How to Setup Local Mesh Refinement & Verify Mesh Convergence in ANSYS Mechanical
Master finite element mesh independence studies in ANSYS Mechanical: apply local sizing, inflation layers, quadratic tetrahedral/hexahedral elements, and convergence criteria while avoiding stress singularities.
⚡ Quick Answer / Key Takeaway
Use second-order (Quadratic) elements, apply local Body/Face/Sphere of Influence Sizing at high-gradient fillets, insert a Convergence object under your Equivalent (von Mises) Stress result with an allowable change of 2%–5%, or perform a 3-level manual h-refinement study (h, h/2, h/4).
Step-by-Step Instructions & Commands
Step 1: Enforce Quadratic Elements & Local Feature Sizing
Never refine the entire global assembly uniformly—that explodes solve time by $O(N^3)$. In ANSYS Mechanical **Mesh** details, set **Element Order** to `Quadratic` (10-node tetrahedrals or 20-node hexahedrals to prevent shear locking). Insert local **Sizing** controls on critical load-bearing fillets, ensuring at least 3–4 elements span across the fillet arc and through thin wall thicknesses.
Step 2: Configure Adaptive Convergence or 3-Point h-Refinement
Right-click your **Equivalent (von Mises) Stress** result (scoped strictly to the physical fillet face, never the entire body) and insert a **Convergence** tool. Set **Allowable Change** to `3%` and max refinement loops to `3` under Analysis Settings. Alternatively, parameterize local element size $h$ in Workbench (`4mm`, `2mm`, `1mm`) and plot stress vs degrees of freedom to confirm asymptotic flattening.
Step 3: Diagnose & Isolate Artificial Stress Singularities
If peak stress climbs endlessly (+30% on every refinement pass) without leveling off, the peak is located at a **Mathematical Stress Singularity**—such as a sharp 0mm internal re-entrant corner, a point load, or the edge of a rigid Fixed Support. Scope your stress probe away from the idealized boundary constraint (per Saint-Venant's Principle) or model the true physical fillet radius.
Common Issues & Troubleshooting Guide
| Common Failure / Problem | Root Cause & Recommended Solution |
|---|---|
| Adaptive convergence fails because geometry has sweeping or hex meshing | ANSYS automated adaptive h-refinement only supports tetrahedral meshes. For hex-dominant or swept bodies, use parameterized Body of Influence (BOI) sizing in the Workbench Parameter Set. |
| Unaveraged nodal stress plot shows colorful checkerboard bands | Compare 'Unaveraged' vs 'Averaged' contour results. If the discrepancy at your critical fillet exceeds 5%–10%, the local mesh is still too coarse to resolve the strain gradient. |
Cross-CAD Compatibility & Alternatives
Before meshing in ANSYS, Abaqus, or COMSOL, defeature tiny cosmetic logos, part-number engravings, and non-structural 0.5mm chamfers in your CAD system to prevent sliver elements.
Engineering Best Practices Checklist
- Always verify Element Quality (Skewness < 0.85, Jacobian Ratio > 0.1) in Mesh Metrics before solving.
- Never evaluate fatigue or yield failure at the boundary edge of a rigid Fixed Support.
- Document a 3-point mesh independence table in every formal engineering simulation report.
Related Concepts & Further Learning
Underlying Kernel Mechanics & Automated Prevention Protocol
To permanently prevent recurrence of How to Setup Local Mesh Refinement & Verify Mesh Convergence in ANSYS Mechanical across enterprise project directories, CAD managers must understand how the underlying DWG object database (AcDbDatabase / GcDbDatabase) and graphics display pipeline manage entity handles, symbol tables, and external dependencies:
| Diagnostic Command / Variable | Recommended Production Value | Engineering Function & Impact |
|---|---|---|
| AUDIT / RECOVERALL | Fix Errors = Yes (Y) |
Validates B-tree symbol tables, repairs orphaned dictionary handles, and heals nested Xrefs. |
| -PURGE → Regapps (R) | Verify Each = No (N) |
Strips thousands of unreferenced third-party Registered Application IDs that bloat DWG memory. |
| GRAPHICSCONFIG | Hardware Acceleration = ON | Verifies DirectX 11/12 or OpenGL GPU driver allocation and clears corrupted display cache buffers. |