232
Z. Wang et al.
Table 18.3 Rolling contact cycle numbers of samples at different static rolling loads
Static
pressure
[N]
Rolling contact cycle Numbers [10 6 ]
Untreated 0.2134 0.5131 0.5832 0.7323 0.9138 1.5379 1.5325 2.3432
6.3218
600
0.6432 0.8521 1.2214 1.5896 2.5846 3.5341 5.4678 6.7457
8.3841
800
0.9645 1.2095 2.0721 3.2385 4.1137 4.5704 6.4519 8.2194
1.2546
1000
3.3758 5.5541 7.6862 8.3258 10.428 12.659 14.3791 17.5694
21.3731
1200
0.7957 1.0253 2.5479 4.1921 4.7138 6.4318 7.1139 13.3648
20.7337
Fig. 18.10 Weibull
distribution curves of contact
fatigue life of samples at
different rolling static loads
Failure probability/(%)
untreated
Revolution number/(N t )
600N
800N
1000N
1200N
contact fatigue life of this group of samples is the longest, and the curve convergence
is the highest with the K10 value of 1.71. Secondly, the curves of the 800 and 1200 N
samples are intersection. The K8 value of the 800 N samples is 1.41, and the K12
value of the 1200 N samples is 1.17, indicating that the 800 N samples process better
stability; When the static load is 600 N, the Weibull curve is only to the right of the
curve of the untreated samples, indicating that the contact fatigue life of the samples
at this static load is higher than that of the untreated samples, but lower than that of
other groups.
Based on the Weibull distribution curve of fatigue life of samples at different
rolling static loads, three classical fatigue life values of each group of samples are
obtained, including rated life (L10), median life (L50), and characteristic life (L63.2)
as shown in Table 18.4. The rated life (L10), median life (L50) and characteristic life
(L63.2) of the untreated sample are only 0.2134 × 10
6 , 0.9138 × 10
6 and 1.5249
× 10
6 revolutions, while at the static load of 1000 N, the tappet material obtain the
longest contact fatigue life, and the three classic lives are 1.3758 × 10
6 , 8.1428 ×
10
6 , and 11.2821 × 10
6 revolutions respectively, which are 6.4, 8.9 and 7.4 times
of the corresponding fatigue life of the untreated samples. the static load of 800 N
and 1200 N have a similar effect on the fatigue life of the samples. The median life
Z. Wang et al.
Table 18.3 Rolling contact cycle numbers of samples at different static rolling loads
Static
pressure
[N]
Rolling contact cycle Numbers [10 6 ]
Untreated 0.2134 0.5131 0.5832 0.7323 0.9138 1.5379 1.5325 2.3432
6.3218
600
0.6432 0.8521 1.2214 1.5896 2.5846 3.5341 5.4678 6.7457
8.3841
800
0.9645 1.2095 2.0721 3.2385 4.1137 4.5704 6.4519 8.2194
1.2546
1000
3.3758 5.5541 7.6862 8.3258 10.428 12.659 14.3791 17.5694
21.3731
1200
0.7957 1.0253 2.5479 4.1921 4.7138 6.4318 7.1139 13.3648
20.7337
Fig. 18.10 Weibull
distribution curves of contact
fatigue life of samples at
different rolling static loads
Failure probability/(%)
untreated
Revolution number/(N t )
600N
800N
1000N
1200N
contact fatigue life of this group of samples is the longest, and the curve convergence
is the highest with the K10 value of 1.71. Secondly, the curves of the 800 and 1200 N
samples are intersection. The K8 value of the 800 N samples is 1.41, and the K12
value of the 1200 N samples is 1.17, indicating that the 800 N samples process better
stability; When the static load is 600 N, the Weibull curve is only to the right of the
curve of the untreated samples, indicating that the contact fatigue life of the samples
at this static load is higher than that of the untreated samples, but lower than that of
other groups.
Based on the Weibull distribution curve of fatigue life of samples at different
rolling static loads, three classical fatigue life values of each group of samples are
obtained, including rated life (L10), median life (L50), and characteristic life (L63.2)
as shown in Table 18.4. The rated life (L10), median life (L50) and characteristic life
(L63.2) of the untreated sample are only 0.2134 × 10
6 , 0.9138 × 10
6 and 1.5249
× 10
6 revolutions, while at the static load of 1000 N, the tappet material obtain the
longest contact fatigue life, and the three classic lives are 1.3758 × 10
6 , 8.1428 ×
10
6 , and 11.2821 × 10
6 revolutions respectively, which are 6.4, 8.9 and 7.4 times
of the corresponding fatigue life of the untreated samples. the static load of 800 N
and 1200 N have a similar effect on the fatigue life of the samples. The median life