Finite Element Modeling of the Bulk Magnitization of Railroad Wheels to Improve Test Conditions for Magnetoacoustic Residual Stress Measurements

The magnetoacoustic measurement technique has been used successfully for residual stress measurements in laboratory samples[1-4]. However, when used to field test samples with complex geometries, such as railroad wheels, the sensitivity of the method declines dramatically[5,6]. It has been suggested that the decrease in performance may be due, in part, to an insufficient or nonuniform magnetic induction in the test sample[6]. The purpose of this paper is to optimize the test conditions by using finite element modeling to predict the distribution of the induced bulk magnetization of railroad wheels. The results suggest that it is possible to obtain a sufficiently large and uniform bulk magnetization by altering the shape of the electromagnet used in the tests. Consequently, problems associated with bulk magnetization can be overcome, and should not prohibit the magnetoacoustic technique from being used to make residual stress measurements in railroad wheels.