Resumen:
The modeling of plastic deformation over the length scales has still been a challengeable problem. One of the most crucial defect interactions related to the plasticity is the reaction between the dislocation and GB, that is, GB strengthening of Hall-Petch law from the materials science view and also improvement of ductility due to the slip transfer across GB from the plastic forming process view. Both are mechanically trade-off and conjugate. To this problem, three approaches are demonstrated; one is from the millimeter-sized tensile testing with different grain sizes and different environmental temperatures. The H-P coefficient for the flow stress is linked to the plastic strain and discuss about the “Incorporation Effect” of the emitted dislocations in the grain adjacent to the grain with the piled-up dislocation via GB. The second is from nanometer-sized molecular dynamics simulation and energy landscape estimation method. The atomistic interactions of dislocation to GB were classified into several types of reactions and the critical interaction shear stress (CISS) for the “Slip Transfer across GB” and the activation volume of the reaction of dislocation to GB were estimated. The last one is from micrometer-sized crystal plasticity finite element method. The proposed constitutive law involves the above-mentioned two contributions of “Slip Transfer across GB” and “Incorporation Effect” and discussed about the localized plastic deformation around the three types of bicrystals with <112>-axis-symmetric tilt GBes of 35A, 11A and 77A. The parameters of constitutive law were determined by the micro-pillar testing using the selective single crystals of the materials, called “Mesotesting”. All the approaches are focused on the title of “How far the defect interaction between dislocation and GB affects the inside of grain?”.

Biografía:
El Prof. Yoji Shibutani se graduó de la Universidad de Osaka en 1981 y de la Escuela de Graduados de la Universidad de Osaka en 1983 con una Maestría en Ingeniería. Trabajó en Toshiba Corp. y participó en el desarrollo de reactores de fusión entre 1983 y 1988. Después de eso, regresó a la Universidad de Osaka como profesor asistente y obtuvo el Doctorado en Ingeniería en 1992 de la Universidad de Osaka. Se quedó en la Universidad de Pensilvania en EE. UU. como investigador visitante y colaboró ​​con los Profs. Vaclav Vitek y John L. Bassani entre 1993 y 1995. Después de eso, fue ascendido a Profesor Asociado de la Universidad de Kobe en 1995 y a Profesor de la Universidad de Osaka en 1999. Su especialidad es la mecánica de sólidos, especialmente la teoría de los defectos de los materiales y la plasticidad de vista multiescala y la técnica de observación no destructiva, que se desarrolló originalmente como microscopio térmico y acústico inducido por electrones de barrido (SETAM), desde la vista multifísica entre elasticidad dinámica, conducción de calor no Fourier y piezoelectricidad.