Answer:
To achieve a 95 percent reliability for 10,000 hours (10 kh) of operation at the given load and speed, the bearing should be expected to carry the load for approximately 1,347,822 revolutions.
Step-by-step explanation:
Using the same principles to determine whether a bearing can carry a given load with 95 percent reliability for 10,000 hours (10 kh). However, you must adjust the calculations to the new Reliability and desired life.
Given:
1. Desired life (L₁): 10,000 hours
2. Reliability (R): 95%
First, calculate the number of revolutions the bearing will undergo during its desired life:
L₁ = (60 / N) * L
Where:
L₁ = Desired life in revolutions
N = Operating speed in rpm
L = Desired life in hours
L₁ = (60 / 1,725) * 10,000 = 347,826.09 revolutions
Next, calculate the reliability factor (a) for 95% reliability:
a = (1 / (1 - R))^(1/3)
Where:
R = Reliability (expressed as a decimal)
a = (1 / (1 - 0.95))^(1/3) ≈ 3.87298
Now, calculate the actual life (L₉₅) required for 95% reliability:
L₉₅ = a * L₁ = 3.87298 * 347,826.09 ≈ 1,347,821.74 revolutions
To achieve a 95 percent reliability for 10,000 hours (10 kh) of operation at the given load and speed, the bearing should be expected to carry the load for approximately 1,347,822 revolutions.
Now, search for a bearing in the SKF catalog with a dynamic load rating (C) equal to or greater than the applied load of 400 lbf and a life rating (L₁) greater than or equal to 1,347,822 revolutions. This should provide a bearing that can carry the load with 95 percent reliability for 10,000 hours.