Following on from our last update, the team have been hard at work completing the setup for the start of the vibration testing. Days 2-3 saw the team complete their inspections and functional tests on PROVE. It was noticed that the TIR lens wasn’t fully secure, this could have been dislodged in transport or the team could have simply been too sparse with the application of their thread locker. This is a type of non-permanent epoxy that allows the team to secure threaded items down but still gives them the ability to remove them with a small addition of torque. The team then developed a procedure to remove the lens, inspect it, clean it and then reattach it safely whilst avoiding unnecessary damage to other components or thread locker fragments contaminating the rest of Pathfinder.
The effect of using UV light for inspections can be seen in Figures 1 and 2, UV inspection lights are used to identify the presence of organic matter or thread locker. This allows the team to clearly check the cleanliness of components, especially when checking for the smallest amounts. The team used UV whilst cleaning the TIR lens with acetone to remove the failed thread locker. It was also used to check for other contaminants such as fingerprints or excess thread locker that had made their way to places that they shouldn’t have.
Once the reinstallation procedure was finished, the final shear panels were installed with bolts torqued and then witness marks were added to each bolt. These marks are used to quickly and visually determine if the bolts have shaken loose in vibration testing.
Figure 3, above, shows examples of witness marks on the PROVE-shaker adapter plate. The control accelerometers, c1 on the far right and c2 on the far left can also be observed. The shaker’s control system uses c1 and c2 in a closed feedback loop to control the profile of the vibrations being applied to the DUT (Device Under Testing). The maximum reading between the two is taken so that it provides the control loop with the maximum vibration that the DUT experiences. They are deliberately placed at points where lines of symmetry on the adapter do not exist. This is because mode shapes often exist along lines of symmetry. If the adapter is resonating and both control sensors are detecting this resonance shape, there is a chance that you shall under-test your DUT.
Pathfinder is now set up on the slip table and ready for testing, next post – some shaking!