Sürdürülebilir Kalkınma Amaçları

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Alt birimler

• Biyomedikal Cihaz Teknolojisi Programı
• Mekatronik Programı

Araştırmacılar(9)

• Aydoğan, Beytullah
• Çolak, Murat
• Gavgalı, Esma
• İğman, Erdal
• Salton, İlknur Umay
• Sekban, Hayriye Tuğba
• Uslu, Emin
• Uyar, Mehmet
• Yilmaz, Galip

• MakaleYalnız künye2026Scopus SJRQ2/r/bayburt/12819
  Comparative investigation of composite-metal lap joints with mono-adhesive and thermoplastic-reinforced mixed adhesive at elevated temperatures

  Erbayrak, Engin; Eker, Beril; Colak, Murat

  This study primarily examines the strength of a single lap joint having a mixed adhesive overlap consisting of a single adhesive and its thermoplastic reinforced state under varying temperatures. In the single lap joint, Titanium-Boron reinforced A356 aluminum was employed as the metal adherend, while plain woven glass fiber-reinforced epoxy (GFRE) was employed as the composite adherend. In the application of the mixed adhesive overlap, the brittle adhesives were employed in the middle section of the lap joint, while the reinforcement of the thermoplastics was employed on the adhesives at both sides of the lap joint. The single lap joints were subjected to tensile tests at 1 mm/min loading rates under room temperature and 120 °C, which is the melting point of the copolyester. In the numerical analysis, the cohesive zone model was applied in order to define the adhesives; however, elastic isotropic and orthotropic material behaviors were employed for the metal and composite adherends, respectively. Eventually, it is determined that the strength of a mixed adhesive lap joint consisting of a single adhesive and its thermoplastic reinforced state is better than a lap joint made with the mono-adhesive alone. Although literature suggests that mixed adhesive overlaps can be formed using at least two different adhesives (one ductile and one brittle), this study demonstrated that a mixed adhesive zone can be created using a single adhesive and thermoplastic reinforcement.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11576
  Low-velocity impact analysis of metal-composite joints with grain-refined A356 and reinforced epoxy adhesive using six node pentahedron cohesive elements

  Erbayrak, Engin; Colak, Murat; Noberi, Cansu

  This study evaluates the strength of double lap joints composed of metal composite adherends and epoxy adhesive subjected to low impact energies (20 J, 40 J). The study was carried out through experimental and numerical methods to understand the strength of lap joints comprehensively. In the production of double lap joints, A356 aluminum and grain-refined aluminum adherends were used as the metal components. To refine the grain structure, titanium (Ti) and boron (B) were added to the liquid metal at a rate of 0.01% of the total metal weight (A356-TiB). The composite laminates consisted of glass/epoxy and aramid/epoxy, made with unidirectionally oriented fibers. Araldite 2015 epoxy adhesive, available in both unreinforced and copolyester-reinforced forms, was utilized to bond the metal and composite materials. In the numerical analysis of double-lap joints, the metal and composite adherends are modeled using 8-node solid elements, while the adhesive is represented by 6-node pentahedron cohesive elements. Furthermore, a surface-to-surface, two-way treatment of contact was created between the impactor and the metal adherend. Consequently, the maximum impact loads obtained from the numerical analysis are in good agreement with the experimental results for both impact energies.

  AtıfScopus4·WoS5·OpenAlex4

  İncele
• MakaleAçık Erişim2026Scopus SJRQ1/r/bayburt/11553
  Permittivity Extraction of Electrically Thin Samples by Reflection-Only Free-Space Measurements

  Hasar, Ugur C.; Xue, Bing; Ozturk, Hamdullah; Kaya, Yunus; Ozturk, Gokhan

  A permittivity extraction procedure is devised for electrically thin samples from reflection-only free-space measurements. Unlike previous studies, this procedure relies on sample-back metal termination measurements especially useful for thinner samples. An objective function independent of antenna transmission characteristics and reference plane position is derived. Minimum and maximum thickness and permittivity values for which our method is applicable are also examined. Free-space measurements at X-band (8.2-12.4 GHz) of a Rogers 4350B sample (approx 1.52 mm) and a FR4 sample (1.60 mm) were performed to validate our method with a dielectric constant less than 5% variation.

