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Anisotropic Materials Group

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About us

We strive on the creation of advanced materials that actively utilize anisotropy, multi-layering, and compositing and that break through the limits of characteristics (toughness and hydrogen embrittlement resistance etc.) of conventional isotropic and homogeneous materials. Towards the goal, we understand the tissue and structure of organisms, evaluate and analyze anisotropic materials and heterogeneous microstructures, and will work in a research style that feeds back the results into the process.

Specialized Research Field

Toughening of structural materials
High tough as well as high strength is always demanded from society because structural metallic materials become brittle due to strengthening. Toughness rather than strength is required for most of the structural materials. We aim at improving both toughness and strength simultaneously through systematically investigating the relationship between toughness and microstructure, in particular, by referring to the complex hierarchical structure of organisms (biomimetic approaches), rather than referring to the conventional design concept of homogeneous and isotropic materials.

Tadanobu Inoue, Yuuji Kimura. Effect of Delamination and Grain Refinement on Fracture Energy of Ultrafine-Grained Steel Determined Using an Instrumented Charpy Impact Test. Materials. 15 [3] (2022) 867 10.3390/ma15030867

Tadanobu Inoue, Rintaro Ueji. Improvement of strength, toughness and ductility in ultrafine-grained low-carbon steel processed by warm bi-axial rolling. Materials Science and Engineering: A. 786 (2020) 139415 10.1016/j.msea.2020.139415

Biomimetics
Research that seeks to mimic the complex hierarchical structures of organisms is often conducted as a technique for breaking through the characteristic limits of materials. ”Biomimetics” research has received increasing interest due to the unusual mechanical and functional properties and complex hierarchical structures these materials possess. Most animals have force several times their body weight, but in animals with body weight in the range of 1 kg, the pinching force of the crustaceans greatly exceeds the force of other animals. Therefore, the exoskeleton of crustacean claws needs to be strong and tough and has a complex structure such as a twisted plywood pattern that is not found in general metallic structures. Understanding such tissue and structures will lead to the development of materials with characteristics not found in conventional metallic materials.

Tadanobu Inoue, Yuka Hara, Koji Nakazato. Mechanical Resistance of the Largest Denticle on the Movable Claw of the Mud Crab. Biomimetics. 8 [8] (2023) 602 10.3390/biomimetics8080602

Tadanobu Inoue, Takanobu Hiroto, Yuka Hara, Koji Nakazato, Shin-ichiro Oka. Tissue structure and mechanical properties of the exoskeleton of the huge claws of the mud crab, Scylla serrata. Journal of Materials Science. 58 [3] (2023) 1099-1115 10.1007/s10853-022-08083-x

Tadanobu Inoue, Shin-ichiro Oka, Toru Hara. Three-dimensional microstructure of robust claw of coconut crab, one of the largest terrestrial crustaceans. Materials & Design. 206 (2021) 109765 10.1016/j.matdes.2021.109765

Development of ultra-high strength steels
Fail-safe steels with ultra-fine elongated grain structures have been demonstrated to exhibit significantly superior strength and toughness balance, compared to conventional steels balance due to their hierarchical, anisotropic grain structures. We aim to create advanced ultra-high strength steels based on microstructure control for fail-safe steels. Focusing on delayed fracture, which is a bolt-neck in the social implementation of ultra-high strength steels, we will elucidate the mechanism of delayed fracture of ultra-high strength steels with anisotropic microstructures and then develop ultra-high strength steels with excellent delayed fracture resistance.

Yuuji Kimura, Taku Moronaga, Tadanobu Inoue. Influence of Thermomechanical Treatment on Delayed Fracture Property of Mo-Bearing Medium-Carbon Steel. ISIJ International. 62 [2] (2022) ISIJINT-2021-407 10.2355/isijinternational.isijint-2021-407

Yuuji Kimura, Tadanobu Inoue. Influence of Annealing on Delamination Toughening of Mo-Bearing Medium-Carbon Steel with Ultrafine Elongated Grain Structure Processed by Warm Tempforming. ISIJ International. 62 [2] (2022) ISIJINT-2021-068 10.2355/isijinternational.isijint-2021-068

Yuuji Kimura, Tadanobu Inoue, Toshio Otani, Akihiro Ochiai, Shohei Ikurumi, Tomohiro Takatsuji. Upsizing High-Strength Fail-Safe Steel through Warm Tempforming. Materials Science and Engineering: A. 819 (2021) 141514 10.1016/j.msea.2021.141514

Yuuji Kimura, Tadanobu Inoue. Mechanical Property of Ultrafine Elongated Grain Structure Steel Processed by Warm Tempforming and Its Application to Ultra-High-Strength Bolt. ISIJ International. 60 [6] (2020) 1108-1126 10.2355/isijinternational.isijint-2019-726

Mechanism of anisotropy properties
The relationship between the microstructure and the properties in isotropic materials has been widely investigated, and good understanding has been achieved. In contrast to the isotropic materials, this kind of the correlation in anisotropic materials is not well understood. Concerns are on the anisotropic materials (exoskeleton of crustaceans, ultrafine elongated-grain-structure steel, and so on), and their strength and toughness are measured via macroscopic and microscopic tests, and the anisotropy of the properties is revealed. Local deformation behavior is observed and measured by means of the in-situ observation-measurement system developed by our group. The formation mechanism of the anisotropy and its dependence of microstructure will be explained by using the obtained experimental data.

Hai Qiu, Rintaro Ueji, Tadanobu Inoue. Yield-Point Phenomenon and Plastic Bands in Ferrite–Pearlite Steels. Materials. 16 [1] (2023) 195 10.3390/ma16010195

Hai Qiu, Tadanobu Inoue. Evolution of Poisson’s Ratio in the Tension Process of Low-Carbon Hot-Rolled Steel with Discontinuous Yielding. Metals. 13 [3] (2023) 562 10.3390/met13030562

Hai Qiu, Rintaro Ueji, Yuuji Kimura, Tadanobu Inoue. Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region. Materials. 14 [8] (2021) 1865 10.3390/ma14081865

Hai Qiu, Rintaro Ueji, Yuuji Kimura, Tadanobu Inoue. Heterogeneous Distribution of Microstrain Evolved During Tensile Deformation of Polycrystalline Plain Low Carbon Steel. Metals. 10 [6] (2020) 774 10.3390/met10060774