13th International Conference on the Technology of Plasticity (ICTP 2021): Microstructure & Damage Development III
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
Wednesday 9:15 AM
July 28, 2021
Room: Virtual: Room D
Location: Virtual
Session Chair: Tudor Balan, Arts et Metiers Institute of Technology
Optimization of Lattice Structures for Additively Manufactured Interpenetrating Composites: Jason Allen1; Abdel Moustafa2; Jiahao Cheng1; Xiaohua Hu1; Derek Splitter1; Amit Shyam1; Zachary Cordero2; 1Oak Ridge National Laboratory; 2Rice University
Additively manufactured (AM) metal-metal composites consisting of PrintCasted 316L austenitic stainless-steel lattice structures infiltrated with A356 casting alloy, have recently been developed for use in high energy absorption systems. The ability to intricately form the composite and control the phase distribution give engineers a greater latitude over material property design with proposed applications ranging from static load bearing to dynamic blast containment structures. In this work, new lattice structures are examined within finite element models in order to determine optimized structures for use in energy absorption systems. 316L austenitic stainless-steel lattice structures taking on face center cubic and diamond cubic structures are examined with varying volume fractions (20-60% by volume; the deficit being A356 casting alloy). Particular attention is given to the analysis of localized/non-localized damage initiation and propagation and the role this plays in energy absorption systems.
Full-field strain measurement in multi-stage shear cutting: High-speed camera setup and variational motion estimation: Christoph Hartmann1; Wolfram Volk1; 1Technical University of Munich
Shear cutting process simulation alone already represents a challenging task, but the numerical analysis of multi-stage shear cutting process is even more challenging. Despite the numerical challenges, also the experimental validation of simulation models represents a major challenge, especially regarding the development of the shear affected zone. Therefore, in this work we address the experimental analysis of multi-stage shear cutting as a basis for validation and, moreover, for data-based modelling approaches. We present an in situ test design and measurement setup that preserves the process boundary conditions of shear cutting. An enhanced high-speed optical full-field evaluation method enables local and time-resolved measurement of strain fields and strain rate fields for each shear cutting stage. A mapping of these state variables between the individual cuts enables us to analyze consistently the shear affected zone throughout the entire multi-stage process and thus to characterize the final state of the shear zone experimentally.
Finite Element Simulation of Edge Fracture by Mapping the Shear-induced Ductile Damage into Hole-expansion Simulation: Lei Mu1; Zhe Jia2; Ben Guan2; Yong Zang2; 1New Mexico State University; 2University of Science and Technology Beijing
A ductile fracture (DF) model (uncoupled type, originally presented at ICTP2017), which is endowed with both stress triaxiality and Lode parameter dependence, is selected to define the ductile damage accumulation from hole-blanking to the subsequent hole-expansion for a DP780 sheet. The calibrated DF model yields an asymmetric 3D fracture surface, which can well describe the material’s ductility within a wide range of stress state from simple shear to balanced biaxial tension. The hole-blanking process is simulated using the DF model for different blanking clearances. With the help of a fully integrated simulation framework, the ductile damage induced by hole-blanking is completely mapped into hole-expansion simulation to incorporate the pre-damage field for the sheared edge. We find that after considering the pre-damage field, the accuracy of edge fracture simulation is significantly improved in terms of both hole-expansion ratio and fracture propagation path.
An Extended Ductile Fracture Prediction Model Considering Hydrostatic Stress and Maximum Shear Stress: Zhe Jia1; Lei Mu2; Ben Guan1; Yong Zang1; 1University of Science and Technology Beijing; 2New Mexico State University
To consider the effect of the second principle stress on the ductile fracture prediction, the Mu-Zang model (uncoupled type), which was originally proposed at ICTP2017, is extended by incorporating with a hydrostatic stress term. An aluminum alloy material (Al 6016-T6) is selected with a series of static ductile fracture tests performed on five different specimen geometries, which can cover a wide range of stress state. A robust simulation-experiment approach is adopted to characterize the correlation between the material’s ductility and distinct stress states. The extended model is then calibrated using least squares optimization. The resulting 3D fracture surface demonstrates acceptable deviations from the tested data, manifesting a promising capability of the extended model to describe the ductility of the considered material within a wide stress state range. In addition, the comparison against other representative ductile fracture models further confirms a good prediction performance of the model proposed.
Pushing Forward the Limit of Transformation-induced Plasticity (TRIP) Effect: Nnew Strategies in Mechanically Metastable Alloy Design: Shaolou Wei1; Jaclyn Cann1; Cem Tasan1; 1Massachusetts Institute of Technology
Decades of effort in high-strength alloy investigations has well documented the significant role of strain-induced martensitic transformation in mechanical performance advancement (namely, the transformation-induced plasticity effect, TRIP). Albeit TRIP-assisted alloys benefit from stress delocalization and thereby deformation homogenization resulting from the transformation, the resultant product, martensite, is yet problematic: its extensive defects density and hardenability discrepancy with the adjacent austenite can lead to local embrittlement and hence fracture. In this presentation, we aim to propose three new mechanistic strategies that can potentially overcome this dilemma: first, triggering a plastic strain-induced FCC-HCP-FCC sequential martensitic transformation pathway; second, mitigating blocky HCP-martensite formation via the nucleation of extensive stacking faults; and third, designing superelastic nano-precipitates that reduce martensite retention in cyclic loading conditions. More detailed discussion about the deformation micro-mechanisms and the resultant plastic strain accommodation characteristics will also be provided.