Yazar "Delibas, Hulusi" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • [ X ]
    Öğe
    A novel repair method for the lifespan and performance improvement of a shell-and-tube heat exchanger: A thermo-mechanical approach
    (Pergamon-Elsevier Science Ltd, 2025) Delibas, Hulusi; Yilmaz, Ibrahim Halil
    Heat exchangers play a critical role in the functioning of many engineering systems. Shell-and-tube heat exchangers (STHEs) are more traditional and widely used devices due to their efficiency, versatility, and ability to handle a range of flow conditions and fluid types. STHEs experience a number of problems over time, including corrosion, mechanical wear, or leaking, and thus need repairs to keep operating. This study has introduced a novel repair approach for extending the lifespan of damaged STHE tubes by fitting new tubes. An original thermo-mechanical model, including the analyses of the STHE, thermal contact resistance between the fitted tubes, and mechanical design of the built structures, is proposed for the problem solution, and all governing equations are simultaneously solved in Engineering Equation Solver (EES). All submodels are validated with analytical or experimental data, and good agreements are obtained. The most significant design parameters and their effects on the thermal and mechanical performances of an STHE are parametrically investigated. Results reveal that increasing the contact surface slope over 10 degrees but lowering the effective surface roughness below 3 mu m provides an advantage for keeping the heat load of the STHE high. Among the interference fits, the locational interference fit is the most advantageous in terms of thermal and mechanical performances relative to other fit conditions. Both increasing operating pressure and tube diameter are two key pillars that can allow for a safety factor > 1.5. Fitting tube materials are parametrically independent and applicable to any STHE tube diameter as the yield strength > 300 MPa. Even if all tubes are press-fitted, the maximum heat load drop in the current repair method corresponds to 4.23 % which is lower than the tolerable value i.e., <10 % of the initially planned heat load.
  • [ X ]
    Öğe
    Effects of Short-Term Thermal Aging on the Fracture Behavior of 3D-Printed Polymers
    (Springer, 2021) Daricik, Fatih; Delibas, Hulusi; Canbolat, Gokhan; Topcu, Alparslan
    3D printing technologies offer numerous advantages and have attracted the attention of researchers recently. Yet, the most commonly preferred additive manufacturing system is the extrusion-based process that is called fused deposition modeling (FDM) as it is simple, low cost, and prone to customization. In this paper, the effects of the short-term aging of the additively manufactured PLA and ABS specimens were investigated experimentally. The test specimens were aged by keeping them at ambient temperatures of - 80, - 20, 60, 100 degrees C for 10, 20, and 30 days. Thermally aged specimens and the pristine specimens were forced to fracture with bending load at room temperature. Thus, the permanent effects of thermal aging of the specimens were investigated utilizing the load-deflection curve, plane-strain fracture toughness, and the morphologies of fracture surfaces. It was concluded that the printed PLA materials are more susceptible to the thermal aging than the ABS printed materials. The contraction and expansion of the fused polymer filaments affect directly the bonding strength between the adjacent layers. Therefore, plane-strain fracture characteristics of the FDM polymer materials exposed to thermal aging differ according to the filament orientation and the aging time.
  • [ X ]
    Öğe
    Effects of Short-Term Thermal Aging on the Fracture Behavior of 3D-Printed Polymers
    (Springer, 2021) Daricik, Fatih; Delibas, Hulusi; Canbolat, Gokhan; Topcu, Alparslan
    3D printing technologies offer numerous advantages and have attracted the attention of researchers recently. Yet, the most commonly preferred additive manufacturing system is the extrusion-based process that is called fused deposition modeling (FDM) as it is simple, low cost, and prone to customization. In this paper, the effects of the short-term aging of the additively manufactured PLA and ABS specimens were investigated experimentally. The test specimens were aged by keeping them at ambient temperatures of - 80, - 20, 60, 100 degrees C for 10, 20, and 30 days. Thermally aged specimens and the pristine specimens were forced to fracture with bending load at room temperature. Thus, the permanent effects of thermal aging of the specimens were investigated utilizing the load-deflection curve, plane-strain fracture toughness, and the morphologies of fracture surfaces. It was concluded that the printed PLA materials are more susceptible to the thermal aging than the ABS printed materials. The contraction and expansion of the fused polymer filaments affect directly the bonding strength between the adjacent layers. Therefore, plane-strain fracture characteristics of the FDM polymer materials exposed to thermal aging differ according to the filament orientation and the aging time.
