Keywords: axle box acceleration, detection, fish-plated joint, bolt tightness, crack, battered end.

There are many fish-plated joints in conventional railways, metro and tram ways. The discontinuity at the joints causes large dynamic contact force, resulting in rapid degradation. So far there is still no automatic method of inspection. Inspection by human is labour intensive, unreliable, intrusive and unsafe.

Axle box acceleration (ABA) has until recently has been mainly limited to low frequency applications and to the detection of moderate and severe defects of periodicity characteristics such as corrugations and wheel flats [1], or to large discrete rail defects such as severe squats [2]. In [3] a recently developed ABA system is presented for detection of early squats for life cycle cost management.

This paper first presents the design and calibration of an axle box acceleration measurement system for detection of bolt tightness of fish-plated joints (FPJ). Measured data can be real-time wirelessly transmitted to a data and analysis centre, or they can be stored on a hard-disk on the train or tram, and be fetched at regular interval for analysis. Data analysis can be performed with automatic diagnosis software. The system is subsequently applied to field measurement on a tramway, and bolt tightness is predicted based on the measurement. The prediction is then verified.

Based on the measurement, analysis and verification, the following conclusions can be drawn:

• From ABA three states can be distinguished: tight FPJ, intermediately loose FPJ and completely loose FPJ.
• ABA can detect misaligned or battered rail ends.
• Both Fourier transform and continuous wavelet transform are needed for the diagnosis.

Future work may include

• Developing numerical models to systematically study the relationships between axle box acceleration measurement, various degradation modes and degradation rates of fish-plated joints, so that further development of the system can be less dependent on expensive field testing.
• Extending the instrumentation and algorithm to identification of misaligned and battered rail ends, to detection of certain types of cracks in the rail at fish-plated joints,
• Extending the application to insulated rail joints.

The extensions can mainly be based on numerical modelling, assisted with measurement for calibration and validation.

1

A.M. Remennikov, S. Kaewunruen, "A review of loading conditions for railway track structures due to train and track vertical interaction", Struct. Control Health Monit., 15, 207-234, 2008. doi:10.1002/stc.227

2

M. Molodova, Z. Li, R. Dollevoet, "Axle box acceleration, Measurement and simulation for detection of short track defects", Wear, 271, 349-356, 2011. doi:10.1016/j.wear.2010.10.003

3

Z. Li, M. Molodova, X. Zhao, R. Dollevoet, "Squat Treatment by Way of Minimum Action Based on Early Detection to Reduce Life Cycle Costs", Proceedings of the ASME Joint Rail Conference 2010, JRC2010, 1, 305-311, 2020. (ISBN 978-0-7918-3867-9)

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