Arc far Side Impact Collaborative Research Program – Task 5b: Test Procedures Crash Tests and Sled Tests for the Far-side Environment

4.1Introduction

The objective of this Task is to use the MADYMO computer simulation tool to determine whether a square acceleration pulse of equal energy to a peaked crash pulse is suitable for far-side cadaver Hyge sled tests.

The Hyge sled at Medical College of Wisconsin was designed to run square shaped deceleration profiles. This sled will be used for future far-side human cadaver or dummy experiments.

A previous cadaver test for far-side utilized a full-vehicle - Holden Commodore. This vehicle was struck on the far-side according to ECE 95 protocol. The test produced a multi-peaked acceleration pulse, as measured in full-vehicle crashes (Fildes et al., ICROBI, 2002).

Figure 1 contains an overlay of the full-vehicle pulse and a square pulse from the test buck at MCW. Both deceleration curves contain equal energy.

Figure 1: Peaked and Square Lateral Acceleration

4.2Results

The two curves from Figure 1 were used as the input for a MADYMO model with the TNO human faceted occupant. The model was only accelerated in the y-direction (lateral) according to the curves. Any accelerations in the x or z directions were ignored, in addition to not accounting for vehicle roll, pitch, and yaw. Both simulations were run from 0 to 200 milliseconds. For any time beyond 170ms, the acceleration was assumed to be 0 ^m/_s².

Figure 2 contains snapshots of the two animations simultaneously.

The model predicted the occupant excursion in a square wave impact was slightly greater than the excursion in a peaked wave impact, this is demonstrated in the snapshot at 175ms. Also, the occupant’s reaction to the peaked pulse is delayed to that of the square pulse. This is evident at the snapshot taken at 150ms.

The Figures 3, 4 and 5 below are the pelvis, chest, and head acceleration time histories for the human facet model when subjected to the two different pulses.

Figure 3. Pelvic Acceleration

Figure 4. Chest Acceleration

Figure 5. Head Acceleration

4.3Discussion

When visually examining the two human facet models together, minor differences are noticeable. The human model subjected to the square acceleration plot had slightly higher excursion toward the impact, approximately 4 cm further. In addition, the human model subjected to the square pulse traveled forward in time when compared to the peaked pulse by 5 to 10 ms. However, the path of motion between the two remained quite similar.

When analyzing the pelvis, chest, and head acceleration recorded by MADYMO, the two simulations demonstrated similar magnitudes and shapes, however, the occupant reactions during the square wave simulation were shifted earlier in time by a few milliseconds. These kinematics may be explained because the square acceleration profile slopes up more quickly and continues to accelerate the occupant, while the peaked pulse drops lower before peaking again. The constant acceleration from the square wave gets the occupant moving more quickly to the center console.

4.4Conclusions

Despite these differences in excursion distance and time delay - which ought to be noted – the motion of the two human remain remarkably similar based on these results from MADYMO modeling. Nearly the same result was achieved between the two with acceleration pulses of equal energy. Similar peak acceleration magnitudes of the head, chest, and pelvis were produced.

4.5References

Alonso, B., Far-side Impact Simulations with MADYMO, Report written to George Washington University – National Crash Analysis Center, October 2004.

Alonso, B., MAYDMO Human Facet Model Validation for Far-side, Memo written to George Washington University – National Crash Analysis Center, October 2004.

Fildes, B., Sparke L., Bostrom O., Pintar, F., Yoganandan N., and Morris, A. Suitability of Current Side Impact Test Dummies in Far-side Impacts, Proceedings of the 2002 International IRCOBI Conference on the Biomechanics of Impact, Munich, Germany, September 2002.

5Far-Side Impact Vehicle Simulations with MADYMO

5.1Introduction

Collisions occurring on the far-side of the vehicle to the occupant position account for a significant portion of automotive fatalities and HARM annually. All side impacts generally account for 35% of road trauma (Fildes 2002). Of these side-impact injuries, those resulting from impacts on the far-side of the vehicle account for 40% of HARM (Fildes, Digges, etc.). Despite these statistics, most research and regulations to date for side-impacts are dedicated to near-side, without further understanding of injury mechanisms of far-side.

Impacts on the far-side are most commonly characterized by a head injury and fewer chest and abdominal injuries (Fildes 1994). These outcomes stem from occupants excursion out of the seat and contacting the far-side door, impacting vehicle or object, or occupant (Fildes 1994). This same excursion and occupant kinematics are not seen in near-side impacts due to the nature of the event.

Since most side impact research and regulations are focused on near-side impacts, side-impact dummies are designed to consider injury criteria and biofidelic requirements of near-side hits. These are characterized by broad intruding impacts to one side of the body. Conversely, far-side is marked by excursion out of the seat and towards source of impact. Typical modern vehicle interior arrangements are limited in the ability to hold the occupant in place during this situation and thus results in upper torso movement and spinal bending. Meanwhile, the occupant usually absorbs near-side impacts in the ribs and hips. The stark differences in these two side-impact scenarios places the suitability of current side-impact ATDs for far-side impact testing into question.

Fildes, Sparke, Bostrom, Pintar, Yoganandan, and Morris reported that current WorldSID prototype and BioSID dummy with a modified lumbar spine provide the most reasonable simulations to occupant kinematics and injuries. This study was based upon comparison of a Post Mortem Human Subject (PMHS) and four ATDs – BioSID, BioSID with lumbar spine modification, EuroSID 1, and WorldSID. Some of the metrics used to evaluate these dummies to the PMHS were torso shear, spine straightening, and head impact. The authors reported that the BioSID, EuroSID 1, and WorldSID did not reproduce a head strike with the far-side door as the PMHS did.

This paper seeks to further evaluate these dummies and others by using computer simulations to assess dummy responses in far-side impact scenarios and measure their responses to countermeasures. For thoroughness, multiple angles and multiples speeds were used in the simulations.