tailieunhanh - Substrate and Coating Erosion_7

Tham khảo tài liệu 'substrate and coating erosion_7', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Erosion of Organic Coatings 221 Fig. Relationship between rebound resilience and specific erosion of unfilled elastomers Hutchings et al. 1987 . Results of erosion tests delivered values between and for normal impact angles and values between and for shallow impact angles Arnold and Hutchings 1993 . Figure shows the effect of the rebound resilience on the erosion resistance of unfilled elastomers. The quantity 100 - resilience represents the fraction of the initial energy of the impinging particles which is absorbed by the target material. An inverse relationship can be found in Fig. for shallow as well as for perpendicular impact. At constant rebound resilience a low material hardness correlated with a high erosion resistance for a range of polyurethane elastomers Li and Hutchings 1990 . Tensile strength is not a measure of erosion resistance rubbers with quite different values for tensile strength exhibited similar erosion behaviour. Glass transition temperature also did not show any unique relationship to the erosion resistance of rubbers Hutchings et al. 1987 Erosion of Organic Coatings Material Removal Mechanisms Generally elastic and elastic-plastic response mechanisms may act during coating erosion. The transitions between these two groups depend among others on temperature strain rate and coating thickness. A transition coating thickness can for 222 5 Substrate and Coating Erosion example be assumed for organic coatings. Elastic response brittle fracture can be expected in the coating material when the coating thickness is rather large and when the coating thickness is much larger than the size of the plastic zone around an inherent flaw. This was shown by Moore 2001 for epoxy coatings. Microscopic inspections of impact sites in epoxy-based organic coatings revealed a large variety of crater topologies. If adhesion strength between substrate and coating was lower than the cohesion strength of the bulk coating