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Diamond Bearing Tribology Fundamentals
Tribology comes from the Greek word ‘tribos’ which means ‘rubbing’. It is a relatively new science that considers the friction, wear and lubrication at moving contacts. Diamond bearing tribology looks at the physics between two diamond surfaces moving relative to one another, most of the time in the presence of a lubricant.Diamond Bearing Tribology Fundamentals
PCD Bearing Research
US Synthetic Bearings understands that meeting every customer's exact needs is crucial to a successful product. Because of the drive to meet customers' every need, USS Bearings is fully dedicated to developing a close working relationship with each customer -- providing ongoing research and development designed to find the best solution possible. To ensure product quality is met, the engineering teams do extensive, rigorous testing in our in-house bearing testing facility. This ensures that the best products are developed for customers through extensive testing and evaluation.
Laboratory tests conducted by US Synthetic Bearings have validated the numerous advantages of PCD bearings:
- Low friction coefficients, even with full diamond-to-diamond contact
- Ability to operate in boundary, mixed-mode and hydrodynamic regimes
- Resistance to damage during starting and stopping (when operating in mixed-film or hydrodynamic regimes)
- Ultra-long life
- High load capacities
US Synthetic Bearings has recently commissioned a new high capacity bearing test machine. This new machine is capable of several types of tests including wear tests (that last up to several months), capacity tests, friction tests, and fluid film tests. The results from these tests are used to improve the bearing products offered to all customers for their specific applications.
During wear testing, a high axial load is applied for extended periods of time -- from hours to even months. The total diamond wear in the bearing is then measured and converted to a wear rate. Test results are then used to compare the relative wear resistance of different diamond blends, bearing insert geometries, and bearing insert configurations. The results of these wear tests help the US Synthetic Bearings engineering team design the best bearing possible for a given application. Wear test results are also used to predict bearing life in specific applications. The following are examples of wear test results:
During performance testing, US Synthetic's bearings are tested under constant speed, gradually increasing load until bearing failure occurs. Test parameters and bearing designs can be adjusted to meet the customer's design, speed, load, and cooling flow rate. The data gathered during this testing is used to generate pressure/velocity (PV) failure curves which define the safe operating envelope for a given bearing. Test results can also be used to predict required cooling flow rate, expected heat generation, and frictional loss in customer applications.
FLUID FILM AND FRICTION TESTS
During friction testing, a constant axial load for the duration of the test, gradually increasing speed until the test is complete, is applied to all tests. Test parameters and bearing design can be adjusted to meet every customer’s design, load, and cooling flow rate requirements. The data gathered from these tests is used to generate Stribeck curves, which define the lubrication regimes (boundary, mixed film, and hydrodynamic) present at various speeds. This helps the engineering team at USS Bearings understand and predict the expected friction coefficients associated with the bearings for each given application.
PROTOTYPE MACHINE SHOP
US Synthetic Bearings is committed to fast turnaround times on new bearing designs and bearing test results. For this reason, USS Bearings utilizes a skilled prototype machine shop dedicated to making new bearings quickly and at the highest level of quality. This enables costumers make decisions quickly and with confidence.
In addition to laboratory testing, US Synthetic Bearings' engineering staff uses finite element models and proprietary bearing design tools to help predict field performance.