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 To date, the shrink fit method has been replaced by an interference fit method.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.
Highlights
Wheelsets with axle assemblies are the most important elements of undercarriage in railway cars
The wheelset manufacturing technology implies using fixed detachable joints made by the interference-fit method
Due to insufficient strength of these joints, which is partly associated with a loose inner bearing ring, axle assemblies of wheetsets may fail during operation
Summary
Wheelsets with axle assemblies are the most important elements of undercarriage in railway cars. The wheelset manufacturing technology implies using fixed detachable joints made by the interference-fit method. Due to insufficient strength of these joints, which is partly associated with a loose inner bearing ring, axle assemblies of wheetsets may fail during operation. The interference fit of the inner bearing ring onto an axle journal is determined before installation of the axle assembly. Special devices are used to measure diameters of seating faces of the ring and axle in loose state. Based on a difference in diameters, the interference fit is estimated. Measurement errors, scuffing from press fitting, and rotation of the ring during operation can deteriorate the quality of fit. In order to ensure traffic safety, reduce downtime of trains and cut costs of unscheduled repairs, these joints should be subject to complete inspection
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