LSDYNA ELEMENT TRIAXIALITY HISTORY¶
Extracts the per-element stress-triaxiality (eta = sigma_m/sigma_vm) and equivalent-plastic-strain time-histories for a single element from a finished LS-DYNA run’s elout (binout) data, for fracture-locus characterization. Reuses the platform’s stress-tensor-to-triaxiality math. Also returns the normalized Lode angle (theta_bar) history and the plastic-strain-weighted path-averaged triaxiality + Lode angle to failure (the locus abscissa) alongside the plastic strain at failure (the ordinate). v1 requires an explicit element id; critical-element auto-detection is planned for a later increment. The simulation must have been run with *DATABASE_ELOUT for the relevant element type.
When to use¶
Tagged: triaxiality, lode, fracture_locus, eps_p, element, elout, lsdyna.
Inputs¶
| Label | ID | Type | Default | Required | Description |
|---|---|---|---|---|---|
| Simulation | simulation_id | remote_lookup | — | LS-DYNA simulation whose elout will be read. Must have *DATABASE_ELOUT output. | |
| Element ID | element_id | string | — | Element whose triaxiality/eps_p history to extract. OPTIONAL: leave blank to auto-detect the critical element (the one with maximum equivalent plastic strain at the fracture time). | |
| Element type | element_type | string | solid | elout sub-branch to read: ‘solid’ (elout/solid) or ‘shell’ (elout/shell). Solids report eps_p as ‘yield’; shells as ‘plastic_strain’. | |
| Fracture time | fracture_time | text | — | Optional. Time (in the solver’s output units) at which to report eta_at_failure / eps_p_at_failure. Empty = use the last available state. | |
| Fracture site mode | fracture_site_mode | text | max_eps_p | Which element carries the locus point. ‘max_eps_p’ (default) auto-detects the maximum-plastic-strain element. ‘axis’ parses the attached keyword deck and selects the notch minimum-section axis element (Bridgman center) where a round notched bar’s triaxiality peaks. Ignored if element_id is given; ‘axis’ applies to solids only. | |
| Necking time mode | necking_time_mode | text | last_state | How the fracture time is chosen when fracture_time is empty. ‘last_state’ (default) uses the last available output state. ‘secforc_peak’ uses the time of maximum section axial load (secforc x_force) = necking onset, the pure-FE fracture-point proxy. Requires *DATABASE_CROSS_SECTION; falls back to last_state if absent. | |
| Clip to last tensile state | clip_to_last_tensile | text | 0 | When ‘1’, if the triaxiality at the fracture time is non-positive (post-necking hydrostatic compression at the center), the averaging window is clipped back to the last tensile state, so the plastic-strain-weighted path average stays meaningful. Default ‘0’ (off). |
Outputs¶
| Label | ID | Type | Description |
|---|---|---|---|
| Element ID | element_id | string | |
| Triaxiality vs time | triaxiality_history | dataset | |
| Normalized Lode angle (theta_bar) vs time | lode_history | dataset | |
| Equivalent plastic strain vs time | eps_p_history | dataset | |
| Triaxiality at failure | eta_at_failure | scalar | |
| Path-averaged triaxiality (locus abscissa) | eta_avg | scalar | |
| Path-averaged normalized Lode angle | lode_theta_bar_avg | scalar | |
| Plastic strain at failure (locus ordinate) | eps_p_at_failure | scalar | |
| Fracture time | fracture_time | scalar | |
| Provenance / warnings | note | string |
Disciplines¶
- engineering.material.characterization
- data.curve.transform
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