Theoretical Reevaluation of Basic Dynamic Load Rating and Rating Life for Linear Bearings

• Published in: Tribology transactions Vol. 51; no. 4; pp. 460 - 468
• Main Authors: Shimizu, Shigeo, Shimoda, Hirokazu, Sharma, Chandra S.
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 29-07-2008; Taylor & Francis; Taylor & Francis Inc
• Subjects: Applied sciences; Basic Dynamic Load Rating; Bearings; Bearings, bushings, rolling bearings; Drives; Exact sciences and technology; Life Formula; Life Modification Factor; Linear Bearing; Load; Mechanical engineering. Machine design; Precision engineering, watch making; Rating Life; Rolling contact; Tribology; Line contact; Point contact; Probabilistic approach; Ball screw; Life Formula; Durability; Basic Dynamic Load Rating; Life Modification Factor; Linear Bearing; Modeling; Rolling bearing; Linear guide; Contact line; Rating Life; Scaling; ISO standard; Bearing cage; Dynamic load
• ISSN: 1040-2004; 1547-397X
• DOI: 10.1080/10402000802016926

Linear motion rolling bearings, also known as linear bearings, were included as standard rolling bearings by ISO in 2004. In this standard, the basic dynamic load rating C and the rating life L
10
are based on only for a standard stroke S
St
defined by a linear movement with twice the raceway length 2l
t
for a carriage. However, if the stroke S
t
is shorter than S
St
the rating load becomes considerably smaller than the defined C value due to the effect on the probability of flaking occurrences for the rolling bodies and, conversely, if the stroke is larger than the S
St
, the rating load becomes larger than the C value due to an increase in the rating load for the rail raceway surface. This article deals with the theoretical re-evaluation of the basic dynamic load rating and the rating life for linear bearings based on the Lundberg-Palmgren theory, but with a minimum life for the population as the third parameter. The rating load is defined by 100 km as unit running life (URL) mentioned in the ISO standard, and an arbitrary stroke is defined along with a stroke factor a
ST
, which is introduced into the life formula as a life modification factor for the linear bearings. As a result, a
ST
= 0.4-1.07 (for point contact) and a
ST
= 0.3-1.14 (for line contact) from a very small stroke, 0.2 times of the rolling body pitch to a large stroke, S
t
= 10l
t
, are obtained.