4. Regulatory and consumer test protocols

Restraint system virtual validation is only meaningful when the simulation is anchored to a defined test protocol. Each regulation and consumer program specifies its own impact configuration, dummy family, injury criteria, and pass/fail thresholds. A MADYMO model that passes one protocol may fail another simply because the boundary conditions differ. This chapter maps the four most relevant protocols for restraint sign-off and shows how their requirements translate into model setup decisions.

FMVSS 208 — Occupant Crash Protection

FMVSS 208 is a self-certification regulation. The manufacturer certifies compliance; NHTSA audits through random compliance testing. The standard covers frontal rigid barrier impacts at 56 km/h (35 mph) for both driver and passenger positions, plus an optional 40 km/h (25 mph) unbelted test for vehicles without belt reminders. The primary dummy is the Hybrid III 50th percentile male, with the 5th percentile female used for the out-of-position (OOP) and low-risk deployment (LRD) evaluation.

Key injury criteria and thresholds for the 50th percentile male in the 56 km/h frontal test:

CriterionSymbolThresholdMeasurement Location
Head Injury CriterionHIC15≤ 700Head CG resultant acceleration
Chest deflectionDchest≤ 63 mmSternum relative to spine
Chest accelerationAchest≤ 60 gChest accelerometer (3 ms clip)
Femur axial forceFfemur≤ 10 kNEach femur load cell
Neck injury criterionNij≤ 1.0Upper neck load cell

For MADYMO, the critical modeling implications are: the rigid barrier is modeled as a fixed plane with a coefficient of friction of 0.8; the seat belt must include a pretensioner and load limiter whose force–displacement curve is supplied by the supplier; and the airbag must be modeled with a validated gas inflow curve (mass flow rate vs. time) rather than a simple uniform pressure. The OOP tests require the dummy to be positioned at multiple locations relative to the airbag module, and the airbag must not exceed the specified injury thresholds during deployment. In MADYMO, this is handled by running a design-of-experiments matrix over dummy position and airbag timing.

ECE R94/R95 — European Frontal and Side Impact

ECE R94 (frontal) and R95 (side) are type-approval regulations. Unlike FMVSS 208, they require approval by a designated technical service. R94 uses a 40% offset deformable barrier (ODB) at 56 km/h, which produces a different intrusion pattern than the full-width rigid barrier. The dummy is the Hybrid III 50th percentile male. Injury criteria are similar to FMVSS 208 but with some differences: HIC ≤ 1000, chest deflection ≤ 75 mm, and a viscous criterion (VC) ≤ 1.0 m/s for the chest.

R95 side impact uses a moving deformable barrier (MDB) at 50 km/h impacting the driver side at 90°. The dummy is the EuroSID-2 (ES-2). Key criteria: HIC ≤ 1000, rib deflection ≤ 42 mm, abdominal force ≤ 2.5 kN, and pubic symphysis force ≤ 6 kN. In MADYMO, the MDB is modeled as a rigid body with a deformable honeycomb face; the door trim and side airbag must be represented with validated material models. The seat and door interaction is critical — a common modeling error is neglecting the door trim stiffness, which leads to under-predicted rib deflection.

Modeling note: For R94, the ODB is modeled as a deformable barrier with a honeycomb block. The barrier face must be calibrated to the EC regulation's force–deflection corridor. In MADYMO, this is typically done with a MULTIBODY barrier or a FE honeycomb model. The offset is 40% of the vehicle width, measured from the driver side.

Euro NCAP — Consumer Rating

Euro NCAP is not a regulation; it is a consumer information program. It uses a 64 km/h ODB frontal test (40% offset), a 50 km/h side MDB test, and a 32 km/h side pole test. The dummy fleet includes the Hybrid III 50th male, the 5th female, and the WorldSID 50th for side impact. Euro NCAP also evaluates whiplash (rear impact), pedestrian protection, and active safety.

Euro NCAP scoring is points-based. For frontal impact, the assessment combines dummy readings with structural inspection. The overall rating (1–5 stars) depends on the total score across all categories. For restraint system sign-off, the key is to achieve a minimum score in each body region. A common target is to keep HIC below 500 and chest deflection below 40 mm to secure maximum points, even though the regulatory thresholds are higher.

In MADYMO, Euro NCAP requires the model to include the 64 km/h ODB, the 50 km/h MDB, and the 32 km/h pole. The pole test is particularly demanding because the side airbag and curtain airbag must deploy within 20–30 ms. The model must capture the interaction between the pole, the door, and the airbag. A typical validation step is to compare the simulated pole intrusion with the physical test measurement at the door inner panel.

C-NCAP — China New Car Assessment Program

C-NCAP is managed by CATARC. It has evolved significantly. The 2021 version includes a 50 km/h full-width rigid barrier frontal test, a 64 km/h ODB frontal test, a 50 km/h side MDB test, and a 32 km/h side pole test. The dummy set includes the Hybrid III 50th, the 5th female, and the WorldSID 50th. C-NCAP also includes a whiplash test and a pedestrian protection test.

