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: