On models of blast overpressure effects to the thorax

Shock waves from explosions can cause lethal injuries to humans. Current state-of the-art models for pressure induced lung injuries were typically empirically derived and are only valid for detonations in free-field conditions. In built-up environments, though, pressure-time histories differ significantly from this idealization and not all explosions exhibit detonation characteristics. Hence, those approaches cannot be deployed. However, the actual correlation between dynamic shock wave characteristics and gradual degree of injury have yet to be fully described. In an attempt to characterize the physical response of the human body to complex shock-wave effects, viscoelastic models were developed in the past (Axelsson and Yelverton, in J Trauma Acute Care Surg 40, 31S-37S, 1996; Stuhmiller et al., in J Biomech. https://doi.org/10.1016/0021-9290(95)00039-9, 1996). We discuss those existing modeling approaches especially in view of their viscoelastic behavior and point out drawbacks regarding their response to standard stimuli. Further, we suggest to fully acknowledge the experimentally anticipated viscoelastic behavior of the effective thorax models by using a newly formulated standard model for viscoelastic solids instead of damped harmonic oscillators. Concerning injury assessment, we discuss the individual injury criteria proposed along with existing models pointing out desirable improvements with respect to complex blast situations, e.g. the necessity to account for repeated exposure (criteria with time-memory), and further adaption with respect to nonlinear gas dynamics inside the lung. Finally, we present an improved modeling approach for complex blast overpressure effects to the thorax with few parameters that is more suitable for the characteristics of complex blast wave propagation than other current models.