Experimental Investigation Into the Condition of Insulated Rail Joints by Impact Excitation

M Oregui,M Molodova,A Núñez,Z Li,R Dollevoet

doi:10.1007/s11340-015-0048-7

Abstract

This paper presents a feasibility study to determine if the health condition of Insulated Rail Joints (IRJs) can be assessed by examining their dynamic response to impact excitation. First, a reference dynamic behavior is defined in the frequency domain of 50-1200 Hz based on field hammer test measurements performed on a IRJ baseline (i.e., a set of IRJ without visible damage). Then, measurements on IRJs with different damage states are compared to the IRJ baseline response via the frequency response function (FRF) based statistical method. Three cases of IRJs are analyzed: a IRJ with a broken fastening, a IRJ with a damaged insulation layer and a IRJ with a rail top with plastic deformation. Combining hammer test measurements, hardness measurements and pictures of the IRJs, two frequency bands were identified as characteristic for damaged IRJs. In the identified high frequency band (1000-1150 Hz), the measured dynamic response with both a vehicle-borne health monitoring system and hammer tests shows a clear difference between the damaged IRJs and the IRJ baseline. Furthermore, different damage types may be able to be identified by examining the dynamic responses in the identified mid-frequency band (420-600 Hz). Further analysis over a larger number of IRJs may complete and support the promising results so that the information can be employed for the condition assessment and monitoring of IRJs.

Highlights

The information obtained in this paper could be used and further completed, if the difference in the loading of the track between the hammer test measurements and the axle box acceleration (ABA) system does not influence the frequency bands related to damaged Insulated Rail Joints (IRJs)
A feasibility study is presented to assess if the health condition of Insulated Rail Joints (IRJs) can be determined by analyzing their response to impact excitation
The condition of IRJs was investigated by comparing the vertical dynamic behavior of damaged IRJs to a IRJ baseline response via the frequency response function (FRF) based statistical method

Summary

Introduction

The wavelength of the measured hardness profile is between 35 and 45 mm (Fig. 12(a)), which combined with the nominal train speed of 140 km/h, results in vibrations at the frequency range of 865– 1111 Hz. For the N4 configuration, the FRF-based statistical method identifies 566 Hz as a possible frequency related to the IRJ with broken fastening. For the N4 configuration, the FRF-based statistical method identifies 566 Hz as a possible frequency related to the IRJ with broken fastening This type of damage affects the interaction between the sleeper and the rail, which is one of the dominant phenomena defining the dynamic response of the track in the medium frequency range [17, 21, 30, 31]. The rail top is plastically deformed, the structure of the IRJ has not changed enough for hammer tests to detect the changes

Findings

Discussion

Conclusions