Ikumu Watanabe

Relation extraction with weakly supervised learning based on process-structure-property-performance reciprocity

ABSTRACT In this study, we develop a computer-aided material design system to represent and extract knowledge related to material design from natural language texts. A machine learning model is trained on a text corpus weakly labeled by minimal annotated relationship data (~100 labeled relationships) to extract knowledge from scientific articles. The knowledge is represented by relationships between scientific concepts, such as {annealing, grain size, strength}. The extracted relationships are represented as a knowledge graph formatted according to design charts, inspired by the process-structure-property-performance (PSPP) reciprocity. The design chart provides an intuitive effect of processes on properties and prospective processes to achieve the certain desired properties. Our system semantically searches the scientific literature and provides knowledge in the form of a design chart, and we hope it contributes more efficient developments of new materials. Graphical Abstract

Maximization of Strengthening Effect of Microscopic Morphology in Duplex Steels

An inverse analysis method based on nonlinear finite element analysis is developed to find an optimized morphology of periodic microstructure for improving the macroscopic mechanical properties in duplex elastoplastic solids. Here a gradient-based computational optimization method and two types of homogenization methods are employed. In this study, the optimization problem is defined as the maximization of the sum of macroscopic external works for several macroscopic deformation modes, enabling us to obtain a high strength material. The morphologic strengthening effect is discussed through a comparison with experiments and classical theories.

Two-Scale Finite Element Analysis of Equaled Channeling Angular Extrusion of Polycrystalline Metal

A two-scale finite element analysis method based on a micro-macro decoupled scheme is applied to an equaled channeling angular extrusion. At first, the macro-scale finite element analysis for one process of an equaled channeling angular extrusion is carried out with a non-liner explicit method to handle the contact and friction between die and bullet. Using the deformation history at a macroscopic material point in this process, the micro-scale finite element analysis is conducted for the multiple processes with a single crystal plasticity and a nonlinear implicit method. As the results, the deformation process of the polycrystalline aggregate during the equaled channeling angular extrusion is numerically reproduced.

Tensile testing with cyclic strain holding to analyze dynamic recrystallization of pure lead

We analyzed the dynamic recrystallization of pure lead by tensile testing with cyclic strain holding at room temperature. The specimens were held at an identical strain and subsequently reloaded, providing the strength before and after the strain holding process. The difference in strength enables factors affecting dynamic recrystallization behavior to be analyzed through mechanical testing. For instance, the effects of strain rate on dynamic recrystallization were analyzed by comparing the results obtained from tensile tests with and without strain holding. This experimental technique demonstrated some parts of contribution of elastic strain, dynamic recovery, dynamic recrystallization, and necking to stress-strain responses.

Two‐scale characterization of deformation‐induced anisotropy of polycrystalline metals

The anisotropic macro‐scale mechanical behavior of polycrystalline metals is characterized by incorporating the micro‐scale constitutive model of single crystal plasticity into the two‐scale modeling based on the mathematical homogenization theory. The two‐scale simulations are conducted to analyze the macro‐scale anisotropy induced by micro‐scale plastic deformation of the polycrystalline aggregate. In the simulations, the micro‐scale representative volume element (RVE) of a polycrystalline aggregate is uniformly loaded in one direction, unloaded to macroscopically zero stress in a certain stage of deformation and then re‐loaded in the different directions. The last re‐loading calculations provide different macro‐scale responses of the RVE, which can be the appearance of material anisotropy. We then try to examine the effects of the intergranular and intragranular behaviors on the anisotropy by means of various illustrations of plastic deformation process in stead of the use of pole figures for the chang...