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Friction, Lubrication, and Wear Technology (1997) Part 8

Tham khảo tài liệu 'friction, lubrication, and wear technology (1997) part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | L L62L 2it 1.10 exp I- Eq 26 Isotropic elasticity theory has been used to obtain these relationships for dislocation density and correlation parameters. In applying Eq 24 one need not assume that the material is isotropic. Table 1 lists results for both face- and body-centered cubic materials. A common pattern is apparent. For cold-work fdings one finds that i.33 - 2.17 Eq 27 For the most part the dislocation density is high and in the lO Vcm2 range. Dislocations are highly correlated with Rc close to the average diameter of the subgrain for metallic filings and ZrO2 debris. Table 1 Results for body-centered cubic materials face-centered cubic aluminum and partially stabilized cubic zirconia Material . . nm n X 10 n cm2 RJ L X 104 X 10 Cr 28.5 3.67 1.79 2.63 1.47 V 20.0 6.56 2.17 3.46 4.05 Mo 26.0 4.60 1.99 3.30 2.72 w 21.5 7.32 1.66 4.56 3.27 Nb 20.0 1.53 1.33 0.84 0.29 Al 32.0 4.41 1.64 2.32 1.60 ZrO2 8.6 12.70 1.42 4.84 4.90 Aluminum filings are prepared under liquid nitrogen. Source Ref 18 The results given in Table 1 for body- and face-centered cubic material allow a simple explanation to be given for the structure of cold-worked fragments. Filings show a high degree of correlation small RJ L and high dislocation densities. This is related to sample conditions such as the temperature and local conditions at which a high-density dislocation structure is produced. Fragments produced by filing or grinding at room temperature or even at liquid nitrogen temperature cannot be cold. Instead they are rapidly heated to a high temperature during fracture and rapidly quenched because of their high surface-to-volume ratio. Dislocations are mobile for short periods of time over short distances and can cluster. Table 1 includes results from cubic debris particles obtained from a worn PSZ. The substrate contains three phases as already discussed. It should be noted that the cubic phase is stable at high temperatures making it reasonable that only the cubic form should be .