6. Measurement method of contact force and contact position between wheel and rail using shear strain

In running tests for evaluating vehicle running safety, the force in lateral direction (lateral force Q) and the force in vertical direction (wheel load P) acting between the wheel and rail are measured using a special wheelset called an instrumented wheelset. In the current instrumented wheelset, which converts the bending strain occurring in the wheel plate into lateral force, there is a problem where the position of the wheel load affects the measured value of lateral force, resulting in errors (Figure 1).

In this study, we developed a "shear strain-based lateral force measurement method" that is less affected by wheel load than the current method (Figure 2), and have proven that it can reduce the error in the derailment coefficient Q/P, which is used as an index for evaluating running safety, by up to 18% (Figure 3). This enables more accurate running safety evaluations at the same cost as conventional method.

We also developed a method to measure the position in which the wheel contacts the rail from the strain output waveform of the instrumented wheelset, and found that the contact position can be measured with an error of about 5 mm within the range where contact is not reached at the flange straight section (Figure 4). This method can be used for various technological developments related to wheel and rail contact (e.g., performance evaluation of new wheel profiles).