Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session V
Sponsored by: TMS Extraction and Processing Division, TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Materials Characterization Committee
Program Organizers: Arul Kumar Mariyappan, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Olivia Jackson, Sandia National Laboratories
Wednesday 8:30 AM
March 22, 2023
Room: Aqua 311A
Location: Hilton
Session Chair: Ram Devanathan, Pacific Northwest National Laboratory; Carlos Tome, Los Alamos National Laboratory
8:30 AM Invited
Elasto-visco-plastic Crystallographic Modeling of Thermal Ratcheting in Uranium: Carlos Tome1; Youngung Jeong2; 1Los Alamos National Laboratory; 2Changwon National University
Alpha-uranium crystals exhibit orthotropic symmetry and very anisotropic elastic, plastic and thermal properties. As a consequence, high internal stresses induced in uranium aggregates subjected to thermal cycling are relaxed plastically. This induces pronounced cumulative dimensional changes (ratcheting) in textured aggregates. Only crystal-based models, accounting for slip, twinning and anisotropic elastic and thermal moduli can realistically tackle the simulation of the ratcheting process. In this work we utilize an incremental elasto-visco-plastic self-consistent (ΔEVPSC) crystal plasticity formulation to do so. The plastic constitutive law is based on a dislocation-density-evolution hardening model, and includes twinning effects. The model is used to simulate thermal ratcheting of clock-rolled uranium between 800 K and 300 K. The dependence of ratcheting on texture is studied. The evolution of internal strains is compared against neutron diffraction results and are used as an indicator of slip and twinning systems involved.
9:00 AM
Experimental and Modeling Study of Steel Bending and Springback Using an Elasto-visco-plastic Self-consistent Polycrystal Model Interfaced with a Finite Element Code: Youngung Jeong1; Mooyeong Joo1; Bohye Jeong1; Jaeseong Lee1; Dirk Steglich2; Frederic Barlat2; Carlos Tome3; 1Changwon National University; 2Pohang University of Science and Technology; 3Los Alamos National Laboratory
Springback following plastic forming is a technologically critical effect and predicting it requires precise hardening and back stress models. In this work we utilize an incremental elasto-visco-plastic self-consistent (ΔEVPSC) crystal plasticity formulation, implement it as a user material subroutine (UMAT) in the FE solver Abaqus/standard, and apply it to a mild steel sample. The hardening behavior is described using a dislocation-density evolution hardening model. An empirical back-stress contributes to the Bauschinger effect, and creep contributes to stress relaxation. The model parameters were calibrated using a set of uniform mechanical tests. The crystal plasticity model was used to predict the springback that occurs after 3-point-bending in samples that were previously prestrained. The predictions are compared with experimental result. The results indicate that the crystal plasticity FE simulation can quantitatively capture the effect of prestrain on the springback.
9:20 AM
Size Effect in Polycrystalline Nickel-Based Superalloys in The Presence of a Free-Surface: Identification of the Crystal Plasticity of Surface Grains Versus Core Grains: Damien Texier1; Vincent Velay2; Antonio Castro-Moreno3; Daniel Monceau4; Eric Andrieu4; 1CNRS - Institut Clément Ader; 2Institut Clément Ader - UMR CNRS 5312; 3IRT Saint-Exupery; 4CIRIMAT - UMR CNRS 5085
Surface effects on the mechanical response of polycrystalline materials are particularly important for miniaturized components due to their high surface-to-volume ratio. Different grain-size microstructures and metallurgical states of an Alloy 718 Ni-based superalloy were purposely produced to investigate the influence of these microstructural features on the polycrystalline-to-multicrystalline transition (PMT). Ultrathin tensile specimens were thinned down (thickness of 15 to 500 µm) then tested. The macroscopic tensile properties were found insensitive to the specimen thickness beyond a certain thickness. Below the PMT, the yield strength, ultimate tensile strength and work-hardening decrease with the specimen thickness. This loss in mechanical properties is mainly attributed to a significant decrease in dislocation density within surface grains compared to core grains due to dislocation escape at the free-surface. A mean-field homogenization crystal plasticity model using fraction of core grains and surface grains was implemented for the identification of the mechanical behavior of miniaturized specimens.
9:40 AM
On the Selection of Flow Rule and Slip System in Crystal Plasticity Simulations of Cyclic Deformation in Martensitic Steels: Tim Fischer1; Carl Dahlberg1; Peter Hedström1; 1KTH Royal Institute of Technology
The prediction of microscopic fatigue crack initiation in high-strength steels requires constitutive models that reflect the local stress and strain fields as accurately and efficiently as possible. Only few research works have been devoted to the investigation of the power law-based flow rule (Hutchinson or Chaboche) and the slip systems ({110}<111> and {112}<111>) in crystal plasticity simulations of body-centred cubic metals under cyclic loading. This paper, aims to shed some light on these two effects by studying a lath martensite-based high-strength steel under varying loading conditions. It can be shown that the commonly used Hutchinson and Chaboche flow rule provide comparable predictions. However, using the Hutchinson setting increases the computational performance considerably. If plastic deformation is assumed not only on the slip systems {110}<111>, but also on the {112}<111> type, a clear redistribution of the local stresses occurs. The Hutchinson flow rule performance remains less affected by this.
