Protection and comfort are two key armor requirements to the US warfighter. NRL has supported this effort by developing QuadGard extremity protection [1], and instrumented surrogate torso and brain to assess armor and helmet systems performance [2, 3], among others. Surrogate systems for analyzing personal protection equipment for torso and brain have also been developed by other researchers in US, Australia and Canada and are reported in the literature, but no publications were found on assessment of extremity armors.

In current US Military operations, warfighters are frequently subjected to blast events, which can lead to traumatic brain injury (TBI). The causes of mild and moderate TBI are not yet well understood by the medical community, and current diagnoses rely on identifying behavioral or physiological symptoms. Characterizing the brain response to various threats should provide a better understanding of possible injury mechanisms, and this knowledge could be applied to equipment design for prevention of TBI.

In current US Military operations, warfighters are frequently subjected to blast events, which can lead to traumatic brain injury (TBI). In response to this recent and increasingly prevalent threat, helmet systems must protect the head against high velocity, short duration overpressures in addition to blunt and ballistic impacts. Understanding the blast impact response characteristics of helmet systems may improve the design and selection process for headborne equipment and contribute to reducing blast-related brain injury.

Measuring the response of soft materials to high strain rate deformation is extremely challenging because of the difficulty of achieving dynamic equilibrium during high strain rate mechanical testing such as Kolsky bar testing. Digital image correlation (DIC) using high speed cameras is well suited for improving the ability to characterize the non-equilibrium deformation of soft samples subject to dynamic loading conditions, providing a rich data set that can be used to better deduce the dynamic constitutive response of the material. A prospective tissue simulant material is tested in compression at high strain rate using a Kolsky bar. The non-equilibrium deformation of the specimen, including the surface (Rayleigh) wave motion, is captured using a high speed stereo camera pair recording at 180,000 frames per second. The image correlation results are used in conjunction with finite element modeling to deduce the dynamic constitutive response of the material in this high strain rate test.

Most fluid-filled storage tanks are constructed of mild steel plate. A method for measuring the thickness of corroded steel plates, in-situ, using ultrasonic spectral tracking is described. Measurements using pulse-echo time-of-flight and this spectral tracking technique are compared. The plate used in the measurements was a section of a steel plate from an oil storage tank that had been failed (as opposed or “passed”) during an inspection and was removed. The plate that was scanned had areas that are described as ‘lightly’ corroded (no apparent thickness loss or scaling) to ‘heavily’ corroded (much apparent thickness loss and/or much scaling). The nominal thickness of the steel plate was 0.25 inches (6.3 mm). Pulse-echo measurements were made at 15 MHz and 5 MHz and the spectral tracking measurements were made using a 1 MHz center frequency, dual, annular element, ultrasonic transducer. It was possible to measure the thickness at almost all locations of the steel plate using the spectral tracking technique, whereas, it was not possible to do so using a pulse-echo method. The ultrasonic wavelength was too long to utilize 1 MHz or 2.25 MHz for pulse-echo measurements, as echo resolution was not possible at these lower frequencies.

An experimental system is described for in situ passive measurement of changes in the magnetic field of ferromagnetic materials subject to tensile deformation. Changes in magnetic field during deformation are monitored using a three-axes first-order superconducting quantum interference device (SQUID) gradiometer. The gradiometer is held in a fixed position while a horizontal load frame has been constructed from nonferromagnetic materials. Results are presented for cold-rolled steel specimens. The magnetic field gradient was measured by scanning the specimen in the x-y plane while at a constant stress at a fixed distance from the tail of the SQUID dewar.< >

A non-magnetic horizontal load frame has been constructed allowing for x-y motion and rotation about the specimen axis in order to investigate the state of stress in steel components with a SQUID gradiometer. Tensile and cyclic loading can be performed under load or strain control. Data are taken by a Masscomp data acquisition system. Initial tests of this system have been made using a vertically-mounted SQUID gradiometer.