Mesh Quality Checker

Engineering Tools — Mesh Quality Checker (00237)

What this tool does

Streams every shell or solid element in the active model through a battery of mesh-quality metrics and tiers the results into four bands — Failing, Bad, Caution, OK — using thresholds that align the Failing band with Nastran's default GEOMCHECK FATAL trigger and the Bad / Caution bands with tighter SE-Structures defaults. Optionally creates a group per band and color-codes the elements so problem areas are visible in the GUI immediately.

The intent is to answer one question quickly: "If I submit this model to Nastran right now, will any elements get rejected as FATAL by GEOMCHECK?" — with a Caution / Bad band on top to flag elements that are technically legal but are likely to give bad results in non-linear or large-deformation analyses.

The four tiers

TierWhat it meansAction expected
Failing Exceeds Nastran's default GEOMCHECK FATAL threshold for at least one metric. Nastran will refuse the run. Must fix before submit.
Bad Worse than SE-Structures defaults but Nastran will accept. Likely to produce questionable stress / strain locally. Should fix; ignoring is a judgment call.
Caution Worse than ideal but acceptable in most contexts. Inspect; usually fine.
OK Within all clean-mesh defaults. No action.

Metrics checked

  • Aspect ratio — longest edge / shortest edge. Failing > 100, Bad > 20, Caution > 10.
  • Skew — angular deviation from ideal. Failing > 80 deg, Bad > 60 deg, Caution > 45 deg.
  • Taper — non-parallelism of opposite edges for quads. Failing > 0.95, Bad > 0.8, Caution > 0.5.
  • Jacobian — element shape determinant. Failing < 0.01, Bad < 0.4, Caution < 0.7.
  • Interior angle — min / max corner angle. Failing min < 5 deg or max > 175 deg, Bad min < 20 deg or max > 160 deg.
  • Internal angle >= 180 deg — the "ear" condition (concave quad). Always Failing; triggers Nastran FATAL 4297 EQD4S.
  • Warp — out-of-plane deviation of quad corner nodes. Failing > 30 deg, Bad > 10 deg, Caution > 5 deg.

For each element the worst-offending metric drives the tier.

How to use it

  1. Open from Custom Tools > Model Audit - Query > Mesh Quality Checker.
  2. Pick scope: full model or a selected element set.
  3. Optionally check Create groups (one per non-OK tier) and Color elements (red / orange / yellow / green by tier).
  4. Optionally check Fatal-only quick scan if you only care about Failing — faster on large models.
  5. Click OK. Per-tier counts print to the message window, plus the worst-offending element id per tier for fast navigation.

Fatal-only quick scan

For pre-submit gating on huge models, the fatal-only mode skips all the Bad / Caution / OK accounting and short-circuits as soon as any one metric pushes an element into Failing. Runs in roughly half the time on solids-heavy models. Use it when you just need to know "will this submit clean?"

How the Failing thresholds line up with Nastran

The Failing band is calibrated against Nastran's default GEOMCHECK output on real-world models. Verified 2026-05 against subset runs of the project test deck: every Failing-tier element produced an EQD4S / EQAR0 / EQSK0 / EQTA0 FATAL on the Nastran side, and zero non-Failing-tier elements caused FATALs. If you find a counterexample (Failing here but accepted by Nastran, or accepted here and rejected by Nastran) it's a bug — please share the model so the thresholds can be updated.

For the underlying Nastran behaviour see the Nastran GEOMCHECK documentation — this tool reproduces the default thresholds exactly so models passing Mesh Quality Checker pass GEOMCHECK by construction.

Related tools

  • List Element Data — per-element raw geometry table when you need to inspect specific elements after the tier scan flags them.
  • Get FEM CG — aggregate CG + per-element centroids in Excel; useful when triaging where the bad mesh sits in the structure.

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