Enlighten™ Lightweighting Optimisation

Introduction

Enlighten™ is a solver based on topometry for lightweighting, designed to tackle complex non-linear dynamic challenges like automotive crashworthiness.

Topometry has established itself as a robust tool in both linear and non-linear statics. We have developed this method for use in the non-linear dynamics through the creation of a bespoke optimisation solver. Topometry, which involves adjusting shell thicknesses, is particularly well-suited for designing thin-walled structures like body-in-white (BIW).

The solver can be used as a generative design tool to create new and novel design solutions, as a refining tool on more mature designs or anywhere in-between.

The challenge of converting optimisation outcomes into practical design solutions is well-known. Therefore, we have dedicated considerable effort to integrating geometric constraints that accommodate standard manufacturing processes.

Enlighten™ uses LS-Dyna and Radioss/OpenRadioss crash solvers.

Case-Study: Nissan Rogue Body-In-White

Background:

To benchmark, highlight and develop Enlighten’s optimisation capabilities Vortex-CAE created the following case-study. The aim was to benchmark a modern vehicle for multiple crash and performance attributes, measure the baseline performance, use these performance metrics to design a body-in-white. The results will be critiqued for mass-saving potential and design feasibility.

As a benchmark vehicle an LS-Dyna Nissan Rogue model provided by https://www.ccsa.gmu.edu/models/2020-nissan-rogue/ was selected. It should be noted that the baseline results are not fully validated for OpenRadioss but are expected to be suitably accurate for the purposes of this study.

Loadcases:

The following loadcases were chosen to cover a broad range of vehicle safety and performance attributes:

Frontal Impacts

  • Full Frontal Barrier 0 Degrees (FFB 0)

  • Full Frontal Barrier 30 Degress (FFB 30)

  • Offset Deformable Barrier (ODB)

  • Small Offset Rigid Barrier (SORB)

  • Frontal Centre Pole (FCP)

Side Impacts

  • Front Door Deformable Barrier (FDDB)

  • Rear Door Deformable Barrier (RDDB)

Rear Impact

  • Rear Deformable Barrier (RDB)

Durability and Abuse

  • Kerb Strike Rear Wheel

  • Kerb Strike Front Wheel

Additional

  • Roof Crush

  • Seatbelt Anchorage (SBA)

  • Torsional Stiffness and Strength

Assessment Criteria

Frontal Impacts:

  • Energy absorbing zone is optimised to ensure correct crush as measured at front seat rails

  • Safety cell is optimised to control intrusions and deformations

Side Impacts:

  • Barrier intrusion into vehicle is kept below baseline

  • Safety cell is optimised to control intrusions and deformations

Rear Impacts:

  • Energy absorbing zone is optimised to ensure correct intrusion between barrier and rear seats

  • Safety cell is optimised to control intrusions and deformations

Durability and Abuse

  • Subframes and suspension remain firmly attached to the body-in-white

Additional

  • Roof Crush, the peak roof strength should meet or exceed baseline

  • Seatbelt Anchorage (SBA), the seatbelt anchorage points should not fail

  • Torsional Stiffness and Strength, the peak reaction forces at all suspension mounts should meet or exceed baseline

Design Volumes

The primary structures were removed from the baseline model and replaced with optimisation design volumes. The optimisation model uses two design volumes. One design volume is used to A-surface components such as body panels, design volume erosion is therefore disabled. The second design volume is a space-filling scaffold that is used to generate new and novel structures, design volume erosion is enabled.

Geometric constraints

  • The design volume for the generative design has gauge limits between 0.5mm and 10.5mm with discrete steps of 2mm. Erosion enabled.

Materials

  • While Enlighten can used multiple materials in it’s analysis, for simplicity a 800MPa UTS steel model (taken from the baseline vehicle rocker) was applied.

  • The remaining vehicle components did not have their material definitions modified.

A-surface

Design Volume

Iteration 0

Additional Modules

Results in progress

To solve OpenRadioss was used as the CAE solver. A total of 448 CPU’s on Vortex CAE’s HPC were allocated to this problem. The heatmap demonstrates thick sections (pink) and thin sections (blue).

Iteration 9/50 - Work in Progress

Observations

By iteration 9, clear and familiar primary structures are notably forming. Specifically:

  • Upper and lower load paths are visible in the frontal crush zone, accompanied by the development of a bumper beam.

  • A significant amount of material is being allocated to the rocker region.

  • The CANT rail is starting to take shape, providing additional strength at the top of the A-Pillar.

  • Floor cross-members are emerging for SBA attachment, complemented by B and C-Pillar reinforcements.

  • Reinforcement of the upper B-Pillar is underway to satisfy Roof Crush requirements.

  • Brackets for subframe and suspension attachments are beginning to form.

  • The rear crash zone is materializing, along with the rear bumper beam.

Current Conclusion

Conclusions will be presented at the OpenRadioss User’s day in Philadelphia on the 26th September