Measuring rail/wheel contact points of running railway vehicles

It has been difficult to detect lateral contact point of rail and wheel, though technology of instrumented wheelset has advanced in the last 20 years. Therefore, it is interesting and worth while to study on method of measuring rail/wheel contact point and contact force of running railway vehicles, since many things in real rail/wheel contact phenomenon are still unknown. Recently, we have tried to develop a method of measuring rail/wheel contact point by improving conventional method of measuring wheel load and lateral force in which strain of the disk surface is used for measuring these forces. Firstly surface strain on disk type wheel is analyzed by an FEM program, NASTRAN, under the condition that vertical, lateral, or longitudinal force separately acts on various points along the wheel profile. By the calculated result, it shows possibility of detecting the rail/wheel contact point by means of measuring lateral distribution of compress strain which changes according to the load position, i.e. rail/wheel contact point. Secondly the idea above is verified by static load experiments using an actual disk type wheelset. The location of an area where lateral force affects little on surface strain is investigated, since the lateral distribution of strain should be measured in such an area to avoid the interference of bending by lateral force. And the theory for the measurement is modified for on-track testing and the best position and direction for strain gauges is proposed in accordance with the calculated and experimental results. Finally, two wheelsets for the measurement are made and field running test using this method is performed to collect data in various kind of running conditions.