Ping hammering: how to choose peaks as modes/natural frequencies?
Ping hammering: how to choose peaks as modes/natural frequencies?
(OP)
I work in a lab that is performing ping hammer on automotive components in three directions: cross-car, fore-aft, and vertical.
We are looking for modes or natural frequencies in each of these directions.
Is there a specification or procedure detailing how to identify the first mode or natural frequency?
How does the first mode differ from the natural frequency?
In cases of natural frequency...
We often discount "insignificant" peaks with no clear way of determining what an insifnificant peak is, when measuring natural frequency.
In cases of modes...
We have had cases where a peak is not counted as the "first mode" because it was seen, in greater intensity, in a different direction. For example, if a large peak was present at 45Hz in the fore-aft direction a peak 1/4 the size was found in the cross-car direction at the same frequency, the peak was not counted as the first mode in the cross-car direction.
Can anyone shed some light on this and help clear this up for me?
Regrads,
windo4life
We are looking for modes or natural frequencies in each of these directions.
Is there a specification or procedure detailing how to identify the first mode or natural frequency?
How does the first mode differ from the natural frequency?
In cases of natural frequency...
We often discount "insignificant" peaks with no clear way of determining what an insifnificant peak is, when measuring natural frequency.
In cases of modes...
We have had cases where a peak is not counted as the "first mode" because it was seen, in greater intensity, in a different direction. For example, if a large peak was present at 45Hz in the fore-aft direction a peak 1/4 the size was found in the cross-car direction at the same frequency, the peak was not counted as the first mode in the cross-car direction.
Can anyone shed some light on this and help clear this up for me?
Regrads,
windo4life





RE: Ping hammering: how to choose peaks as modes/natural frequencies?
To understand what is happening, you can study Plate and Panel books. Because a car can be modeled as a plate in vibration analysis. (You can use this book; http://b
The insignificant peaks may come from components of car. Because cencors that you use to measure vibration are so sensitive. For example, when you ping the car, the excitation frequency may coincide with the natural frequency of a seat, and you see this seat vibration in your graph.
I do not know very much about standartization.
RE: Ping hammering: how to choose peaks as modes/natural frequencies?
Forgive if assumption is wrong.
RE: Ping hammering: how to choose peaks as modes/natural frequencies?
Things that are roughly beam shaped will have modes that can be described as vertical bending etc, but that is a conceptual description.
"How does the first mode differ from the natural frequency?"
I am not aware of any practical difference.
Cheers
Greg Locock
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