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
• Common Patterns
• Troubleshooting Guide