Constructing a new methodology for teaching internal friction of amorphous solids: models, experiments and simulations

Internal friction is an important tool to understand the movement of atoms and molecules in solid materials. It is widely used to study the evolution of microstructures, significantly contributing to our understanding of the dynamic relaxation processes affecting the atomic-scale structure of solids. This paper derives the formula for internal friction in solid mechanics by examining the energy and stress-strain hysteresis curves. It subsequently outlines the research frontiers related to the mechanical relaxation modes of crystalline and amorphous solids, highlighting the intrinsic connection between internal friction and the relaxation of microstructural defects in solids. Additionally, this work shows how to employ molecular dynamics simulation methods to quantify the internal friction and to directly observe the evolution of structural and dynamic characteristics. Based on the authors teaching experience and recent research findings regarding the theory of solid internal friction, this paper presents a course program with various dimensions, including content, methods, and instructional flow. The proposed teaching strategies aim to serve as a reference for other educators involved in courses of solid mechanics.