Last week we performed our first vibration test, where we tested our vacuum chamber, the D-SUB holder and our electronics box with the PCB's. Dummy weights were placed on each PCB to simulate the weight of the actual components we will use. This first test was performed to see that our main structures could withstand the expected vibrations from the rocket. We also wanted to ensure that the PCB's with the dummy weights would not crack due to the vibrations (I guess that the electronics group would have gone mad if we broke their real PCB's during the "real" and final vibration test).
The test was done in four steps:
1. We made a sine sweep at 0.25g to search for eigen-frequencies.
2. We made a sinusodial test at Qualification Level i.e. at 4g.
3. We made a random vibration test at Acceptance Level i.e. at 6 grms.
4. We made an additional sine sweep at 0.25 g to compare to the first one to see if the structures had changed (different or modified eigen frequencies).
The results were good and all parts still seems to be alive. However the two graphs from the sine sweeps was not identical, but we found that one of our dummy weights almost was loose, which probably explains the unequality of the graphs.
Here is the experiment mounted on the shaker before the test
Unfortunately the quality was deteriorated after the transfer from my phone, but hopefully you can enjoy it anyway.
In the beginning the frequencies are low and you can see the vibrations clearly, but at the end the experiment seems to be stationary. This is due to the high frequencies (ca 2000 Hz), so actually it is oscillating extremely fast, or more exactly; ca 2000 times/sec.