Examinando por Autor "Abdullah, Mahmoud E."

Mostrando 1 - 4 de 4
  • Miniatura
    Ítem
    AA5754–Al2O3 nanocomposite prepared by friction stir processing: microstructural evolution and mechanical performance
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024-04) Mohammed, Moustafa M.; Abdullah, Mahmoud E.; Rohim, M. Nafea M.; Kubit, Andrzej; Derazkola, Hamed Aghajani
    The utilization of Al2O3 nanopowder to reinforce AA5754 aluminum alloy through blind holes employing the friction stir processing (FSP) technique to produce an aluminum matrix nanocomposite is explored in this paper. Motivated by the necessity to enhance the strength and ductility of welded joints, the impacts of varying the tool rotational speed (rpm) and blind hole diameter on the microstructure and mechanical properties of the joints are investigated. Experimental characterization techniques including SEM, optical microscopy, microhardness, and tensile tests were employed to analyze the welded joints produced under different processing parameters (tool rotational speeds of 910, 1280, and 1700 rpm, and blind hole diameters of 0, 1, 1.5, and 2 mm). Comparative analyses were conducted against base metal properties and joints without reinforcement powder. It was found that the addition of nanopowder resulted in a decrease in the maximum generated heat during FSP, while also reducing the stir zone size compared to samples without nanopowder. Moreover, enhancements in both the strength and ductility of the joints were observed with the incorporation of Al2O3 nanoparticles. The optimal combination of welding conditions, observed at 1280 rpm rotational speed and 1.5 mm hole diameter, yielded a remarkable ultimate tensile strength of 567 MPa, accompanied by a hardness of 45 HV. These results underscore the potential of nano-Al2O3 reinforcement in significantly improving the mechanical properties of the produced nanocomposite, with implications for advancing the performance of welded structures in various engineering applications
  • Miniatura
    Ítem
    Effects of partial-contact tool tilt angle on friction stir welded AA1050 aluminum joint properties.
    (MDPI, 2023-05-31) Abdullah, Mahmoud E.; Rohim, M. Nafea M. ; Mohammed, Moustafa M. ; Derazkola, Hamed Aghajani
    This study aims to investigate the impact of partial-contact tool tilt angle (TTA) on the mechanical and microstructure properties of the AA1050 alloy friction stir weld (FSW). Three levels of partial-contact TTA were tested, 0°, 1.5°, and 3°, compared to previous studies on total-contact TTA. The weldments were evaluated using surface roughness, tensile tests, microhardness, microstructure, and fracture analysis. The results show that in partial-contact conditions, increasing TTA decreases the generated heat in the joint line and increases the possibility of FSW tool wear. This trend was the opposite of joints that were friction stir welded via total-contact TTA. The microstructure of the FSW sample was finer at higher partial-contact TTA, while the possibility of defect formation at the root of the stir zone in higher TTA was more than in lower TTA. The robust sample prepared at 0° TTA had 45% of AA1050 alloy strength. The maximum recorded heat in 0° TTA was 336 °C and the ultimate tensile strength of this sample was 33 MPa. The elongation of the 0° TTA welded sample was 75% base metal, and the average hardness of the stir zone was 25 Hv. The fracture surface analysis of the 0° TTA welded sample consisted of a small dimple, indicating the brittle fracture mode.
  • Miniatura
    Ítem
    Effects of underwater friction stir welding heat generation on residual stress of AA6068-T6 aluminum alloy
    (MDPI, 2022-03-17) Khalaf, Hassanein I. ; Al-Sabur, Raheem ; Abdullah, Mahmoud E. ; Kubit, Andrzej ; Derazkola, Hamed Aghajani
    This article aims to study water-cooling effects on residual stress friction stir welding (FSW) of AA6068-T6 aluminum alloy. For this reason, the FSW and submerged FSW processes are simulated by computational fluid dynamic (CFD) method to study heat generation. The increment hole drilling technique was used to measure the residual stress of welded samples. The simulation results show that materials softening during the FSW process are more than submerged. This phenomenon caused the residual stress of the joint line in the submerged case to be lower than in the regular FSW joint. On the other hand, the results revealed that the maximum residual stresses in both cases are below the yielding strength of the AA6068-T6 aluminum alloy. The results indicated that the residual stress along the longitudinal direction of the joint line is much larger than the transverse direction in both samples.
  • Miniatura
    Ítem
    Investigation on polypropylene friction stir joint: effects of tool tilt angle on heat flux, material flow and defect formation
    (Elsevier Editora Ltda, 2023-03) Fan, Guangle; Tomków, Jacek ; Abdullah, Mahmoud E. ; Derazkola, Hamed Aghajani
    Tool tilt angle (TTA) is a critical factor that can control material flow in polymeric materials' friction stir joining (FSJ). This study selected a TTA range between 0° to 4° for FSJ of polypropylene (PP) polymer sheet. A modified computational fluid dynamic (CFD) technique was implemented to gain a deep understanding of the effects of TTA during FSJ of PP. The PP joint's internal flow, defect formation, heat generation, and tensile strength were investigated experimentally. The fracture surface of tensile samples was analyzed by scanning electron microscopy (SEM). Heat generation, heat flux, and defect formation results from simulation were evaluated by experimental tests output. The results indicate that the PP flow during FSJ is susceptible to TTA. Non-uniform volumetric weight transfer was caused at higher TTA in the joint line, which leads to tilted heat flux. At higher TTA, the generated heat increases, leading to PP exit from the joint line and internal gaps. According to selected parameters, the most robust joint (66 MPa) was produced at 1° TTA. The main reason for the mechanical properties of the PP joint was a dimension of the stir zone and internal defects. Shrinkage gaps were the root of crack initiation during the tensile test, and some local stretching in the fracture surface of the tensile sample after the test was detected.