Aleksandar Sedmak
University of Belgrade, Serbia
Biography: Aleksandar Sedmak was born on May 2nd, 1955 in Belgrade, Serbia. He graduated from Faculty of Mechanical Engineering, University of Belgrade, where he spent his whole academic career and became professor emeritus in 2021. He was assistant Minister for Science and Technology Development in Serbian government 2003-2006, Vice-rector for international cooperation, University of Belgrade, 2006-2009 and visiting professor at the Drexel University, USA, 1999-2002. He is the President of Serbian Structural Integrity and Life Society and editor emeritus of Structural Integrity and Life Journal, the president of European Structural Integrity Society (ESIS) since 2022, member of editorial boards, guest editor and reviewer of a prominent journals in Fracture Mechanics, EFA, EFM and FFEMS. He was the chairman of European Conference on Fracture (ECF22), Belgrade, 2018. His research is focused on fracture mechanics and structural integrity of weldments, biomaterials and AMM.
Prof. Aleksandar Sedmak published 406 scientific papers listed in SCOPUS with 4012 citations, h=29. He was coordinator and participant of 12 international projects in the scope of EU programs such as EUREKA, bilateral cooperation, H2020, FP7, COSME and Interreg. He delivered many invited and plenary lectures all over the world, including Xidian University, Xian and Institute of mechanics, CAS, Beijing.
Invited Lecture: Structural integrity and life of materials and components made by additive manufacturing
Abstract: In spite of the growing usage of Additive Manufacturing (AM) for producing components in different fields such as aeronautics, biomechanics and automotive, the criteria and methods for the safety evaluation of AM components has not been well established. Therefore, the lack of knowledge of AM material quality effects on the load bearing capacity of the components hinders the industrial exploitation of AM. Keeping in mind porosity, heterogeneity and layered structure of AM materials, it is clear that the most critical issue of heavy loaded AM components is their structural integrity and life. To address this issue, fracture mechanics and fatigue testing of materials and components made by additive manufacturing attracted a lot of research attention in last few years. Recently, EU project SIRAMM (Structural Integrity and Reliability of Additive Manufactured Materials) was completed, providing solid basis for further research of relevant fracture mechanics properties of various 3D printed materials made by different AM technologies such as Selective Laser Sintering (SLS) and Fused Deposition Modelling (FDM). In this paper two case studies are presented. The first one presents results of fracture mechanics and fatigue testing of AM PLA three-point bending specimens made by FDM with different infills (10-100%) and layer thicknesses (0.1-0.3 mm). This material is not only sensitive to cracking both under static and dynamic loading, but also exhibits unusual behaviour in respect to different levels of infills and to some extent, different layer thicknesses. In addition, standard fracture mechanics testing procedures are not always applicable for such a complex material, including difficulties in monitoring the crack propagation, and thus requiring special procedures which are still not generally accepted. Therefore, results and procedure presented here should be treated as an initial step toward standard testing of AM materials. In the second case study, fatigue lives of two different designs of the torque links of the light aircraft are evaluated by a numerical approach based on the Separating Morphing and Adaptive Remeshing Technology (SMART) using in the scope of classical FEM. Firstly, the fatigue life of the damaged torque link was assessed for actual load conditions. Then, improved torque links, obtained through topological optimization, were analyzed and their fatigue life was calculated. Finally, the numerical simulations of the additive manufacturing (AM) process of optimized torque links were carried out, and the fatigue life of these torque links, including residual stresses from AM, were estimated too. The obtained numbers of cycles in all cases were compared and discussed for all torque links cases. Such an advanced approach to fatigue life assessment of optimized printed 3D parts provided important data for improvement of AM process with an aim to produce a component more resistant to cracking.