After years of research and development, NSK is revising the basic dynamic load
rating of many bearings by up to double the equivalent rolling contact fatigue life
(with no change in design or materials). NSK is the first company in 60 years to make
a significant breakthrough in bearing life calculation techniques, helping end users
to improve productivity and boost environmental protection.
Some engineers may be surprised to learn that the fundamental formulas used to calculate
bearing life are more or less the same as those defined in a 1962 report by the International
Federation of the National Standardizing Associations (ISA), the precursor to the
International Organization for Standardization (ISO). In 2023, over six decades later, NSK
has learned a few more things about calculating and predicting bearing life, making it time
to reconsider the evaluation techniques for this critical parameter.
The project began around 20 years ago, when NSK noticed a growing gap between the
bearing life calculated in the ISO standard and the actual bearing life verified by endurance
testing. A more detailed study commenced.
At that time, NSK confirmed that the life of its bearings was approximately 20 times longer
than the life expected under ISO standards. And today, in 2024, the life of NSK bearings
can be more than 50 times longer. Erring on the side of caution is fine, but longer bearing
life is beneficial to improve production efficiency and protect the environment by reducing
the frequency of replacement and quantity of waste.
NSK research demonstrated that, under well-lubricated conditions, the composition and
quality (amount of impurities) of the bearing steel is a more accurate indicator in predicting
how long a bearing will last. However, as the company continued its research, engineers
realised that an evaluation method based on fracture mechanics might provide more
meaningful insight.
Technology development commenced via an open innovation project between NSK and
Kyushu University. The result was the establishment of a quantitative evaluation method
that could determine which factors influenced the process of crack propagation in a
material, and to what extent. Notably, by combining the new method with an ultrasonic
inspection technique that scans the non-metallic inclusions in a large volume of steel, NSK
discovered it could predict the life of its bearings with much higher accuracy.
With the establishment of the Micro-UT ultrasonic inspection method, it is today possible to
PR Ref. B142023-N | 1/3
1/3
inspect more than 3,000 times the volume of steel compared with conventional microscope
methods in just 20% of the time. NSK already has these innovative testing systems in place
at its Technology Centres around the world.
The company's current catalogue contains a very large number of bearing types, and the
applications and conditions of use by customers are also diverse. In order to ensure that
customers can use NSK bearings with confidence, the company is reviewing the basic
dynamic load ratings in consideration of an appropriate safety margin. Customers can rest
assured that the updating process will take place based on well-researched methodology
supported by extensive empirical data. Any uprated values will be well within the safe
range.
Press pictures:
1) Non-metallic inclusions in the inner raceways are a significant factor behind flaking
2) Diagram of Micro-UT method (ultrasonic testing to detect non-metallic inclusions)
3) The size and amount of non-metallic inclusions helps predict the life of rolling bearings
PR Ref. B142023-N | 2/3
2/3
About NSK Europe
NSK Europe Ltd. is the European organisation of the Tokyo-based bearing manufacturer NSK, which was
founded in Japan in 1916 and today employs nearly 29,882 people in its worldwide operations. The products
and solutions provided by the industrial and automotive supplier can be found wherever things move. In addition
to nearly all types of rolling bearings, the company's portfolio includes housed bearings, linear technology,
wheel bearing units, transmission and engine bearings. The company is oriented to perfection in all of its
business activities. Its aim is quality leadership in its industry, which it strives for through a continuous process of improvement, excellent product development, optimised production processes and customer-oriented service processes. In fiscal year 2022, the more than 4,030 employees of NSK Europe Ltd. generated sales of over €893 million

MENAFN08012024005446012082ID1107697315