  AtıfScopus1·WoS1

  İncele
• MakaleYalnız künye2026Scopus SJRQ1/r/bayburt/11397
  Reference-Invariant Permittivity Determination of Low-Loss Solid Dielectric Samples Using Spectral Free-Space Measurements Without Prior Thickness

  Hasar, Ugur C.; Ali, Husain; Kaya, Yunus

  An extraction method has been proposed for relative permittivity determination εrs of low-loss solid dielectric samples using free-space measurements. It relies on a reference-plane invariant expression with no thickness information a priori, making resistant to conventional free-space measurement errors which may arise from improper information of sample position and thickness. In addition, the method constructed by the state transition matrix (STM) uses closed-form expressions – a feature distinguishes our method from previous STM-based extraction methods requiring a numerical tool or optimization procedure. Furthermore, provided that the sample thickness L is evaluated, as a by-product, first using the derived closed-form objective function away from any thickness-resonance region, the proposed method then determines εrs and L free from thickness-resonance effect, which otherwise can introduce ripples around or at the thickness-resonance frequency. Numerical analysis is performed to validate and assess the performance of our method. Free-space measurements at X-band of two low-loss samples with substantial thickness are performed for validation and accuracy comparison of our method against other similar methods.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ2/r/bayburt/11272
  Relationship Between Aluminum Liquid Metal Quality and Defects

  Kutsal, Umit; Colak, Murat; Ertugrul, Onur

  Aluminum alloys are commonly used in various industries today. In order to produce defect-free high-quality alloys with sustainable processes, defects must be reduced, and liquid metal quality must be improved. There are various methods that can be used for the measurement of liquid metal quality. Some of which are density index, bifilm index, K-Mold index, PoDFA, Prefil, fluidity test, and thermal analysis. The relationship and validation between these methods are still not clear. In this study, the relationship between aluminum liquid metal quality and defects is analyzed. Three different conditions were utilized. These conditions are (1) before a controlled degassing, (2) after the controlled degassing and (3) after the liquid metal is transferred to the holding furnace. According to the results, it was observed that the reduction of bifilms index did not reduce other inclusions and did not always favorably affect other measurement methods. It was also observed that the reduction of bifilm index did not improve the porosity level. Moreover, it was found that elongation values are related to the largest defect diameters. Bifilm index are not the only factor affecting the elongation and the density index directly affects the defect distribution. K-Mold index has an impact as it shows macro-inclusions. However, bifilm index, density index, fluidity index and K-Mold index are not as sufficient as numerical calculation of defect size by computed tomography (CT). The main factor directly affecting the elongation and tensile strength was found to be the inclusion size and diameter in the CT result. Examination of the fracture surfaces revealed that oxide contents are present, and the oxygen orientations and aluminum orientations are compatible. This harmony is thought to be related to the orientation of the bifilms in the structure.

  AtıfScopus8·WoS8

  İncele
• MakaleYalnız künye2026Scopus SJRQ2/r/bayburt/11231
  Identifying the optimal flexural performance of metal-composite single-lap joints with copolyester-reinforced epoxy adhesive under various loading rates using the Grey Relation Analysis

  Erbayrak, Engin; Erbayrak, Seda; Eker, Beril; Colak, Murat

  This study examines the best flexural performance of metal composite single-lap joints fabricated with copolyester-reinforced epoxy adhesives at various loading rates using the Grey Relation Analysis (GRA). The study consists of three parts. The first part involves the formation of metal composite single-lap joints and their experimental approach under different loading rates. In the experimental approach, A356 aluminum was used as the metal material with the addition of titanium (Ti) and boron (B) additives. Plain-woven glass fiber-reinforced epoxy (GFRE) and plain-woven carbon fiber-reinforced epoxy (CFRE) were served as the composite materials. The lap joints were tested in three-point bending tests under loading rates of 1, 10, and 50 mm/min, respectively. In the second part, a numerical analysis was conducted using boundary conditions similar to the experimental conditions. In the numerical analysis, a 6-node pentahedral cohesive element was utilized, representing a novel approach for modeling adhesives in finite element analysis (FEA). When experimental and numerical results were compared, a difference of 4.36% was observed between the maximum load values and 6.80% between the failure displacements. Based on these results, it can be said that the experimental results converge with the numerical results. In the last part of the study, performance rankings of metal composite joints were determined using the Grey Relational Analysis (GRA) method, which enabled us to identify the optimum joint. This systematic approach facilitated the scientific design of joints that demonstrate optimal flexural performance under various loading conditions.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ1/r/bayburt/11188
  Permittivity extraction of sandy soils through uncalibrated and thickness-independent meniscus-free measurements using a hollow coaxial line

