Yazar "Olabi, Muhammed Nadir" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Öğe
    Determination of “tribological performance working fields” for pure PEEK and PEEK composites under dry sliding conditions
    (Elsevier Ltd, 2024) Maslavi, Ahmet; Ünal, Hüseyin; Olabi, Muhammed Nadir
    Poly-ether-ether-ketone (PEEK) and PEEK composites are widely used polymers in many engineering applications where dry sliding is required. In this study, the influence of sliding velocity and applied load values on the friction and wear behavior of pure PEEK, 30 wt% glass fiber reinforced PEEK (PEEK-30GF), 30 wt% carbon fiber reinforced PEEK (PEEK-30CF) and 10 wt% carbon fiber+10 wt%graphite +10 wt%poly-tetra-fluoro-ethylene (PTFE) filled PEEK (ie. High (H) pressure (P) and velocity (V) resistant PEEK (PEEK-HPV)) composites rubbing against AISI 304 stainless steel disc was investigated. The experiments were carried out at room temperature under dry sliding conditions in a pin-on-disc wear rig. The applied loads ranged from 30 to 250 N, while the sliding velocities ranged from 1.0 to 4.0 m/s. At these load and velocity ranges, the friction coefficient-wear rate relationship of pure PEEK and composites was established and evaluated. In addition, the operating load-velocity limits of each material were determined and stated. The lowest coefficient of friction and wear rate were obtained in PEEK-HPV, PEEK-30CF, PEEK-30GF composites and pure PEEK polymer, respectively. In addition, it was observed that the coefficient of friction (CoF) decreased and the specific wear rate (SWR) increased with the increase in sliding velocity and applied load in all PEEK materials. The wear rate values of PEEK-HPV and PEEK-30%CF composites are in the range of 10?7 - 10?6 (mm3/Nm), while the wear rate values of pure PEEK and PEEK-30%GF are in the range of 10?6 - 10?5 (mm3/Nm). It was determined that carbon fiber, graphite and PTFE additives added to PEEK polymer as hybrid were very effective in reducing the wear rate of PEEK composite (PEEK-HPV). An adhesive wear mechanism was observed in PEEK-HPV and PEEK-30CF composites both at low load and velocity values and at high load and velocity values. © 2024 Elsevier B.V.
  • Küçük Resim Yok
    Öğe
    Energy characterization through OpenSees nonlinear simulation of shear walls without confined boundary zones
    (Springer Science and Business Media Deutschland GmbH, 2023) Olabi, Muhammed Nadir; Çağlar, Naci; AlShawa, Omar; Mollaioli, Fabrizio
    Understanding the behavior of nonconforming RC shear walls is crucial in the energy-based seismic assessment and response prediction of existing buildings constructed without following modern seismic standards. Macroscopic numerical modeling approach is very effective and practical in simulating the behavior of reinforced concrete elements in general and shear walls in particular. Using the available materials and elements in the OpenSees domain it is feasible to construct numerical models that can predicate the hysteretic response and energy dissipation of shear walls without confined boundary zones found in old and existing buildings. A simple and practical macro model based on the fiber beam-column element is developed to reproduce the behavior of shear walls without confined boundary zones. The developed OpenSees model performance is benchmarked against experimentally tested shear walls from the literature. Furthermore, utilizing two of the most important energy-based dissipation parameters the dissipated energy characteristics are investigated and compared between the numerical model and the experimental test. As a result, the developed OpenSees based numerical model can simulate the behavior of old and existing shear walls without seismic detailing, and can be used in the evaluation procedures in terms of effective stiffness, maximum lateral capacity, ductility, and dissipated energy characteristics. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.