Browsing by Author "Akkas, M."

Now showing 1 - 4 of 4

Effect of Ni:Si Ratio on Microstructure and Properties of Powder Metallurgical Corson Alloy
(2023.01.01) Akkas, M.; Atapek, S.H.; Polat, S.
In this study, powder metallurgical Cu-Ni-Si alloys with different Ni:Si ratios are produced by cold pressing sintering (600 MPa, at 950 degrees C for 60 min) and bulk materials are solution annealed at 950 degrees C for 60 min, quenched in water and aged at 450 degrees C for 60 min. A fine distribution of Ni-Si compounds embedded in a netted-free structure is formed in the matrix. Although a conductivity level of at least 22% IACS is achieved in all powder metallurgical alloys, the impurity effect is dominant and a decrease in the conductivity is detected by increasing Ni:Si ratio. However, a slight increase in electrical conductivity is achieved by the precipitation of nickel silicides in the a-Cu matrix under aging conditions. Increasing Ni:Si ratio directly increases the hardness of the powder metallurgical matrix, and a hardness value of 73 HV0.1 is obtained for the aged alloy having the highest Ni:Si (5:1) ratio.
Nonlinear vibration analysis of fluid-conveying cantilever graphene platelet reinforced pipe
(2024.01.01) Ali, B.M.; Akkas, M.; Hançerliogullari, A.; Bohlooli, N.
This paper is motivated by the lack of studies relating to vibration and nonlinear resonance of fluid -conveying cantilever porous GPLR pipes with fractional viscoelastic model resting on nonlinear foundations. A dynamical model of cantilever porous Graphene Platelet Reinforced (GPLR) pipes conveying fluid and resting on nonlinear foundation is proposed, and the vibration, natural frequencies and primary resonant of such system are explored. The pipe body is considered to be composed of GPLR viscoelastic polymeric pipe with porosity in which Halpin -Tsai scheme in conjunction with fractional viscoelastic model is used to govern the construction relation of the nanocomposite pipe. Three different porosity distributions through the pipe thickness are introduced. The harmonic concentrated force is also applied on pipe and excitation frequency is close to the first natural frequency. The governing equation for transverse motion of the pipe is derived by the Hamilton principle and then discretized by the Galerkin procedure. In order to obtain the frequency -response equation, the differential equation is solved with the assumption of small displacement, damping coefficient, and excitation amplitude by the multiple scale method. A parametric sensitivity analysis is carried out to reveal the influence of different parameters, such as nanocomposite pipe properties, fluid velocity and nonlinear viscoelastic foundation coefficients, on the primary resonance and linear natural frequency. Results indicate that the GPLs weight fraction porosity coefficient, fractional derivative order and the retardation time have substantial influences on the dynamic response of the system.
The Effect of Molten Salt on the Mechanical Properties and Microstructure of CuNiSi Alloys with Reinforced Fe
(2024.01.01) Akkas, M.
In this study, CuNiSi alloys were produced using powder metallurgy in molten salt (KBr). In the Cu, Ni, and Si powder mixture, Fe was added at a rate of 2.5%, 5 and 7.5% and mechanical alloying was carried out for 4 hours at 400 rpm. Prepared powder mixtures were cold pressed under 600 MPa pressure and sintered for 3 hours at 900 degree celsius in an argon atmosphere. Phase formation, microstructure, microhardness, electrical conductivity, and corrosion of the produced samples were analyzed in detail. Scanning electron microscope (SEM) was used to detect the changes in the microstructure of the produced samples, and an X-ray diffractogram (XRD) was used to determine the phases formed in the internal structure of the materials. In order to determine the mechanical properties of the produced samples, hardness analyzes were made with a microhardness measuring device. The electrical conductivity properties of the produced CuNiSi and CuNiSiFe alloys were determined due to the increase in the Fe ratio. Corrosion tests of the produced samples were determined by potentiodynamic polarization curves in a 3.5% NaCl solution. Fe -reinforced CuNiSi composite materials have been successfully produced in molten salt (KBr). CuNiSi alloy, the microstructure is dominated by the typical large and small particles. Fe element is homogeneously dispersed in the CuNiSi alloy instead of being separated using the Ni element. Fe particles have decreased the hardness of produced alloys. The electrical conductivity properties changed with increasing voltages depending on the increase of Fe supplementation, and as a result, the sample containing 7.5% Fe had the best electrical conductivity values. Results showed that by increasing the amount of Fe, the mechanical properties and corrosion resistance increased.
The Green Cooling Factor: Eco-Innovative Heating, Ventilation, and Air Conditioning Solutions in Building Design
(2024.01.01) Ali, B.M.; Akkas, M.
This research investigates the compatibility of conventional air conditioning with the principles of green building, highlighting the need for systems that enhance indoor comfort while aligning with environmental sustainability. Though proficient in regulating indoor temperatures, conventional cooling systems encounter several issues when incorporated into green buildings. These include energy waste, high running costs, and misalignment with eco-friendly practices, which may also lead to detrimental environmental effects and potentially reduce occupant comfort, particularly in retrofit situations. Given the emphasis on sustainability and energy conservation in green buildings, there is a pressing demand for heating, ventilation, and air conditioning (HVAC) solutions that support these goals. This study emphasises the critical need to reconsider traditional HVAC strategies in the face of green building advances. It advocates for the adoption of innovative HVAC technologies designed for eco-efficiency and enhanced comfort. These technologies should integrate seamlessly with sustainable construction, use greener refrigerants, and uphold environmental integrity, driving progress towards a sustainable and occupant-friendly built environment.