| 研究開始時の研究の概要 |
To investigate the role of large compressibility in the development of flowing instabilities, we explore experimentally the mechanical response of an assembly of ring-shaped grains, a model system at the border between porous and granular media. Under compression, the rings show heterogeneous and large deformations, which promote the development of irreversible displacements under oscillatory shear. While structural deformations seem to lead to system spanning reorganisations, shape fluctuations may act as an apparent activity leading to diffusive behaviours.
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| 研究実績の概要 |
Continuing from the previous fiscal year, we studied the oscillatory shear response of a sponge-like granular assembly made up of highly compressible elastic rings. Understanding how the geometrical variations at the microscopic scale of disordered materials impact the response of the assembly, particularly rigidity transitions, is an ongoing challenge in soft matter physics.
Our research revealed a progressive rigidity transition that occurs when the density is increased or the shear amplitude is decreased. As we observed, the rearranging fluid state is made up of crystal clusters separated by melted regions, while the solid state remains amorphous and absorbs all imposed shear elastically. We found that this transition is due to an effective, attractive shear force between the rings that emerges from a friction-geometry interplay. If friction is sufficiently high compared to shear, the extent of the contacts between rings, captured analytically by elementary geometry, controls the rigidity transition.
This work has unveiled groundbreaking insights into how geometrical changes fundamentally alter the jamming transition. Ring assemblies, with their high adjustability and straightforward manufacturing process, serve as an ideal model experimental platform to delve into the role of geometrical changes in disordered media, thereby paving the way for this novel branch of disordered media. Significant shape alterations at the particle scale are also prevalent in biological and geological systems and underpin critical processes such as morphogenesis and landslide flows.
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