ABSTRACT
Six European laboratories have evaluated the biomechanical response of the new advanced frontal impact dummy THOR-alpha with respect to the European impact response requirements. The results indicated that for many of the body regions (e.g. shoulder, spine, thorax, femur/knee) the THOR-alpha response was close to the human response. In addition, the durability, repeatability and sensitivity for some dummy regions have been evaluated. Based on the tests performed, it was found that the THOR-alpha is not durable enough. The lack in robustness of the THOR-alpha caused a problem in completing the full test program and in evaluating the repeatability of the dummy. The results have demonstrated that the assessment of frontal impact protection can be greatly improved with a more advanced frontal impact dummy. Regarding biofidelity and injury assessment capabilities, the THOR-alpha is a good candidate however it needs to be brought up to standard in other areas. Based on the results obtained recommendations were defined for the improvement of the THOR-alpha dummy.
ABSTRACT
Researchers worldwide try to define a unique test procedure for the assessment of whiplash protection of seats and restraint systems in low speed rear-end impact. Apart from valid injury criteria and uniform crash conditions, there is no clear answer to the question, which dummy to use. There are two impact dummies currently available, which have been designed for rear-end impact testing: BioRID and RID2. Both dummies have been evaluated in several test programs, however, both dummies have never been compared with each other in the test conditions, which form the basis of their design. BioRID was based on and validated against volunteer tests performed by Davidsson and Ono, while RID2 was designed with and validated against PMHS tests done by Bertholon and compared to volunteer tests reported by Van den Kroonenberg. This paper compares the responses of both rear impact dummies and the Hybrid III for the test conditions mentioned above. The setup of Davidsson used a rigid seat with flexible back and head restraint panels, while the setups from Ono and Bertholon used a rigid seat without a head restraint, in spite of being not representative for real car seats. This configuration creates a well defined test environment which will not affect nor obscure the dummy response Results of the performance of both rear impact dummies and the Hybrid III in comparison to the human responses will be presented in this paper. The results show that both rear impact dummies are capable of simulating rear impact responses, especially the head-neck kinematics. A difference in load pattern was found, which could be relevant when injury criteria will be based on neck forces and/or torques. Moreover, the dummies show a different interaction with the seat back, illustrated by the differences in T1 kinematics: BioRID shows larger T1 rotation and more ramping up than RID2, while spine straightening is comparable for both dummies. The current study showed good scores for both dummies in the setup on which they are based. The biofidelity score of BioRID is slightly better than for RID2, while the performance of the Hybrid III is relatively poor. However, repeatability, reproducibility and handling are not part of the evaluation, even though they are important for the practical use of the dummies.
ABSTRACT
Low severity neck injuries due to vehicle accidents are a serious problem in our society. In 1997 the European Whiplash project started with the aim to develop passive safety methodologies to reduce the frequency of neck injuries in rear-end impacts. This project has resulted, among others, in a rear impact crash dummy, the so-called RID2. The objective of this paper is present the design of this dummy and to present its performance in comparison with human volunteer and post mortem human subject (PMHS) tests. Also a comparison is made with the Hybrid III dummy in similar test conditions. In the comparison with human volunteers in a real car seat, both the RID2 and the Hybrid III showed realistic kinematics. Lower neck rotation as well as the typical S-shape in the neck were found in the RID2, but not in the Hybrid III dummy. Ramping up was not found in the Hybrid III, while the RID2 did show limited ramping up. The upper neck forces measured in both dummies were reasonably good in the regular car seat, but upper neck torques were not well predicted in either dummy. Compared to post mortem human subjects placed on a rigid seat without a head restraint, the Hybrid III was found to be less biofidelic than the RID2, as the kinematics of the human subjects were better approximated by the RID2 than by the Hybrid III, which was mainly attributed to the stiff spine and neck of the Hybrid III.
ABSTRACT
For the determination of material parameters, it is a common practice to extract specimens with well-defined geometries. The design of the samples and the choice of the applied load are meant to lead to a homogeneous stress and strain distribution in a part of the sample. When applied to biological materials, this raises a number of problems: homogeneous strains cannot be obtained because the materials have inhomogeneous properties, and the manufacturing of samples is hard or sometimes impossible. In this technical note a different approach is presented, based on the use of a digital image technique for the measurement of nonhomogeneous strain distributions, finite element modeling and the use of a minimum-variance estimator. The method is tested by means of experiments on an orthotropic elastic membrane of a woven and calendered textile. Five parameters are identified using the experimental data of one single experiment.
