Mesh-Sensitivity Example

A worked example showing how a penetration result changes with mesh density and how to assess mesh convergence.

Ballistics & Penetration4 min read

worked examplemesh sensitivitypenetrationconvergenceexplicit FEA

Problem

A penetration analysis is run with three mesh densities in the impact zone: 2 mm, 1 mm and 0.5 mm elements. The predicted residual velocity after perforation is: 2 mm mesh: 185 m/s, 1 mm mesh: 152 m/s, 0.5 mm mesh: 148 m/s. Is the mesh converged?

Solution

Change from 2 mm to 1 mm:
  Delta_v = 185 - 152 = 33 m/s (18% change)

Change from 1 mm to 0.5 mm:
  Delta_v = 152 - 148 = 4 m/s (2.6% change)

The result is converging — the change decreases
with mesh refinement. The 0.5 mm mesh gives a
result within 3% of the 1 mm mesh, which is
typically acceptable for engineering purposes.

Interpretation

The mesh is approaching convergence. The 2 mm mesh is too coarse (18% change on refinement). The 1 mm mesh is marginal (2.6% change on further refinement). The 0.5 mm mesh is the recommended mesh for the final analysis. The mesh-sensitivity study should be documented, showing that the result is robust to mesh refinement within the acceptable tolerance.