Learning Forum

[BALA]

Hello all

I am doing Random vibration analysis of pcb with components. I want to calculate the curvature at pcb but Ansys does not give it directly so can anyone suggest is there anyway to calculate it.

[Armin]

Hello,

Curvature is essentially the second derivative of displacement with respect to a path. Currently, in Mechanical, you can create results along a path, but you cannot perform operations such as taking the second derivative. Therefore, you will need to use APDL commands. Below is a test case featuring a generic PCB where curvature along a path is calculated using APDL commands. See if you can modify and utilize this for your application.

RESUME
/POST1
set,first                ! load the first set of results in the results file
path,p1,2,10,50          ! define a path made of 2 points, store up to 10 results, 50 intermediate points
ppath,1,,-160,0.8,-58.5  ! define point 1
ppath,2,,0,0.8,-58.5     ! define point 2
pdef,uymap,u,y           ! map UY displacement onto path
pcalc,deri,slope_x,uymap,s ! calculate first derivative of UY w.r.t. distance along the path
pcalc,deri,curv_x,slope_x,s ! calculate second derivative of UY w.r.t. distance along the path
/show,png
plpath,uymap             ! plot UY
plpath,curv_x            ! plot curvature
/show,close

[BALA]

thank you for your reply, i have read that in Random Vibration as displacement is RMS so taking double derivative is not correct? is it right?

[Armin]

No problem at all.
When performing random vibration analysis, the displacement results are typically reported as root mean square (RMS) values, which represent a statistical measure of the response due to non-deterministic, broadband excitation. Calculating curvature by taking the second spatial derivative of RMS displacement along a path is a valid approach, as long as you understand that the resulting curvature is also an RMS value. However, other forum members may chime in and share their experiences.