Title:

Fatigue threshold experiments and their implications for fatigue strength assessment of AM materials

Speaker:

Prof. Stefano Beretta

Affiliation:

Politecnico di Milano

When:

Thursday, April 17, 2025 at 11:00:00 AM   Add to Calendar

Where:

Love Building, Room 184

Host:

Rick Neu
rick.neu@gatech.edu

Abstract

The first who launched the concept of new threshold experiments was J.C. Newman when he introduced the 'compression precracking' and the demonstration that most conservative values of the fatigue thresholds could be obtained with new techniques CPCA and CPLR [1]. The concept of 'cyclic R-curve' established by R. Pippan and co-workers then offered a new way for providing an interpretation of the results shown by Newman and they also used it for describing the so called 'Kitagawa diagram' [2]. In this presentation the historical evolution will be discussed together with the latest applications to AM materials through the model proposed by Chapetti [3, 4]. References [1] Newman Jr, J., Schneider, J., Daniel, A., & McKnight, D. (2005). Compression pre-cracking to generate near threshold fatigue-crack-growth rates in two aluminum alloys. International journal of fatigue, 27(10-12), 1432-1440. [2] J. Maierhofer, R. Pippan, H.-P. Ganser, International Journal of Fatigue 2014, 59 200. [3] Chapetti, M. D. (2022). Fracture mechanics for fatigue design of metallic components and small defect assessment. International Journal of Fatigue, 154, 106550. [4] D. Perghem et al. (2025) Comparison of fatigue life and strength models for defective materials: application to Scalmalloy in different surface conditions. Fatigue Fract. Engng. Mater. Struct., in press.

Biography

Stefano Beretta got his PhD at Kyushu University in 1997 (Supervisor Prof. Y. Murakami) and since then he has been making his career at the Politecnico di Milano, where he became Full Professor in 2002. He teaches the courses on: i) Advanced Machine Design; ii) Structural Reliability of Aerospace components. From 2024 he has been appointed Visiting Professor at Auburn University, National Center for Additive Manufacturing Excellence (NCAME). S. Beretta has a long record of services for ESIS (European Structural Integrity Society): member of ESIS Exco from 2002 to 2010 as Newsletter Editor and webmaster, then Vice-President from 2010 to 2014. He is Chairman of TC24 since 2010, where he organized and hosted many international meetings. He was Chairman and organizer of the 3rd Int. Symposium Fatigue Design and Material, held in Lecco, September 2017 and Co-Chair of ASTM Symposium on Structural Integrity of AM Parts (November 2018) in Washington DC. His main research interests are: fatigue and damage tolerance assessment of railway components together with planning of maintenance and inspections; development of probabilistic methods for defect analysis and assessment under LCF and HCF; the application of DIC to the analysis of fatigue damage and crack closure; ii) the fatigue and fracture of AM materials and metamaterials. In the last years the research activity was devoted to structural integrity assessment of AM components in the aerospace field, a research area where S. Beretta and his group developed a new software benchmarked by the European Space Agency on Al and Ti64 components. He is the inventor of 4 patents in this research topic. In 2019 he was conferred the ASTM Award of Excellence in Additive Manufacturing Research.