Abaqus Load Skill
Apply mechanical and thermal loads to FEA models - forces, pressures, gravity, and heat flux.
When to Use This Skill
Route here when user mentions:
- "Apply a force", "add pressure", "put a load on"
- "Gravity", "self-weight", "body force"
- "Point load", "distributed load", "traction"
- "Heat flux", "thermal load"
- "Force in the X/Y/Z direction"
Route elsewhere:
- Fixed supports, displacements, symmetry →
/abaqus-bc - Contact forces between parts →
/abaqus-interaction - Initial temperature fields, pre-stress →
/abaqus-field - Time-varying load profiles →
/abaqus-amplitude
Key Decisions
1. Which Load Type?
| User Describes | Load Type | Units |
|---|---|---|
| Force at a point/vertex | ConcentratedForce | N |
| Force spread over surface | SurfaceTraction | MPa |
| Normal pressure on surface | Pressure | MPa |
| Force along edge | LineLoad | N/mm |
| Self-weight, acceleration | Gravity | mm/s² |
| Heat input to surface | SurfaceHeatFlux | mW/mm² |
| Convective cooling/heating | FilmCondition | mW/(mm²·K) |
2. When to Convert Force to Traction
If user gives total force but it must be distributed:
Traction (MPa) = Total Force (N) / Surface Area (mm²)
Example: 1000 N on a 50×20mm face = 1000 / 1000 = 1.0 MPa
Sign Conventions
| Load Type | Positive (+) | Negative (-) |
|---|---|---|
| Pressure | Compression (into surface) | Tension (away from surface) |
| Force components (cf1, cf2, cf3) | Positive axis direction | Negative axis direction |
| Gravity | Positive axis acceleration | Negative axis (comp2=-9810 for -Y) |
What to Ask User
If not specified, clarify:
| Question | Why It Matters |
|---|---|
| Force magnitude? | Required for all loads |
| Direction (X, Y, Z)? | Needed for directional loads |
| Point or distributed? | Determines ConcentratedForce vs SurfaceTraction |
| Which surface/vertex? | Defines load application region |
| Constant or time-varying? | May need amplitude definition |
Direction Specification
| Load Type | How Direction Works |
|---|---|
| ConcentratedForce | cf1, cf2, cf3 = X, Y, Z components |
| SurfaceTraction | directionVector=((origin), (endpoint)) |
| Pressure | Always normal to surface (no direction needed) |
| Gravity | comp1, comp2, comp3 = acceleration components |
| LineLoad | comp1, comp2, comp3 = force/length components |
Common Scenarios
Standard Gravity Setup
- Acceleration: comp2 = -9810 mm/s² (for -Y direction)
- Requires material density defined - without it, gravity has no effect
Pressure vs Traction
- Pressure: Always normal to surface, simpler to define
- Traction: Arbitrary direction, use when force isn't perpendicular
Thermal Loads
- Heat flux: Direct heat input (mW/mm²)
- Film condition: Convection with ambient temperature
Time-Varying Loads
For loads that change over time:
- First define amplitude using
/abaqus-amplitude - Reference amplitude name when creating load
Modifying Loads Across Steps
| Action | Method |
|---|---|
| Change magnitude | setValuesInStep() |
| Turn off load | deactivate() |
| Different load in each step | Create load with step name |
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Zero reaction forces | Wrong direction or tiny magnitude | Check direction vector and units |
| Gravity has no effect | Missing density | Add density to material definition |
| Load region not found | Typo in set/surface name | Verify name matches exactly |
| Equilibrium not achieved | Load too large | Reduce magnitude or improve convergence |
| Negative eigenvalue | Structure unstable | Check BCs provide adequate support |
Validation Checklist
Before running analysis:
- Load applied to correct region (surface, vertex, edge)
- Direction matches physical scenario
- Magnitude in correct units (N, MPa, mW/mm²)
- Load assigned to correct step (not Initial)
- Density defined if using gravity
- Reactions should balance applied loads
Code Patterns
For API syntax and implementation examples, see:
