abaqus-load

# 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: 1. First define amplitude using `/abaqus-amplitude` 2. 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: - [API Quick Reference](references/api-quick-ref.md) - [Common Patterns](references/common-patterns.md) - [Troubleshooting Guide](references/troubleshooting.md)