abaqus-amplitude

# Abaqus Amplitude Skill This skill defines time-varying load and boundary condition profiles in Abaqus. Amplitudes act as multipliers that scale loads/BCs over time. ## When to Use This Skill **Route here when user mentions:** - "Gradually increase the load", "ramp up the force" - "Cyclic loading", "sinusoidal excitation" - "Pulse load", "impulse", "impact loading" - "Time-varying boundary condition", "loading history" - "Smooth transition", "avoid sudden load application" - "Earthquake input", "harmonic excitation" **Route elsewhere:** - Constant static loads (no amplitude needed) → `/abaqus-load` - Initial conditions, predefined fields → `/abaqus-field` - Dynamic analysis setup → `/abaqus-dynamic-analysis` ## Workflow: Defining Amplitudes ### Step 1: Understand User's Load Profile Ask if unclear: - **What shape?** Ramp, sinusoidal, pulse, decay, custom? - **What timing?** Duration, frequency, peak time? - **What magnitude?** Amplitude is a multiplier (0.0-1.0 typical) ### Step 2: Choose Amplitude Type | User Describes | Amplitude Type | Key Parameters | |----------------|----------------|----------------| | Linear increase/decrease | TabularAmplitude | Time-value pairs | | Smooth transition (no shock) | SmoothStepAmplitude | Time-value pairs | | Sinusoidal/harmonic | PeriodicAmplitude | Frequency, coefficients | | Exponential decay | DecayAmplitude | Initial, decayTime | | Custom time history | TabularAmplitude | User-provided data | | Sudden on/off | TabularAmplitude | Step-like data points | **Most common:** TabularAmplitude with linear ramp (0,0) to (1,1) ### Step 3: Determine Time Reference | Setting | When to Use | |---------|-------------| | `timeSpan=STEP` | Time relative to current step start (most common) | | `timeSpan=TOTAL` | Time from analysis beginning (multi-step analyses) | ### Step 4: Define Data Points For TabularAmplitude and SmoothStepAmplitude: - Data is (time, amplitude_factor) pairs - Time values must be strictly increasing - Factor typically ranges 0.0 to 1.0 (can exceed if needed) - Factor multiplies the load/BC magnitude ### Step 5: Apply to Load or BC Amplitudes are referenced by name when creating: - Loads: ConcentratedForce, Pressure, Gravity, etc. - BCs: DisplacementBC, VelocityBC, etc. ## Key Decisions ### Common Load Profiles | Profile | Data Pattern | Use Case | |---------|--------------|----------| | Linear ramp | (0,0), (1,1) | Quasi-static loading | | Ramp up/down | (0,0), (0.5,1), (1,0) | Load cycle | | Hold at peak | (0,0), (0.1,1), (1,1) | Ramp then sustain | | Triangular pulse | (0,0), (0.001,1), (0.002,0) | Impact/impulse | | Step function | (0,0), (0,1), (1,1) | Sudden application | ### Smooth vs. Tabular | Use SmoothStepAmplitude when | Use TabularAmplitude when | |------------------------------|---------------------------| | Dynamic analysis (avoid shocks) | Static analysis | | Convergence issues from sudden loads | Exact load profile needed | | Continuous derivatives required | Step functions needed | ## What to Ask User | Input | Required | How to Get | |-------|----------|------------| | Load profile shape | YES | Ask: "How should the load vary over time?" | | Peak time | YES | Ask: "When should the load reach its maximum?" | | Duration | YES | Typically matches step time | | Frequency (if cyclic) | If periodic | Ask: "What frequency in Hz?" | | Smooth or sudden | Recommended | Ask if dynamic analysis | ## Validation Checklist After defining amplitude: - [ ] Time values are strictly increasing - [ ] Factor range is appropriate (usually 0.0-1.0) - [ ] timeSpan matches analysis intent (STEP vs TOTAL) - [ ] Amplitude name matches what load/BC references - [ ] For dynamic: smooth transitions to avoid numerical shocks - [ ] For periodic: frequency and coefficients are correct ## Troubleshooting | Problem | Likely Cause | Solution | |---------|--------------|----------| | "Amplitude not monotonic in time" | Time values not increasing | Fix time sequence | | Convergence issues with sudden load | Discontinuity in profile | Use SmoothStepAmplitude | | Load too high/low | Misunderstanding multiplier | Amplitude is factor; adjust load magnitude | | Wrong timing in multi-step | STEP vs TOTAL confusion | Check timeSpan setting | ## Code Patterns For API syntax and code examples, see: - [API Quick Reference](references/api-quick-ref.md) - Full parameter details - [Common Patterns](references/common-patterns.md) - Ready-to-use snippets - [Troubleshooting Guide](references/troubleshooting.md) - Error solutions