PSI - Issue 71

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 71 (2025) 445–452

5 th International Structural Integrity Conference & Exhibition (SICE 2024)

An Implicit Cycle Scale Integrator For Accelerated Fatigue Simulations Manan Ghosh * , Ayub Khan, Pritam Chakraborty Dept. Of Aerospace Engineering, IIT Kanpur, Kanpur -208016, India Abstract The properties of polycrystalline materials are strongly influenced by the underlying microstructural features such as grain size, orientation, grain boundaries and crystal defects. Various methods such as Discrete Dislocation Dynamics (DDD), Crystal Plasticity Finite Element Method (CPFEM), Crystal Plasticity Fast Fourier Transform (CPFFT), etc. are used to simulate the mechanical behaviour of polycrystalline materials at the microstructural level; and numerous examples can be found in the literature which show the fidelity of these methods to capture microstructure sensitive grain-level phenomena in polycrystalline materials in a computationally efficient manner for problems with monotonic loading. However, very limited attempts can be seen for problems involving cyclic loading. This paper presents a comprehensive study using CPFEM to predict crack nucleation in polycrystalline materials under high cycle fatigue. However, due to the large number of cycles till crack nucleation, such analysis can be computationally exhaustive. So, an implicit multi-time scale method involving cyclic scale integration is used in this study. The implicit method used in this study has an advantage over other conventional techniques which assumes periodicity and can provide incorrect response due to the strong non-periodic temporal evolution of plastic variables and localization in the spatial domain. In this method, first fine scale cyclic integration is done for few number of cycles, which is then followed by coarse scale cyclic integration resulting in significant acceleration. A cubic polycrystalline domain is simulated using the method to demonstrate its accuracy and efficiency. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SICE 2024 organizers

Keywords: Crystal plasticity; Microstructure; Polycrystals; Fatigue; Multi-time scaling

1. Introduction Many metals and alloys, such as titanium, nickel, aluminium alloys and steel are widely used in aerospace industry. Though during design it is ensured that the loads experienced by the components don’t result in inelastic deformation and fracture, these materials can undergo cyclic deformation during service which may lead to fatigue failure. More specifically, long-time service failure can happen due to High Cycle Fatigue (HCF), where the stress experienced by

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SICE 2024 organizers 10.1016/j.prostr.2025.08.060 ∗ Corresponding author. Tel.: +91-7432957753. E-mail address: manang23@iitk.ac.in