--- pretty_name: "Automotive Underbody Panel Impact Dataset" license: mit tags: - 3d - timeseries - finite-element-analysis - impact-mechanics - graph-neural-networks viewer: false --- # Automotive Underbody Panel Impact Dataset **Version:** 1.1.1 **Data type:** finite-element simulation trajectories **Task:** impact-conditioned displacement and shell von Mises effective-stress field prediction The Automotive Underbody Panel Impact Dataset contains independent impact simulations on three automotive structural geometries. Each geometry has 500 Latin-hypercube-sampled impact conditions. Every case stores 17 aligned states of the full three-dimensional nodal displacement field and shell-element von Mises effective stress. The dataset supports research on graph neural operators, mesh-based surrogate models, spatiotemporal field prediction, peak-event prediction, and simulation-based design screening. Detailed generation documentation is provided in: - `metadata/SIMULATION_PROTOCOL.md` for units, the impactor, boundary/contact conditions, and solver/output settings; - `metadata/LHS_DESIGN.md` for parameter definitions, design bounds, and the geometry-specific constrained-LHS construction; - `metadata/TEMPORAL_SAMPLING.md` for the 17-state reduction and the discrete peak-time definition. ## Dataset summary | Geometry | Cases | Nodes | Directed graph edges | Shell elements | Displacement | von Mises effective stress | |---|---:|---:|---:|---:|---|---| | `floorfrontdriver` | 500 | 7,408 | 29,572 | 7,374 | `[7408,17,3]` | `[7374,17]` | | `floorfrontR` | 500 | 12,011 | 48,138 | 12,055 | `[12011,17,3]` | `[12055,17]` | | `trunkfloor` | 500 | 14,440 | 58,074 | 14,589 | `[14440,17,3]` | `[14589,17]` | The three geometries are independent datasets. Equal case identifiers across geometries do **not** denote paired physical simulations. ## Conditions and units The simulations use the 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. | Symbol | Released field | Definition | Design domain | Unit | |---|---|---|---|---| | p | `impact_xyz` | centroid of the selected eligible panel shell | geometry-dependent discrete candidate set | mm | | v | `velocity_xyz` | initial rigid-impactor translational velocity | derived from speed and angles | mm/s | | s | `impact_speed` | velocity magnitude | [1732.05, 5196.15] | mm/s | | mu | `mass_ratio` | common scale factor for reference impactor mass and density | [0.75, 1.25] | dimensionless | | theta | `theta_deg` | polar angle measured from global +Z | [0, 15] | degree | | phi | `phi_deg` | azimuth in global XY, from +X toward +Y | [0, 360] | degree | | E | `material_young_mpa` | rigid-impactor Young's modulus | {70000, 110000, 210000} | MPa | | nu | `material_poisson` | rigid-impactor Poisson ratio | {0.33, 0.34, 0.30} | dimensionless | The velocity is constructed as `v = s [sin(theta) cos(phi), sin(theta) sin(phi), cos(theta)]`. The mass-ratio convention is `impactor_mass = 0.01 tonne * mu` and `impactor_density = 5.205e-5 tonne/mm^3 * mu`. Impact positions are not sampled as three independent continuous coordinates. Eligible positions are shell-element centroids at least 80 mm from the topological outer boundary. Two LHS coordinates are mapped in normalized XY to the nearest unused eligible centroid; the released Z coordinate is the actual centroid height. ## Constrained-LHS design Each design uses seven normalized coordinates: position X, position Y, speed, mass ratio, theta, phi, and material class. Candidate designs are generated by Latin hypercube sampling, and the design with the largest normalized minimum pairwise distance among 128 trials is retained. Material is a balanced three-level categorical coordinate. `floorfrontR` and `trunkfloor` use independent single-batch designs with seeds 20260728 and 20260723, respectively. `floorfrontdriver` is a staged design: cases 001--100 use seed 20260721, cases 101--200 are a complementary nested extension using seed 20260722, and cases 201--500 form an independent augmentation using seed 20260722. The geometries share parameter bounds and simulation rules but do not share paired physical conditions. ## Impactor and simulation setup The impactor is a rigid spherical shell with radius 12.5 mm and an initial 5.0-mm gap from the target centroid along the direction opposite to travel. It uses shell ELFORM 2, shear factor 0.833333, three through-thickness integration points, thickness 0.1 mm, and `*MAT_RIGID`. The material class changes only the rigid impactor's E and nu; mass ratio changes only its density and nominal mass. All nodes on the panel's topological outer boundary are constrained in all six degrees of freedom. Impactor--panel interaction uses `*CONTACT_AUTOMATIC_SURFACE_TO_SURFACE_ID` with static and dynamic friction coefficients of 0.15. A