The ?C-219 instrument for testing the tightness of bearing races

Abstract

This instrument is based on a new method for testing the quality of fitting the inner bearing race on a wheelset axle of a railway car. The operating principle of this instrument is described, and its performance characteristics are presented.One of the problems associated with the provision of railroad safety is the absence of both reliable methods and commercially produced instruments for testing the quality of fitting (i.e., tightness) of inner bearing races on the wheelset axles of railway cars [1][2][3][4][5][6][7]. The standard technique currently in use [8] is characterized by inadequate reliability, because it consists of measuring the diameters of a race and an axle before they are assembled. In this case, it ignores the fact that the procedure of heating the race and setting it on the axle, which is characterized by a great number of random parameters, has a very strong effect on the quality of the fit.Below we describe a èë -219 instrument based on a more reliable inspection method in which a race that has been fitted on an axle is subject to inspection. The function of the instrument consists in measuring the period of time it takes for a pendulum that collides with a race that has been fixed over an axle (Fig. 1) to perform a predetermined number of oscillations. The fit (tightness) is considered normal if the measured time interval is greater than a certain preset value.In a laboratory experiment carried out before designing the instrument, a 12-mm-diameter steel ball was suspended on a thread 70 mm long. The optical axis of a photon-coupled pair (an LED and a photodetector) was located 12 mm away from impact point A .Upon incidence and following recoil, the ball shut off the optical beam's path. As a result, a sequence of output pulses was formed by the photodetector. By processing these signals with a counter and a timer, it was possible to measure the time taken for a predetermined number of pendular oscillations. The first oscillation began when the pendulum was released at starting point B .When the ball collided with the race, a portion of its kinetic energy was transformed into the potential energy of elastic deformation, and the other portion was converted into the energy of a longitudinal acoustic wave propagating toward the axle. The coefficient of the wave's reflection from the race-axle interface varied according to the quality of the race's fit on the axle. As a result, the reflected wave (its front reached point A before the mechanical interaction between the ball and the race ended) changed in amplitude, which altered the kinetic energy of the ball after recoil.The external appearance of the instrument is shown in Fig. 2. There is a semicircular mounting seat at its bottom; its width is equal to that of the raceway in a bearing. When the instrument is placed on the race being tested, the mounting seat must register perfectly with the raceway. A liquid-crystal display, a control panel, and a level are all located on the upper panel of the instrument. The body of the instrument is prote...

Capabilities of acoustic methods in testing of interference-fit joints

“…Acoustic methods described in [1][2][3][4][5][6] are the most advanced approach to testing interference fits. The ultrasonic method is based on a dependence of the reflection coefficient of ultrasonic waves at the joint interface on the tightness of fit [7].…”