Documentation:FIB book/problems/Sled test1
Sled tests are a useful tool for simulating driver and vehicle response in a crash. Please consider the following described crash scenario and questions with regard to designing a sled test for injury biomechanics purposes.
The crash scenario described can be seen depicted in Figures 1 and 2. The red car, driven by a woman with her stocky male partner as a passenger, was traveling counter-clockwise around the roundabout when the blue car merged from the left entry point. The driver of the blue car (alone in the vehicle) entered the roundabout at too high of a velocity. Despite braking, the red car was still rear-ended by the blue car and propelled out of the roundabout to impact a nearby tree. Figure 1 shows the scene immediately before the initial car-on-car impact and Figure 2 shows the scene a few seconds after both impacts occurred.
Question 1
Briefly describe the types of sled tests you would use to model the two impact scenarios, testing the red car in particular:
1) blue car into red car, and
2) red car into tree.
Please address the following points for each scenario:
a) Would a buck sled test suffice or should a destructive crash test be carried out?
b) What type of sled test is relevant?
c) What type of ATD(s) would you recommend using?
SOLUTION (expand to show) |
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1) a) The buck of the car would likely suffice for this type of test but a vehicle answer is also acceptable.
b) This would be best modelled by an acceleration sled test, as the red car was impacted by the blue car. c) Two ATD's should be included in this test, a driver and passenger. As the initial impact is from the rear, the Hybrid III would not be appropriate, and a model designed for rear impacts such as the BioRID would be a more biofidelic option. The driver ATD should be smaller and lighter in design to representative the typical female anthropomorphics. Furthermore, it would be nice (but is not necessary to give in the answer) for the student to observe that the red car seems to be impacted at some angle. It would be ideal to recommend that the buck be positioned and fixed at a particular angle relative to the sled in order to better simulate the crash conditions. 2) a) The buck of the car would likely suffice for this type of test but a vehicle answer is also acceptable. b) This would be best modelled by a deceleration sled test, as the red car impacted the stationary tree. c) Two ATD's (driver and passenger) should be included in this test, and particularly that the driver is female and likely smaller/lighter. The Hybrid III would be a suitable dummy for this frontal impact, perhaps the 5-Female for the driver and the 95-Male for the passenger. |
Question 2
Please describe three differences between acceleration and deceleration sleds.
SOLUTION (expand to show) |
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Can include any of the following:
acceleration: "something-hit-you" forward-facing, applied using a powerful pneumatic actuator, starts from v=0, needs less room, requires huge force and metering pin to get correct impact acceleration pulse, no initial velocity = no dummy movement out of place, may be conducted using a large linear motor if a deconstructed sled (i.e. car seat + ATD only) is being tested deceleration: "you-hit-something" forward-facing, sled is slowly accelerated and crash pulse is applied using pneumatic, hydraulic or structural (cables) braking systems, start from some initial velocity, need lots of room to accelerate before deceleration, run into ram with hydraulic outlets, easier testing of additional factors such as pre-braking |
Question 3
What sort of outcome parameters would be useful to evaluate in such sled tests? Please describe at least two that relate to injury biomechanics and two that relate to the vehicle response in a crash.
SOLUTION (expand to show) |
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Any of the following, among other answers that are reasonable:
injury: head injury, accelerometer data, thorax loading due to the seatbelt, motion of the ATD, potential ejection vehicle: seatbelt functionality, airbag deployment, crush of vehicle, effect of braking before impact, possible intrusion of exterior carriage into interior of vehicle |
Question 4
Please give two examples of interior vehicle components specifically that can be evaluated for research or consumer information purposes, and what research questions can be evaluated using a sled test.
SOLUTION (expand to show) |
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Students should list at least two of the interior components and related justification that can be found in the following list. Other answers that are reasonable and well justified would also be acceptable.
Seats: Do seats stay in place or collapse/fold down in an impact? Headrests: Do headrests prevent whiplash and protect the neck accordingly? Do they stay in place in a crash? Restraints: Do the restraint systems function properly in a crash of considerable magnitude? Any unexpected failures? Airbags: Are airbags employed properly in expected conditions? How do the airbags impact the ATD? Various other answers that are appropriately thought out and justified may be accepted for this question. |