Shock test simulation using Ansys workbench

[Harisrimt]

Hello...

I am performing a shock test of a PCB assembly using Transient Structural module of Ansys Workbench. I am giving a peak load of 15 mm/s2 within a duration of 10 ms (peak load occurs at 5ms). I am using modal analysis results as initial condition for the simulation. However, the peak response happens at 4.6 ms which is less than 5 ms. If my understanding is right, the peak response should come after the time of peak input or at least at 5 ms.

Can someone please let me know why this happens and where am I going wrong with my analysis?
Thank you
Hari.

 

[GregLocock]

I don't think you are necessarily wrong. The structure is responding to the frequency content of your pules, not the pulse itself. So if it has a resonance at 1/4*1000/4.8 Hz say then that would give that effect.

Cheers

Greg Locock


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[hacksaw]

the inertial response always lags in single mode systems.
So the shock force is applied at t=0, with unspecified rise time (rate of rise), but fast enough to excite higher order modes, before the force is removed.