### Abstract

In this paper, a triple-scale crystal plasticity model bridging three hierarchical material structures, i. e., dislocation structure, grain aggregate and practical macroscopic structure is developed. Geometrically necessary (GN) dislocation density and GN incompatibility are employed so as to describe isolated dislocations and dislocation pairs in a grain, respectively. Then the homogenization method is introduced into the GN dislocation-crystal plasticity model for derivation of the governing equation of macroscopic structure with the mathematical and physical consistencies. Using the present model, a triple-scale FE simulation bridging the above three hierarchical structures is carried out for f. c. c. polycrystals with different mean grain size. It is shown that the present model can qualitatively reproduce size effects of macroscopic specimen with ultrafine-grain, i. e., the increase of initial yield stress, the decrease of hardening ratio after reaching tensile strength and the reduction of tensile ductility with decrease of its grain size. Moreover, the relationship between macroscopic yielding of specimen and microscopic grain yielding is discussed and the mechanism of the poor tensile ductility due to fine-graining is clarified.

Original language | English |
---|---|

Pages (from-to) | 483-491 |

Number of pages | 9 |

Journal | Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A |

Volume | 76 |

Issue number | 764 |

Publication status | Published - 2010 Apr |

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### Keywords

- Crystal plasticity
- Dislocation
- Finite element method
- Geometrically necessary dislocation
- Homogenization method
- Plasticity
- Size effect
- Ultrafine-grained metal

### ASJC Scopus subject areas

- Mechanical Engineering
- Mechanics of Materials
- Materials Science(all)

### Cite this

*Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A*,

*76*(764), 483-491.

**A triple-scale crystal plasticity modeling and simulation on size effect due to fine-graining.** / Kurosawa, Eisuke; Aoyagi, Yoshiteru; Tadano, Yuichi; Shizawa, Kazuyuki.

Research output: Contribution to journal › Article

*Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A*, vol. 76, no. 764, pp. 483-491.

}

TY - JOUR

T1 - A triple-scale crystal plasticity modeling and simulation on size effect due to fine-graining

AU - Kurosawa, Eisuke

AU - Aoyagi, Yoshiteru

AU - Tadano, Yuichi

AU - Shizawa, Kazuyuki

PY - 2010/4

Y1 - 2010/4

N2 - In this paper, a triple-scale crystal plasticity model bridging three hierarchical material structures, i. e., dislocation structure, grain aggregate and practical macroscopic structure is developed. Geometrically necessary (GN) dislocation density and GN incompatibility are employed so as to describe isolated dislocations and dislocation pairs in a grain, respectively. Then the homogenization method is introduced into the GN dislocation-crystal plasticity model for derivation of the governing equation of macroscopic structure with the mathematical and physical consistencies. Using the present model, a triple-scale FE simulation bridging the above three hierarchical structures is carried out for f. c. c. polycrystals with different mean grain size. It is shown that the present model can qualitatively reproduce size effects of macroscopic specimen with ultrafine-grain, i. e., the increase of initial yield stress, the decrease of hardening ratio after reaching tensile strength and the reduction of tensile ductility with decrease of its grain size. Moreover, the relationship between macroscopic yielding of specimen and microscopic grain yielding is discussed and the mechanism of the poor tensile ductility due to fine-graining is clarified.

AB - In this paper, a triple-scale crystal plasticity model bridging three hierarchical material structures, i. e., dislocation structure, grain aggregate and practical macroscopic structure is developed. Geometrically necessary (GN) dislocation density and GN incompatibility are employed so as to describe isolated dislocations and dislocation pairs in a grain, respectively. Then the homogenization method is introduced into the GN dislocation-crystal plasticity model for derivation of the governing equation of macroscopic structure with the mathematical and physical consistencies. Using the present model, a triple-scale FE simulation bridging the above three hierarchical structures is carried out for f. c. c. polycrystals with different mean grain size. It is shown that the present model can qualitatively reproduce size effects of macroscopic specimen with ultrafine-grain, i. e., the increase of initial yield stress, the decrease of hardening ratio after reaching tensile strength and the reduction of tensile ductility with decrease of its grain size. Moreover, the relationship between macroscopic yielding of specimen and microscopic grain yielding is discussed and the mechanism of the poor tensile ductility due to fine-graining is clarified.

KW - Crystal plasticity

KW - Dislocation

KW - Finite element method

KW - Geometrically necessary dislocation

KW - Homogenization method

KW - Plasticity

KW - Size effect

KW - Ultrafine-grained metal

UR - http://www.scopus.com/inward/record.url?scp=77954744349&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77954744349&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:77954744349

VL - 76

SP - 483

EP - 491

JO - Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A

JF - Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A

SN - 0387-5008

IS - 764

ER -