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Jac S H M Wismans

Publications and source records attributed to Jac S H M Wismans.

2 recordsLinked to original sources

Improving pedestrian safety using numerical human models.

Pedestrian accidents are one of the main causes of traffic fatalities and injuries worldwide. New pedestrian safety regulations are being proposed in Europe and Japan to improve the protection afforded to pedestrians. Numerical simulations with biofidelic pedestrian models can be used to efficiently assess the risk to injury in pedestrian-vehicle impacts and to optimize the pedestrian protection in the early stages of the vehicle design process at relatively low costs. The goal of this study was to develop and validate a scaleable mid-size male pedestrian model. The model parameters were derived from published data and a large range of impactor tests. The biofidelity of the model has been verified using a range of full pedestrian-vehicle impact tests with a large range in body sizes (16 male, 2 female, height 160-192 cm, weight 53.5-90 kg). The simulation results were objectively correlated to the experimental data. Overall, the model predicted the measured response well. In particular the head kinematics were accurately predicted, indicated by global correlation scores over 90 %. The correlation score for the bumper forces and accelerations of various body parts was lower (47-64 %), which was largely attributed to the limited information available on the vehicle contact characteristics (stiffness, damping, deformation). Also, the effects of the large range in published leg fracture tolerances on the predicted risk to leg fracture by the pedestrian model were analyzed in detail. The validated mid-size male model was scaled to a range of body sizes, including children and females.

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On the potential importance of non-linear viscoelastic material modelling for numerical prediction of brain tissue response: test and application.

In current Finite Element (FE) head models, brain tissue is commonly assumed to display linear viscoelastic material behaviour. However, brain tissue behaves like a non-linear viscoelastic solid for shear strains above 1%. The main objective of this study was to study the effect of non-linear material behaviour on the predicted brain response. We used a non-linear viscoelastic constitutive model, developed on the basis of experimental shear data presented elsewere. First we tested the numerical implementation of the constitutive model by simulating the response of a silicone gel (Sylgard 572 A&B) filled cylindrical cup, subjected to a transient rotational acceleration. The experimental results could be reproduced within 9%. Subsequently, the effect of non-linear material modelling on computed brain response was investigated in an existing three-dimensional head model subjected to an eccentric rotation. At the applied external load strains in the brain were approximately ten times larger than was expected on the basis of published data. This is probably caused by the values of the shear moduli applied in the model. These are at least a factor of ten lower than the ones used in head models in literature but comparable to material data in recent literature. Non-linear material behaviour was found to influence the levels of predicted strains (+20%) and stresses (-11%) but not their temporal and spatial distribution. The pressure response was independent of non-linear material behaviour. In fact it could be predicted by the equilibrium of momentum, and thus it is independent of the choice of the brain constitutive model.

Journal Article↗