Improve local head Acceleratoin output

Dear developers, recently I used the PIPER model to simulate sledging accidents, which is a popular winter pastime in alpine countris in Austria. One of the objectives was to demonstrate the effect of wearing a helmet on reducing head injury metrics, such as HIC. Therefore, simulations of a child riding on a sledge and colliding with a tree were conducted. In some of the simulations, the child was wearing a helmet, while in the other simulations it was not. When analysing the results, we found that the HIC was very high in case of using the nodal accelerations of the local acceleration sensor (ID 1150000). We found, thatwas due to the fact that the *CONSTRAINED_EXTRA_NODES keyword used in the definition of the nodal output, stiffening the skull at some points (close ot the nodes included in the CNRB definition). We also found that HIC was different when using the local sensor (ID 1150000) vs. the global sensor (ID 1150003). Hence, I propose to switch to a *CONSTRAINED_INTERPOLATION for the local sensor (as used for the global sensor) to improve the stability of the acceleration outputs. In case you need some more specific information, dont hesitate to contact me under stefan.smit@tugraz.at

Thanks, Stefan Smit