Fatigue in Materials: Fundamentals, Multiscale Characterizations and Computational Modeling: Advanced Experimental Characterization of Microstructurally Driven Fatigue Behavior
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

Monday 2:00 PM
February 28, 2022
Room: 254B
Location: Anaheim Convention Center

Session Chair: Garrett Pataky, Clemson University


2:00 PM  Invited
NOW ON-DEMAND ONLY - Coupled Characterization Approaches for Fatigue Assessment of High-strength Steel and Light Metal Alloy Structures : Alexander Koch1; Nikolas Baak1; Jochen Tenkamp1; Anke Schmiedt-Kalenborn1; Frank Walther1; 1TU Dortmund University
    High-performance structures based on high-strength steels and light metal alloys offer huge potential for increasing capability and efficiency for automotive and aerospace industries. Advanced characterization techniques – based on coupled testing strategies and measurement methods – are investigated to pave the way for development acceleration and market acceptance, especially for innovative material systems with regard to high-performance and long-term sustainability under service loading. For high-strength steels, a monitoring and control of the production process by micro-magnetic evaluation offers the possibility to detect the development of various local material properties during drilling, milling, and forming processes. For light metal alloys processed by conventional or additive manufacturing, a damage tolerant design for fatigue applications can be ensured by defect detection techniques like computed tomography. The defect distribution can be combined with simulation approaches in order to estimate the effect of defects on the fatigue behavior and damage tolerance.

2:30 PM  
Slip Localization, Fatigue Strength and Microstructural Effects in Polycrystalline Alloys.: J.C. Stinville1; T.M. Pollock2; 1 University of Illinois Urbana-Champaign; 2University of California-Santa Barbara
    Statistical analyses of slip events for a large collection of polycrystalline materials with face-centered cubic, hexagonal close-packed and body-centered cubic structures have been performed. Relations between the yield and ultimate tensile strength, fatigue strength and the slip character are uncovered. Of main importance, the highest amplitude of the localization by slip that develops during early cycling is observed to control the fatigue life in the very high cycle fatigue regime. The locations at the grain structure scale where the highest amplitude slip localization developed are investigated. Specific grain configurations that develop during processing of metallic materials are observed to promote slip localization over a range of metallic materials.

2:50 PM  Invited
Direct Observations and Characterization of Crack Closure during Microstructurally Small Fatigue Crack Growth via In Situ High-energy X-ray Characterization: Michael Sangid1; Priya Ravi1; Diwakar Naragani1; Peter Kenesei2; Jun-Sang Park2; 1Purdue University; 2Argonne National Laboratory
    Direct observation of the crack closure mechanism of a naturally occurring, tortuous, 3D microstructurally small fatigue crack (SFC) are presented based on in situ high-energy X-ray diffraction experiments. These techniques provide the 3D microstructure and micromechanical response in the vicinity of the crack front. Specifically, the evolution of the stress state was analyzed for grains at the crack tip during cyclic loading and compared to observations of crack opening/closing events enabled by tomography. From this analysis, three grains that displayed different degrees of crack closure were further investigated, based on the orientation of the crack relative to the grains and the associated modality of crack growth. The stress normal to the crack plane and the associated degree of Mode I crack behavior were correlated with events of the crack opening earlier during the loading cycle. The mechanisms governing crack closure are discussed based on the associated grain-scale stress state.

3:20 PM Break

3:40 PM  Invited
Tracking Crystal-scale Cyclic Plasticity in Inconel 718 Using In Situ Loading and High Energy X-rays: Dalton Shadle1; Kelly Nygren2; Matthew Miller1; 1Cornell University; 2Cornell High Energy Synchrotron Source
    Fatigue crack initiation in ductile polycrystals during low cycle fatigue conditions depends strongly on the plastic strain history experienced by each crystal. In this work, a High Energy X-ray Diffraction Microscopy (HEDM) experiment conducted at the FAST beamline at the Cornell High Energy Synchrotron Source (CHESS) was used to quantify the evolving 3D stress state and intragrain lattice orientation of each crystal within a deforming Inconel 718 sample subjected to fully reversed cyclic loading. Correlation of the orientation distributions to the aspects of the evolving stress states - such as stress triaxiality – is used to understand the potential for crack initiation. Connections to crystal plasticity simulations are discussed.

4:10 PM  
Grain Reorientation and Stress-state Evolution during Cyclic Loading of an α-Ti Alloy below the Elastic Limit: Rachel Lim1; Darren Pagan1; Joel Bernier2; Paul Shade3; Anthony Rollett4; 1Pennsylvania State University; 2Lawrence Livermore National Laboratory; 3Air Force Research Laboratory; 4Carnegie Mellon University
    Local stress state and grain orientation evolution are tracked through 200 cycles of loading at 90% of Ti-7Al’s yield strength using high energy x-ray diffraction microscopy to elucidate the microscale plastic deformation that occurs during nominally elastic macroscopic cyclic loading. Significant changes in the stress state occur during the first loading cycle to relieve initial microscale residual stresses. Additionally, examination of the aggregate of grains through subsequent cycles shows continuous lattice reorientation and evolution of von Mises stresses within grains despite the macroscopic loading remaining below the elastic limit. Lattice orientation and maximum resolved shear stresses applied to grains are found to highly influence the activation of specific slip systems and, as a result, the direction of lattice reorientation.

4:30 PM  
In-situ Diffraction Studies of the Fatigue-crack-growth Behavior in a TRIP-assisted Advanced High Strength Steel: Di Xie1; Yi Yang1; Lu Huang2; Yang Ren3; Yanfei Gao1; 1University of Tennessee Knoxville; 2United States Steel Corporation; 3Argonne National Laboratory
    Steels assisted by transformation-induced plasticity (TRIP) have been developed and attracted great attention. To date, the roles of alloy design and martensite transformation kinetics on fatigue behavior are mostly investigated through post-mortem metallographic characterizations, which result in the limited information to quantify the contributions of the TRIP effect into fatigue resistance. The occurrence of phase transformation from the retained austenite into martensite in the plastic zone ahead of the crack may lead to the crack closure and reduce the fatigue crack growth rate. In this work, we exploit in-situ synchrotron X-ray diffraction to provide the high-resolution strain mapping near a fatigue tip in the TRIP-assisted XG-3 steel with both high-spatial and strain resolution. These in-situ, nondestructive measurements can yield information about phase transformation and lattice strains, which will allow us to bridge the gap between microscopic failure processes and macroscopic fatigue crack growth properties.