Using virtual tests

Science topics February 2015 Road safetyHuman behaviourModelling and computer simulation

Jean-Pierre Verriest, Emeritus researcher - TS2 Department , LMBC Laboratory

Essential regulatory and consumerist tests

The aim of a test is to make sure that a product complies with a set of safety and/or quality specifications that are laid down in a standard or a regulation1. In the case of human protection, regulatory tests consist of subjecting a vehicle to certain crash conditions and assessing that the risk faced by the potential human casualties inside the vehicles is below a limit specified by the regulations. Consumerist tests (such as EuroNCAP set out to measure the effectiveness of protection measures and allocate scores (stars) to the tested products. In the case of cars, the full-scale tests are destructive (« crash tests ») and have a cost which is not negligible. In aeronautics, the cost of a test on a real plane is completely prohibitive consequently other test methods have been developed.
 

The benefits of numerical simulation

Advances in mathematical modelling, and in particular the continuous increase in computing power, mean that we are now able to simulate the behaviour of more and more complex objects with affordable computing times.
Numerical simulation is beneficial, particularly in terms of costs. These are mainly related to the development of the model of the tested product. As soon as the model is available, each simulation is inexpensive to perform, making it possible to test a very large number of situations without a major increase in the budget. However, in the case of physical tests each new test requires a financial investment.
Numerical simulation has been used for some years in the automotive industry to test products during the design phase. It is used at all stages of the process from single components through subassemblies to the entire vehicle. At the most important stages the results of simulation are validated by real tests.
During the design phase simulation considerably reduces the number of physical tests. This limits the cost of manufacturing prototypes which are destined for destruction.

What role for the virtual human?

Until now, simulation of crash tests was performed with a numerical model of the crash test dummies (used in real crash tests). Numerical human body models have now reached a satisfactory level of development2. They will therefore gradually replace the models of the  dummies. However the validation process3 is much more difficult than for an inert object such as a dummy.
Their use in a regulatory context is not envisaged for the next 10 years4. In order for this to be done, numerical simulation with models of manikins have proved its feasibility and cost-effectiveness.


1 A regulation lays down a legal obligation which must be complied with, whereas adherence to a standard is a voluntary act that guarantees a certain level of quality or performance.

2 A global project that brings together all motor vehicle manufacturers and some research centres of excellence has developed the most recent generation of numerical model for the human body : http://www.ghbmc.com/.
Its abdominal model was developed by the Laboratory of Impact Mechanics and Biomechanics (LBMC), a research unit that is jointly managed by IFSTTAR and Université Claude Bernard Lyon 1.

3 The validation of a model is based on comparing the results of simulation with the results of real tests.

4 A European project that involves collaboration between motor vehicle manufacturers, design software publishers and research centres including the Laboratory of Impact Mechanics and Biomechanics (LBMC) has recently laid down the basis for a virtual test procedure : www.imviter.com/overview