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Tech Talk v58 – Recent Frontal Crash Test Simulation

Elio Motors, Together with Altair Engineering, Takes Another Step Forward

As part of the conception, development and launch of any new vehicle, automotive safety engineers perform a series of crash simulations to evaluate safety performance. These computer simulations provide valuable data in predicting the vehicle’s capability in absorbing the impact and protecting the occupant. It allows the engineering team to make adjustments to the vehicle prior to actual physical crash tests.

Elio Motors has the good fortune to work with Altair Engineering on our crash test simulations. Altair’s simulation tools are considered the gold-standard in the auto industry and are used by automakers around the world to gather important engineering information and make critical design changes.

Recently, Elio Motors and Altair made an important step in the crash testing process, simulating a belted occupant and driver airbag in a frontal crash. Previous crash simulations for the Elio were done with only the vehicle structure. The addition of the simulated occupant, airbag and belts helped the engineering team understand the predicted occupant kinematics for a given crash pulse, make design changes and reevaluate to support achieving safety performance requirements. A crash pulse is a time-history signature of a vehicle collision event and its characteristics such as shape, peak acceleration and duration influence occupant safety.

In engineering parlance, this model is referred to as the Full Vehicle Model with Restraints and Crash Dummy. The crash dummy is the Hybrid III 50th percentile anthropomorphic test device (ATD) that is the most commonly used worldwide (and required by Federal regulation in the US) for frontal impact testing and simulation. The Hybrid III standard crash dummy approximates an average North American male, about 5’9” tall and weighing approximately 172 lbs.

One of the keys to good occupant safety performance is how the crash energy is being managed. This is done using an engineering design element called a “crush zone.” An effective crush zone is an area of the frame that is designed to crush/collapse/stack or deform in a controlled manner so that the structure will absorb as much of the impact energy as possible. The Elio’s front rails are designed with effective crush zones to manage the impact energy and allow the occupant restraint system to perform well. The front rails can be tuned through design, crush initiators and reinforcements to give the ideal crash pulse for enhanced occupant safety.

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The other key to occupant safety is restraints optimization. This is the process of ensuring the seatbelt and airbags work together in terms of belt payout (the amount of travel in the belt and occupant movement during a crash event), airbag deployment timing and airbag venting to cushion the occupant during an impact event.

In addition to energy management, it is critical that the structure be strong to prevent intrusion into the occupant compartment. The Elio is designed using a spaceframe architecture, which utilizes a set of tubular steel struts, custom fitted and arranged in straight or curved geometric patterns for shape and/or strength. Optimally positioned, the struts will promote the greatest rigidity in structure for three-dimensional load-bearing points. The sturdy spaceframe construction along with the use of advanced high strength steels (i.e. Martensite, Boron and High Strength Low Alloy steels), provides enhanced structural strength to minimize intrusion into the occupant compartment during an impact.

Altair has used computer simulations extensively to predict safety performance for the major automakers. These simulations are well understood in the industry and correlations with real world testing have been established. The current simulation run was to establish a baseline safety performance for the Elio.  This will serve as a starting point for Altair to make refinements to the spaceframe and restraint systems to improve the overall safety performance. Once the spaceframe and restraint systems have been optimized through simulations, physical crash tests will be performed as a further validation.

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