The Investigation of Macroscopic Mechanical Characteristic and Formability of Material with Periodical Sub-macroscopic Structure

周期的なサブマクロ構造を有する素材の巨視的な力学特性および成形性の発現メカニズムの解明

2020-03-25

2020-03-25

In recent decades, lightweight has become an important issue from the viewpoint of realizing a low carbon society and securing collision safety. Materials with periodic structures have been widely applied as lightweight constructions. It is considered that the flexural rigidity and functionality can be enhanced by embossing process. Sheet metal has uniform characteristics depending on aggregate structure. After being subjected to embossing process, properties would also depend on this sub-macroscopic structure. Therefore, such an embossed sheet is considered to be a sheet with a new macrostructure superposed by microscopic and sub-macroscopic features. This thesis aims to evaluate the macroscopic mechanical characteristic and formability and their relationship of embossed sheets. In the Chapter 3, to investigate the apparent elastic rigidities of embossed sheets, uniaxial tensile and bending tests for embossed sheets were conducted. From the results, the intrinsic apparent elastic rigidities and their variations depend on pre-uniaxial tension deformation were investigated. In the Chapter4, to understand the apparent plastic anisotropy of an embossed sheet under uniaxial tension, experiments and simulations were conducted. From the results, their intrinsic apparent plastic deformation anisotropies were investigated. It was confirmed that the apparent plastic anisotropy emerges as a superposition of two anisotropies. A simple superposition model was also proposed. In the Chapter5 and 6 the effect of work hardening and thickness distribution derived from the embossing process on apparent mechanical properties were also investigated. It is considered that the formability is correlated with the mechanical properties. In the Chapter 7, Swift deep drawing test was conducted in order to investigate the deep drawability and flange deformation behavior of embossed sheets. It was thought that embossed sheets have a strong SD effect. In the Chapter8, in-plane compression tests were investigated numerically. The apparent in-plane compression properties and the difference from that of uniaxial tension was investigated. In the Chapter 9 and 10, the stretch-flange ability and punch stretch ability of embossed sheets were evaluated by hole expansion and punch stretch. The effects of embossing process on these deformation behavior and fracture style were investigated and discussed.

博士(工学)

京都工芸繊維大学

14303甲第955号

http://hdl.handle.net/10212/2565

eng

ETD

13

Thesis or Dissertation

Thesis