13th International Conference on the Technology of Plasticity (ICTP 2021): Rob Wagoner Honorary Symposium II
Program Organizers: Glenn Daehn, Ohio State University; Libby Culley, The Ohio State University; Anupam Vivek, Ohio State University; Jian Cao, Northwestern University; Brad Kinsey, University of New Hampshire; Erman Tekkaya, TU Dortmund; Yoshinori Yoshida, Gifu University

Tuesday 10:20 AM
July 27, 2021
Room: Virtual: Room A
Location: Virtual

Session Chair: Glenn Daehn, Ohio State University


Experimental Study on Texture Evolution of Mg-Y Magnesium Alloy in Extrusion: Dayong Li1; Weiqin Tang1; Ding Tang1; Yinghong Peng1; 1Shanghai Jiao Tong University
     Addition of rare earth (RE) elements, such as Y, Ce, Gd, etc., has been used as texture modifiers to improve the formability of Mg alloys. In hot extrusion, the non-RE alloys generally exhibit a {10-10} or {10-10}-{11-20} fiber texture, depending on the recrystallized fraction, whereas the yttrium containing alloys develop weaker texture and a {11-21} fiber component. Recent experiments showed that formation of the {11-20} and {11-21} fiber textures are closely related to continuous dynamic recrystallization (CDRX) of Mg alloys.In this work, a CDRX model is implemented into the visco-plastic self-consistent (VPSC) framework by quantifying the transformation of low angle boundaries into high angle boundaries inside each grain. Furthermore, a phenomenological multiple slip model is integrated into the polycrystal model for better predictions of the recrystallization texture in the extrusion. The effective multiple slip modes that operate during the dynamic recrystallization are determined through simulation.

Nonlinearity of the Crystal Yield Function in the Rate-independent Crystal Plasticity and Its Effect on the Evolution of Anisotropy: Taejoon Park1; Ji Hoon Kim2; Hojun Lim3; Sobhan Alah Nazari Tiji1; Amir Asgharzadeh1; Farhang Pourboghrat1; 1The Ohio State University; 2Pusan National University; 3Sandia National Laboratories
    In typical crystal plasticity framework, the constitutive functions for the slip rate is commonly described by the rate-dependent formulation to avoid the non-uniqueness of the active slip systems due to the interdependency of the slip systems. These rate-dependent models are computationally expensive as these models impose numerically stiff, highly non-linear equations that need to be solved at every integration point. Alternatively, the rate-independent crystal plasticity model uses the crystal yield function to describe the slip deformation and plastic spin by the active slip systems without the non-uniqueness problem. In this study, the effect of nonlinearity between resolved shear stress and slip rate on the shape of the crystal yield function in the formulation of the rate-independent crystal plasticity was rigorously investigated. In addition to the effects of the crystal plasticity model, the influence of the nonlinearity of the single crystal yield function on the evolution of anisotropy for various polycrystalline materials was evaluated.

Predictive Model for the Strength of Self-piercing Riveted Joints: Chanyang Kim1; Wooram Noh2; Myoung-Gyu Lee1; 1Seoul National University; 2Korea Institute of Industrial Technology
    An analytical model for assessing the joint strengths of self-piercing riveted (SPR) sheets was newly proposed in this study. The strength prediction model has parameters associated to the complex geometrical relationship between a rivet and jointed workpieces, and the mechanical properties of both rivet and surrounding materials. The parameters introduced in the model were referred to the results of finite element simulations of the SPR process. The proposed analytical model was validated by comparing the strengths of the SPR jointed tensile-shear (or lap shear) and cross-tension samples with experimental results. The calculated strengths were in good agreements with measured values for various combinations of sheet metals.

A Predictive Strain-gradient Treatment with No Undetermined Constants or Length Scales: G. Zhou1; W.J. Chung2; Eric Homer3; David Fullwood3; M. G. Lee4; J. H. Kim5; H. Lim6; Hussein Zbib7; Robert Wagoner1; 1Ohio State University; 2Korea University; 3Brigham Young University; 4Seoul National University; 5Pusan National University; 6Sandia National Laboratories; 7Washington State University
    A crystal-plasticity FE material model (“SD” model) was previously shown to predict, quantitatively and without arbitrary fit constants, the mechanical behavior of metal polycrystals. Confirmed quantitative predictions were achieved for the Hall-Petch Effect, the Bauschinger Effect, and Pre-Yield Nonlinear stress-strain behavior. The last of these was predicted inherently by the SD model before its existence was known experimentally, thus emphasizing its predictive nature. The SD model incorporated two simplifying fundamental assumptions: 1) only edge dislocations were assumed to be active, and 2) only like-dislocation interactions were considered within a single slip system and grain. Separately, two approximate treatments were adopted to achieve numerical stability: 1) column element-sampling (i.e. only elements along a slip direction to integrate the internal back stress), and 2) implementation of the back stress as a friction stress (opposite in sign and not exceeding the applied local stress).The resulting new General Mesoscale (“GM”) model eliminaes both of the fundamental SD assumptions and both of the approximate SD treatment without invoking any arbitrary parameters. The new GM model retains the predictive nature of SD while permitting solutions for much more general problems and materials. Results for the two methods are compared and a series of numerical tests presented.

On the Newly Proposed Shear Constraint for Orthotropic Plasticity Modeling of Sheet Metals: Jie Sheng1; Mohammed Alharbi1; Wei Tong1; 1Southern Methodist University
    A new shear constraint has appeared recently in the literature as an general restriction on the anisotropic yield criteria of sheet metals. An evaluation of such a shear constraint was carried out in terms of Hill's 1948 quadratic and Gotoh's 1977 quartic yield functions in plane stress. It was shown that the so-call non-physical numerical artifacts of their non-equivalence in pure shear in stress and strain are in fact the intrinsic features of an anisotropic material. The shear constraint itself should be regarded instead as merely a simplifying but overly restrictive assumption of reduced anisotropy without a general physical basis.