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    Bioinspired Sternal Implant Design for Generic Anatomical Reconstruction: An In Silico Framework for Material Selection and Biomechanical Validation
    (MDPI, 2026) Kutbay, Isil; Gerdan, Zeynep; Colak, Murat; Tabak, Yasemin; Sensoy, Abdullah Tahir
    The sternum protects the intrathoracic organs and contributes to chest wall mechanics, which makes reconstruction after tumor resection, trauma, or infection a demanding biomechanical problem. This study presents an in silico workflow for preselecting materials for sternal implants before physical prototyping. After a virtual resection, an anatomically conformal implant was designed and candidate biomaterials were screened in CES Selector using density, elastic modulus, fatigue strength, fracture toughness, toxicity, medical grade suitability, and MRI safety. A representative subset of the screened candidates was then compared by finite element modeling in terms of stress transfer and deformation. Seventeen candidates met the screening criteria. Ti-13Nb-13Zr showed an elastic modulus of about 80 GPa, and the titanium-based candidates showed deformation values of about 0.96 to 1.03 mm, whereas GF PEEK reached about 1.74 mm. The stress shielding index also showed that titanium-based materials remained on the implant-dominant side, while polymer-based materials shifted stress transfer toward bone. Taken together, the findings suggest that Ti-13Nb-13Zr offers the best overall balance for load-bearing sternal reconstruction, whereas PEEK-based systems may be more suitable within the present model for hybrid or adjunct designs. The proposed workflow can support early implant planning and guide future experimental and clinical studies.
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    Effect of Erbium Addition to A380 Aluminum Alloy on Mechanical and Microstructural Properties
    (Springer, 2026) Gultekin, Cagri; Colak, Murat; Tabak, Yasemin; Sensoy, Abdullah Tahir
    There are many studies on improving the properties of aluminum alloys, but the addition of rare earth elements occupies a particularly important place among them. In this study, the effect of erbium (Er) addition on the microstructure and mechanical properties of A380 aluminum casting alloy was systematically investigated. A series of alloys with varying Er contents (0.03%, 0.05% and 0.1 wt.%) was fabricated using the conventional casting method. The addition of Er led to significant grain refinement, primarily due to the formation of Al3Er intermetallic particles, which acted as potent nucleation sites during solidification. Optical microscopy and SEM analyses confirmed the morphological transformation of the eutectic silicon phase into a finer and more fibrous structure. Mechanical testing revealed that the alloy containing 0.1 wt.% Er exhibited the highest ultimate tensile strength (236 MPa), elongation (4.56%), and hardness (87.6 HB), indicating an optimal balance between strength and ductility. The improvement is attributed to both microstructural refinement and dispersion strengthening mechanisms. These results suggest that controlled Er addition can be an effective strategy for enhancing the performance of cast Al-Si alloys, making them promising candidates for demanding structural applications in the automotive and aerospace industries.
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    Küresel Grafitli Dökme Demirin Mikroyapısı ve Mekanik Özellikleri Üzerinde Döküm Modülünün Değerlendirilmesi
    (Bayburt Üniversitesi, 2025) Çolak, Murat; Çolak, Oğuzhan; Tabak, Yasemin
    Küresel grafitli (Sfero) dökme demir, çift aşamalı bir işlemle üretilmektedir: **Nodülerizasyon / Küreselleştirme** (Mg ve/veya Nadir Toprak Elementleri ile işlem) ve **Aşılama** (FeSiX alaşımı ile işlem, X = Ca, Ba, Sr, Ce, La, Zr vb.). Her aşama belirli amaçlara hizmet etmektedir. Grafitin küreselleşmesi, kalıp kalınlığına bağlı olup, bu nedenle soğuma hızı önemli bir faktördür. Bu çalışmada, **GGG70L alaşımı**, farklı kesit kalınlıklarına sahip plakalar halinde dökülmüştür. Modül değişimi, mikroyapı ve mekanik özellikler açısından incelenmiştir. Nodule boyutu küçüldükçe çekme gerilmesi ve kırılma uzaması azalırken, sertliğin arttığı gözlemlenmiştir. Sonuç olarak, kesit kalınlığının, **küresel grafitli dökme demirlerin mikroyapısını ve mekanik özelliklerini belirleyen önemli bir parametre olduğu** sonucuna varılmıştır.