Analysis of the mechanical properties is of great importance in evaluating the performance of materials. With the rapid development of nanomaterials, most of the traditional techniques for the analysis of the materials’ properties and structures have been rendered insufficient. Presently, molecular dynamics simulations techniques have been commonly used to analyze the characteristics of most nanomaterials i.e. plastic deformation mechanism and the surface orientation and direction of scratching. Recently, several multi-scale methods have been developed for the analysis of the materials’ structures. Among these methods, the quasi-continuum method is increasing becoming a popular technique for simulating mechanical deformation of nanocrystalline solids.
Generally, it uses a mixture of atomistic and continuum algorithms to analyze various contact problems. For example, it has been used to analyze the crack growth and expansion characteristics and to determine the macroscopic properties of single aluminum crystals. Unfortunately, the friction and characteristics of rough aluminum surfaces have not been fully explored.
To this note, Researchers at National Kaohsiung University of Science and Technology: Anh-Son Tran (PhD candidate), Professor Te-Hua Fang, Li-Ren Tsai and Chung-His Chen from the Department of Mechanical Engineering investigated the friction and scratch characteristics of textured and rough pure aluminum surfaces using the quasi-continuum method. Fundamentally, the authors altered the surface profiles of pure aluminum regular and irregular arrangements along the X- and Y- directions respectively. On the other hand, a scratching process was used to determine the scratching material’s internal strain and surface smoothness. Their research work is currently published in Journal of Physics and Chemistry of Solids.
Briefly, the research team commenced the research work by cross-examining the coupling of the atoms in the continuum region using the quasi-continuum method. Generally, they examined the local regions where the gradient was trivial and the non-local regions where the gradient was more pronounced. Additionally, they applied different model profiles to explore the surface smoothness characteristics and internal effects of the materials. Consequently, the friction behavior was used to determine the scratching process. Therefore, various calculations were majorly based on the representation of the atoms which greatly helped in saving time and improving the calculation efficiency. Eventually, they analyzed the effects of various parameters: the ratio of the pump width to pump pitch, average surface roughness, scratching depth and the indenter radius.
The authors observed that the bump width to bump pitch ratio (W/P) significantly affected the surface smoothness since its increase resulted in a corresponding increase in the internal materials’ strain. For instance, with W/P=100%, no defect was observed on the material’s surface and the material exhibited much superior smoothness property. Additionally, the scratching depth values and the indenter radius were observed to increase proportionally to the coefficient of friction. Furthermore, using a smaller indenter radius resulted in uneven surface smoothness while greater indenter radius resulted in more arced and inclined surface profiles. Altogether, the study by Professor Te-Hua Fang and the research team provides additional insights that will be of great importance in analyzing and improving structural and mechanical properties of nanomaterials thus enhancing their performance.
Tran, A., Fang, T., Tsai, L., & Chen, C. (2019). Friction and scratch characteristics of textured and rough surfaces using the quasi-continuum method. Journal of Physics and Chemistry of Solids, 126, 180-188.Go To Journal of Physics and Chemistry of Solids