10:00 AM Break
10:20 AM Invited
Alloy Rupture Strength Prediction Using Machine Learning and Microstructure Analysis: Ram Devanathan1; Osman Mamun1; Mohammad Taufique1; William Frazier1; Arun Sathanur1; Keerti Kappagantula1; Jing Wang1; Marissa Masden1; Madison Wenzlick2; Kelly Rose2; 1Pacific Northwest National Laboratory; 2National Energy Technology Laboratory
We present a machine learning approach to predict the creep rupture strength of 9-12% Cr ferritic martensitic steels and austenitic stainless steels using curated experimental datasets. We evaluated three algorithms, namely Gaussian Process Regression, Neural Network, and Gradient Boosted Decision Tree (GBDT). We identified the most important features that govern the rupture strength for these two classes of alloys. The GBDT algorithm showed excellent predictive performance for unseen test data as shown by correlation coefficient better than 0.95 for both alloy datasets. To further improve the predictive power by including microstructural features, we have evaluated the potential of several deep learning models to identify grain boundaries in realistic steel microstructures We also used a topology-based loss function to improve recognition of grain boundaries, which is a challenging task. Our approach, when used with high quality training data, can reduce the need for a time consuming and expensive mechanical test campaign.
10:50 AM
Damage Accumulation during Creep in Metals: The Role of Microstructure: Andrea Rovinelli1; Laurent Capolungo1; Ricardo Lebensohn1; 1Los Alamos National Laboratory
The creep rupture life of metals is conditioned both by stress and temperatures. Further, it is known to vary significantly in alloys of similar grades; thus causing large uncertainties in the design of metallic structures. The work presented here introduces a new spectral based model predicting the primary, secondary and tertiary creep response of structural alloys. The model leverages the EVPFFT-based mechanical solver and describes plastic relaxation using a crystal plasticity formalism accounting for dislocation glide and climb. Plasticity resulting from vacancy diffusion is also modeled. Critically, the framework introduces a new mechanical damage formalism that can track nucleation of cavities and their growth. The effect of cavities is accounted for by a crystallographically resolved extension of the damage formalism proposed by Leblond Perrin and Suquet. The creep model is applied to a Zirconium alloy and found to satisfactorily predict the effects of temperature, stress, and microstructure variability.
11:10 AM
Radiation Damage Defect Characterization Using In-situ Positron Spectroscopy: Rasheed Auguste1; M. Oskar Liedke2; Maik Butterling2; Blas Uberuaga3; Farida Selim4; Peter Hosemann1; 1University of California, Berkeley; 2Helmholtz-Zentrum Dresden - Rossendorf; 3Los Alamos National Laboratory; 4Bowling Green State University
Radiation induced defects in materials originate with the energy transfer from an incoming particle to a lattice and the displacement of the atoms from their original location. Larger defects evolve from the resulting non-equilibrium point defects created surviving the initial events as a function of dose rate, material, and temperature. Positron annihilation spectroscopy is a unique, nondestructive technique to investigate these small defects in materials difficult to investigate by other tools. Even though dynamic point defect populations are captured in rate theory, this work presents direct experimental validation of non thermal equilibrium vacancies during irradiation. In-situ positron annihilation spectroscopy was used to find direct evidence of the generation of non-equilibrium defects in silicon.
11:30 AM
Application of Constant Contact Pressure Nanoindentation on Room Temperature Creep: Reliability and Advantage: Lizhong Lang1; Zhiying Liu1; Yu Zou1; 1University of Toronto
Creep is a serious concern reducing service life of metallic components. Two prevalent indentation methods, constant strain rate (CSR) and constant load (CL), have been applied to study small-scale creep behavior or strain rate sensitivity. However, CSR is time-consuming low strain rates, and CL shows low repeatability. Here, we modified a newly proposed indentation creep method, constant contact pressure (CCP) method. This method is to control the contact pressure for a time after loaded to a depth. The effectiveness and repeatability of the CCP method have been demonstrated by measuring the indentation creep rate of near-α titanium (Ti) and pure tin (Sn) at room temperature. A segmented creep depth vs. time relation are observed, and these results are compared with creep behavior in bulk counterpart. The new CCP method can also extend to measure creep behaviors of a large range of materials.