Development of Double-Insulated Ring Sensors for Hollow Pin Preload Measurement

Abstract

The hinge mechanism of aviation flap is composed of joint bearing, single lug, double lugs, hollow pins and self-locking nuts, etc. This hinge mechanism has accurate requirements for the preload of the hollow pin. When no seizure of the joint bearing occurs, the bolts are required to have sufficient preload to clamp the inner ring of the bearing. Meanwhile, when the seizure of the joint bearing occurs, there shall be no movement between the bearing and pin shaft or the end face of the bushing shall arise. This requires that the tension of the hollow pin shaft shall not be too high, otherwise the friction torque isn’t easy to overcome. However, the method to directly measure the preload in the hollow pin is not available, and the influence law of preload decline on the seizure resistance of the bearings also can’t be evaluated. This paper presents a method suitable for measuring the preload of hollow thin-walled pin parts. By applying permanent piezoelectric thin film transducer onto the end face of the hollow pin, the standardization technology is used to measure the propagation time change of the ultrasonic signal generated by the transducer in the pin as a function of the temperature and preload, thus realizing the accurate measurement for the preload of the hollow pin during installation. Finally, the application verification is conducted by using the measurement method proposed in this paper. The results show that this method can effectively optimize the installation and service performance for the hollow pin.