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 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 HV 120 Maraging steel HV ơm MPa MPa R X Y MPa ƠU1Ị Otiỉ Ựarea m 740 -255 667 727 730 -196 549 0 961 652 744 196 461 -0 402 528 704 412 383 446 780 471 510 -0 040 37 0 0 723 572 0 892 740 0 686 -1 1 0 912 752 0 912 740 0 677 -1 1 677 740 0 559 -1 1 0 907 616 740 0 530 -1 1 578 740 0 471 -1 1 576 740 0 441 -1 185 0 1 0 856 515 s 10C 105 98 157 151 98 142 134 98 132 118 -98 206 198 -98 201 177 -98 176 163 0 172 -1 1 170 0 157 -1 1 151 0 142 -1 185 0 1 135 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. . By considering values of a in Fig. and H values for the two materials we can obtain an equation for a as a Hy X 10 4 Table compares values of the experimental fatigue limit ơw with those for the fatigue limit 7 calculated using Eqs. and . They agree to within 15 . 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 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 .
