Capabilities of acoustic methods in testing of interference-fit joints

Abstract

Tightness of joints on railway wheelsets is controlled by instruments based on a shrink fit method. To date, the shrink fit method has been replaced by an interference fit method. As a result, standard values of tightness have doubled. Therefore, there is an urgent need to upgrade and develop new methods for testing interference-fit joints. A promising solution is to use acoustic methods based on influence of material properties on propagation patterns of elastic waves. The purpose of this study is to evaluate the possibility to test fixed detachable joints by acoustic methods. Reference samples of interference-fit joints with known interference fits (29, 72 and 126 μm) were designed and produced. Experimental tests of samples and wheelset axles with inner bearing rings were conducted by a pulse-echo method and a method of free oscillations. The authors developed a procedure for determining the equivalent thickness of oil clearance using the proportionality factor of echo amplitude and sequence number of echo signals. When testing reference samples and loose bearing rings, frequency responses of the signals were obtained.