Tools › Mechanical Design › Bearings › Bearing Life › Example
SKF 6210 angular-contact ball bearing under combined load: equivalent load, L10 life, reliability and the rating required (Shigley Example 11-3)
| Tool | Bearing Life |
| Source | Budynas, R. G., and Nisbett, J. K. (2015). Shigley's Mechanical Engineering Design, 10th ed. McGraw-Hill Education, New York. Example 11-3 (Table 11-1 equivalent load, Eq. 11-3 rating life); Section 11-5 and Table 11-6 (Weibull reliability, Eq. 11-6 and 11-9). |
| Level | Undergraduate |
Problem
An SKF 6210 angular-contact ball bearing carries an axial load of 400 lbf and a radial load of 500 lbf with the outer ring stationary; its basic static rating is C0 = 4450 lbf and its basic load rating C10 = 7900 lbf. Estimate the L10 life at 720 rev/min, the life at other reliabilities, and the catalogue rating a 10,000 h design life at 90 percent reliability would need.
Inputs to Enter
- Angular-contact ball bearing (a = 3), ISO/ABMA basis (10^6 rev; Weibull x0 0.02, θ 4.459, b 1.483); C10 7,900 lb, C0 4,450 lb
- F_r 500 lb, F_a 400 lb, V 1.0, 720 rpm, application factor 1.0; design life 10,000 h at R = 0.90, queried life 5,000 h
Answers
- F_a/C0 = 0.0899 → e = 0.285, Y2 = 1.527 (Table 11-1 interpolated); F_a/(V F_r) = 0.8 > e → F_e = 0.56(500) + 1.527(400) = 890.9 lb (book 890.8 lb with F_a/C0 rounded to 0.090)
- L10 = (7900/890.9)^3 = 697 × 10^6 rev = 16,140 h at 720 rev/min (book 16,150 h)
- Reliability of reaching 10,000 h 0.950; L1 life 3,544 h; median life 56,270 h; x_R(0.90) = 0.9933
- x_D = 60(10,000)(720)/10^6 = 432 → C10 required = 890.9 (432/0.9933)^(1/3) = 6,750 lb; M.S. on the rating = 7,900/6,750 − 1 = +0.17
Notes
The tool's default inputs are this bearing; press Submit. The small differences from the printed values come from the book rounding F_a/C0 to 0.090 before interpolating. The same page offers the Timken 90 × 10^6 rev basis, tapered-roller pairs with induced thrust (Section 11-9), duty cycles (Eq. 11-14) and the ISO 281:2007 modified life.