Regarding NTN-SNR’s State of the Art, the qualification of the bearings with ceramic rollers needs many research activities. The maturity of hybrid ball bearings is high (TRL5) but there are some differences between the behaviour of a ball bearing and a tapered roller bearing due to the difference in types of contact. (Elliptic contact for ball bearing and linear contact for roller bearing + contact between shoulder and roller face). The Technology Readiness Level (TRL) for hybrid tapered roller bearings at the beginning of the project was around 3. To be able to introduce the hybrid bearing on all the aerospace applications, it is necessary to qualify all types of bearings. The demonstration of a TRL 5 on the technology is also mandatory to be allowed to perform some tests on the complete system.
The innovative test plan will allow to demonstrate the TRL 5 at the end of HEROe Bearing project. These means of demonstration will prove:
- the better behaviour of hybrid tapered roller bearings in comparison with full steel bearings,
- the non-instantaneous failure mode,
- the allowable limit contact pressure,
- the definition of the critical defects
- and the better oil off behaviour.
All these answers will prove that hybrid tapered roller bearings are safe for aerospace applications.
The NTN-SNR objectives for this project are to develop, design, manufacture, test and simulate the new generation of tapered bearings for aerospace applications and especially for the helicopter gearbox bearings. For NTN-SNR, hybrid bearing is a promising solution for aerospace market especially thanks to the weight saving and the potential improvement of the bearing life duration it offers.
To do so, the hybrid bearing prototypes will be designed, calculated, manufactured, and tested to compare steel and hybrid bearing behaviour and to demonstrate the benefits.
For test activity, the objective is to perform the back-to-back assessment under several test conditions (clean environment, contaminated conditions, poor lubrication conditions, oil shut off conditions and tests with defect on rollers) in order to demonstrate the benefits offered by hybrid tapered roller bearings.
In order to start aerospace mass production of hybrid tapered roller bearings, the critical defects (size, shape, location on the rolling element) have to be defined. Hence one of NTN-SNR’s objective is to determine the size of critical defect on tapered roller bearing performance. This critical size will allow to define the efficient quality inspection to be performed and define the methods of inspection.
The last objective is to simulate the hybrid bearing behaviour in order to update NTN-SNR’s handbook and design rules to guarantee the quality, the robustness and the optimization of our bearing designs.
