Figure 5 - uploaded by Per Gunnar Brolinson
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The ANSI headform has the correct anthropometric features for testing eye and face protection, but no instrumentation for measuring impact forces.
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... of the limited array of instrumentation, there is no way of detecting any type of impact to the eyes and assess eye injury risk. Other ATD headforms are used for standards testing of protective goggles and other eye protective equipment. The American National Standards Institute (ANSI) headform was developed from the Hybrid-II ATD, the predecessor to the Hybrid-III. While both the ANSI and the Hybrid-II headforms include geometric representations of the eyes, nose, and mouth, the difference between the ANSI headform and the Hybrid-II headform is the detailed ear (Figure 5). The ear allows eye and face protection to be worn correctly on the headform during testing. Although this headform’s main application is standards testing for eye and facial protective equipment, it is not capable of predicting eye or facial injuries, because it carries no instrumentation. Instead, protective devices are evaluated for pass-fail based on whether there is contact to the eyes or face, as well as inspection of the structural integrity of the protective equipment post-impact. Additional ATD headforms, such as the National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform or the THOR (Test device for Human Occupant ...
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Citations
... The FOCUS head is modified from the Hybrid III dummy head, the latter used in frontal impact studies in automotive accidents. The external geometry of the FOCUS headform (and hence the RED head) is designed to replicate a 50 th percentile male soldier across the three branches of the military (Army, Navy and Air Force) [186]. where, is the pressure, is the constant-pressure to constant-volume specific heat ratio (=1.4 for air), is the initial air mass density, and is the current mass density and e is the internal volumetric energy density. ...
Blast induced neurotrauma (BINT) has been designated as the “signature injury” to warfighters in the recent military conflicts. The occurrence of traumatic brain injury (TBI) in blasts is controversial in the medical and scientific communities because the manifesting symptoms occur without visible injuries. Whether the primary blast waves alone can cause mechanical insult that is comparable to existing traumatic brain injury thresholds is still an open question, and this work is aimed to address this issue.
In the first part of this dissertation, mechanics of primary blast loading on Realistic Explosive Dummy (RED) head with and without helmets is studied using experiments and a validated numerical model. It is shown that geometry of the head and helmet, their configurations and orientations with respect to the direction of the blast govern the flow dynamics around the head; these factors in turn determine the surface pressures. The blast wave can focus under the helmet if there is a gap between the head and the helmet leading to an increase in surface pressures beneath the focused regions.
In the second part of this dissertation, the response of post-mortem human specimen (PMHS) heads is studied. Three PMHS heads are subjected to primary blast of varying peak incident intensities or overpressures (70 kPa, 140 kPa and 200 kPa). When the incident blast intensity is increased, there is a statistically significant increase in the peak intracranial pressure (ICP) and total impulse (p<0.05). Further, for blast overpressures of 140 kPa and 200 kPa, ICP values exceed brain injury thresholds available in the literature based on blunt impacts. From the parametric studies on the validated human head model, it is seen that the wave propagation through skin-skull-brain parenchyma plays prominent role in governing ICP-time histories. The effect of helmets on PMHS head is also analyzed. The results suggest that based only on ICP blast mitigation offered by the current helmets may be marginal, if at all.
Advisers: Namas Chandra and Linxia Gu
... The realistic explosive dummy (RED) head used as the surrogate is based on the Facial and Ocular CountermeasUre Safety (FOCUS) head which is modified from the Hybrid 123 Fig. 1 Experimental setup a schematic of the 711 × 711 mm shock tube system b realistic explosive dummy (RED) head with hybrid III neck placed inside the test section of the shock tube c sensor locations along the midsagittal plane of the RED head III dummy head, the latter developed for frontal impacts in automotive accidents. The external geometry of the FOCUS headform (and hence RED head) is designed to replicate a 50th percentile male soldier across the three branches of the military Army, Navy, and Air Force (Kennedy 2007). The RED head consists of a polyurethane skull with an opening for the brain and cerebrospinal fluid and is attached to the neck through the base plate. ...
Blast waves generated by improvised explosive devices can cause mild, moderate to severe traumatic brain injury in soldiers and civilians. To understand the interactions of blast waves on the head and brain and to identify the mechanisms of injury, compression-driven air shock tubes are extensively used in laboratory settings to simulate the field conditions. The overall goal of this effort is to understand the mechanics of blast wave-head interactions as the blast wave traverses the head/brain continuum. Toward this goal, surrogate head model is subjected to well-controlled blast wave profile in the shock tube environment, and the results are analyzed using combined experimental and numerical approaches. The validated numerical models are then used to investigate the spatiotemporal distribution of stresses and pressure in the human skull and brain. By detailing the results from a series of careful experiments and numerical simulations, this paper demonstrates that: (1) Geometry of the head governs the flow dynamics around the head which in turn determines the net mechanical load on the head. (2) Biomechanical loading of the brain is governed by direct wave transmission, structural deformations, and wave reflections from tissue-material interfaces. (3) Deformation and stress analysis of the skull and brain show that skull flexure and tissue cavitation are possible mechanisms of blast-induced traumatic brain injury.
