tailieunhanh - Substrate and Coating Erosion_6

Tham khảo tài liệu 'substrate and coating erosion_6', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 212 5 Substrate and Coating Erosion angle of impingement in degrees Fig. Erosion mechanisms for polymer materials Walley and Field 1987 embedment of spherical abrasives took place. The impact velocity needed to cause the latter two mechanisms to occur had a minimum at an impact angle of about V 70 . Walley et al. 1984 1987 applied the damage number according to for the construction of general damage maps for polymers see Sect. . From the geometry point of view craters could be classified into four types smooth ploughed cut and sharply dented. The frequency of occurrence of the certain geometry depended mainly on impact angle as verified by the results listed in Table for PE and PEEK. For PE lip volume and crater volume increased with increasing impact velocity according to a power function Vm a va B The power exponent had values aB for the crater volume and aB for the lip volume Walley and Field 1987 . The specific energy for lip formation as well as for crater formation decreased with increasing impact velocity implying that a greater fraction of the energy dissipated went into permanent material displacement as the velocity rose. For an impact velocity Ỉ Ị 200 m s the specific energy values were about mm3 for crater formation and about J mm3 for lip formation Walley and Field 1987 . Scratch deformation maps for polymers very similar to that shown in Fig. are issued by Briscoe and Sinha 2003 . Aspects of thermal effects were also investigated by Walley and Field 1987 . Based on a heat transfer analysis they found that a particle impact frequency of Erosion of Bulk Polymers and Elastomers 213 Table Percentage of crater types in bulk polymers for various impact angles see Fig. Walley et al. 1987 Walley and Field 1987 Impact Percentage of crater type in angle in Smooth Ploug hed Cut Sharp ly dented PEa PEEKb PE PEEK PE PEEK PE PEEK 10 45 30 11 14 20 28 62 43 21 22 14 7 3 30 42 37 40 32 5 24 13 6 40 62 42