  • [ X ]
    Öğe
    Evaluating the performance of Bi58Sn42 mold produced by material extrusion additive manufacturing system for agile manufacturing
    (Emerald Group Publishing Ltd, 2024) Delibas, Hulusi; Geren, Necdet
    PurposeThe purpose of this study is to produce a low-cost sheet metal forming mold made from the low melting point Bi58Sn42 (bismuth) alloy by using an open-source desktop-type material extrusion additive manufacturing system and to evaluate the performance of the additively manufactured mold for low volume sheet metal forming. Thus, it was aimed to develop a fast and inexpensive die tooling methodology for low-volume batch production.Design/methodology/approachInitially, the three-dimensional printing experiments were performed to produce the sheet metal forming mold. The encountered problems during the performed three-dimensional printing experiments were analyzed. Accordingly, both tunings in process parameters (extrusion temperature, extrusion multiplier, printing speed, infill percentage, etc.) and customizations on the extruder head of the available material extrusion additive manufacturing system were made to print the Bi58Sn42 alloy properly. Subsequently, the performance of the additively manufactured mold was evaluated according to the dimensional change that occurred on it during the performed pressing operations.FindingsResults showed that the additively manufactured mold was rigid enough and proved to have sufficient strength in sheet metal forming operations for low-volume production.Originality/valueAlternative mold production was carried out using open-source material extrusion system for low volume sheet metal part production. Thus, cost effective solution was presented for agile manufacturing.
  • [ X ]
    Öğe
    Evaluating the performance of Bi58Sn42 mold produced by material extrusion additive manufacturing system for agile manufacturing
    (Emerald Group Publishing Ltd, 2024) Delibas, Hulusi; Geren, Necdet
    PurposeThe purpose of this study is to produce a low-cost sheet metal forming mold made from the low melting point Bi58Sn42 (bismuth) alloy by using an open-source desktop-type material extrusion additive manufacturing system and to evaluate the performance of the additively manufactured mold for low volume sheet metal forming. Thus, it was aimed to develop a fast and inexpensive die tooling methodology for low-volume batch production.Design/methodology/approachInitially, the three-dimensional printing experiments were performed to produce the sheet metal forming mold. The encountered problems during the performed three-dimensional printing experiments were analyzed. Accordingly, both tunings in process parameters (extrusion temperature, extrusion multiplier, printing speed, infill percentage, etc.) and customizations on the extruder head of the available material extrusion additive manufacturing system were made to print the Bi58Sn42 alloy properly. Subsequently, the performance of the additively manufactured mold was evaluated according to the dimensional change that occurred on it during the performed pressing operations.FindingsResults showed that the additively manufactured mold was rigid enough and proved to have sufficient strength in sheet metal forming operations for low-volume production.Originality/valueAlternative mold production was carried out using open-source material extrusion system for low volume sheet metal part production. Thus, cost effective solution was presented for agile manufacturing.
  • [ X ]
    Öğe
    Morphological, mechanical, magnetic, and thermal properties of 3D printed functional polymeric structures modified with Fe2O3 nanoparticles
    (Wiley, 2021) Aktitiz, Ismail; Delibas, Hulusi; Topcu, Alparslan; Aydin, Kadir
    The Fe2O3 nanoparticle structures, which have many application areas such as electronics, marine, and aviation, have been studying extensively due to the compliance between organic polymer and inorganic Fe2O3 nanoparticles. Nanocomposite structures are successfully produced in the desired complexity with the additive manufacturing method. In the current study, Fe2O3 nanoparticles were doped into the photocurable resin at different concentrations (pristine, 0.25%, 0.5%, and 1% in wt), and the prepared 3D polymer nanocomposite mixtures were printed via stereolithography method. To investigate the morphological, mechanical, magnetic, and thermal properties of the printed nanocomposite structures, scanning electron microscopy, hardness, vibrating sample magnetometer, thermogravimetric analysis, and differential scanning calorimeter analysis were performed, respectively. It was revealed that the Fe2O3 nanoparticles improved the thermal stability of the structures. Moreover, an increase in magnetic properties has been observed up to 459%.