C-NCAP thresholds are generally aligned with Euro NCAP but with some differences. For example, the frontal ODB test uses a 64 km/h impact speed, and the side pole test uses a 32 km/h impact speed. The scoring system is similar: points are awarded for each body region, and the overall star rating is based on the total. A key difference is that C-NCAP places strong emphasis on the restraint system's performance in the full-width rigid barrier test, which is more severe for the rear seat occupants.

For MADYMO modeling, the C-NCAP full-width test requires the rear seat to be modeled with a belt system and a rear dummy. The rear seat belt geometry and the seat cushion stiffness are critical. A common issue is that the rear dummy's head may strike the front seat back; the model must include the front seat as a deformable structure.

Protocol Comparison: Impact Configuration and Key Parameters Protocol Impact Type Speed Dummy Key Criteria FMVSS 208 Self-certification Full-width rigid barrier 56 km/h HIII 50th HIII 5th (OOP) HIC ≤ 700 D_chest ≤ 63 mm F_femur ≤ 10 kN ECE R94 Type approval 40% ODB frontal 56 km/h HIII 50th HIC ≤ 1000 D_chest ≤ 75 mm VC ≤ 1.0 m/s ECE R95 Type approval MDB side impact 50 km/h ES-2 Rib defl. ≤ 42 mm Abd. force ≤ 2.5 kN Pubic force ≤ 6 kN Euro NCAP Consumer rating 64 km/h ODB + side pole 64 / 32 km/h HIII 50th/5th WorldSID HIC ≤ 500 (target) D_chest ≤ 40 mm Points-based C-NCAP Consumer rating Full-width + ODB + side pole 50 / 64 / 32 HIII 50th/5th WorldSID Aligned with Euro NCAP, rear seat emphasis

Translating Protocol Requirements into MADYMO Setup

The table and figure above show that each protocol imposes a unique combination of impact speed, barrier type, dummy, and injury threshold. When building a MADYMO model for restraint sign-off, the following decisions must be made explicitly:

  • Barrier model: Rigid wall for FMVSS 208 and C-NCAP full-width; deformable honeycomb for ECE R94, Euro NCAP ODB, and C-NCAP ODB; MDB for side impacts. The barrier's force–deflection curve must match the regulation's corridor.
  • Dummy positioning: The H-point and joint angles must be set according to the protocol's seating procedure. For OOP tests, a matrix of positions is required.
  • Restraint timing: Pretensioner fire time, load limiter force level, and airbag deployment timing must be calibrated to the specific impact speed. A 56 km/h full-width test requires earlier deployment than a 64 km/h ODB test because the vehicle decelerates faster.
  • Injury calculation: HIC15 is computed from the head CG resultant acceleration over a 15 ms window. Chest deflection is measured from the sternum to the spine. These calculations must be implemented in the MADYMO post-processor using the same filtering (SAE J211 CFC 600 for HIC, CFC 180 for chest deflection).

Practical tip: When switching between protocols, do not simply change the impact speed. The barrier stiffness, dummy type, and injury thresholds all change. A model validated for Euro NCAP 64 km/h ODB will not automatically pass FMVSS 208 56 km/h full-width because the full-width barrier produces a different deceleration pulse and the unbelted OOP requirement adds a separate load case.

Sign-Off Checklist for Protocol Compliance

Before submitting a MADYMO model for restraint system sign-off, verify the following for each applicable protocol:

  1. The barrier geometry and material properties match the regulation's specification (e.g., EC R94 ODB honeycomb cell size and density).
  2. The dummy model is the correct percentile and version (e.g., Hybrid III 50th percentile, revision level).
  3. The seat belt routing and anchorage locations match the vehicle's CAD data.
  4. The airbag model includes the correct gas inflow curve, vent size, and fabric permeability.
  5. The contact definitions between the dummy, seat, belt, airbag, and vehicle interior are active and stable.
  6. The simulation time step is small enough to capture airbag deployment (typically 1–2 μs for explicit FE airbag models).
  7. The injury criteria are computed with the correct filtering and windowing per the protocol.
  8. The model has been correlated against at least one physical test for the same impact configuration.

Each protocol has its own pass/fail logic. FMVSS 208 and ECE R94/R95 are binary: the vehicle either meets the threshold or it does not. Euro NCAP and C-NCAP are points-based: the goal is to maximize the score, which often means targeting thresholds well below the regulatory limits. In practice, restraint engineers design to the most stringent consumer target and then verify that the regulatory minimums are also met. This dual-target approach is the core of virtual sign-off: one model, multiple protocols, each with its own boundary conditions and acceptance criteria.

← Previous 📖 Contents Next →