Tham khảo tài liệu 'substrate and coating erosion_3', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Impact Processes 185 Fig. Tensile stresses due to solid particle impingement calculated for a typical substratecoating arrangement Energy Absorption A simple analysis delivers the following subdivision of energy terms mP 2 mP 2 . _ . _ . _ EP 2 vP 2 vr Epp Eep Epm - Eem - E0m E particle target restitution The first subscript p stands for plastic deformation and the first subscript e stands for elastic deformation. The second subscript p stands for particle and the second subscript m stands for target material. Energy absorption mechanisms related to E surface heating mechanical activation light emission are discussed later in this section. Figure illustrates the situation as expressed by and provides a qualitative assessment of the energy situation. The initial kinetic energy of the particle EP is absorbed by both particle grain and target material. The energy dissipated by the target is subdivided into elastic deformation energy plastic deformation energy and the surface energy. The latter parameter is frequently called fracture energy and relates to the thermodynamic specific surface energy see Griffith 1923 . Uetz and Fohl 1978 related this parameter to the erosion rate by assuming ER k0 E0m. It can be seen from Fig. that the value for the parameter k0 depends 186 5 Substrate and Coating Erosion Fig. Qualitative proportion of kinetic energy for different target materials during solid particle impinging processes Uetz and Fohl 1978 . 1 - specific surface energy 2 - elastic deformation energy 3 - plastic deformation energy on the target material. It is rather high for the metals and rather low for the rubber. Figure illustrates the situation in a quantitative way for an impinging steel sphere. It can be seen that the concrete energy situation depended on the abrasive materials hardness. The higher this value the more energy was transferred to the target. For lower abrasive hardness values a higher amount of energy was .
