulink toolbox of Matlab. The PDCS model and the PID controller design method based on the computer aided design proposed in this study can be used by the PDCS designers as an essential part of the system level design issues. © 2019 IEEE.
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    Cyber security in material manufacturing
    (TUBITAK, 2020) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, Reşat
    Industry 4.0, a new industry revolution, is happening now and several developed countries are leading the path. Internet of things (IoT) is also encompassed by Industry 4.0. In the future, more devices in factories are to be connected to Ethernet or Internet. However, this makes the companies, devices and researchers vulnerable to cyber-attacks. Recently, some cyber-attacks which have happened to some companies or countries verify the danger. Sintering systems and furnaces are used for research by universities and for series manufacturing by factories. Arc furnaces and induction furnaces are also commonly used devices in metal factories. A sintering system, an arc furnace or an induction furnace which is connected to Internet or Ethernet may also be under cyber-attack threat. The danger may be prevented by taking necessary precautions. In this study, these threeproduction systems are first briefly introduced and then inspected assuming that they have been connected to internet and examined with considering cyber-attack point of view. Some basic solutions against cyber-attacks to the aforementioned devices are suggested. © 2020, TUBITAK. All rights reserved.
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    Finite Difference Analysis of a Resistive Sintering System Container
    (Amer Scientific Publishers, 2019) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, Reşat
    Resistive sintering is a new method which enables the production of different material types by using mechanical load and electric current. For the required process performance, it is necessary to set the parameters such as current, voltage, dissipated power, electric energy, and production time correctly. The container is an important component of the resistive sintering system. Container electrical resistance is a value that is difficult to calculate in terms of the geometry of the build and to measure due to the smallness of the value. In this study, assuming that the container temperature is constant, the Laplace equation of the electric potential is solved in the cylindrical coordinates considering the axial symmetry by the finite difference method and then the electrical current and resistance of the sintering container was calculated by post-processing of the solved electric potential using Ohm's law in vector form. The volumetric power density is used to calculate the dissipated power in the container and the container current is calculated on the stiff area. It is seen that the current density is almost doubled at the stiff-container edges and the power density at these points reaches its maximum. At points distant from the stiffs, the electrical potential is almost constant and the potential difference is negligible. The main source of heating is shown to be the resistance of the stiffs. The resistance of the structure is found to be about 70 mu Omega. This method given here can be used in more sophisticated models to size an ECAS system.
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    Memristor-based timing circuit
    (Institute of Electrical and Electronics Engineers Inc., 2017) Yener, Şuayb Çağrı; Mutlu, Reşat; Yener, Tuba; Kuntman, Hulusi Hakan
    Memristor has been proposed as the fourth missing fundamental circuit element in 1971. This new circuit element has a charge controlled resistance, saturation mechanism and zero-crossing hysteresis loop which cannot be mimicked by previously known circuit elements. It is a promising candidate for both digital and analog electric circuit applications. In this work, a memristor based timer circuit is proposed. Concept of the circuit is presented and its analysis is done. Simulation of the timer is done using the linear drift model of the TiO2 memristor and the result is compared to the analytical calculations. © 2017 IEEE.
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    Power system harmonic analysis of a pulse DC sintering system
    (Iop Publishing Ltd, 2020) Yener, Şuayb Çağrı; Yener, Tuba; Mutlu, Reşat
    Pulse DC Sintering System (PDCS) produces metallic and nonmetallic samples in a cheap and efficient way in a short time. Some PDCS systems possess thyristor-based rectifiers to control their output power. This results in PDCS systems creating power system harmonics. The harmonic content of an PDCS system varies during sample manufacturing process since the PDCS container resistance is temperature dependent. In this study, power system harmonics of a PDCS system is examined for the first time in literature. A power analyzer device is used to measure and record the supply side current, voltage and power of the PDCS system as a function of time. Besides, an infrared temperature meter module is a used to measure PDCS container temperature and record it with respect to time during sample production. Total harmonic distortion is found to be decreasing with container temperature increasing.
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    Thermal Circuit Model of the Pulse DC Sintering System Container During Cooling
    (2019) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, Reşat
    Pulse DC Sintering System (PDCS) is a cheap and quick way of producing different types of materials. After sintering of the sample, the cooling of the PDCS container is needed before taking it out. The sample production time is the sum of the sintering and the cooling time. Therefore, estimation of the sample cooling time must be made accurately to model sample production. Its container dimensions and the material, it is made of, determines its temperature during cooling. In this paper, a thermal circuit which models a pulse DC sintering system container during cooling is given. Its thermal circuit model is made assuming that some heat leaks from the steel container to the cooper bars, the copper bars and the container all have natural convection and also radiate heat to cool down. The thermal model is described with a set of nonlinear state-space equations. The state-space equations are solved numerically using Runge-Kutta 4 method. The time required to make the sample cool down to ambient temperature is calculated using simulations. The temperatures of the container and the copper bars of an PDCS system are measured to find the experimental cooling time. The results are compared. The PDCS thermal model is able to verify the experimental results. It has also been experimentally shown that the cooling time is not dependent on the sample type produced for the examined PDCS system. Such a model can be easily implemented in an engineering software which aims to model the sample production process of the PDCS system and can also be used for its optimization considering its physical parameters such as dimensions, electrical and mechanical constants etc.