Use of Magnetic Flux Techniques to Detect Wheel Tread Damage

Rail vehicle wheelsets are regularly maintained to ensure their safe operation on track and prolong their life. This is achieved through measurements to inspect roundness, profile shape (wear), rim thickness and visual inspections of surface damage. If necessary, wheels are turned on a lathe to preserve the optimal wheel shape/profile and remove any visible surface damage.

Surface damage is difficult to classify visually, leading to highly subjective results. It is also not possible to establish defect depth through visual inspections. Wheel turning removes this damage, but there is a crucial balance between removing enough material to eliminate the defects whilst taking the minimum cut to preserve the rim thickness (i.e. wheel life). As such, the wheel lathe operator will take multiple small cuts to prevent excessive material removal. This increases the time that the vehicle is on the wheel lathe (out-of-service) rather than in revenue-earning service.

Magnetic flux technology has been successfully applied to the detection of surface and sub-surface defects in rails. Work is currently on-going to adapt this technology for the evaluation of wheel damage. This will produce a fast, repeatable method of quantifying damage on railway wheels. Resulting in reduced inspection times and optimised wheel turning; saving time and increasing wheelset life. Management and trending of the recorded data will enable maintainers to identify problem vehicles or wheelsets and plan maintenance in advance. This will also assist train operators when evaluating wheelset performance and costs.

This paper will describe the theory behind the magnetic flux technique and how it has been applied to the detection of wheel tread damage. This will include a summary of the assessment of the surface size, shape, position and depth of damage into the wheel tread for a range of in-service and scrap wheelsets. The benefits to an operator of adopting this technology will also be described.