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1 |
Question:
Is there a published vibration test level
for testing automotive components?
Answer:
The proper method is to take accelerometer
measurements on a representative vehicle at the component mounting
location. The vehicle should be driven over a variety of road
surfaces and at various speeds. This can be done at a proving
ground, such as the Bosch test facility in New Carlisle, Indiana.
Or you could do this on actual highways. or rough roads in the
mountains or desert. You can then develop your own test levels.
Also, refer to MIL-STD-810F, Method 514.5, Vibration. See paragraph
2.2.1 and Figure 514.5C-1. This document is available at: Testing
Standards.
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2 |
Question:
What is the damping value for a particular
material?
Answer:
There are many types of damping, such
as viscous, hysteresis, acoustic coupling, air pumping at joints,
energy radiation to the soil, etc. Also, boundaries and bearings
contribute damping.
In addition, structures have many modes.
Each mode may have a unique damping value.
Damping may be non-linear. It may vary
with the excitation level.
Thus, testing is necessary to determine
the damping value for a given material and design configuration.
Some references are given at: Damping
Page.
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3 |
Question:
How can I measure dynamic displacement
or velocity with an accelerometer?
Answer:
I recommend using a B&K 2635 (or equivalent)
charge amp with a B&K charge mode accelerometer. (Disclaimer:
I am not a B&K salesman).
This charge amp model performs integration
on the analog acceleration signal in the time domain after passing
the signal through an analog high-pass filter. The high-pass
filter frequency has several settings. A typical setting might
be 1 Hz. The filter removes the DC offset which would otherwise
cause the slope effect in the velocity signal.
The alternative is to integrate the digital
accelerometer signal to obtain velocity. The acceleration signal
can be double-integrated to obtain displacement. The problem
is that any spurious offset in the acceleration signal will be
magnified in the integration process, resulting in the slope
effect.
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4 |
Question:
What is a good reference for learning
finite element analysis?
Answer:
I recommend:
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