1 Introduction
2 Principles of bi-directional strain method in measuring rail stress
2.1 Analysis of the states of rail stress and strain
2.1.1 Rail stress–strain relation under the changes of rail temperature
2.1.2 Stress–strain relations under additional longitudinal force
2.2 Bi-directional method improvement for rail stress measurement
3 Rail stress monitoring device
3.1 Stress sensor module
3.2 Rail stress measurement process
4 Correction of measured results
4.1 Analysis of measured results correction due to changes in rail temperature
4.2 Analysis of measured corrected results with sensor under additional longitudinal force
4.3 Analysis of corrected measurement results in total rail stress
5 Test of rail stress using monitoring sensor
5.1 Test of basic temperature stress in rail
5.2 Test of additional longitudinal stress in rail
5.3 Test results
5.3.1 Test of basic temperature stress in rail
No. | Initial rail temperature \( T_{0} \) (°C) | Actual rail temperature \( T_{{\text{c}}i} \) (°C) | Stress measured (MPa) | Theoretical stress (MPa) | Error (%) |
---|---|---|---|---|---|
1 | 25 | 27 | 4.7 | 4.9 | 4.08 |
2 | 25 | 29 | 10.3 | 9.7 | 6.19 |
3 | 25 | 31 | 16.0 | 15.6 | 2.56 |
4 | 25 | 33 | 21.1 | 19.4 | 8.76 |
5 | 25 | 35 | 26.3 | 24.3 | 8.23 |
6 | 26 | 28 | 4.8 | 4.9 | 2.04 |
7 | 26 | 30 | 10.5 | 9.7 | 8.25 |
8 | 26 | 32 | 14.4 | 15.6 | 7.69 |
9 | 26 | 34 | 20.3 | 19.4 | 4.64 |
10 | 26 | 36 | 25.7 | 24.3 | 5.76 |
5.3.2 Test for additional longitudinal rail stress
Exerted axial force \( F_{i} \) (kN) | Stress measured (MPa) | Theoretical stress \( F_{\text{i}} /A \) (MPa) |
---|---|---|
0 | 0 | 0.0 |
10 | 0.9 | 1.3 |
30 | 2.9 | 3.9 |
50 | 5.4 | 6.5 |
70 | 7.7 | 9.0 |
90 | 9.9 | 11.6 |
110 | 12.1 | 14.2 |
130 | 14.9 | 16.8 |
150 | 17.1 | 19.4 |
170 | 19.2 | 22.0 |
190 | 21.9 | 24.5 |
210 | 24.6 | 27.1 |