Fatigue in Materials: Fundamentals, Multiscale Characterizations and Computational Modeling: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Additive Manufacturing 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 5:30 PM
March 21, 2023
Room: Exhibit Hall G
Location: SDCC
M-18: Comparison of Defect Structures and Fatigue Behavior of Ti-6Al-4V Specimens from Two Different L-PBF Machines: Mohammad Salman Yasin1; Jia Liu1; Shuai Shao1; Nima Shamsaei1; 1Auburn University
Although additive manufacturing (AM) can be used to form complex functional parts, defects within the built parts can deteriorate their structural integrity significantly. The current study aims to use two different laser-powder bed fusion machines (EOS M290 and Renishaw AM250) to gauge the difference in the formed defects and resultant fatigue behavior of Ti-6Al-4V specimens. All specimens are fabricated in a vertical direction with optimized process parameters from the original equipment manufacturer. Post-fabrication, specimens are stress-relieved at 700°C for an hour and then furnace cooled. Finally, the specimens are machined to geometry and size according to ASTM E606. The internal defect structure within the machined specimens is inspected using X-ray computed tomography. Strain-controlled fatigue tests are conducted and fractographic analysis is conducted to analyze the failure mechanism. Finally, the relationship between the defects and corresponding fatigue life is analyzed for both machines.
M-19: Creep and Dwell Fatigue Studies of Ti-7Al with High-Energy Diffraction Microscopy and Acoustic Emission Measurements: Yuefeng Jin1; Amlan Das2; Wenxi Li1; Katherine Shanks2; Ashley Bucsek1; 1University of Michigan; 2Cornell High Energy Synchrotron Source
Though plasticity is traditionally modeled as a smooth process in space and time, in past two decades, studies has shown that it can also occur in localized bursts known as intermittent plasticity. Such bursts can happen not only after but also before the macroscopic yield. In this work, two Ti-7Al samples were loaded under creep and dwell fatigue conditions, respectively, and grain-scale stresses and plastic deformation activity were tracked using combined far-field high-energy diffraction microscopy (ff-HEDM) and acoustic emissions (AE) measurements. The results reveal the initiation, evolution, and effects of intermittent plasticity and how intermittent plastic events can be observed in ff-HEDM and AE data sets. This experiment shows how ff-HEDM and AE can be integrated to spatially and temporally resolve local plasticity events to design creep- and fatigue-resistant alloys for the future.
M-20: Fatigue Behavior of 304SS using Synchrotron X-ray Tomography and Diffraction: Ryan Schoell1; Li Xi1; Harvey West1; Peter Hosemann2; Jun-Sang Park3; Peter Kenesei4; Jonathan Almer4; Zeev Shayer5; Djamel Kaoumi1; 1North Carolina State University; 2University of California Berkeley ; 3Argonne National Laboratory ; 4Argonne National Laboratory; 5Colorado School of Mines
A microstructural study on the effect of fatigue on four-point bend specimens of three variations of 304 stainless steels (Commercial 304, 304H, and 304L) was investigated using synchrotron x-ray tomography and diffraction followed by transmission electron microscopy. X-ray tomography revealed the formation of the fatigue-induced microvoids and cracks to varying degrees in the different alloys. The diffraction data was used to quantify the amount of deformation-induced martensite found after fatigue in all samples. Transmission electron microscopy evidenced the role of the precipitates/inclusions on the microvoid formation which was found to depend on the type of precipitate. The shape of the precipitates/inclusions was also found to influence the microvoid shape (elongated vs. spherical)
M-21: Fatigue Crack Initiation and Growth Behaviour Within Various Notch Geometries in the Low-cycle Fatigue Regime of FV566 In-service Steam Turbine Blade Material: Benjamin Cunningham1; Philippa Reed1; Ara Khodavirdi1; 1University of Southampton
Plain bend bars made from FV566 martensitic stainless steel were extracted from the root of ex-service power plant turbine blades and several industry relevant notches introduced. Some of the samples were shot peened. The notched bend bars were loaded plastically in the low cycle fatigue regime and FE modelling carried out to investigate the effects of changing notch geometry combined with shot peening on fatigue behaviours such as crack initiation, short crack growth and coalescence. Shot peening damaged the notch surface accelerating initiation behaviours but had a lifetime extending effect by retarding short crack growth in all tested notch geometries. At total strain range higher than 1.2%, the lifetime extension benefit from shot peening was diminished due to compressive residual stress relaxation in the notch stress field. Notch geometry was found to have no notable difference on fatigue life when tested at identical strain ranges.
M-22: Fatigue Evaluation of Additively Manufactured 316L Stainless Steel: Khandokar Abu Talha1; 1University of Southmapton
Additively manufactured 316L stainless steel (SS) is of interest to many industries but limited studies have been conducted to understand the material’s fatigue behaviour. A systematic approach was taken to understand the fatigue behaviour of laser powder bed fusion processed 316L SS. Preliminary studies were conducted to observe the fatigue behaviour of bend bar specimens to understand crack initiation, propagation and coalescence mechanism and key parameters (e.g. defects, porosity and surface roughness) affecting them. Especially, the role of porosity in crack initiation has been investigated in detail. Further studies have been conducted to compare the microstructure of these failed specimens in terms of subcellular structure, grain boundary distribution and localised strain deformation. Additional studies were conducted to understand the role of processing parameters such as scanning strategy, build direction and geometry size scale on the microstructure, which can provide valuable insight to understand the crack initiation and propagation mechanism.