Hello all,
I am developping a prototype of PCB that will hold a motor running at constant speed along with a couple of accelerometers. In order to estimate the effect of vibration induced by the motor on the other components I am building a simplifided model using only the toolbox Solid Mechanics.
Attached is my model which is inspired by the blasting_rock one. It looks like that:
The top material is Aluminium 3003-H18. I am doing a material sweep for the remaining two bottom blocks, material 1 is the same Aluminium 3003-H18, material 2 is FR4 (Circuit Board).
On the top face I am applying 4 periods of a time dependent sinus stress along Z, with max value at 1MN/m^2. One of the remaining side of this whole thing is set as symetric, the other side is low-reflecting boundary. The bottom side is free.
I am doing a time dependent study and I am comparing the displacement on the input point and output point as pointed out below:
For the first case since both materials are Aluminium I want to observe that the displacement wave is the same between input and output (propagation attenuation rather negligeable at this scale). For the FR4, since it has a lower impedance, I want to visualise the displacement wave is less important, which would reflect the non-perfect match of impedance at the interface between materials.
Below are the results:
Each color correspond to a material switch, input is the dashed line, solid is the output. Although a little bit of propagation time is visible as phase on this graph, I don't see any difference in the wave magnitude. No impedance match effect is visualized which is a problem.
Am I missing something in my model? Is there a parameter that let the wave be attenuated, even more on interfaces?
Side problem, I had to set a very high stress otherwise the resolution on the displacement would be extremely low. I think that would be linked to my mesh that is too big. Any tip on that would be much appreciated. The concrete case for the motor is a MEMS motor that will spin at around 20 kHz and will produce a super small vibration, hence very far from my MN/m^2.
Any help or tip on how to visualise impedance match effect would be much appreciated.
Thanks in advance