Strain Gauge Laboratory Experiment Enrico Lubbe – 23573260 1. Background of experiment This experiment will investigate the capturing and understanding of vertical wheel force loads on a rail section using strain gauges. The Chinese standard TB/T 2489-2016 will be utilised to obtain a deeper understanding of how the measurements are taken and what the output will be. This experiment will provide insight into what type of results can be expected and how the boundary conditions affect the results. 2. Test procedure 2.1. Objectives The main objectives for the experiment include the following: • • • • Understanding the test procedure in TB/T 2489-2016. Validate the results with the weight of the wheel. Evaluate how static and dynamic loads affect the measurements. Understanding the effect of boundary conditions on the measurements. Alongside the main objectives, the following secondary objectives to satisfy: • • • • Gain exposure to strain gauge setup on a rail section. Familiarizing with the setup of the measurement equipment. The time required to perform a full setup before measurement occurs. Testing of the neutral axis finder prototype. 2.2. SU Equipment and resources The following tools and equipment are required to perform the test. Description Laptop (1 or 2) Quantum Backplane CX22 MX1615B Extension cord Power Drill Wire brush (Drill bit) Sanding paper (varying grit) Strain Gauges Asset Number 539986/539985 - Serial Number 801432022002 F0F9F782EAB5 0009E5024A2A - Location Red Cupboard Red Cupboard Backplane Backplane Red Cupboard MMW Red Cupboard MMW - MMW/Red Cupboard Strain gauge equipment (Acid, Base, Acetone, etc.) Soldering Iron & wire Tripod Ruler - - MMW - - MMW Personal Personal 2.3. Test procedure All safety procedures, as pointed out in the safety report for this experiment, will be adhered to. Strain gauge setup 1. The TANDM procedure for applying strain gauges will be followed. 2. After the surface has been prepared, use the neutral axis finder prototype to obtain the neutral axis and evaluate the efficiency. 3. Apply the strain gauges to the rail. The general configuration of the strain gauges is displayed in Figure 1. A total of 8 strain gauges will be installed. Figure 2 provides a closeup of the configuration. Figure 1: General strain gauge application Figure 2: Close-up of the configuration 4. Wire the strain gauge in a full bridge configuration as depicted in Figure 3. Figure 3: Full bridge configuration for testing vertical wheel-rail force Pay special attention to the numbering scheme. Correlate it to the HBM configuration guide. The setup guide for the HBM equipment can be found in Appendix A. Setup of measurement equipment 1. 2. 3. 4. 5. 6. Place the backplane on a secure workbench and switch on the laptop. Switch on the backplane and connect the laptop to the CX22. Connect the wired full bridge strain gauge connector to the MX1615B. Configure within Catman AP the sensor. Display the force measurement on the screen. Place a known weight over the test section to calibrate and validate the strain gauge readings. Test Procedure The test procedure will be broken up into 2 parts. The first part will address the static load of the wheel, while part two will focus on the dynamic load of the wheel on the measurements. Static Testing 1. Before moving the wheel, ensure that the strain gauge measurement is zeroed. 2. Mark on the rail the centre point between the strain gauge setup with chalk. 3. Roll the wheelset to the centre of the strain gauge setup. Place chock blocks on either side of the wheel to ensure the wheel does not move during measurement. 4. Start the measurement on Catman and run for 15 seconds. 5. Stop the measurement and save it using the following naming convention. (Static test #). 6. Move the wheel back to the end of the rail and secure it with chock blocks. 7. Make sure the force measurement has returned to equilibrium on Catman. 8. Repeat steps 1 to 6. The static testing will be done at least 5 times to ensure the measurement equipment works. The results will be compared to the expected vertical force of the wheel. The result table can be found in Appendix B.1. Dynamic testing For dynamic testing, a cell phone will capture video footage of the wheel passing by the measurement equipment. This footage will be imported into the Tracker Software to determine the speed of the wheelset. 1. 2. 3. 4. 5. 6. Place a ruler with known dimensions in the field of view of the camera. Mark the starting position of the wheelset on the rail with a piece of chalk. Before moving the wheel, ensure that the strain gauge measurement is zeroed. Start the measurement on Catman as well as the video on the cell phone. Remove the chocks and provide a gentle push to the wheelset. Allow the wheelset to roll past the measurement equipment and come to a complete stop. Place the chock in front of the wheel. 7. Stop the measurement and video. Save the measurement using the naming convention (Dynamic test #) 8. Roll the wheelset back to the starting point. 9. Repeat steps 3 to 8 The dynamic testing will be performed at least 10 times. The reason is that the speed of the wheelset will only be evaluated after the tests have been done. This will ensure that enough data has been captured to group similar speed measurements together. The results table can be found in Appendix B.2. Special attention should be given to temperature effects. All sets of tests (static or dynamic) should be done at relatively the same temperature. More tests can be run to ensure data repeatability. Notes should be made of the known defects on the wheel to explain abnormalities in data measurement. See Appendix C. Appendix A The Quantum MX1615B configuration for a full bridge, resistive circuit, can be depicted in Figure 4. Figure 4: QuantumX documentation Comparing this Figure 3, the new configuration, using the HBM configuration, is displayed in Figure 5 Figure 5: Final configuration of Wheatstone bridge Appendix B Appendix B.1 Static measurement Table 1: Static measurement results Wheelset mass No load measurement Test Number 1 2 3 4 5 Appendix B.2 Force measurement Dynamic measurement Table 2: Dynamic measurement results Wheelset Mass No load measurement Test Number 1 2 3 4 5 6 7 8 9 10 Force measurement Speed Appendix C Defects Wheel ID Defect
