Robustness and Reliability of Front Underrun Protection Systems

In 2001, the United Nations Economic Commission for Europe decided that all trucks manufactured as from that year need a front underrun protection system (FUPS). This as a step in order to decrease fatalities in head-on collisions between heavy goods vehicles (HGV) and passenger cars. A further development of the FUPS is an energy absorbing FUPS (EA-FUPS). For a safety system like the EA-FUPS it is important that its functions work properly in both expected and unexpected crash scenarios. In other words, the system should be robust. In addition to a robust behaviour one would like to determine the successfulness of the system, i.e., the reliability of the system should be evaluated. This Master's Thesis contains a reliability and robustness study of an EA-FUPS, where stochastic analysis of a head-on collision between an HGV and a passenger car has been utilised. In this analysis the probability density functions (PDF:s) of collisions and structural parameters have been set up according to statistics from real-world accidents and manufacturing data. Several responses from the numerous crash simulations, solved with an explicit nite element method, were logged and statistics were used to set up, e.g., probabilities and scatter plots to evaluate the system. The results show a FUPS that, although the energy absorbing capabilities are rather non-robust and unreliable, fulls its prime objective, which is protecting the passenger car from underrunning the HGV. However, when the vehicle overlap is small the FUPS is not still enough to protect the wheel from being hit. There are several reasons for the unreliable energy absorption level, e.g., the energy absorbing mechanism has poor compatibility with the front structure of many passenger cars. Besides the resulting reliability and robustness analyses, an algorithm for performing robust CAE is presented