body acceleration of 9810 mm/s^2 is applied in global +Z. Simulations end at 0.03 s. They were run with LS-DYNA SMP single precision R12 through ANSYS v221 `lsdyna_sp.exe` using `ncpu=8` and `memory=400m`. The panel material definitions and shell sections remain those of the cited upstream Version 3 model; their full keyword cards are not redistributed in this compact release. ## Stress definition The `effective_stress` field is the shell-element von Mises equivalent stress exported from LS-PrePost. The LS-PrePost `etime 9` component corresponds to `Effective Stress (v-m), ip#max`: for each shell element and retained state, the stored scalar is the maximum von Mises stress over all through-thickness integration points. The maximizing integration-point index is not retained. Stress values are in MPa, and the tensor shape is `[Ne, 17]`. ## Repository structure ```text underbody-impact-data/ ├── data/ │ ├── floorfrontdriver/cases_001_100.zip ... cases_401_500.zip │ ├── floorfrontR/cases_001_100.zip ... cases_401_500.zip │ └── trunkfloor/cases_001_100.zip ... cases_401_500.zip ├── meshes/ ├── metadata/ ├── generation_evidence/ ├── scripts/ ├── manifest.csv ├── checksums.sha256 ├── DATASHEET.md └── schema.json ``` Each ZIP member is stored as `cases/caseNNN.pt`. The files are PyTorch-serialized plain dictionaries. `manifest.csv` records the byte size and SHA-256 digest of every case. ## Download ```python from huggingface_hub import snapshot_download dataset_root = snapshot_download( repo_id="structmeshdata/underbody-impact-data", repo_type="dataset", revision="v1.1.1", ) ``` ## Loading a case PyTorch 2.6 or newer is recommended. The loader uses `weights_only=True` and reads cases directly from ZIP shards: ```bash python scripts/load_case.py \ --dataset-root . \ --geometry floorfrontdriver \ --case case001 ``` ```python from pathlib import Path import sys sys.path.insert(0, str(Path("scripts").resolve())) from load_case import load_case, load_mesh case = load_case(Path("."), "floorfrontdriver", "case001") mesh = load_mesh(Path("."), "floorfrontdriver") print(case["disp"].shape) print(case["effective_stress"].shape) ``` ## Validation ```bash python scripts/validate_dataset.py --dataset-root . --verify-checksums ``` The validator checks the case schema, tensor shapes, finite values, aligned time arrays, split coverage, mesh connectivity, archive membership, and SHA-256 digests. ## Fixed split and peak-event task The fixed split is 400 train / 50 validation / 50 test cases per geometry with seed 12345. Normalization statistics must be computed from the training cases only. For peak-event prediction, the supplied script selects the state containing the global maximum valid nodal displacement magnitude and uses the von Mises effective-stress field from that same state. ## Temporal sampling The solver writes D3PLOT output at a nominal interval of 0.0002 s. Compact conversion retains every tenth raw state and appends the final state. Every released case therefore uses indices `[0, 10, 20, ..., 150, 151]`; the first 16 retained states have a nominal 0.002-s spacing, while the appended terminal state can be very close to index 150. Exact floating-point times are stored in each case and should be used instead of reconstructing them from the nominal interval. The peak time `t*` is discrete: it is the argmax of nodal displacement magnitude over valid nodes and the 17 retained states only. It is not a continuous-time solver maximum. Stress at the same selected retained state is used as the paired peak-event stress target. ## Data-version note The included `floorfrontR` data passed the release quality audit. Files from earlier internal builds must not be mixed with this release; see `metadata/floorfrontR_DATA_NOTE.md`. ## Limitations - The fields are numerical simulation results, not physical crash-test measurements. - The dataset covers three fixed meshes and their documented sampled conditions. - It does not establish generalization to arbitrary vehicle geometries or real tests. - Public test labels reproduce the fixed paper protocol but are not a hidden benchmark. - The exact LS-DYNA R12 sub-build is not retained for every case. - The recorded `impactor_mass` is the generator-defined nominal mass; users requiring an independently recomputed solver mass should inspect an original solver `MATSUM` output. - Peak-event time is quantized to the released 17-state temporal grid. ## License This repository is released under the MIT License. Third-party names and source model provenance are documented in `THIRD_PARTY_NOTICES.md`. ## Citation Please cite the versioned Hugging Face repository for release `v1.1.1`: https://huggingface.co/datasets/structmeshdata/underbody-impact-data/tree/v1.1.1. Citation metadata is also provided in `CITATION.cff`.