Non-Contact 3D-Vision System for Rail Neutral Temperature Measurements


Reference #: 01303

The University of South Carolina is offering licensing opportunities for Non-Contact 3D-Vision System for Rail Neutral Temperature Measurements



Continuous Welded Rail (CWR) has become the standard in modern railway track construction around the world because it alleviates the well-documented disadvantages of rail joints in a track. CWR practice results in very long segments of continuous rail in the track that will develop significant thermal elongation. To avoid the use of impractical large thermal expansion joints, while limiting the expected larger thermal elongation of the rail, the latter is anchored to the ties in the longitudinal direction. Consequently, the rail is exposed to higher thermal stress demands as temperature varies. At the time a CWR is laid, the rail is free of thermal stresses; the temperature at that time is known as the Rail Neutral Temperature (RNT). As temperatures deviate from the RNT, significant tensile or compressive thermal stresses are introduced in the longitudinal direction that can lead to a variety of potential problems, including pull-apart and buckling that compromise the integrity of the track and the safety of train operation.


Existing technologies for RNT measurements are not free of shortcomings. Therefore, there is a need for determining the state of stress in the rail at different temperatures, as well as changes of the RNT over time, in a reliable, efficient, and cost-effective manner.


Invention Description:

This invention is a non-contacting, reference-free measurement system and procedure that is used to estimate the temperature at which the rail of a railroad track is stress free (Rail Neutral Temperature - RNT), as well as tracking the change of RNT over time. The proposed system is based on 3D vision and Digital Image Correlation (StereoDIC) techniques and is capable of measuring simultaneously shape and curvature, full field deformations and strain, along with the thermal field throughout the region being viewed.


Advantages and Benefits:

1. Eliminates the need for prior knowledge of thermal strains at time of installation, or any other baseline measurements.

2. Eliminates the need of applying a permanent pattern on the rail since for long term monitoring to estimate the change of the RNT the pattern can be reapplied as needed.

3. The proposed method can be self-validating since the RNT can be estimated in two distinct approaches.

4. Eliminates instrumentation installation and costs since the proposed StereoDIC is a non-contact method. For strain and deformation measurements, the StereoDIC requires only that high contrast patterns be temporarily adhered, engraved or painted on the rail surface, while curvature and out of plane deformation measurements can be also achieved by high contrast patterns projected to the rail surface.

5. Eliminates errors associated with the typical sensor “drift” for long term monitoring.

6. In contrast to strain gages and extensometers that acquire average data at discrete surface locations, the StereoDIC acquires the full field deformations and strains across the entire field of view in the cameras.


This innovation can provide a variety of important benefits when put into practice:

1. It is a simple and cost effective technology that can be deployed quickly on a routine basis, or on demand, and is easy to implement without disrupting service.

2. It improves safety of operations due to timely detection of imminent track instability, or rail failure.

3. It reduces costs for track maintenance because interventions can be prioritized based on knowledge of rail conditions.

4. Data produced by our technology can be integrated with information acquired by other track sensing technologies to provide both comprehensive understanding and also detailed records of the state of the track over time.


Patent Information:
Title App Type Country Serial No. Patent No. File Date Issued Date Expire Date Patent Status
Non-Contact Methods of Rail Assessment for a Railroad Track Nationalized PCT European 19796009.9   4/8/2019     Filed
Non-Contact Methods of Rail Assessment for a Railroad Track PCT PCT PCT/US2019/026267   4/8/2019     Expired
Non-Contact Methods of Rail Assessment for a Railroad Track Nationalized PCT United States 17/051,225   10/28/2020     Published
For Information, Contact:
Technology Commercialization
University of South Carolina
Dimitris Rizos
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