Dr. Ries presented doc. GTR9-1-04 on behalf of OICA reporting about the long-time durability of one of the prototypes (number SN-02) of the FlexPLI. The respective impactor was used for more than 300 tests in different configurations. It was highlighted that this impactor obviously is the last one in its original state including the bone core made of polyester. Dr. Ries concluded that the impactor is still working properly despite of its frequent usage but that some further guidance will be needed to further guarantee this after a longer period of time.

After finalization of the presentation, Mr. Bilkhu asked again whether there are experiences with how much damage to the bone core (as shown in the presentation) is acceptable. Manufacturers would be concerned using an impactor that shows so clear damages. Dr. Konosu added that the certification procedure is done for these purposes. Mr. Knotz added that the certification test may be met but it is unclear what the damages mean for the performance of the impactor when it comes to high test results close to the injury criteria.

Mr. Zander mentioned that the purpose of introducing the inverse certification test was that the performance of the assembled impactor is checked against realistic vehicle impact conditions. Mr. Been stressed that the impactor does not look too bad when considering that the impactor has been frequently used and that it was used to collect first experiences which may include overloading and poor handling. European OICA members replied that the agreed criteria were slightly exceeded in very few cases only.. In addition, they would prefer to go on with their round robin testing with this impactor as unmodified prototype status, as long as no major failure occurs. This could finally provide also indications on when impactors need to have comprehensive maintenance or even to be replaced.

Mr. Kolb added that his company had similar experiences with their legform regarding the wear as described in the presentation. On request he clarified that the Bertrandt legform is already equipped with vinyl ester bones and that around 60 pendulum tests as well as 30 inverse tests (but just around 10 vehicle tests) had been conducted before the bone core was replaced. Mr. Kolb presented a diagram showing how the performance of the impactor was worsening (more scatter) during an extensive pendulum test series (document GTR9-1-11) which finally led to the decision to exchange the bone core. Dr. Konosu added that obviously the certification tests give a clear indication on whether issues with components are occurring; Mr. Been agreed to this.

Dr. Ries clarified that the main issue seems to be that detailed guidelines are needed on how and when to conduct a disassembly. Mr. Been responded that there are guidelines for the certification tests procedures and following these should assure that no impactor malfunction should be overseen. However, Humanetics will think over whether more details should be provided for this. Mr. Hohmann requested to have checklists for these purposes that would ease the processes in test labs.

Mr. Zander mentioned that BASt conducted a large number of certification tests with impactor SN-02 but, by now, the performance of the impactors seems not to be significantly influenced by impactor wear. Mr. Zander promised to present more details on the impactor performance of a certain (longer) period of time.

Finally it was announced that BASt as well as Bertrandt will provide more detailed information regarding the long time performance at the 2nd meeting of the informal group.

Mr. Been provided some further comments on the presentation of OICA:

• - Regarding the loose screws, Humanetics could foresee some holes that allow the checking of screws. Dr. Konosu added that the holes in any case should be very small to avoid damages during the testing and possible influences on the test results especially in cases as shown were the screw is at the struck side of the impactor.
• - Regarding the shown bending of a string potentiometer’s steel string, Mr. Been was wondering whether the potentiometer should already have been replaced. This will be further investigated. However, Mr. Kinsky mentioned that initially it will not influence the performance since all measuring channels are zeroed before the test. However, it is unclear whether the bended string will stretch during the testing and therefore may influence (decrease) the test result.
• - The steel cables representing the ligaments show considerable wearing. However, it seems to be unavoidable and it does not seem to influence the test results.
• - The design of connector block showing the scratch in the connector socket has already been changed. Due to this, such damages are no longer possible.
• - The availability of spare parts is also seen as a problem at Humanetics and it was promised to improve soon.
• - Finally, the prices for spare parts will be checked at Humanetics. However, some of the prices are caused by the fact that parts are hand-made parts at a very small volume.

Ms. Versailles (NHTSA, US) mentioned that their test labs also recognized some durability issues that were reported to GRSP in the May 2011 session (see GRSP informal document no GRSP-49-23; added as document GTR9-1-12). Ms. Versailles concluded that durability has improved with the Flex-GTR legform impactor compared to earlier versions of the impactor and therefore did not see any further issues related to durability. Mr. Been thanked NHTSA for this and stated that the results of the testing at NHTSA were used to further improve the legform durability.

The chair concluded that currently a task force on review and update of certification corridors (TF-RUCC) is working on the issues with the certification as mentioned above and will come up with recommendations on the type of certification tests needed for the impactor. Based on the recommendations, the informal group has to decide if the pendulum and inverse certification tests are sufficient, or if certification tests at component level have to be implemented either in the regulatory text or the user manual. Dr. Konosu will report on the TF-RUCC activities under agenda item 9.5.

Mr. Takahashi also presented the document on the biofidelity issues. He concluded that, compared to the EEVC LFI, biofidelity has improved significantly. First, the risk of bone fracture is evaluated over the entire length of the tibia. As the peak stress of the bone is generally located below the impact point, the injury risk could not be addressed using the EEVC LFI accordingly. Second, an elongation of the cruciate ligaments is caused by both shear and valgus bending which is addressed accordingly by the FlexPLI while the EEVC LFI is using two separate thresholds for the knee shear displacement and the knee bending angle.

For the tibia fracture prediction, Mr. Takahashi had presented results for three different vehicle front ends (passenger car, SUV with low lower bumper reference line and SUV with high lower bumper reference line) in their original state as well as in a modified state. Mr. Zander wondered why for vehicles A and B the performance with the EEVC LFI was worse while it improved for vehicle C. Mr. Takahashi explained that vehicles A and B had relatively soft front ends and were modified to be stiffer while vehicle C already had a stiff front end and was modified to become softer. This explains the different results.

Also, Mr. Zander asked which simulation models were used. Mr. Takahashi stated that the human model was developed jointly by Honda and JARI. Detailed information on the human model is available in the references listed in the document GTR9-1-05. The vehicle models are simplified vehicle models and the derivation is described in detail in the reference paper (see list of references at the end of document GTR9-1-05) of Konosu et al. from the IRCOBI 2009 conference.

Mr. Bilkhu added that the EEVC LFI had been developed to address knee injuries. So, one should not be surprised that the performance regarding tibia injuries is limited. However, also with the FlexPLI the correlation of the knee response with the human model is not yet perfect compared to that of the tibia. Mr. Takahashi replied that they are aware of this and plan to study this in more detail in the future. On request he confirmed that this should not affect the design of the current impactor.

Besides, Mr. Bilkhu stated that both impactors do not seem to be very good for knee injury prediction (r value below .8) Mr. Takahashi answered this being one of the limitations of the legform only representing the isolated human leg. He stated that JARI is currently working on a study to incorporate the upper body mass effect. However, the study is at a too early stage for conclusions.

Ms. Versailles added that the US also had shown in their document GTR9-1-12 that the performance had been improved. Mr. Kinsky stated that however the presentation of the US may cover a mistake in its conclusions: due to the fact that the FlexPLI has an overload protection device (the steel cables along the long bones) and the EEVC LFI does not have such a device it is not possible to compare test results well above the limits. This was confirmed by Mr. Been (Humanetics).

Mr. Takahashi promised to also provide an updated version of this presentation that will include some slight corrections (see doc. GTR9-1-05r1).