  Hasar, Ugur C.; Korkmaz, Huseyin; Kaya, Yunus

  Measurement techniques for accurate moisture level determination of various soil conditions are becoming popular in recent studies. Microwave-driven techniques, as positioned into indirect methods, could be tailored for precise and real-time detection of soil moisture. However, improper implementation of calibration techniques or usage of imperfect calibration standards required for precise measurements by these techniques presents a challenging limitation for their widespread usage. Besides, meniscus formation on top of soil samples with a sufficient moisture level could adversely influence the performance of these techniques. In this study, we present a microwave extraction method for eliminating the requirement of a formal calibration procedure and additionally removing the effect of meniscus on measurements through relative measurements of sandy soil samples while maintaining accurate permittivity extraction with no information of sample thickness. To achieve our goal, a mathematical framework unifying wave-cascading matrix and state-transition matrix presentations is proposed for permittivity determination from three measurement configurations (empty line, the (sandy) soil sample sandwiched between two identical plugs, and a shifted version of this plug-sample-plug configuration) and their inverses implemented by port switching operation. The proposed method is first validated by permittivity measurements of two liquid samples (distilled water and methanol). Then, permittivity measurements of two sandy soil samples (having more than 90% sand content) were conducted using Type-N-to-EIA 1-5/8” coaxial lines (with no universal calibration standard) over 0.05 GHz–3.0 GHz. From these measurements, it is noted that our meniscus-free method determines permittivity with a maximum absolute difference of 3.4% (evaluated from five independent measurements) while another similar method, suffering from meniscus presence, extracts permittivity with a maximum absolute difference of 4.0%. This indicates a clear advantage of our method for measurements of sandy soil samples having meniscus formation. We then utilized to construct a calibration curve, compared with other calibration curves using by other methods, allowing prediction of moisture volume content () of the tested sandy soil samples from measured permittivity data whose conformity analysis implemented by the three-pole Debye model and the Mironov-Fomin model. It is observed that this calibration curve could be utilized to predict within margin from measured permittivity data.

  İncele
• MakaleAçık Erişim2026Scopus SJRQ3/r/bayburt/11135
  Optimization of Rotary Degassing Parameters to Improve Melt Cleanliness and Mechanical Properties in A356 Aluminum Alloy

  Kutsal, U.; Çolak, M.; Sağnak, Y.; Bardakci, S.; Ammas, G.; Sarper, G.

  Melt cleanliness is a critical factor that directly affects the quality of aluminum castings and becomes even more significant in recycling-oriented production, where high scrap utilization is inevitable. Increasing the proportion of scrap intensifies the risk of oxide films, inclusions, and gas porosity in the molten metal; therefore, efficient refining techniques are essential. In this study, the effects of rotary degassing parameters—including rotor speed, rotation time, and gas flow rate—on melt cleanliness of A356 aluminum alloy were systematically investigated. Experimental melts containing 20% primary and 80% scrap aluminum were treated under various degassing conditions using a commercial flux cleaning flux. Characterization was performed through the Reduced Pressure Test (RPT), bifilm index analysis, fluidity measurements, microstructural examinations, and mechanical testing (tensile test and Brinell hardness measurement). The results demonstrated that increasing the rotor speed from 200 rpm to 500 rpm significantly reduced both the density and bifilm indices, indicating a notable improvement in melt cleanliness. Furthermore, higher gas flow rate (10 L/min) and longer rotation time (10 min) provided additional but secondary improvements. Consequently, the optimization of rotary degassing parameters enhanced not only melt quality but also tensile strength and ductility. These findings offer practical insights for optimizing process control in recycling-based aluminum foundries.

