Yapısal Çelik ve Bakır Alaşımlarında Çentik Darbe Testinin Sonlu Elemanlar Yöntemiyle Analizi

Year 2025, Volume: 7 Issue: 2, 331 - 348, 31.08.2025

Sümeyye Erdem Korkmaz , Esma Gavgalı

Abstract

Bu çalışmada, yapısal çelik ve bakır alaşımlarının çentik darbe davranışları, gelişmiş sayısal yöntemlerle detaylı biçimde incelenmiştir. ASTM E23 standardına göre boyutlandırılan Charpy V-çentikli numunelerin (uzunluk=55 mm, genişlik=10 mm, kalınlık=10 mm; çentik derinliği=2 mm, kök yarıçapı=0,25 mm) üç boyutlu katı modelleri SolidWorks yazılımında oluşturulmuş ve ANSYS programında 19.088 eleman ve 22.484 düğümden oluşan yüksek hassasiyetli bir sonlu eleman modeliyle analiz edilmiştir. Malzemelerin doğrusal olmayan davranışı, gerinim hızının etkilerini de kapsayan Cowper-Symonds modeli (çelikte C=40,4 s⁻¹, bakır alaşımında C=1169 s⁻¹) ile bilineer izotropik pekleşme kullanılarak tanımlanmıştır. Darbe hızları, enerji korunumu ilkesine göre hesaplanmış (300 J için 5,42 m/s, 150 J için 3,83 m/s) ve sürtünmeli temas koşulları (μ=0,2) gerçekçi biçimde tanımlanarak simülasyonlar gerçekleştirilmiştir. Analizler, maksimum gerilmelerin çentik bölgesinde yoğunlaştığını, yapısal çelikte 6438,8 MPa, bakır alaşımında ise 839,61 MPa’ya ulaştığını ortaya koymuştur. Bu değerler, her iki malzemenin de dinamik akma dayanımlarını (çelik için 485 MPa, bakır alaşımı için 252 MPa) önemli ölçüde aşarak, sırasıyla 0,075 ve 0,300 gibi oldukça düşük dinamik emniyet katsayılarına sebep olmuştur. Kırılma anında oluşan maksimum plastik deformasyon, yapısal çelikte 34 mm, bakır alaşımında ise 32 mm olarak belirlenmiş olup, çeliğin darbe yüklemesi altında daha üstün enerji emme kapasitesine sahip olduğu (287 J çelik, 142 J bakır alaşımı) görülmüştür. Elde edilen sonuçlar literatürdeki deneysel verilerle karşılaştırılmış ve yapısal çelikte %4,4, bakır alaşımında ise %5,2’lik düşük hata oranlarıyla doğrulanmıştır. Sonuç olarak, bu çalışma, çentik darbe etkisi altında dinamik kırılma mekanizmalarının, gerilme dalga yayılımının ve deformasyon davranışlarının doğru bir şekilde değerlendirilmesinde sonlu elemanlar yönteminin etkinliğini vurgulamakta, malzeme seçiminde ve yapı güvenliğinin artırılmasında kritik öneme sahip detaylı bilgiler sağlamaktadır.

Keywords

Bakır alaşımı , Çentik darbe testi , Sonlu elemanlar yöntemi , Yapısal çelik

Finite Element Analysis of Notch Impact Test in Structural Steel and Copper Alloys

Abstract

This study investigates the notch impact behavior of structural steel and copper alloys using advanced numerical simulation based on the finite element method (FEM). Charpy V-notch specimens conforming precisely to ASTM E23 standards (L=55 mm, W=10 mm, B=10 mm; notch depth=2 mm, root radius=0.25 mm) were accurately modeled in SolidWorks and subjected to explicit dynamic analyses within the ANSYS environment using a refined mesh comprising 19,088 elements and 22,484 nodes. Nonlinear material behavior was incorporated using bilinear isotropic hardening combined with strain-rate sensitivity modeled through the Cowper-Symonds relationship (C=40.4 s⁻¹ for steel and 1169 s⁻¹ for copper alloys). Realistic impact velocities of 5.42 m/s (300 J) and 3.83 m/s (150 J) were calculated based on energy conservation principles, and frictional contact interactions (μ=0.2) were rigorously defined. Results indicate pronounced stress concentrations localized around the notch region, where peak von Mises stresses were recorded as 6438.8 MPa in structural steel and 839.61 MPa in copper alloy, significantly surpassing their respective dynamic yield strengths (485 MPa for steel, 252 MPa for copper alloy). These stress levels corresponded to notably low dynamic safety factors of approximately 0.075 for structural steel and 0.300 for copper alloy, suggesting imminent fracture initiation under impact loading. Furthermore, structural steel specimens exhibited greater maximum plastic deformation (34 mm) compared to copper alloys (32 mm), highlighting steel's superior impact toughness and energy absorption capabilities (287 J vs. 142 J). Validation against previously reported experimental data demonstrated excellent agreement, with discrepancies limited to 4.4% for structural steel and 5.2% for copper alloy. This comprehensive numerical investigation emphasizes the efficacy of finite element-based approaches for accurately capturing dynamic fracture mechanisms, transient stress waves, and deformation behaviors, providing crucial insights for optimizing material selection and enhancing structural safety against impact loading.

Keywords

Copper alloy , Finite element method , Notch Impact Test , Structural Steel

Ethical Statement

This study is an original research article designed and developed by the authors.

Thanks

The authors are very grateful to Karamanoğlu Mehmetbey University for their support in the data collection process for this study and for providing the ANSYS Workbench program.

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