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    Analytical and Experimental Investigation of Product Geometry and Dimensional Accuracy in the Punching Process of AA 1050 and AA 1070 Sheets
    (Gazi Univ, 2024) Yetgin, Abdullah; Demir, Bilge; Gurun, Hakan; Ali, Khalil Belras
    Punching is a widely used and economical manufacturing method. The forces that occurred during punching and the dimensional accuracies of the parts obtained from punching are significant in manufacturing processes. This study aimed to examine the cutting forces that occur in the punching process and the dimensional accuracy of the parts. AA 1050 and AA 1070 sheet materials were used in the experimental studies. Five punches with various cutting-edge geometries were employed in the punching processes. Punching operations were carried out at a constant clearance value and press speed. The geometries of the specimens obtained from the experimental studies were examined using stereo and shuttle-pix microscopes. In addition, the finite element method was used to study punching processes. The consistency of the finite element model was analyzed by comparing experimental and numerical studies. When the flat punch geometry was used, the cutting force was at its greatest. Using the largest angled punch geometry resulted in the lowest cutting force. It has been determined that the dimensional accuracy of the blank and the falling part is better when using the flat punch geometry compared to the other punches used. In addition, it was observed that experimental and theoretical studies are compatible with each other. It is thought that finite element software can provide time and cost savings in determining the cutting force of materials.
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    INFLUENCE OF PUNCH SHAPES ON FORCES AND PART QUALITY IN THE PUNCHING OF EXPLOSIVELY WELDED DP600, A11100, AND DP600-A11100 COMPOSITE PLATES
    (Univ Zagreb Fac Mechanical Engineering & Naval Architecture, 2022) Ali, Khalil Belras; Demir, Bilge; Gurun, Hakan; Acarer, Mustafa
    This study theoretically and experimentally investigates blanking/piercing operations of explosively welded commercial DP600 advanced steel sheets, Al1100 aluminium sheets, and DP600-Al1100 composite plates, in which punches with different tip shapes are used. The experimental studies included several methods, such as explosive welding, punching, tensile testing, and macro image analyses using digital, optical, and SEM microscopes. The theoretical studies comprised finite element modelling using 3D models. The explosive weld was successfully applied, and the obtained Fe-Al weld microstructure was evaluated. A total of five punches, which have different tip shapes -flat-ended (0??), angled (16??), concave (R1 and R2), and V-shaped (V16) tips -were used in the experiments. Blanking forces were obtained using a load cell mounted to the die, a data acquisition card, an amplifier, and computer software. The simulation and the experimental study results were in agreement and clearly showed the effects of the punch shear angle and shape on the forces required for blanking/piercing.
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    An investigation of the PMEDM processing and surface characterizations of AZ61 matrix composites via experimental and optimization methods
    (Elsevier Science Sa, 2023) Mustu, Mustafa; Demir, Bilge; Aydin, Fatih; Gurun, Hakan
    In this study, AZ61/15 wt%TiB2 and AZ61/15 wt%TiB2-0.5 wt%GNPs composites were manufactured by hot pressing, and the machinability of the produced samples was carried out by powder mixed electrical discharge machining (PMEDM). The influence of PMEDM parameters, namely pulse on time, current and materials, were studied by surface roughness (SR) and material removal rate (MRR) using the Taguchi design. The microstructure and surface quality of the machined surfaces and cross-sections were investigated using 3D microscopy, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Results showed that PMEDM produced a melting, white layer and transition zone direct proportionally to the processing parameters. The white layer did not differ from the metal integrity of the transition zone. Additionally, volcanic craters, holes, cracks, debris covered with molten metal, and reinforcement particles were observed at the machined surface and cross-section. A high amount of oxygen was detected on the machined surface as a result of the interaction between kerosene and generated heat changing proportionally to the amount of the EDM parameters. The analysis of variance (ANOVA) showed that the pulse on time and materials, with 65.46% and 40.86%, were the most significant parameters on the SR and MRR, respectively. For regression models, the determination coefficient (R2) for the prediction of SR and MRR was noted to be 0.98 and 0.85, respectively.
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    An investigation of the shearing performance and sheared surface characterisation of ultra-strength DP steel-Al explosive welded plate composite
    (Springer London Ltd, 2023) Demir, Bilge; Ali, Khalil Belras; Gurun, Hakan; Acarer, Mustafa
    This study investigated the manufacturability of ultra-strength steel-Al plate composite, the punch-cutting performance of these composites and base materials, and the cutting surface properties. Therefore, experimental studies included explosive welding, punching process, and materials characterisations (microstructure and sheared surface image analyses via SEM, hardness and tensile test). In the punching process, five different types of punches were used. Additionally, the load cell was mounted on the punch and connected to the computer by an amplifier and a data acquisition card; the force values corresponding to the processing times were directly monitored, and the data were obtained. Shear process analyses were performed using finite elements. Microstructure and mechanical test results show that the DP1200 steel-Al 1100 aluminium laminated bimetal composite was produced by explosive welding of acceptable quality. The flat punch showed the highest shearing force, and other punches (angled and concave ends) reduced the shearing forces P R2, P V16, P R1, and P 16, respectively. Punches with different cutting-edge forms reduced the shearing force by up to 75%. The sheared surfaces were investigated in detail. Shearing marks were observed on both sides of the bimetal similarly. The punching process force vs time results showed good agreement between modelling and experimental punching values.