Abaqus Bc

Abaqus Boundary Conditions Skill

This skill defines boundary conditions (BCs) in Abaqus models. BCs constrain motion and prevent rigid body movement.

When to Use This Skill

Route here when user mentions:

• "fixed", "encastre", "clamped", "welded"
• "pinned", "hinged", "simply supported"
• "roller", "sliding support"
• "symmetry", "half model", "quarter model"
• "constrain", "prevent movement"
• "prescribed displacement", "move by X mm"
• "rigid body motion error"

Route elsewhere:

• Forces, pressures, gravity → /abaqus-load
• Contact between parts → /abaqus-interaction
• Initial temperature/stress → /abaqus-field

Key Decisions

Step 1: What Type of Support?

Default choice: Encastre for fixed supports (most common).

Step 2: Which Step to Apply?

Default: Apply supports in 'Initial' step.

Step 3: Rigid Body Motion Check

For 3D static analysis, constrain at least 6 DOFs total:

• 3 translations (X, Y, Z)
• 3 rotations (about X, Y, Z axes)

"Zero pivot" error = insufficient constraints.

Step 4: Symmetry Plane Selection

Apply symmetry BC to the face AT the symmetry plane.

What to Ask User

If unclear, ask:

1. Where is it supported?

   • "Which face/edge is fixed?"
   • "Where does it mount to the frame?"

2. What type of support?

   • "Fully fixed (welded) or can it rotate (pinned)?"
   • "Free to slide in any direction?"

3. Is the model symmetric?

   • "Can we use half symmetry to reduce model size?"
   • "Is the loading also symmetric?"

4. Any prescribed motion?

   • "Does anything move by a known amount?"
   • "Is this a displacement-controlled test?"

Validation Checklist

Before running analysis:

• At least one region has fixed support
• All 6 rigid body modes constrained
• BCs applied in correct step
• Symmetry planes match actual symmetry (geometry AND loads)
• No conflicting BCs on same DOF

After analysis:

• Reaction forces at supports balance applied loads
• No "zero pivot" or "rigid body motion" warnings
• Displacements at fixed regions are zero

Common Mistakes

Troubleshooting

Code Patterns

For API syntax and code examples, see:

• API Quick Reference
• Common Patterns
• Troubleshooting Guide