PSI - Issue 72

Dragana Mihajlović et al. / Procedia Structural Integrity 72 (2025) 195 – 202

196

Keywords: Anodic oxidation; Finite element method; Complete Gurson Model; Tensile properties; Ti-13Nb-13Zr alloy

1. Introduction Titanium and titanium alloys have characteristic such as low density, low weight and biocompatibility, better corrosion resistant because of the spontaneous formation of TiO 2 layer on the surface, Barjaktarevi ć et al. (2019). These characteristics make titanium and titanium alloys more suitable for use in the manufacture of medical implants than other metallic biomaterials. On the other hand, titanium alloys show better mechanical and physical properties in comparison to commercially pure titanium. Initially, titanium alloy with Al and V as alloying elements was developed, but the presence of Al and V in the titanium alloys leads to releasing of toxic ions in the human body which causes harmful health problems, Nikolova and Apostolova (2023). Today, the development of titanium alloys is focused on the use of Nb, Zr, Ta, Mo, Mn or Sn as alloying elements, thereby avoiding harmful effects on human health, further such alloys have characteristics that are good mechanical properties, better formability, lower elastic modulus (around 50 GPa) and higher wear and corrosion resistance, Abd-Elaziem et al. (2024). Anodic oxidation is a widely used process to enhance the surface properties of titanium and titanium alloys, improving aspects such as corrosion resistance, hardness, and aesthetic appearance. The anodic oxidation process involves immersing the materials in an electrolyte solution and applying an electric current, which forms a stable oxide layer on the surface. The surface morphology can vary in thickness of oxide layer, diameter of nanotube, wall thickness of nanotube, and colour of the surface, which depending on the anodic oxidation parameters, such as voltage, electrolyte composition, duration of anodic oxidation and anodizing current , Barjaktarević et al. (2016), BArjaktarević et al. (2018) and Mihajlović et al. (2024) ]. The influence of anodic oxidation on the mechanical and physical properties of titanium alloys has been extensively studied , Barjaktarević et al. (2021). Nonetheless, anodizing is generally beneficial for applications requiring improved surface durability and resistance to harsh environments, such as in aerospace, medical implants, and automotive components. The interplay between the anodized surface and the underlying titanium alloy's mechanical behaviour remains a critical area of investigation for optimizing the balance between surface performance and bulk material properties. In order to better understanding ductile fracture different micro-mechanical models are developed. The complete Gurson model is an advanced extension of the original Gurson model, designed to simulate the entire ductile fracture process in polycrystalline metals, Zhang et al. (2001), Zhang et al. (2000). The Gurson model is based on the hypothesis that the deformation of the material which surrounding a void is homogenous. By joining the Gurson model and the plastic limit load model, lead to the fact that the Gurson model becomes complete. The complete Gurson model deals with microvoid nucleation and growth, and a physical microvoid coalescence criterion based on the plastic limit load model. It accounts for void nucleation, growth, and coalescence, providing a comprehensive framework for analyzing ductile fracture mechanisms Zhang et al. (2001), Zhang et al. (2000). This model is particularly useful for predicting failure in materials subjected to complex loading conditions, including those involving shear and triaxial stress states Zhang et al. (2000). By incorporating factors such as void volume fraction and stress triaxiality, the complete Gurson model enhances the accuracy of fracture predictions, making it a valuable tool in materials science and engineering. According to this, the mail goals of this study were presenting influence of anodic oxidation on the Ti – 13Nb – 13Zr alloy tensile characteristics and numerical analysing of tensile behaviour of Ti-13Nb-13Zr alloy after anodic oxidation using complete Gurson model. 2. Materials and Methods The conventional Ti-13Nb- 13Zr alloy (TNZ) was produced by rolling near β alloy. One group of the TNZ alloy samples were modified using anodic oxidation process in order to obtain nanostructured oxide layer on the surfaces. The anodic oxidation was done in the solution of orthophosphoric acid, at a potential of 25 V and during 90 minutes. In order to analyze characteristics of the nanostructured modified surface, scanning electron microscope (SEM) MIRA3 TESCAN was used.