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name: abaqus-interaction description: Define contact and interactions - contact pairs, tie constraints, connectors. Use when user mentions contact, friction, tie, parts touching, or bonded surfaces. allowed-tools:

• Read
• Write
• Edit
• Glob
• Grep
• Bash(abaqus:*)

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Abaqus Interaction Skill

Define contact pairs, tie constraints, coupling, and connectors between parts in an assembly.

When to Use This Skill

Route here when user mentions:

• "Contact between surfaces"
• "Friction", "sliding contact", "frictionless"
• "Tie constraint", "bonded surfaces", "welded"
• "Parts touching", "parts can separate"
• "Coupling", "connector", "spring element"
• "Join different meshes"

Route elsewhere:

• Complete contact analysis workflow → /abaqus-contact-analysis
• Fixed supports or displacements → /abaqus-bc
• Applied forces or pressures → /abaqus-load

Key Decisions

1. What Type of Connection?

User Describes	Interaction Type	Key Feature
Welded, glued, bonded	Tie constraint	Permanent, no relative motion
Parts can slide and separate	Surface-to-surface contact	Friction, gap allowed
Load from point to surface	Coupling	Reference point control
Spring, damper, hinge	Connector	Stiffness/damping behavior
Adhesive, delamination	Cohesive	Damage initiation criteria

2. Contact Formulation

Formulation	When to Use
Surface-to-surface	General contact (recommended default)
Node-to-surface	Legacy compatibility, special cases
General contact	Automatic detection (explicit dynamics)
Self-contact	Folding, buckling, large deformation

3. Typical Friction Coefficients

Surface Pair	Friction Coefficient
Frictionless	0.0
Lubricated metal	0.1 - 0.3
Dry metal-to-metal	0.3 - 0.5
Rubber on surface	0.5 - 0.8
No slip (rough)	Use ROUGH formulation

What to Ask User

If unclear, ask:

1. Bonded or sliding?

   • Bonded (no relative motion) → Tie constraint
   • Sliding allowed → Contact with friction

2. Friction coefficient?

   • If not specified, suggest typical value for material pair
   • Frictionless is valid for lubricated or normal-dominant cases

3. Which surface is master/slave?

   • User may not know - guide them (see below)

4. Can surfaces separate?

   • Yes → allowSeparation=ON
   • No (always in contact) → allowSeparation=OFF

Master/Slave Selection Guidelines

Criterion	Master Surface	Slave Surface
Stiffness	Stiffer body	Softer body
Mesh density	Coarser mesh	Finer mesh
Size	Larger surface	Smaller surface
Geometry	Flat/convex	Curved/concave

When in doubt: The coarser mesh should be master.

Workflow: Setting Up Interactions

Step 1: Identify Contact Pairs

List all surfaces that interact. For each pair determine:

• Type (contact vs tie)
• Master and slave assignment
• Friction requirements

Step 2: Create Surfaces

Surfaces must be defined on assembly instances before creating interactions.

Step 3: Define Contact Properties

For contact interactions, define:

• Normal behavior: Hard contact, allow separation
• Tangential behavior: Friction formulation and coefficient

Step 4: Create Interaction

Assign contact property to surface pair in appropriate step.

Step 5: Verify Setup

Check for:

• Correct master/slave assignment
• Appropriate initial gap/overclosure
• Contact pair is active in correct step

Common Gotchas

Symptom	Likely Cause	Solution
Contact not detected	Surfaces too far apart	Use adjust=ON or reduce initial gap
Severe discontinuity warnings	Contact chattering	Add stabilization, use smaller increments
Negative eigenvalue	Wrong master/slave	Swap master and slave surfaces
Overclosure too large	Initial interference	Use shrink fit option or adjust geometry
Tie not working	Surfaces not close enough	Increase position tolerance

Validation Checklist

Before running analysis:

• All contacting surface pairs identified
• Master/slave correctly assigned
• Contact properties defined (normal + tangential)
• Interaction assigned to correct step
• Initial gaps/overclosures within tolerance
• Friction coefficient appropriate for materials

Code Patterns

For API syntax and code examples, see:

• API Quick Reference
• Common Patterns
• Troubleshooting Guide