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Rail Neutral Temperature/Buckling Detection in Continuous Welded Rail (CWR) from UCSD

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Contact Information

University: University of California, San Diego    

Team Member(s): Xuan 'Peter' Zhu, Thompson Nguyen, Claudio Nucera, Robert Phillips

Faculty Advisors: Francesco Lanza di Scalea

Email Address:

Country: U.S.

Project Information

Title: Rail neutral temperature/ buckling detection in Coutinuous Welded Rail (CWR), U.S.

A major problem for CWR which has been widely used in highspeed rail industry is the buckling and breakage induced by thermostress during the hot and cold weathers. According to FRA Safety Statistics Data, rail buckling was responsible for 48 derailments and nearly 30 million U.S. dollas in 2006. A related critical parameter is the rail Neutral Temperature (NT)- the temperature at which the net longitudinal force in the rail is zero. To ensure safety of operation in CWR, information on the level of stress in the rail (or NT) is critical. While there are inherent drawback for conventional methods including time consuming, requiring removal from service, and low sensitivity, the proposed ultrasonic guided wave-based method could monitor the stress level in real time and characterize the Neutral Temperature after one temperature variation cycle.


NI LabView 2011, NI PXI 1033, PXI 5411, PXI 5105, PXI 6115

The Challenge:

The proposed method is based on high frequency ultrasonic techniques. The data acqusition system should be composed by arbitrary waveform generator, high speed digitizer. Thus, the PXI 5411 was used to configure and generate the high frequency sinusliodal waveform on the transducer side; PXI 5105 was used to acquire and record the stress waves propagated through cerntain length of rail track on the receiver side. During the practical application, a gate function sychronized with the generated waveform was required for gate amplifier to higher the signal to noise ratio (PXI 6115). The wave generation, data acqusition should be triggered and sychronized simutansously. And in the aspect of operation, the manual mode and auto mode were needed to be user friendly, which turned out to take some more effort than the simple functionality realization.

The Solution:

The vi was composed by two seperated but logically interacted while loops.

For the perspective of functionality, the upper loop configured the  waveform configuration/generation (PXI 5411) and gate function generation (PXI 6115), while the lower loop configured the waveform acquiring and data storage (PXI 5105). Once the data generation and acquistion event was triggered (either manually or automatically), PXI 5411 would be triggered by a software trigger and send the marker event out as the trigger for PXI 6115 and PXI 5105, which insured an integreted generation/ acqusition mechanism.

On the other hand, the event structure and user event were used to control the manual mode and the automatic mode, which was mainly in the upper loop, while the lower side was simply controled by certain boolean values to prevent the data flow stuck.