Mechanics of amorphous solids

Understanding amorphous solids and relevant properties is the deepest and most fascinating scientific problem in our time. Classical theories of solid mechanics are built on the continuum scale, and they can successfully describe the deformation and fracture of various crystalline solids by taking into account the concepts such as dislocations, grain boundaries, and cleavage. However, this classical route faces great conceptual and theoretical challenges when applied to amorphous solids lacking long-range period order. The fundamental reason is that the traditional crystallographic concepts are not defined in topologically disordered structures, which leads to the breakdown of solid mechanics theories established on this basis. In this paper, we take amorphous alloys and their atomic or colloidal simulation counterparts as model systems, and review the research progress of the five representative aspects related to their mechanical behaviors or properties, including plastic carriers, plastic constitutive theories, creep and stress relaxation, shear banding, and fracture failure. It is noted that these relevant studies are open and still under developing, and some views, methods, models, etc., remain much controversial, far away from forming a generally accepted theoretical system. Meanwhile, the long-term study on the mechanics of amorphous solids in many fields seems to be on the eve of a major breakthrough. We believe that researchers in the field of mechanics should take this opportunity to focus on the following major scientific issues or key technologies (but not limited to): (1) High spatiotemporal resolution technology to probe amorphous plastic carriers based on advanced electron microscopes, light sources, etc.; (2) the spatiotemporal relationship between vibration and rearrangement of disordered systems; (3) elastic fluctuations and correlations of amorphous solids; (4) the trans-scale amorphous constitutive theory considering multiple processes and out-of-equilibrium; (5) extreme mechanical responses of amorphous solids, including dynamic shock, laser irradiation, long-duration rheology, ultra-high cycle fatigue, etc.; (6) material strengthen-toughening technology by tailing topological disorder; (7) physical aging, structural rejuvenation, and memory effects; (8) high-efficiency damage and protection technologies based on amorphous materials. These pieces of research will enrich and develop the theoretical systems and technological innovation of solid mechanics, and will also contribute to the fields of materials, physics, etc., promoting the interdisciplinary harmonization and development.

Automated summary

Understanding amorphous solids and their properties is a fascinating and deep scientific problem. However, classical solid mechanics theories face challenges when applied to amorphous solids. This paper reviews the research progress in understanding the mechanical behaviors and properties of amorphous alloys and their simulation counterparts, highlighting the open questions and controversial views in this field. The long-term study on mechanics of amorphous solids seems to be on the verge of a major breakthrough.