This new method of predicting steel product lifespan is more accurate and more efficient
Manufacturer NSK has unveiled an efficient method for accurately predicting rolling bearing lifespan based on the size and number of non-metallic inclusions in the bearing’s steel.
Normally, a manufacturer’s catalogue is used to predict how long a rolling bearing might last. Another way to predict rolling bearing lifespan is through a calculation involving the external loads and bearing information. These methods are in accordance with the ISO 281:2007 standard developed in 1962, which requires 90% reliability, with nine out of every 10 identical bearings making it through those million revolutions without a problem.
This calculation can increase the predicted service life of rolling bearings. There are drawbacks, however, one being that any modifications made to rolling bearings needs to be tested further, using time and resources.
NSK’s new prediction method is less invasive due to less disruptive testing, but it can also predict lifespan more accurately, lengthening the time rolling bearings can operate before being replaced. Some can even last twice as long as what the old calculation predicted.
NSK’s research found that the proportion of steel containing non-metal impurities has a significant impact on the bearing’s service life. Because of this, the company’s engineers based their evaluation method on fracture mechanics, analysing the propagation of cracks in the rolling’s material over time.
From there, NSK introduced computer-aided models to create a “digital twin”, whose digital measurements would replace service life tests. The company collaborated with Kyushu University in Japan to determine which factors influenced the process of crack formation. By combining the new method with ultrasonic inspection techniques that scan non-metal inclusions in steel, NSK can now predict the longer lifespan of its bearings more accurately.
"We are delighted by this breakthrough, which we believe will be of clear and tangible benefit to our customers," said Paul Cranston, the NSK European aftermarket director. "The industry has been calculating bearing lifespans the same way for decades, despite huge developments in knowledge and technology during that time. Our new calculation method will see the lifespans of several of our leading products extended, some quite significantly, and I am delighted that NSK has been the driving force in bringing this new method to the market."
If the lifespan of bearings is longer, then it can handle higher load conditions, meaning a company can have smaller bearings perform the same as larger ones. This allows for machine downsizing and weight reduction.
Bearings are found in machinery and equipment across industries, limiting motion to a desired level and reducing friction by preventing metal-on-metal sliding.
There are a variety of bearing types, one of the most common being the rolling bearings. Rolling bearings contain rolling cylinders that encourage movement without metal scraping. It is important to maintain rolling bearings to prevent the cylinders from wearing down and limiting function.
NSK has a range of products that will now incorporate its method of measurement to optimise performance, including angular contact ball bearings, cylindrical roller bearings, deep groove ball bearings and tapered roller bearings.
