Innovative Process Design and Processing for Advanced Structural Materials: Mechanics and Modeling
Program Organizers: Ju-Young Kim, UNIST; Jae-il Jang, Hanyang University; Sung-Tae Hong, University of Ulsan; Rongshan Qin, The Open University
Monday 2:00 PM
October 10, 2022
Room: 327
Location: David L. Lawrence Convention Center
Session Chair: Sukbin Lee, UNIST; Ju-Young Kim, UNIST
2:00 PM Invited
Enhancement of Mechanical Properties in Nanoporous Gold: Ju-Young Kim1; 1UNIST
Nanoporous gold (np-Au) is a material with sponge-like structure, composed of continuously connected ligament and pore in nanoscale. Due to low density and high surface area-to-volume ratio, np-Au is applied as catalyst, actuator, and sensor. However, in np-Au, brittleness remains as an issue to be overcome. Brittleness appears as pore generates stress concentration and ligaments are sequentially failed right after crack nucleation. Grain boundary is, also, another cause of stress concentration, so early crack nucleation is observed at grain boundary. Here, we focus on microstructure of np-Au for the enhancement of mechanical properties. Sputtering and rolling process are used to design grain boundary characteristics and grain morphology of Au-Ag precursor alloy. Free corrosion is performed on Au-Ag precursor alloys to fabricate np-Au with diverse ligament/pore. Mechanical properties are measured with multi-scale mechanical test, and influence of microstructure on the mechanical behavior is investigated with SEM, EBSD, and TEM.
2:20 PM Invited
Recent Nanoindentation Studies on Innovative Process Design for Advanced Structural Materials: Zhe Gao1; A-Hyun Jeon1; Jae-il Jang1; 1Hanyang University
Over the past 3 decades, nanoindentation has been used to measure the various mechanical properties of the small volume in a material at much smaller loads and size scales than conventional micro-/macro-indentations. Now, the nanoindentation technique is being considered not only as a characterizing tool but as a promising technology for better understanding of the mechanisms of small-scale mechanical/physical behavior from materials science viewpoints. In this talk, based on our research, we would like to attempt to show which properties can be "additionally" estimated by nanoindentation and then to explain how this becoming-somewhat-old technique can be "still" very useful for developing new structural materials.
2:40 PM
Residual Stress in Steel H-beam Produced by Hot-rolling and QST Investigated by Instrumented Indentation Testing: So-Hyeon Lee1; Eunji Song1; Gyeong-Seok Hwang1; Ju-Young Kim1; 1UNIST (Ulsan National Institute of Science and Technology)
H-beam for marine is produced by hot-rolling and QST(Quenching and Self-Tempering) process for improving low-temperature toughness due to degradation of mechanical properties at low temperature. However, there is a critical issue that residual stress is involved during the production process. Therefore, measurement of residual stress is very important since unexpected failure can occur under the lower applied load than estimated yield strength by residual stress. In this study, we suggest method of estimating residual stress of hot-rolling and QST processed H-beam with non-destructive instrumented indentation testing. we measured pile-up in direction of principal residual and obtained degree of pile-up versus residual stress curve. By using this curve, we could estimate the residual stress of H-beam using pile-up calculated from indentation curve without stress-free sample.This work was supported by Korea Evaluation Institute of Industrial Technology(KEIT) program (20010453, 20011735) funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea).
3:00 PM Invited
Manufacture of Advanced 3D Composites Using a New 3D Weaving Technique and Their Design Using a Neural Network: Hyun Joon Yang1; Kyeong Mo Kang1; Heung-Nam Han1; Woong-Ryeol Yu1; 1Seoul National University
A new manufacturing method was developed to fabricate 3D woven fabric preforms. The new method can solve problems such as delamination and fiber buckling in composites. The new 3D weaving equipment allows for continuous and rapid production of 3D woven fabric preforms with various 3D structures. We manufactured lightweight 3D woven carbon fiber-reinforced composites using the 3D fabric preforms and epoxy resin via the resin transfer molding process. The internal architecture of the 3D composites was evaluated using micro-computed tomography and compared to the 3D modeling results; it was confirmed that 3D fabric preforms with the desired structure can be manufactured successfully by adjusting the weaving conditions of our novel weaving machine. Lastly, A neural network is constructed to relate the elastic constants with the manufacturing parameters and will be used to explore specific 3D woven structure, e.g., the mechanical properties of which exhibit isotropic behavior in 3D.
3:20 PM Break
3:40 PM Invited
Monte Carlo Simulations for Microstructure Evolution via Diffusion: Sukbin Lee1; Youngkyun Son1; Ju-young Kim1; 1Ulsan National Institute of Science and Technology
We present the Monte Carlo simulation methods for the microstructure evolution via various diffusion mechanisms. Firstly, a conservative Monte Carlo algorithm is explained using a two-phase coarsening example. Specifically, the coarsening behavior of nanoporous gold during annealing is compared to the simulation results. As the second topic, we discuss a new Monte Carlo method, developed to simulate the diffusion of the second constituent atom through the polycrystalline matrix. The method incorporates the effect of crystal anisotropy, the difference in grain boundary vs. bulk diffusion and the free energy calculation using a multi-scale approach.
4:00 PM Invited
Improvement of Mechanical Properties of Metallic Materials by Multilayered Structure: Shoichi Nambu1; 1University of Tokyo
Multilayered metal composites have been developed in order to improve the combination of strength and ductility of structural materials. The key concepts for the multilayered metal composites are the control of interfacial toughness between components, fracture toughness of more brittle component as well as layer thickness and so on. Based on the concepts, multilayered steels, consisting of martensitic steels and ductile steels such as austenitic stainless steels or TRIP steels was developed, and achieved improved strength and ductility combinations as well as good formability. For the extensions of the multilayered structure, Mg alloys were also selected for the component in the multilayered metal composites, and higher specific strength and ductility combination was achieved.
4:20 PM
Mechanical Properties and Reliability of Nanolayered Stretchable Interconnect with Nanocrystalline Copper and Ternary Metallic Glass: Gyeong-Seok Hwang1; Eunji Song1; Sohyeon Lee1; Ju-Young Kim1; 1UNIST (Ulsan National Institute of Science and Technology)
In recent, research on stretchable electronics becomes active following the explosive commercialization of flexible electronics. There are several structures for stretchability, the ‘island and interconnect’ structure shows high performance with a simple structure and fabrication process. The conventional high conductive metals can be plastically deformed due to the small elastic deformation limit. It limits the stretchability of the whole stretchable device. Therefore, the development of material should be conducted to commercialize stretchable electronics. Thus, we fabricated nanolaminates with copper and ternary metallic glass by using the sputtering process. The mechanical properties and reliability were measured through in-situ uni-axial tensile testing and the transfer method. Finally, the wireless communicative stretchable sensor was fabricated to demonstrate it for the stretchable electronics.This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIT) (2020R1A5A6017701) and the Ministry of Trade, Industry and Energy (MOTIE, Korea) (20011735)