Tobias Pertoll graduated in Mechanical Engineering at Graz University of Technology in 2019. He is actually a third-year PhD candidate in mechanical engineering at Graz University of Technology working as university assistant with Prof. Martin Leitner at the Institute of Structural Durability and Railway Technology. His main research focuses on the fatigue assessment of deep rolled railway axles based on numerical analysis with the aim to optimize the post treatment process holistically. In addition, research in the area of fatigue behaviour of welded joints is ongoing. Besides research work, he teaches in the field of finite element analysis and structural durability assessment at Graz University of Technology. During his studies focusing on vehicle technology he gained valuable practical experience in the field of automotive and rail vehicle technology working on specific projects and companies. During his studies, he completed successfully the academic education to become an International Welding Engineer.
Deep rolling is a powerful tool to increase the fatigue life of railway axles. The application introduces compressive residual stresses into the area near the surface, which are the most effective positive influence on the fatigue behaviour and the remaining service life in the presence of a crack.
This paper investigates the remaining service life of deep rolled railway axles. Previous research studies are used as basis for this work whereas, firstly, an elaborated crack growth model for the application on railway axles applicable for common railway axle steels was developed. This model is based on the NASGRO equation considering crack closure as well as load sequence effects and local residual stress conditions. Secondly, a numerical deep rolling simulation model validated with experimental residual stress measurements to determine the introduced residual stress state and to investigate the influence of various process parameters such as deep rolling force, feed rate, friction coefficient and tool geometry on the introduced residual stress state.
In this study, the comprehensive outcome of both studies is connected in order to evaluate and compare the residual fatigue life with the presence of different deep rolling-induced in-depth residual stress distributions at the railway axles. The crack growth study involves combinations of different deep rolling parameters, load amplitudes as well as initial crack sizes and compares the residual life results. Finally, the study further leads to an evaluation of optimal deep rolling parameters in regard to the remaining service life which facilitates an elaborated fatigue design of railway axles.
|Room 6||Thursday 30th November||14:30-15:00||Tobias Pertoll|
S06-2 Damage tolerance and fatigue life
18 - Residual life assessment of deep rolled railway axles considering the effect of process parameters