arXiv:2610.30541v1 Announce Type: new Abstract: This study evaluates a non-contact screening method for stationary railroad wheelsets using air-coupled ultrasonic measurements excited by hammer impacts. Two decay features are considered. First, an effective damping ratio is obtained by normalizing the measured decay rate by the dominant response frequency. Second, strike-to-strike variations are measured to assess the quality of the energy-decay fit for the overall wheel. The method was evaluated using 22 wheelsets at two railroad facilities. The analysis indicates that a random forest trained on one dataset and tested on another performed poorly. This result motivated a simpler approach based on thresholds applied to the two decay features, which fixed the feature definitions and calibrated the thresholds on either dataset. This approach correctly classified every wheelset in the other dataset. A more stringent wheel-level validation repeated second-feature selection and threshold calibration while each test wheelset was withheld. This procedure correctly classifies 21 of 22 wheelsets. All defective wheelsets are identified, while one healthy wheelset yields a false positive. The results further show that the two-feature detector transferred between the tested datasets for stationary assessment of wheel damage. Further evaluation is required using worn but serviceable wheels, controlled support conditions, and additional independent datasets.