Control of crack formation and material property by using nonlinear response of memory in paste under external perturbations

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05485
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Mathematical physics/Fundamental condensed matter physics
• Research Institution: Nihon University
• Principal Investigator: NAKAHARA Akio 日本大学, 理工学部, 教授 (60297778)
• Co-Investigator(Kenkyū-buntansha): 狐崎 創 奈良女子大学, 自然科学系, 准教授 (00301284) ; 松尾 洋介 日本大学, 理工学部, 研究員 (40611140)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 破壊の制御 / レオロジーと塑性変形 / 亀裂パターンの多様性と普遍性

Outline of Final Research Achievements

Due to its plasticity, a densely packed colloidal suspension, called a paste, remembers the direction of its vibration, shear and magnetic field, and these memories control preferential directions for cracks to propagate. To reveal the mechanism of this memory effect of paste, systematic experiments to imprint and rewrite memories in paste and numerical simulations based on theoretical models are performed. It is shown that a memory of vibration is kept as a residual tension along the vibration inside plastic media and a memory of shear is maintained as an elongated clusters of colloidal particles along shear direction. As for a memory of magnetic field, X-ray CT scan reveals that magnetic colloidal particles rotate and move to make chains toward the direction of magnetic field. These structures called memories in paste control the crack formation. By irradiating ultrasonic waves to paste, we find that memories in paste are erased and the breaking strength of the material increases.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

我々が安全な日常生活を送るためには破壊現象の理解と制御は不可欠である。通常予測不能な破壊がいつどのように起きるかまで制御できる例として、建築資材などの固液混合材料に対し事前に振動や流動や磁場などの外場を加えることで割れやすい方向を記憶させることに我々は成功してきた。本研究では、ペーストの記憶を司るメカニズムの解明を行うとともに、超音波照射で記憶を消去することで壊れにくい材料を作成する手法を開拓した。