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Attenuation of Shock Load in Linear Dynamics

Thursday May 30, 2013 at 11:49am
 
Just discovered this useful nugget! This is not in the Help files nor in any training course so SOLIDWORKS have hidden it well :)
 
My discovery relates to the input load to a 'Modal Time History' study in Linear Dynamics (Simulation Premium). This study type allows us to evaluate how structures respond to dynamic loads over a short time period.
 
Linear Dynamics users will be aware that we can create a 'Time Curve' of load (or excitation) v time. This can be entered manually as a series of points in a table (see below) ....
 
 
.... or (this is less well known) the drop down can be set to 'Harmonic Loading' to allow a sinusoidal oscillation of the load. The amplitude and frequency and phase can all be set. The preview shows a typical sine wave with a frequency of 10Hz  over a time period of 1 sec. .....
 
 
 
I already knew this and have used it on many occasions. What I had missed was the 'Exponential Coefficient' - probably becasue you need to scroll down to see it! This exponent modifies the constant amplitude of the wave and reduces it ("attenuates" is the posh name). This means I can easily create a more complex load that diminishes (or increases) over time. If the exponent is negative it reduces; if it is positive it increases. The magnitude of the exponent determines how quickly it reduces / increases. Below are plots of the input table and the graph. Note that these inputs can be saved as curves for use in other studies.
 
This is very useful for anyone who wants to see how a short decaying sinusoidal vibration will affect a structure. The study will output the resulting velocity and acceleration as well as stress and strain. Cool!
 
 
 
 
 
Andy Fulcher
 
Technical Manager
 
Solid Solutions Management Ltd

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