I’m currently performing an elastic wave simulation in a 3D cuboid-shaped multilayer structure. To excite the wave, I applied a velocity boundary condition (BC) to the model in two different ways:

1. Applied over an entire surface (as shown in Figure 1), and
2. Applied at a single point (as shown in Figure 2).

However, when I plot the stress component σ₁₁ (S11) versus time using field history outputs, the resulting graphs differ significantly. Figure 3 shows the elastic wave pulse that was used in both cases.

This leads me to ask:

• Could the method of applying the boundary condition be the main reason behind the difference in the plots?
• Are there any other possible reasons that might explain the variation?
• Most importantly, is there any standard way to validate these stress–time plots obtained from the history output?

For your reference, I’ve attached:

• Figure 4: Stress vs. time plot when BC was applied to the surface, and
• Figure 5: Stress vs. time plot when BC was applied to a single point.

Figure: 4

Figure: 5