Session: CT-07-01 Computational Applications in Fatigue, Fracture, and Damage Mechanics

Paper Number: 106419

106419 - Development of a Numerical Framework for Microstructure Sensitive Fatigue Life Investigations 

Mechanical properties of modern steels grades gain of importance in our society. Developing materials that are stronger, last longer and work more efficient is the major key for less CO₂ emissions in proceeding industry branches. However, especially the tuning of mechanical properties comes with the cost of very complex microstructures. For numerical investigations of microstructures Representative Volume Elements (RVEs) are often used. Common RVE generators show a certain lack of accuracy when it comes to the morphological description of the microstructure. Our recent studies, however, show that morphological properties can be the major causes for damage initiation. This leads to the assumption that many studies in the field of microstructure modeling oversimplify the problems using homogenization. Which again leads to a lack of understanding the reasons for damage initiation. Especially microstructural features such as phase boundaries with a hardness gradient have a significant influence on properties such as fatigue life.  Also, the surface roughness and residual stresses in the surface of the material have a significant influence on these properties.

Therefore, in this study a framework is presented that tackles the modelling of modern microstructures using a new RVE generator called DRAGen (Discrete Rve Automation and Generation), and a strategy for the numerical investigation of the influence of the surface roughness and residual stresses on the fatigue life and endurance is proposed. The proposed framework consists mainly of three parts: microstructural characterization, generation of statistical RVEs and the investigation of micromechanical behavior under extrinsic loading conditions. The microstructural characterization is supported by neural networks while the generation algorithms of the RVEs uses the information generated by those neural networks. The mechanical behavior of these RVEs is simulated with Abaqus.

The results of this study show that the new RVE generator can produce very realistic microstructure models on a statistical basis with an unprecedented level of detail. It is also possible to introduce features such as surface roughness and residual stresses into the simulations of DRAGen RVEs. This leads to very robust fatigue life estimates and provides a good basis for numerical optimization of the structural integrity of safety-related components.

Presenting Author: Manuel Henrich RWTH-Aachen University

Presenting Author Biography: Manuel Henrich got his master’s degree in Materials Engineering at RWTH-Aachen University where he is currently part of the group "Integrity of Materials and Structures" at the steel institute under the supervision of Prof. Münstermann. His main focus is the development of a new RVE-Generator called "DRAGen" as well as the integration of DAGen into a Framework for microstructure sensitive fatigue calculations based on crystal plasticity models.

Authors:

Manuel Henrich RWTH-Aachen University
Michael Dölz RWTH-Aachen University
Sebastian Münstermann RWTH-Aachen University