  İncele
• MakaleYalnız künye2026Scopus SJRQ1/r/bayburt/11105
  Upcycling marble waste into construction materials and heavy metal adsorbents via hot-pressed geopolymerization technique

  Öksüzer, Nurullah; Uslu, Emin; Gökçe, H. Süleyman

  This study presents a sustainable approach to utilizing marble dust waste by producing bifunctional metakaolin-based geopolymers via a synchronized hot-pressing technique. In this study, the environmental footprint was minimized by designing mixtures in which marble waste constituted 50% of the total volume. Three stoichiometric series were investigated by varying the activator modulus (SiO2/Na2O = 3 and 4) and the Si/Al ratio (2 and 3) under two curing temperatures (150 and 300 °C) and three compaction stresses (5, 25, and 50 MPa). Thus, a high-volume industrial byproduct was transformed into a functional component. In this context, it investigated the transformation of industrial products into next-generation materials by using them to produce cementless composite geopolymers for civil engineering and to adsorb heavy metal (Cu2+). As a result of the research, an early compressive strength of 58 MPa was obtained through heat treatment and pressing applied at 300 °C and 50 MPa. This optimum strength was achieved in the SiO2/Na2O = 3, Si/Al = 3 series, whereas excess silica (SiO2/Na2O = 4) and excess aluminum (Si/Al = 2) limited the strength to 16.8 and 35.2 MPa, respectively. Microstructural analyses (SEM/EDS and FT-IR) revealed that marble dust was used as a filler material in the microstructure to produce an N-A-S-H-containing matrix. The produced materials were then ground after their service life and used to purify water containing heavy metals. More than 99.75% of Cu2+ was removed through ion exchange between copper ions used as heavy metals. The residual Cu2+ concentration fell below 0.25 mg/L from an initial concentration of 100 mg/L, and the released Na+-to-adsorbed Cu2+ molar ratio of approximately 1.8–2.3 confirmed an ion-exchange-dominated uptake mechanism. This structural and environmental impact demonstrates that marble waste, which is otherwise discarded as waste, is considered inert, offering an alternative model for the circular economy and environmental applications.

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  İncele
• MakaleAçık Erişim2026Scopus SJRQ4/r/bayburt/11052
  Comparative analysis of stress distributions and safety factor in tensile test specimens with different notch and hole geometries by finite element method

  Korkmaz, Sümeyye Erdem; Gavgali, Esma

  This study analyzes the effects of different notch and hole geometries (V-Notched, U-Notched, circular hole) on stress concentration in Ti-6Al-4V (Grade 5) Titanium alloy tensile specimens to provide optimized design recommendations for aerospace and biomedical applications. Finite element method (ANSYS Workbench) was employed to analyze three geometries under 15000 N static tensile loading. Von Mises stress distributions and stress concentration factors (Kt) were calculated and validated against Peterson and Neuber theoretical formulas with average error ±1.5%. Results revealed that V-Notched exhibited highest stress concentration (Kt = 5.78, σmax = 1156 MPa), while circular hole showed lowest (Kt = 2.25, σmax = 454.12 MPa). U-Notched demonstrated intermediate performance (Kt = 2.84, σmax = 995.45 MPa). Increasing notch root radius from 0.5 mm to 2.0 mm achieved 51% reduction in stress concentration factor. Maximum shear stress values were 232.74 MPa, 506.38 MPa, and 640 MPa for circular, U-Notched, and V-Notched respectively, while maximum normal stress values reached 467.06 MPa, 1015.1 MPa, and 1809 MPa. Safety factor analysis showed that circular hole configuration meets aerospace standards (FS = 2.05 > 1.5), while U-Notched (FS = 0.93) and V-Notched (FS = 0.80) fall below minimum safety criteria. U-Notched exhibited highest total displacement (1.210 mm), indicating compliance effects. For aerospace and biomedical applications, circular holes should be preferred over sharp notches (154% stress reduction), and minimum corner radius ≥2.0 mm is recommended. The critical finding that geometric optimization provides 2.6× safety improvement without material changes demonstrates the powerful role of design in structural reliability for weight-critical applications.

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