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Metal Fatigue Part 5

Tham khảo tài liệu 'metal fatigue part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 104 Chapter 6 Table 6.8 Experimental results used to derive the fatigue limit prediction equation as a function of R ratio and evaluation of its accuracy X 1 - 2 2 Y au Jwa 7 1.43 HV 120 Maraging steel HV ơm MPa MPa R X Y MPa ƠU1Ị Otiỉ Ựarea m 740 -255 667 -2.238 56.0 1.62 1.07 727 0.918 730 -196 549 -2.111 92.5 1.56 0 961 652 0.842 744 196 461 -0 402 92.5 0.701 0.785 528 0.873 704 412 383 0.037 92.5 0.482 0.691 446 0.858 780 471 510 -0 040 37 0 0.502 0 723 572 0 892 740 0 686 -1 19.1 1 0 912 752 0 912 740 0 677 -1 37.0 1 1.00 677 1.00 740 0 559 -1 63.2 1 0 907 616 0.907 740 0 530 -1 92.5 1 0.917 578 0.917 740 0 471 -1 94.9 1 0.818 576 0.818 740 0 441 -1 185 0 1 0 856 515 0.856 s 10C 105 98 157 -0.231 46.2 0.616 0.925 151 1.04 98 142 -0.183 92.5 0.592 0.939 134 1.06 98 132 -0.147 185.0 0.574 0.980 118 1.12 -98 206 -2.814 46.2 1.91 1.214 198 1.04 -98 201 -2.902 92.5 1.95 1.330 177 1.14 -98 176 -3.512 185.0 2.26 1.307 163 1.08 0 172 -1 46.2 1 1.01 170 1.01 0 157 -1 92.5 1 1.04 151 1.04 0 142 -1 185 0 1 1.05 135 1.05 parameter which may make the prediction equation more complicated. Thus we again adopt Hyj as the most appropriate material parameter as was done in the derivation of Eq. 6.1. By considering values of a in Fig. 6.28 and H values for the two materials we can obtain an equation for a as a 0.226 Hy X 10 4 6.8 Table 6.8 compares values of the experimental fatigue limit ơw with those for the fatigue limit 7 calculated using Eqs. 6.6 and 6.8. They agree to within 15 . 6.5.2 Effects of Both Nonmetallic Inclusions and Mean Stress in Hard Steels The prediction equation obtained in the previous section is applied to the fatigue behaviour of a high speed tool steel SKH51. Effects of Nonmetallic Inclusions on Fatigue Strength 105 Figure 6.29 S-N curves for high speed tool steel SKH51 Hy 654 . Tool steels are commonly used not only for cutting tools but also for dies. When we use tool steels for cutting tools their small size means that the effects of nonmetallic .