HEMI Seminar: Dr. Timothy Harrigan

Pressure and Momentum Transfer to the body due to Blast exposure: Simulation and Experimental Results

Blast exposure is a significant mechanism for injury in many situations, especially in military applications. The specifics mechanisms whereby blast waves in air transfer pressure and momentum to the body are keys to an understanding of the mechanisms of injury in blast exposure, and to the design of technology to mitigate injury. Blast waves typically have a “Friedlander” pressure history, consisting of an initial shock wave, a decaying rarefaction wave, and a negative pressure phase. Both the peak pressure in the wave and the time scale of the wave are associated with injury likelihood.

Blast and shock wave simulation tools are available in several general-purpose structural analysis programs, such as LS-Dyna. At the Johns Hopkins University Applied Physics Lab, extensive use of this code, along with comparison to experimental data, has allowed some specific understanding of the relevant physical effects in blast loading of the head/neck complex and the torso.

Coupled Eulerian-Lagrangian approaches have been used to model blast wave impingement on the body, with the anatomy of the body taken from standard sources. Several physical effects are significant in the range of anatomical size and material properties relevant to the body. For example, the speed of pressure waves in hydrated tissues (flesh and solid organs) is significantly faster than the speed of blast waves in air, so the transmission of pressure to the body depends on the outer shape and curvature in complex ways. Also, direct transmission of pressure through air cavities (such as the sinuses or lungs) is ineffective, so that mechanical stresses are induced by momentum transfer in many instances, rather than by wave propagation. The results of several simulation studies will be shown, illustrating typical effects in the head and torso.

Seminar will be held at 3:30 PM in Malone G33/35.