// Complete workflow for modal/frequency analysis - extract natural frequencies and mode shapes. Use for vibration analysis and resonance avoidance.
Analyze multi-body contact. Use when user mentions parts touching, friction between surfaces, bolt-plate contact, press fit, or assembly with contact.
Complete workflow for coupled thermomechanical analysis. Use when user mentions thermal stress, thermal expansion, or temperature causing deformation.
Complete workflow for dynamic analysis. Use when user mentions impact, crash, drop test, transient, or time-varying response. Handles explicit and implicit dynamics.
Workflow for fatigue and durability analysis - cycle counting, damage accumulation, and fatigue life prediction.
Complete workflow for static structural analysis. Use when analyzing stress, displacement, or reaction forces under constant loads. For strength and stiffness evaluation.
Complete workflow for heat transfer analysis - steady-state and transient thermal. Use when user asks about temperature distribution, conduction, convection, or heat flow.
| name | abaqus-modal-analysis |
| description | Complete workflow for modal/frequency analysis - extract natural frequencies and mode shapes. Use for vibration analysis and resonance avoidance. |
| allowed-tools | ["Read","Write","Edit","Glob","Grep","Bash(abaqus:*)","Skill"] |
Extract natural frequencies and mode shapes from a structure. Use for vibration analysis, resonance avoidance, and dynamic characterization.
Route here when user mentions:
Route elsewhere:
/abaqus-static-analysis/abaqus-dynamic-analysisBefore modal analysis:
Ask if unclear:
Route to /abaqus-geometry for part creation.
Route to /abaqus-material - density is essential.
Without density, Abaqus cannot compute the mass matrix and modal analysis will fail.
| Material | Density (tonne/mm^3) |
|---|---|
| Steel | 7.85e-9 |
| Aluminum | 2.7e-9 |
| Titanium | 4.5e-9 |
Route to /abaqus-mesh for meshing.
Mesh quality affects mode shapes - finer mesh gives more accurate high-frequency modes.
Route to /abaqus-bc to define support type.
| Configuration | Expected Modes | Use Case |
|---|---|---|
| Free-free (no BCs) | 6 rigid body modes at ~0 Hz, then elastic | Test correlation |
| Cantilever (one end fixed) | First mode is bending | Mounted component |
| Simply supported | Bending, plate modes | Bridge-like structures |
| Fixed-fixed | Higher frequencies than cantilever | Both ends constrained |
Note: Free-free analysis gives 6 modes at ~0 Hz (rigid body translation/rotation). Real elastic modes start at mode 7.
Route to /abaqus-step for FrequencyStep configuration.
Key decisions:
Route to /abaqus-job to submit, then /abaqus-odb to read frequencies from result frames.
| Parameter | Recommended | Notes |
|---|---|---|
| Eigensolver | LANCZOS | Best for most problems |
| numEigen | 10 | Start with first 10 modes |
| Normalization | DISPLACEMENT | Mode shapes max = 1 |
| Mesh size | Adequate for highest mode | Finer mesh for high frequencies |
After analysis, verify:
For cantilever beams, first mode can be verified analytically:
Compare FEA result to analytical for validation.
| Problem | Likely Cause | Solution |
|---|---|---|
| "Material has no density" | Density not defined | Add density to material |
| Negative eigenvalue | Unconstrained/unstable | Check BCs or add soft springs |
| 6 zero-frequency modes | Free-free (expected) | Real modes start at mode 7 |
| Frequencies too high/low | Unit error | Verify mm-tonne-s-N-MPa units |
| Memory error | Too many modes/elements | Reduce numEigen or coarsen mesh |
/abaqus-material - Must include density/abaqus-bc - Define modal boundary conditions/abaqus-step - FrequencyStep configuration/abaqus-odb - Extract frequencies and mode shapes/abaqus-geometry - Create geometry/abaqus-mesh - Mesh affects mode accuracyFor API syntax and code examples, see: