Mohammad Hedayatzadeh Roudsari

Ph.D. candidate in Ingegneria Meccanica , 40^th cycle (2024-2027)
Department of Mechanical and Aerospace Engineering (DIMEAS)

mohammad.hedayatzadeh@polito.it

Profile

PhD

Research topic

Experimental Analysis and Numerical Prediction of Fatigue Crack Propagation in High-Speed Train Brake Discs

Tutors

Keywords

Railway engineering / Ingegneria ferroviaria

Finite element analysis / Analisi a elementi finiti

Fatigue and fracture / Fatica e frattura

Machine design / Progetto di macchine

Biography

nng elastic modulus, yield strength, ultimate tensile strength, and ductility. In addition, low-cycle fatigue tests will follow ASTM E606 or its equivalent ISO 12106 standard to characterize the cyclic plasticity behaviour and fatigue resistance of the material under strain-controlled loading conditions. For fatigue crack propagation investigations, the requirements of ASTM E647 will be considered to determine crack growth rates and characterize fracture behavior of material under cyclic loading using Paris law. The experimental results obtained from these tests will serve as the foundation for calibrating and validating the numerical models developed in this project.
One of the key motivations behind this research is the limitation of current industrial fatigue assessment methodologies. In many industries, fatigue life estimation is commonly performed according to the FKM guideline, which primarily focuses on high-cycle fatigue. However, brake discs in modern high-speed trains often experience severe thermo-mechanical loading conditions that induce significant material nonlinearity and localized plastic deformation. Under such circumstances, conventional high-cycle fatigue models do not provide accurate lifetime predictions. Moreover, existing industrial guidelines often struggle to address operating temperatures above 400 °C, even though such temperatures can easily be exceeded during emergency braking events and/or repetitive normal braking actions.
This research aims to establish a more reliable and physically representative procedure for fatigue life estimation of brake discs taking into account the contribution of the full history of operational loads. The proposed methodology is expected to improve the current industrial practice by involving nonlinear material behavior, temperature-dependent material properties, and advanced fracture mechanics concepts into the fatigue assessment process.
The planned research activities also include the numerical simulation of fatigue crack propagation to predict crack growth rate of an existing cracks on brake disc surface. Advanced computational techniques such as the Extended Finite Element Method (XFEM) will be employed to simulate crack propagation without the need for continuous remeshing. By using these advanced simulation tools, the project aims to provide a deeper understanding of crack evolution mechanisms and their influence on the structural integrity and service life of brake discs.
Overall, this research combines experimental material characterization, advanced numerical simulation, and fracture mechanics approaches to develop an improved methodology for fatigue life prediction of high-speed train brake discs. The outcomes of this work are expected to contribute not only to the scientific understanding of thermo-mechanical fatigue behavior but also to the development of safer and more reliable braking systems for future high-speed railway applications.