- #1
thender
- 39
- 0
Hello,
I am studying and trying to understand Powertrain / Engine mounts used in automotive such as these:
http://images.gasgoo.com/MiMwMDRfMDA0Izc4MDA3NzIwMA--/auto-part-engine-torque-strut-mount-engine-mounting-for-buick-enclave-chevrolet-traverse-gmc-acadia-25840458.jpg
http://www.carid.com/images/westar/engine-parts/em-2838s.jpgIt is really hard to even get terminology straight.
Damping and Dampening both seem to refer to a means by which vibration energy is canceled out or absorbed.
Isolation seems to refer to preventing energy or force transferring from one system and into another.
And transmissibility seems to be a rating for how easily energy passes through a material or system, and it seems it is normally drawn over a spectrum of frequencies.
Where there will be some point where vibration actually increases, like at resonance, and then tapers off sharply into fully damped "isolation".
Resonant frequency or natural frequency seems to describe a frequency at which an object or system would tend to vibrate at. I get the impression that at a natural frequency the repeating motion of the vibration reinforces itself, whereas at other frequencies is damped out by losses.
As far as automotive is concerned, the body of a vehicle apparently has a resonant frequency around 20 Hz. Which is apparently very close to the rate of combustion events for an idling engine.
If the vibration from the engine isn't isolated, it causes the whole chassis/body to ring. I have studied one hydraulic mount with an "inertia track" orifice, but I am more interested in elastomer / rubber mounts.
From what I can tell, rubber has a natural frequency which is far below the frequency of the engine, the molecules are very large and long with lots of space, and the molecules are flexible.
So when vibration hits rubber it begins to deflect in a disorganized way, and because the vibration is faster, the rubber will not have settled and completed returning when the next wave hits. So as far as I can tell the vibration energy doesn't stack up, but works against itself.
I think this is the mechanism for the suppression of vibration. And when I look at the pictures I linked to at the beginning, it seems like the shape and geometry of the parts are designed to allow some degree of "springing" deflection. The V shape would seem to make it non-linear in terms of stress/strain.
Am I on the right track? Corrections and comments are appreciated,
Thank you.
I am studying and trying to understand Powertrain / Engine mounts used in automotive such as these:
http://images.gasgoo.com/MiMwMDRfMDA0Izc4MDA3NzIwMA--/auto-part-engine-torque-strut-mount-engine-mounting-for-buick-enclave-chevrolet-traverse-gmc-acadia-25840458.jpg
http://www.carid.com/images/westar/engine-parts/em-2838s.jpgIt is really hard to even get terminology straight.
Damping and Dampening both seem to refer to a means by which vibration energy is canceled out or absorbed.
Isolation seems to refer to preventing energy or force transferring from one system and into another.
And transmissibility seems to be a rating for how easily energy passes through a material or system, and it seems it is normally drawn over a spectrum of frequencies.
Where there will be some point where vibration actually increases, like at resonance, and then tapers off sharply into fully damped "isolation".
Resonant frequency or natural frequency seems to describe a frequency at which an object or system would tend to vibrate at. I get the impression that at a natural frequency the repeating motion of the vibration reinforces itself, whereas at other frequencies is damped out by losses.
As far as automotive is concerned, the body of a vehicle apparently has a resonant frequency around 20 Hz. Which is apparently very close to the rate of combustion events for an idling engine.
If the vibration from the engine isn't isolated, it causes the whole chassis/body to ring. I have studied one hydraulic mount with an "inertia track" orifice, but I am more interested in elastomer / rubber mounts.
From what I can tell, rubber has a natural frequency which is far below the frequency of the engine, the molecules are very large and long with lots of space, and the molecules are flexible.
So when vibration hits rubber it begins to deflect in a disorganized way, and because the vibration is faster, the rubber will not have settled and completed returning when the next wave hits. So as far as I can tell the vibration energy doesn't stack up, but works against itself.
I think this is the mechanism for the suppression of vibration. And when I look at the pictures I linked to at the beginning, it seems like the shape and geometry of the parts are designed to allow some degree of "springing" deflection. The V shape would seem to make it non-linear in terms of stress/strain.
Am I on the right track? Corrections and comments are appreciated,
Thank you.