Define time-varying amplitudes. Use when user mentions ramp, time-varying, cyclic, pulse, or gradually increasing loads. Does NOT handle static constant loads.
This skill defines time-varying load and boundary condition profiles in Abaqus. Amplitudes act as multipliers that scale loads/BCs over time.
Route here when user mentions:
Route elsewhere:
/abaqus-load/abaqus-field/abaqus-dynamic-analysisAsk if unclear:
| 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)
| Setting | When to Use |
|---|---|
timeSpan=STEP | Time relative to current step start (most common) |
timeSpan=TOTAL | Time from analysis beginning (multi-step analyses) |
For TabularAmplitude and SmoothStepAmplitude:
Amplitudes are referenced by name when creating:
| 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 |
| 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 |
| 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 |
After defining amplitude:
| 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 |
For API syntax and code examples, see: