abaqus-dynamic-analysis

Abaqus Dynamic Analysis Skill

This skill handles explicit and implicit dynamics for impact, crash, drop test, and transient response analysis.

When to Use This Skill

Route here when user mentions:

• Impact, crash, collision, drop test
• Transient response, time-varying response
• Shock loading, blast loading, explosive loading
• High-speed events, wave propagation
• "What happens when it hits..."

Route elsewhere:

• Natural frequency extraction → /abaqus-modal-analysis
• Static/constant loads → /abaqus-static-analysis
• Harmonic/sinusoidal response → modal + steady-state dynamics
• Very long transients (minutes+) → consider implicit or quasi-static

Prerequisites

Before dynamic analysis:

1. Geometry and mesh ready
2. Material MUST have density defined (required for mass matrix)
3. Understand event duration and loading type

Workflow: Setting Up Dynamic Analysis

Step 1: Gather Information from User

Ask if unclear:

• What's the event duration? Milliseconds, seconds, or longer?
• Initial velocity? For drop tests or impact
• Is contact involved? Parts colliding or touching
• What output needed? Stress, velocity, acceleration, energy?

Step 2: Choose Explicit vs Implicit

Factor	Explicit	Implicit
Time scale	Short (us to ms)	Longer (ms to s)
Step size	Automatic (very small)	User-controlled
Nonlinearity	Handles well	May need iterations
Memory	Lower	Higher
Contact	Natural handling	Needs care
Best for	Impact, crash	Vibration, long transient

Decision rule:

• Event < 10ms with impact/contact → Explicit
• Event > 100ms without severe nonlinearity → Implicit
• In between → Either can work, explicit often easier

Step 3: Set Time Period

Event Type	Typical Duration
High-speed impact	0.1-10 ms
Drop test	1-100 ms
Blast loading	1-50 ms
Seismic/vibration	1-100 s

Step 4: Define Initial Conditions

For drop tests and impact:

• Set initial velocity on the impacting part/region
• Velocity is applied in the Initial step

Step 5: Configure Output

Field outputs: S (stress), U (displacement), V (velocity), A (acceleration), PEEQ (plastic strain)

History outputs for energy balance (explicit): ALLKE, ALLIE, ALLWK, ETOTAL

Step 6: Consider Mass Scaling (Explicit Only)

Option	Effect	When
None	True inertia	Very short events, accuracy critical
At beginning	Scale once	Quasi-static explicit
Throughout	Continuous scaling	When inertia less important

Warning: Mass scaling speeds up analysis but affects inertial response.

Step 7: Run and Validate

Use /abaqus-job to submit, then check:

• Energy balance (ETOTAL approximately constant)
• Stable time increment (explicit)
• Results physically reasonable

Key Parameters

Parameter	Explicit	Implicit
Time period	Event duration	Event duration
Time increment	Automatic	Specify initial, min, max
Element library	EXPLICIT	STANDARD
Element type	C3D8R recommended	C3D8R or C3D8
Hourglass control	ENHANCED	Default

Validation Checklist

• Density defined in material
• Time period appropriate for event
• Initial conditions applied (velocity, position)
• Output frequency captures behavior (100+ frames typical)
• Energy balance acceptable (ETOTAL constant for explicit)
• Results physically reasonable

Troubleshooting

Problem	Likely Cause	Solution
"Time increment too small"	Small/distorted elements	Use mass scaling or coarsen mesh
Energy balance error	Hourglass or instability	Check hourglass energy, add control
Analysis takes forever (explicit)	Long time period	Consider implicit instead
Convergence failure (implicit)	Severe nonlinearity	Use explicit or smaller increments

Related Skills

• /abaqus-material - Define density (required)
• /abaqus-amplitude - Time-varying loads
• /abaqus-field - Initial velocity and predefined fields
• /abaqus-interaction - Contact for impact problems
• /abaqus-odb - Results extraction

Code Patterns

For API syntax and code examples, see:

• API Quick Reference
• Common Patterns
• Troubleshooting Guide