Development of a Hybrid Energy Absorbing Reusable Terminal (HEART) Using Finite Element Modeling in LS-DYNA for Roadside Safety Applications

The Hybrid Energy Absorbing Reusable Terminal (HEART) is a newly developed crash cushion or an end terminal to be used in highway safety applications that will mitigate injuries to occupants of errant vehicles. The HEART is composed of corrugated plates of High Molecular Weight/High-Density Polyethylene (HMW/HDPE), supported on steel diaphragms, which slide on a fixed rail. Kinetic energy from errant vehicles is converted to other energy forms through the folding and deformation of HDPE material. Many previous designs utilize the plastic or permanent deformation of plastics or steels to accomplish this goal. However, HEART is a reusable and self- restoring crash cushion, and therefore has a major cost advantage over the conventional crash cushion designs. HEART has been designed and optimized through an extensive use of finite element modeling. The objective of this paper is to present the finite element modeling and simulation approach adopted to arrive at the final design of the HEART cushion. In order to meet the National Cooperative Highway Research Program (NCHRP) Report 350 guidelines, all roadside safety devices need to pass the report’s requirements from an 820 Kg and a 2000 Kg vehicle impacting at 100 Km/h. For HEART to meet the NCHRP Report 350 evaluation criteria, a large number of design parameters were investigated. Among these were the thickness of the HDPE plates, the height of the plates, the length of the plates between two consecutive steel diaphragms, etc. Initially, simple finite element models were developed using beam elements as HDPE plates in LS-DYNA. A large number of configurations were tested with these simple models to gain an insight to the problem and to narrow down the number of parameters. Later on, detailed finite element models with shell elements as HDPE plates were developed to come up with the final configuration of the device. HEART crash cushion has passed the full-scale test requirements in accordance with guidelines presented in NCHRP Report 350. Development of the HEART cushion is a good example of the use of finite element analysis as a tool for analysis, design and optimization of roadside safety devices.