Datasets:

structmeshdata
/

underbody-impact-data

The dataset supports research on mesh-based surrogate modeling of transient impact response. It was created to evaluate whether neural operators can map a finite-element mesh and impact/material conditions to spatially distributed displacement and shell von Mises effective-stress trajectories.

Composition

3 fixed automotive floor-panel geometries.
500 independent LHS cases per geometry; 1,500 cases total.
17 aligned states per case.
Nodal displacement: three Cartesian components.
Shell-element von Mises effective stress: one scalar per element and state, taken as the maximum over all through-thickness integration points.
Impact position, three-dimensional velocity, mass ratio, and material parameters are stored per case.
Static graph topology and shell element-to-node connectivity are provided per geometry.
One fixed 400/50/50 train/validation/test partition with seed 12345.

Exact tensor shapes are specified in schema.json and geometry metadata files.

Stress definition

The effective_stress target is exported from LS-PrePost using etime 9, labeled Effective Stress (v-m), ip#max. For each shell element and retained state, it stores the maximum von Mises equivalent stress across all through-thickness integration points. The integration-point index producing the maximum is not retained. Values are reported in MPa.

Condition definitions and units

The simulations use a tonne--mm--s--N consistent unit system. Coordinates and displacements are in mm, time is in s, velocity is in mm/s, mass is in tonne, density is in tonne/mm^3, and stress and Young's modulus are in MPa.

The paper-level inputs map to released fields as follows:

p is impact_xyz, the centroid of a selected eligible panel shell;
v is velocity_xyz, the rigid impactor's initial translational velocity;
mu is mass_ratio, a dimensionless scale factor in [0.75, 1.25];
E is material_young_mpa, the rigid-impactor Young's modulus;
nu is material_poisson, the rigid-impactor Poisson ratio.

The impact speed is sampled in [1732.05, 5196.15] mm/s. Theta is sampled in [0, 15] degrees from global +Z, and phi is sampled in [0, 360] degrees in global XY from +X toward +Y. Cartesian velocity is computed from speed and these two angles. The three material categories are discrete rigid-impactor E/nu pairs: (70000 MPa, 0.33), (110000 MPa, 0.34), and (210000 MPa, 0.30).

Mass ratio scales the generator's reference impactor mass and density: impactor_mass = 0.01 tonne * mu and impactor_density = 5.205e-5 tonne/mm^3 * mu. The mass field is the nominal mass recorded by the generator.

Collection and simulation process

Conditions were generated with a seven-dimensional constrained Latin hypercube over position X/Y, speed, mass ratio, theta, phi, and material class. Eligible impact positions are panel-shell centroids at least 80 mm from the topological outer boundary. Normalized LHS position coordinates are mapped to unused eligible centroids, so Z is inherited from the selected shell and is not an independent continuous coordinate. Among 128 trial designs, the normalized maximin design is retained. metadata/LHS_DESIGN.md records the exact geometry-specific batching and seeds.

The simulations were executed with LS-DYNA SMP single precision R12 through ANSYS v221 lsdyna_sp.exe, using ncpu=8 and memory=400m, on panel geometry derived from the 2020 Nissan Rogue finite-element model Version 3. The rigid spherical-shell impactor has radius 12.5 mm, thickness 0.1 mm, ELFORM 2, SHRF 0.833333, NIP 3, and a 5.0-mm initial gap. Panel outer-boundary nodes are fixed in all six degrees of freedom. Impactor--panel interaction uses automatic surface-to-surface contact with static and dynamic friction coefficients of 0.15. A body acceleration of 9810 mm/s^2 acts in global +Z. Further details are given in metadata/SIMULATION_PROTOCOL.md.

Raw solver databases and curve text are not included. Panel material and shell definitions remain those of the upstream Version 3 model. The exact LS-DYNA R12 sub-build is not retained for every released case.

Preprocessing

The released case tensors are the compact 17-state inputs to downstream data preparation. They have not been reduced to a single peak state. The accompanying build_peak_targets.py derives the paper task by selecting the state containing the largest valid nodal displacement magnitude and using stress from the same state.

The solver requests D3PLOT output every 0.0002 s through 0.03 s. Compact conversion retains every tenth raw state and appends the final state. Both nodal and element fields use indices [0, 10, 20, ..., 150, 151] in every released case. The first 16 retained states have a nominal 0.002-s spacing; the appended terminal state can be much closer to index 150. Exact times are stored per case.

Peak time t* is an argmax over valid nodes and these 17 retained states only. It is therefore a discrete, temporally quantized label rather than a continuous-time solver maximum. See metadata/TEMPORAL_SAMPLING.md.

Some source nodes may require filled values; each case retains raw_valid_node_mask, filled_node_mask, filled_node_count, and valid_node_mask to make that processing explicit.

Data quality

The release validator checks:

exactly 500 cases per geometry;
geometry-specific displacement and stress shapes;
17 states in each field;
finite displacement and stress values;
monotonic displacement and element time arrays;
exact alignment of displacement and stress time arrays;
valid static graph and shell-element connectivity;
complete and disjoint split coverage;
archive membership and SHA-256 case digests.

The floorfrontR revision additionally requires the source stress quality audit described in metadata/floorfrontR_DATA_NOTE.md.

Recommended uses

full-field transient surrogate modeling;
graph neural operators and mesh-based learning;
peak-event displacement/stress prediction;
temporal interpolation or sequence modeling within the released protocol;
controlled comparisons on fixed meshes;
simulation-based screening research.

Out-of-scope or unsupported uses

safety certification or replacement of final CAE/physical testing;
claims of arbitrary-geometry generalization;
treating same-numbered cases across geometries as physical pairs;
claims about real-world crash response without external validation;
mixing earlier internal floorfrontR artifacts with this release;
interpreting the public test labels as a permanently hidden benchmark.

Splits and benchmark integrity

The full v1.1 release includes labels for train, validation, and test cases. Consequently, the test split reproduces the paper protocol but is not a hidden benchmark after publication. New benchmark work should define a separate private evaluation set or use an evaluation server.

Personal and sensitive information

The data contain no human participants, personal data, or user-generated content. The main reuse consideration is the documented provenance of the underlying vehicle mesh.

Distribution and maintenance

The archival host is the Hugging Face Hub, with a version tag. Changes to data files require a new dataset version. Metadata changes should be documented without silently replacing data.

Licensing

Project-authored code, documentation, metadata, and derived numerical results are released under the MIT License. The panel meshes are derived from the cited CCSA/NHTSA vehicle model; upstream attribution is preserved and the upstream model is not represented as MIT-licensed project-authored content. Provenance and attribution are documented in THIRD_PARTY_NOTICES.md.