Hakan Ates

Comparison of the constructed control methods for a friction-welding machine

ABSTRACT In the present study, comparison of the three control methods for a friction-welding machine has been carried out. For this purpose, conventional automatic control, programmable logic controller, and peripheral interface controller systems were set up for a friction welding machine in experiments. It has been observed that these systems worked successfully and the peripheral interface controller system was the best performer. The peripheral interface controller is a low-cost, programmable, and high-performance control method.

Effect of Porosity Content on the Weldability of Powder Metal Parts Produced by Friction Stir Welding

Friction stir welding technique (FSW) has many advantages in terms of tool design, rotational speed and traveling speed, and can be adjusted in a precise manner. It enables heat input into the system to be controlled. In this study, Aluminum powders were compacted at 350,400 and 450 MPa pressure and sintered at 450 oC temperature for 30 minutes in Ar atmosphere. Sintered powder metal parts were joined to each other by FSW at the speed of 1800 rpm and traveling welding speed 200 mm/min under a constant friction force. The results show that the amount of porosity affects the weldability of powder metallurgy (P/M) parts. Furthermore, the porosity and microstructural evolution of the Aluminum also affected the hardness values of the tested materials.

A novel control unit for a friction welding machine based on computer

Typical friction welds are made by holding a non-rotating sample in contact with a rotating sample under constant or gradually increasing pressure until the interface reaches the welding temperature and then stopping pressure rotating to complete the weld. This process requires additional time and is labor intensive. Recently, several control systems have been introduced to the industry for improving the welding process such as conventional automatic control, microcontroller control, and Programmable Logic Controller (PLC). However, these processes have limitations either on materials selection or on visualization. In this study, continuous monitoring, control and recording are implemented. Computer-controlled platform for the simulation and control of mechanisms is based on a Microsoft Visual Basic environment. Welding parameters such as friction time, forge time and breaking time are entered with a keyboard and can be saved and used again. To show the feasibility and versatility of the study, the evaluation is used for sample joining. It has been observed that this system works successfully and gives good performance.

Effects of Temperature on the Weldability of Powder Metal Parts Joined by Diffusion Welding

Diffusion welding is an advanced bonding process in which similar or dissimilar materials can be bonded in solid state. In this study, aluminium composite (5% and 15% WC) powders were compacted at 450 MPa pressure and sintered at 550 oC for 45 minutes in argon atmosphere.and joined each other by diffusion bonding. The bonding temperatures (585 oC, 600 oC, 615 oC) and dwell time (185 min) were chosen for the welding process at constant 20 MPa. It has been observed that these variations on the welding parameter strongly affected the microstructure and the weldability of the materials.

Investigation of Weldability of P/M Bronze Materials by Tig Welding Technique

In this study, weldability of bronze parts produced by powder metallurgy has been investigated by using TIG welding technique. Bronze powders were pressed into 55x44x5 mm size specimens under pressure of 350 MPa. Then these specimens were sintered at 650, 750 and 870 °C for 45 minute under argon atmosphere. Finally, the parts were welded by TIG welding method. Hardness values of the welded joints were measured and microstructural features were investigated.

Optical, Electrical, and Crystal Properties of TiO 2 Thin Films Grown by Atomic Layer Deposition on Silicon and Glass Substrates

TiO2 thin films have been deposited on glass and Si(100) by atomic layer deposition (ALD) technique using tetrakis(diethylamido)titanium(IV) and water vapor as reactants. Thorough investigation of the properties of the TiO2/glass and TiO2/Si thin films was carried out, varying the deposition temperature in the range from 100°C to 250°C while keeping the number of reaction cycles fixed at 1000. Physical and material property analyses were performed to investigate optical and electrical properties, composition, structure, and morphology. TiO2 films grown by ALD may represent promising materials for future applications in optoelectronic devices.

Electronic and Optical Properties of Atomic Layer-Deposited ZnO and TiO 2

Metal oxides are attractive for thin film optoelectronic applications. Due to their wide energy bandgaps, ZnO and TiO2 are being investigated by many researchers. Here, we have studied the electrical and optical properties of ZnO and TiO2 as a function of deposition and post-annealing conditions. Atomic layer deposition (ALD) is a novel thin film deposition technique where the growth conditions can be controlled down to atomic precision. ALD-grown ZnO films are shown to exhibit tunable optical absorption properties in the visible and infrared region. Furthermore, the growth temperature and post-annealing conditions of ZnO and TiO2 affect the electrical properties which are investigated using ALD-grown metal oxide as the electron transport channel on thin film field-effect devices.

Characterization of Electrospun Nanofibrous Scaffolds for Nanobiomedical Applications

The electrospinning method is employed in the production of porous fiber scaffolds, and the usage of electrospun scaffolds especially as drug carrier and bone reconstructive material such as implants is promising for future applications in tissue engineering. The number of publications has grown very rapidly in this field through the fabrication of complex scaffolds, novel approaches in nanotechnology, and improvements of imaging methods. Hence, characterization of these materials has also grown significantly important for getting satisfied and accurate results. This advantageous and versatile method is ideal for mimicking bone extracellular matrix, and many biodegradable and biocompatible polymers are preferred in the field of bone reconstruction. In this study, gelatin, gelatin/nanohydroxyapatite (nHAp) and gelatin/PLLA/nHAp scaffolds were fabricated by the electrospinning process. These composite fibers showed clear and continuous morphology according to observation through a scanning electron microscope and their component analyses were also determined by Fourier transform infrared spectrometer analyses. These characterization experiments revealed the great effects of the electrospinning method for biomedical applications and have an especially important role in bone reconstruction and production of implant coating material.