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FEM simulation of shear wave propagation

FEM simulation of shear wave propagation

FEM simulation of shear wave propagation

(OP)
Hi everyone,

I am trying to simulate wave propagation in a purely elastic medium. I am not using any software and trying to write the process in MATLAB.

For my problem, a nearly impulsive body force will generated in a localized region the medium, this will create a disturbance in the medium. Over time, this disturbance will propagate away from the region of excitation. The displacements are on the order of 1 micron. I am using newmark time integration technique. My results seem to be fine for first several time steps. But, over time the wave seems to become diffuse. Can anyone tell me the reason for this?

RE: FEM simulation of shear wave propagation

Well if you remember newmark's integration technique is just an approximation to the exact solution to the differential equation, the smaller the time step the more stable the integration method. Since this is an approximation and assuming the time step is rather large but still within limits for stability's sake your solution will deviate considerably from the exact solution at a given point in time [due to the error accumulated per integration step]. Only solution is to take smaller time steps and sacrifice computational speed, which I guess doesn't really matter much because I assume this is more of an academic problem, you can also get the exact solution [if this is 1d or 2d wave problem with an exact solution] and substract your approximation per time step and see how the error accumulates, when and where and track it down and see what's actually going on in your code.



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