CONVERT TRUE TO EFFECTIVE STRESS VS STRAIN CURVE BY REMOVING ALL ELASTIC STRAINS¶
Converts a true stress–strain curve into an effective (plastic) stress–strain curve by detecting the yield point and removing all elastic strains. Supports multiple yield-detection strategies, post-necking extrapolation methods (Swift, Hockett-Sherby, etc.), and optional curve smoothing and monotonicity enforcement. Use this worker as a pre-processing step before feeding material curves into LS-DYNA MAT_24 or similar elasto-plastic material cards.
When to use¶
Classification: process.
Tagged: curve_transform, effective_stress, hockett_sherby, mat_24, material_characterization, plastic_strain, post_necking, stress_strain.
Inputs¶
| Label | ID | Type | Default | Required | Description |
|---|---|---|---|---|---|
| True Stress Strain Curve | truestressstraincurve | vector | — | ✓ | True stress–strain curve (stress in MPa, strain dimensionless) as an XY vector; the input from which elastic strains will be subtracted to yield the effective plastic curve. |
| Elastic Modulus | elastic_modulus | scalar | 210.0 | ✓ | Young’s modulus of the material in GPa (default 210 GPa for steel); used to compute and remove the elastic strain component from each data point. |
| Yield Calculation Type | yield_type | scalar | effective | Method used to locate the yield point: ‘effective’ (intersection of the effective curve with the strain axis, default), ‘offset’ (0.2% offset rule), ‘strain’ or ‘stress’ (user-specified threshold), ‘linearity’ (end of linear region), or ‘initial_peak_percentage’ (fraction of peak-stress strain). | |
| Yield Offset Or Strain | yield_offsetor_strain | scalar | 0.002 | Strain offset or threshold value used when yield_type is ‘offset’ or ‘strain’/’stress’; default 0.002 (0.2%) is standard for steel — increase for polymers. Not used when yield_type is ‘linearity’. | |
| Post Necking Treatment | post_necking_treatment | string | swift | Extrapolation method applied beyond the necking (diffuse instability) point: ‘none’ (no extrapolation), ‘truncate’ (clip at necking), ‘offset’ (constant offset), ‘swift’ (Swift power-law fit, default), or other supported hardening laws (e.g., Hockett-Sherby). | |
| Post-necking Extrapolation Coefficient | slopefor_extrapolation | scalar | 0.0 | Slope for extrapolation. If 0.0, the necking strain is used for SWIFT based extrapolations. If negative for SWIFT, abs-value becomes the factor. For polymer, this is no-stiffness value. For polymer_segmented, this is no_stiffness:x_sf:y_sf | |
| Last Strain | last_strain | scalar | 1.0 | Last strain value for output curve | |
| Digitize | digitize | scalar | 401 | Number of points in the output curve. If negative, the effective curve is digitized only when the number of points is less than the abs(digitize) value. | |
| Saturation Strain | saturation_strain | scalar | 0 | Stress will be capped beyond this value | |
| Saturation Percentage | saturation_percentage | scalar | 0 | Stress will be capped beyond this percentage | |
| Intersection Point Type | intersection_point_type | scalar | auto | ||
| Digitize Option | digitize_option | scalar | yes | Option to digitize curve to required number of points provided in Digitize input | |
| Necking Strain | necking_strain | scalar | 0 | Necking strain | |
| Poisson’s Ratio | poissons_ratio | scalar | 0 | Poission’s ratio | |
| Loading Type | loading_type | scalar | tension | Tension-Compression-Shear flag to compute strains | |
| Enforce Monotonic Y | enforce_y_monotonicity | select | no | If the input True-stress vs strain has non-monotonic y-values, this option allows to remove them before converting it to effective stress vs strain | |
| Number Of Extrapolation Segments | num_extra_seg | scalar | 1 | This is used when the post-necking treatment is extrapolation_regression. The default is 1 which is one-segment resulting in linear extrapolation | |
| Slope Scale Factor During Extrapolation | slope_sf | scalar | 1.2 | When post-necking treatment type = extrapolation_regression, each segment slope is multipled by this number | |
| Smooth Curve | smooth_curve | float | no | The final hardening curve is smoothed using avaialble options | |
| How To Treat User-defined Yield Value | user_defined_yield_treatment | scalar | offset | When user defined yield is provided, this option allows us to either offset or find a smooth fit to satisy the user-defined yield | |
| Linearly extrapolate when no necking is found | linearly_extrapolate_when_no_necking_is_found | scalar | no | When necking (localization) is not found, this option allows to linearly extrapolate and overrides the extrapolation type chosen above |
Outputs¶
| Label | ID | Type | Description |
|---|---|---|---|
| curve_truetoeffectivestress_output_1 | curve_truetoeffectivestress_output_1 | vector | Effective (plastic) stress–strain curve as an XY vector (stress in MPa, plastic strain dimensionless), with elastic strains removed, post-necking extrapolation applied, and optional smoothing/monotonicity enforcement; ready for direct use in elasto-plastic material cards such as LS-DYNA MAT_24. |
Disciplines¶
- data.curve.transform
- engineering.material.calibration
- engineering.material.characterization
Runnable example¶
A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: /api/workflow/example?id=curve_truetoeffectivestress
Auto-generated from transformation schema. Worker id: curve_truetoeffectivestress. Schema hash: 8cfbe81fc72d. Hand-curated docs in workerexamples/ override this page when present.