Fatigue in Materials: Fundamentals, Multiscale Characterizations and Computational Modeling: Multiscale Modeling Approaches to Improve Fatigue Predictions
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: J.C. Stinville, University of Illinois Urbana-Champaign; Garrett Pataky, Clemson University; Ashley Spear, University of Utah; Antonios Kontsos, Drexel University; Brian Wisner, Ohio University; Orion Kafka, National Institute Of Standards And Technology

Tuesday 8:00 AM
March 1, 2022
Room: 254B
Location: Anaheim Convention Center

Session Chair: Antonios Kontsos, Drexel University


8:00 AM  Invited
PRISMS-fatigue: A General Framework for Fatigue Analysis in Polycrystalline Metals and Alloys Using the Crystal Plasticity Finite Element Method: Mohammadreza Yaghoobi1; Krzysztof S. Stopka2; Aaditya Lakshmanan1; Veera Sundararaghavan1; John E. Allison1; David L. McDowell2; 1University of Michigan; 2Georgia Institute of Technology
    A novel open source framework that enables simulation-based comparisons of microstructures with regard to fatigue resistance is presented here for polycrystalline metals and alloys. The framework uses the crystal plasticity finite element software PRISMS-Plasticity as its microstructural analysis tool. This framework provides a highly efficient, scalable, easily modified, and easy-to-use ICME community platform. The performance and flexibility of this framework is demonstrated with various examples, including effects of crystallographic texture, grain morphology, strain state, free surface effects, and choice of FIP on the driving forces for fatigue crack formation. The results show that the multilevel parallelism scheme of PRISMS-Fatigue framework is more efficient and scalable than ABAQUS for microstructure instantiations having over one million degrees of freedom. The links between the PRISMS-Fatigue and experimental characterization techniques and virtual microstructure generators are elaborated. PRISMS-Fatigue is also linked to the information repository of Materials Commons to store and share inputs and results.

8:30 AM  
Microstructure Effects on the Extreme Value Fatigue Response of FCC Metals and Alloys: Effects of Sample Size and Grain Neighborhood: Krzysztof Stopka1; Mohammadreza Yaghoobi2; John Allison2; David McDowell3; 1Purdue University; 2University of Michigan; 3Georgia Institute of Technology
    Determining the size of representative volume elements (RVEs) for fatigue related applications is difficult. A sufficient volume of material should be addressed to capture the grain/phase heterogeneity that leads to fatigue crack formation at “hot spot” grains. Consequently, single microstructure RVEs are largely computationally intractable and elusive. The present work leverages the open-source PRISMS-Fatigue framework to examine the convergence of extreme value distributions of Fatigue Indicator Parameters (FIPs) in progressively larger polycrystalline microstructures using crystal plasticity finite element method simulations. The results are compared to the traditional method in which ensembles of statistical volume elements (SVEs) are simulated to build up statistics intended to approximate those of a larger volume of material. The RVE size is closely related to the extent of grain nearest neighbor interactions. Accordingly, the sensitivity of local micromechanical response at fatigue hot spot grains is quantitatively investigated by systematically varying the orientations of nearest neighbor grains.

8:50 AM  
Mechanistic Short Crack Growth in Ni Single Crystals: A Study of the Crack Paths and Growth Rates in γ-γ' Microstructure: Vasilis Karamitros1; Duncan MacLachlan2; Fionn Dunne1; 1Imperial College London; 2Rolls-Royce plc
     Short crack growth (SCG) in single crystal Ni has been studied at temperatures of 25°C and 700°C, reflecting γ' anomalous yield strengthening. CP-XFEM modelling [1] is employed explicitly representing γ-γ' phases in which crack paths are confined to octahedral slip planes with highest slip, and growth rates controlled by critical stored energy density (Gc). At 700°C and low applied stress, crack paths are predicted to be confined within γ channels, since crack tip stored energy density remains highest within the γ phase. With increasing crack length and associated higher crack tip stresses, cracks are predicted to shear through the γ'. Changing the γ' phase Gc allows the systematic analysis of resulting crack paths and rates which are evaluated against experiments [2]. [1] D. Wilson et al. JMPS 124, 827 (2019).[2] L. Eisenhut et al. IJF 94, 131 (2017).

9:10 AM  
How Do Heterogeneous Dislocation Distributions Determine the Long-range Internal Stress: Yejun Gu1; Jaafar El-Awady2; 1IHPC/Johns Hopkins University; 2Johns Hopkins University
     We present a new theory for the origins of long-range internal stresses (LRIS) due to heterogeneous dislocation distributions in metals, to understand material fatigues. This theory proposes that the prismatic loop concentration predominantly determines the LRIS. If the hard regions (having high dislocation density) mainly consist of vacancy loops, they are in tension, while the soft regions (having low dislocation densities) are subject to compressive stresses. The opposite is also true. This theory is an extension from the influential composite model by Mughrabi that attributes the LRIS to interfacial geometrically necessary dislocations. Furthermore, this theory has been successfully applied to the cases of dislocation cell structures that formed under different loading conditions in three-dimensional discrete dislocation dynamics simulations.

9:30 AM Break

9:50 AM  Invited
Discovery of a Reciprocal Relationship in Fatigue between Stress-life (S-N) Behavior and Fatigue Crack Growth Behavior: K. S. Ravi Chandran1; 1University of Utah
    The discovery of a reciprocal relationship between the stress-life (S-N) behavior (or curve) and fatigue crack growth behavior (or curve) is presented. This relationship is simple, mathematically symmetric and has been developed from the author’s physical model of S-N fatigue behavior through heuristic arguments. Remarkably, the reciprocal relationship allows the direct conversion of S-N curve into FCG curve and vice-versa. This is shown to be valid for cyclic fatigue of metals, ceramics and polymers. What this means is that the fatigue crack growth data determined from one fracture mechanics specimen would allow the construction of the S-N data without time consuming multi-specimen S-N fatigue testing. Extensive experimental fatigue data of metals, ceramics and polymers have been used to demonstrate the validity of this relationship. The relationship cannot be framed from the crack-centric fracture-mechanics. Rather, the net-section-centric approach leads to a more powerful way of characterizing fatigue behavior of materials.

10:20 AM  
Prediction of Critical Stress by Anisotropic Calculation of Dislocation Core-width: Orcun Koray Celebi1; Ahmed Sameer Khan Mohammed2; Jessica Anne Krogstad2; Huseyin Sehitoglu2; 1University of Illinois at Urbana-Champaign ; 2University of Illinois at Urbana-Champaign
    Fatigue threshold is predominantly dictated by the Critical Resolved Shear Stress (CRSS) for dislocation glide at the front of short cracks. Existing approaches cannot truly predict the CRSS (consequently fatigue resistance) due to inherent empiricism in handling the core of the dislocation. We propose an ab-initio predictive model for the CRSS by determining the dislocation core-width which is determined by minimization of total energy comprising elastic and misfit energies. The elastic strain-energy is calculated by numerical integration of anisotropic strain-fields derived from the Eshelby-Stroh formalism and the misfit energies are determined from the fault energies of the slip system. The predictive efficacy of the approach is demonstrated by estimating CRSS for several metals and alloys showing good agreement with the available experimental data. The model establishes the influence of character of the dislocation for the first time, along with the relative importance of the unstable and stable stacking fault energies.