Documentation:FIB book/problems/Rollover

Even though rollover crashes are rare (less than 3% of all crashes), they are high death related that approximately one third occupant fatalities happened in rollover crashes. As the concern of the issue, vehicle’s static stability factor (SSF) was invented in order to determine the rollover resistance of the vehicle.

Question 1

Question 1.1

Calculate SSF for the following vehicles (Tesla Model S and JEEP Wrangler ) with given data and discuss the results.

SOLUTION (expand to show)

Formula Static Stability Factor $SSF=t/2h$ Tesla Model S: $SSF=1964/(2*457)=2.1488$ JEEP Wrangler: $SSF=1877/(2*686)=1.368$ According to the definition of the Static Stability Factor, a higher value means more stable and less chance get involved in a rollover crash. The result shows that JEEP Wrangler has a much higher chance to roll over. The result also shows the reason why most SUVs are easier to roll over than compact cars because of the higher center of gravity height.

Question 1.2

List two types of rollovers and two types of measurement for the rollover rating.   

SOLUTION (expand to show)
types of rollovers measurements for the rollover rating Tripped Rollover vehicle measurements (weight, width, height of center of gravity) Fish hook maneuver (“road edge recovery”), Fishhook maneuver live tests

Question 2

Vehicle Kinematics in rollover involves deceleration along with a horizontal, vertical acceleration and deceleration, and rotational acceleration and deceleration. Following two images are from a 2006 JRS Dynamic Rollover Test with Anthropomorphic Test Dummy Hybrid III.

Figure 1. 2006 JRS Dynamic Rollover Test (before impact)

Figure 2. 2006 JRS Dynamic Rollover Test (after impact)

Question 2.1

Describe the three possible injuries that ATD can predict from the above rollover test. (at least three)

SOLUTION (expand to show)

We can analysis from the following three aspects. 1:Left side of the dummy head impacted with the roof. Brain injury Traumatic Brain Injury(TBI) Concussion(ATD can not predict concussion, but according to the feedback data, in rollover, it can have a tendency to have a concussion scenario. ) Skull fracture: Zygoma fractures, Maxilla Fractures 2:Loading on the neck while ATD head interacts with the roof. Neck soft tissue injury: whiplash injury(cannot predict by ATD, but due to the feedback data, it can have a tendency to have whiplash associate disorders ) Cervical spine injuries: fracture, ligamentous and dislocation SCI (Spinal Cord Injury): cord compression 3:Contact with the airbag Rib fractures Thoracic organ injuries

Question 2.2

Discuss the roof crush controversy in rollover base on the Malibu studies.

SOLUTION (expand to show)
Controversy about whether roof crush related to injury severity was under debating. Malibu studies aim to investigate the effects of added roof structure on the safety of unrestrained occupants. From the Potentially Injurious Impact (PII) results, injury mechanics are unrelated to roof deformation and adding additional roof structure cannot increase the protection.

Question 2.3

Most of the Rollover tests are using ATD Hybrid III. Describe the limitation for the dummy testing.

SOLUTION (expand to show)

1: ATD Hybrid III is designed for frontal impact. In rollover testing, side impacts happened during vehicle rotating. Hybrid III is lacking the biofidelity to side impact kinematics. 2: ATD Hybrid III is designed with only sitting posture. it is unable to mimic human sitting kinematics for the dynamic rollover tests since the occupant will be lifted during rollover crashes. 3:Hybrid III is lacking the biofidelity on the cervical complex. Therefore, the response to interaction with the roof is questionable. From the previous investigation, six different types of ATDs are used to perform Dynamic Rollover Tests. The results show that all HIC values are under 1000 and Nij values are <1, which gives the conclusion that the current ATDs are not able to predict injuries with injury criterion in the rollover test.