Award Date
12-1-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil and Environmental Engineering and Construction
First Committee Member
Jee Woong Park
Second Committee Member
Hualiang Teng
Third Committee Member
Ying Tian
Fourth Committee Member
Samaan Ladkany
Fifth Committee Member
Yingtao Jiang
Number of Pages
114
Abstract
Rail defects, whether internal or external, present significant safety risks. Acoustic Emission (AE) technology has emerged as a promising technique for monitoring damage progression and detecting these rail defects. This project addresses this critical concern by testing air-coupled optical microphones for non-contact AE detection. The goal of this research is to investigate AE signal characteristics using both rail-mounted and vehicle-mounted methods, establishing the understanding of AE signals in relation to defects and their effectiveness in identifying them.
This research focused on investigating air-conduct sensors in the lab-controlled pencil lead break (PLB) test. The objective was to evaluate the propagation characteristics of AE signals in two scenarios: signal attenuation in the air and within the rail. These tests were particularly designed to assess the prototype's performance under varying conditions, including different speeds and defect types. Following the controlled experiments, the research conducted real-world field tests at two different test locations: the Nevada Railroad Museum and the MxV Rail (formerly known as the Transportation Technology Center, Inc (TTCI)). These sites offered diverse testing conditions, allowing for a broader evaluation of the system capability. Data collected from all tests were analyzed to assess the effectiveness of the system, when mounted on a moving train to detect both internal and external rail defects.
The result of both tests revealed two key findings. First, the AE detection rate varied significantly between tests, with a rate of 8.3% in the Nevada field test and 13.3% in the MxV Rail test. This difference suggests that AE detection rates may be influenced by defect size and conditions in the field environment. Second, wavelet packet power (WPP) analysis highlighted substantial differences between PLB-induced AE signals and those from actual rail defects. While PLB signals displayed broader energy distribution across the frequency range, the AE signals from rail defects exhibited concentrated and intense peaks within the 100-160 kHz range.
Overall, the non-contact sensor system demonstrated promise for detecting internal rail defects, effectively capturing AE signals without disrupting train operations, making it suitable for real-time rail health monitoring. However, the detection of external defects demonstrated low performance due to indistinct AE signal characteristics (compared with internal defect induced AE signals) and significant environmental noise. The application of continuous wavelet transforms (CWT), and wavelet packet power (WPP) analysis presented more results by identifying energy distributions and frequency peaks associated with defect types. Although these methods enhanced the detection of external defects, additional research is required to refine the identification process.
In conclusion, these findings offer valuable insights into developing more effective and reliable AE-based monitoring solutions. They highlight the current capabilities of these systems in detecting different types of defects, ultimately contributing to improved railway safety and maintenance efficiency.
Keywords
acoustic emission detection; rail defect detection; rail health monitoring; railroad infrastructure; wavelet analysis
Disciplines
Civil Engineering
File Format
File Size
2900 KB
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Jia, Lei, "Non-Contact Acoustic Emission Detection of Rail Defects Using Air-Coupled Sensors" (2024). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5180.
http://dx.doi.org/10.34917/38330392
Rights
IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/
