Comparison of Shock Energy from a Punch & a "Flick"
Stephen Hanly
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Often acceleration peak levels become the focus for someone doing shock testing. But acceleration levels are actually fairly meaningless when it comes to the energy input into your system. And energy levels are what cause fatigue and failure, not acceleration levels. So how do we calculate energy?
The Test
We took an enDAQ piezoresistive sensor and strapped it to a punching bag. Then we had a bunch of our employees punch the bag! Stiven, who did this testing will be generating a more formal report that we'll share soon. But I wanted to quickly illustrate the difference between acceleration and energy. So I took one of these punching datasets and compared it to one where I flicked/tapped the sensor quickly.
Acceleration Comparison
You can see from the plot that the acceleration levels of the flick are quite high, but they are over quickly.
Energy Comparison
Using the VibrationData Toolbox I calculated the energy response spectrum of each. Here is some more information on how I did that calculation. And here is the energy comparison!
Attached is a paper from Tom Irvine on how to calculate the energy response spectrum for more information.