Experimental investigation of oscillating bearings in EMA by using accelerated lifetime tests

Kurzfassung

The use of electromechanical actuators (EMAs) for primary flight control is inhibited by the possible occurrence of jamming. During flight operation, a primary flight control actuator (e.g. for roll spoilers or ailerons) perform an oscillating motion. The short-stroke movement has a strong influence on the wear and degradation mechanism of mechanical components such as bearings. In a conventional rotating operating state, bearings fail due to rolling contact fatigue, whereas in an oscillating motion, fretting and false brinelling are the most common expected failure causes. Since the conventional lifetime estimation for bearings (e.g. DIN ISO 3408-5) is not valid for oscillating motion, the lifespan prediction for such applications is difficult. This paper investigates accelerated life testing of needle bearings under short-stroke movement. A test rig is developed and set up to conduct accelerated lifetime tests. The represented application use case is the Liebherr R&D Rotary EMA design for the Airbus A350 roll spoiler.