PSD chart v's simple frequency
PSD chart v's simple frequency
(OP)
Hello
Vibration being my weak area in engineering, I call upon thee to help please.
Can anyone help, I'm having trouble comparing a chart that shows a PSD path against a simple frequency and speed.
I've done a test on a componant to this:
33.3 Hz at 43.12 m/s2
20 Hz to 200 Hz sweep (20-minute reciprocating) at 21.56 m/s2
20 Hz to 200 Hz sweep (20-minute reciprocating) at 9.8 m/s2
I have to try to compare this to a chart that I have been given (see attached), I do not quite understand if this chart is worse than the frequencies I have tested to. At first I though if I squared the PSD numbers it would give me the speed, but I know this is way off. I know this chart shows a random frequency and is not as simple as a staight comparison, however, there must be a rough way of determining which is worse.
Can anyone help me here, I would like it if someone could tell me if the chart is less or more severe. I would like it more if someone could lay out or point me to a simple method of converting the numbers, by simple I mean a method that I could understand. If anyone could point me towards some literature that would help me decide, that would help as well.
Linked file here:
http://f iles.engin eering.com /getfile.a spx?folder =c7c6acda- 4963-4940- a370-e0b61 3033a4d&am p;file=PSD _Chart.JPG
Thank You
Simon
Vibration being my weak area in engineering, I call upon thee to help please.
Can anyone help, I'm having trouble comparing a chart that shows a PSD path against a simple frequency and speed.
I've done a test on a componant to this:
33.3 Hz at 43.12 m/s2
20 Hz to 200 Hz sweep (20-minute reciprocating) at 21.56 m/s2
20 Hz to 200 Hz sweep (20-minute reciprocating) at 9.8 m/s2
I have to try to compare this to a chart that I have been given (see attached), I do not quite understand if this chart is worse than the frequencies I have tested to. At first I though if I squared the PSD numbers it would give me the speed, but I know this is way off. I know this chart shows a random frequency and is not as simple as a staight comparison, however, there must be a rough way of determining which is worse.
Can anyone help me here, I would like it if someone could tell me if the chart is less or more severe. I would like it more if someone could lay out or point me to a simple method of converting the numbers, by simple I mean a method that I could understand. If anyone could point me towards some literature that would help me decide, that would help as well.
Linked file here:
http://f
Thank You
Simon





RE: PSD chart v's simple frequency
I think you are looking for " Sine or Random ? " . Hope fully this coudl throw you some information.
Good luck
Jeyaselvan
RE: PSD chart v's simple frequency
It mentions in that document that there is a 'Q', factor. This is something I do not have available, should I have it? if not, what should it be?
Regards
Simon
RE: PSD chart v's simple frequency
It will depend on whether your system is lightly or heavily damped. You always have to measure that for a given system.
Jeyaselvan
RE: PSD chart v's simple frequency
There is a way to calculate the average energy of each frequency in a PSD. You would have to know something about the sample rate and frequency resolution that was used to generate that particular PSD.
RE: PSD chart v's simple frequency
I agree. I'm finding it increasingly difficult to get an exact answer, so far my answer is:
The random vibration could be worse, depending on the harmonics of the part. Although at first glance it looks less damaging, it could in reality be a lot more damaging depending on how the part reacts.
I feel it is a harsher test because it could find things that a sine wave test vibration would not.
To add to this, surely with that chart I would need a randomiser of sorts. Something that would give me potential numbers and could be calculated using a statistical analysis program. Or again, is this an unknown untill I record this from the part?
I'm begining to get the picture now and is a lot clearer.
Si