A hard case for modeling

What happens to a human head when it is hit in an accident or by a weapon, or subjected to the violence of an emergency ejection from a combat plane? This question is something that interests QinetiQ, part of the former UK Defence Evaluation and Research Agency (DERA). Controlled experimentation on live subjects is hardly an option, but computer modeling of the head, with its constituent parts and materials, is. George Marsh visited David Porter at QinetiQ’s headquarters at Farnborough to investigate the pragmatic approach that he and his colleagues take to biomaterials and biostructures modeling.Some fighter pilots alive today owe their survival to tough, low-weight helmets whose qualities have been refined as a result of biomechanical modeling. Porter and his colleagues have modeled the human head as a mechanical arrangement of a heavy ball on a rod support, as a system of soft matter contained in a hard case, as an arrangement of meso-scale sub-systems, and as a combination of material systems built up from the nano-molecular and atomic scales. An extensive modeling hierarchy (Fig. 1) is held on nothing more esoteric than a networked workstation and server architecture. Nevertheless, thanks to a process of focused simplification at each hierarchical level, it is able to predict the mechanical behavior of the human head and its constituents in reacting to impacts with considerable accuracy.