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According to the best records obtainable, magnetic particle testing was introduced on the railroads to find detail fractures in locomotive and car axles. On the Pennsylvania Railroad the first beginnings came in 1933–1934. There seem to have been two reasons for making a beginning with axles. First, detail fractures in anything as important as an axle are always serious; and secondly, a dismounted axle presents the simplest shape for application of magnetic flux and powder particles. Figure 1 illustrates the earliest form of magnetic particle testing, using a simple permanent magnet of “horseshoe” type. Figure 2 illustrates an early development of testing electric locomotive axles, where the wheel fit portion of the axle was receiving special attention. Magnetic flux was provided by the vertical solenoids near the end of each axle, and the method used was dry powder. Figure 3 shows a later development, designed for testing the journals of mounted wheels by the wet method. The illustration also shows the roller mounting, permitting easy rotation of the wheels, and pneumatic piston hoist for raising the wheels up into position for testing. From the start on axles, the use of magnetic particle testing progressed rapidly in the railroad field, as the necessary technique was developed for handling more and more complicated shapes of iron and steel members. Testing outfits have been set up at the main locomotive and car shops, at principal engine terminals, and in wheel and axle shops. Men specially trained and qualified are assigned to the work, because the successful application of the test requires considerable experience; but where the necessary skill has been developed, tests can be carried on with both speed and accuracy.
Jones, L. B.
Engineer of Tests, The Pennsylvania Railroad, Altoona, Pa.