Small Scale Models Subjected to Buried Blast Loading Part I: Floorboard Accelerations and Related Passenger Injury Metrics with Protective Hulls

Small scale models representing key vehicle structural elements, including both floorboards and bottom-mounted, downward V-shape hulls in various configurations, have been manufactured and subjected to a range of buried blast loading conditions. By varying surface stand-off distance and depth of burial for several hull and structure configurations, the input-scaled response of aluminum full-scale vehicle floorboards has been quantified using high speed stereo-vision. Specifically, the maximum vertical acceleration on the floorboard and the corresponding Head Injury Criterion (HIC₁₅) are quantified as metrics to assess the severity of the blast event. Results show standard V-shaped hulls provide essential blast mitigation, with reductions in floorboard measurements up to 47X in maximum acceleration and HIC₁₅. Though variations in protective hull geometry provide modest reductions in the severity of a floorboard blast event, results also show that personnel on typical floorboard structures during blast loading events will incur unacceptable shock loading conditions, resulting in either serious or fatal injury. A more appropriate design scenario would be to consider situations that employ frame-mounted passenger seating to reduce the potential for injury. A second set of experiments will be presented in Part II that focuses on frame motions and accelerations when steel frames and steel structures are employed with various frame connections and coatings for frame blast mitigation.     

Seife

Ohne Zusammenfassung     

The influence of the geometry of micro-patterned thin films on the effective permeability and resonance frequency by domains development

For the application in high-frequency micromagnetic devices, the permeability and resonance frequency of ferromagnetic components is of high interest. It is dominantly influenced by different factors, the external field and direction and the domain distribution, shape and orientation. By the use of micromagnetic simulation, the domain pattern in films was determined and the effective permeability was calculated. The results of the calculations were compared with the domain shape of patterned microstructures of thin FeCoTaN-films, which were deposited onto oxidised silicon substrates by reactive r.f.-magnetron sputtering by employing 6-in Fe₃₇Co₄₆Ta₁₇ targets. To achieve a high-frequency suitability, the films have to be annealed in a static magnetic field of 50 mT between 400 and 500 °C, which are typical temperatures used in CMOS processes, to induce an in-plane uniaxial anisotropy needed for the high-frequency performance. Magnetic softness was obtained by producing amorphous or nanocrystalline films, and additionally, by aspiring low magnetocrystalline anisotropies for, e.g., certain Fe/Co fractions. The unpatterned films with a lateral dimension of 5×5 mm² were measured in a strip line permeameter in a frequency range up to 5 GHz and exhibited ferromagnetic resonance frequencies between 2 and 2.5 GHz within a low-loss permeability spectrum (low width of imaginary part of permeability). For possible integrations in passive microelectronic components the films were patterned to a few tenths of micrometers by near ultra-violet lithography and plasma beam etching, and then consequently annealed to obtain the static and dynamic magnetic properties. To influence the amount of closure domains, designs were conceived to influence the domain formation by creating additional internal boundaries. As a result, the ferromagnetic resonance frequency and the effective permeability are strongly driven by internal and external boundaries.     

A new strip line broad-band measurement evaluation for determining the complex permeability of thin ferromagnetic films

In the present paper, a new method for determining the frequency dependent complex permeability of thin magnetic films, designed for measurements up to 5 GHz, is presented. The measurement technique described here was carried out by a one-port permeameter, which is based on a short-circuited strip line. The complex permeability was deduced by a new analytical approach from the measured reflection coefficient of a strip line (S₁₁) with and without a ferromagnetic film material inside. An adaptive error correction was applied in the measurement procedure. The spectral permeability of thin FeCoAlN films with an in-plane uniaxial anisotropy of μ₀^*H_a=3.2 mT induced by annealing at CMOS temperatures in a static magnetic field was investigated. The measurements were compared with a theoretical model taking the Landau–Lifshitz and eddy current theories into account. A resonant frequency of about 1.6 GHz was observed.     

Investigations of silicon nitride and boron carbide monolayers and Si<Subscript>3</Subscript>N<Subscript>4</Subscript>/B<Subscript>4</Subscript>C multilayers

Many different coating concepts for improving mechanical properties have been worked out. One of the advanced coating concepts is the multilayer and superlattice concept, mainly with one or two metallic components. Previous work has shown that the mechanical properties of the covalent-bonded Si₃N₄ and SiC could be improved when combining them in a multilayer system. In the present work the silicon nitride monolayer from the earlier work was combined with boron carbide instead of silicon carbide. First, the boron carbide thin films deposited at different substrate temperatures were examined. Then the number of monolayers in the multilayer system with a constant layer thickness was varied in order to investigate the influence of the interfaces on film properties of the multilayer system. PACS 81.05.Je; 81.15.Cd; 82.80.Pv; 87.64.Je     

High-resolution Auger electron spectroscopy of phase boundaries in TiC/TiB2 materials

Summary Multi-phase hard materials free from binder metals are used to meet the requirements of high wear resistance and high temperature stability. Investigations of properties and wear behavior showed extremely high values in carbide/boride combinations, particularly a TiC/TiB₂ mixture of a 11 molar ratio. The pseudobinary phase diagram shows low intersolubilities. High-resolution Auger Electron Spectroscopy was used to examine mixed two-phase TiC/ TiB₂ hard materials and compare them to pure TiC and TiB₂. The AES analyses were carried out on cross sections and fresh fracture surfaces. At the grain boundaries in pure TiC as well as in pure TiB₂, some amounts of Fe, Cr, Co and P can be detected. These elements are already in the powders as received. In addition, an O-rich phase has been identified in hot pressed TiB₂. The same impurity elements as in the pure materials can be found at a few phase boundaries and triple points in two-phase TiC/TiB₂ with a thickness of a few monolayers. However, large areas of the fracture surface were found to carry a TiB_xC_y phase on the grains. The considerable increase in wear resistance and fracture toughness of TiC/TiB₂ compared to pure TiC and pure TiB₂ can be explained by the presence of this TiB_xC_y phase.

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Grenzflächenuntersuchungen an TiC/TiB₂-Hartstoffen mit hochauflösender Auger-Elektronenspektroskopie

     

X-ray diffraction studies of heterostructures based on solid solutions Al x Ga1 − x As y P1 − y : Si

The growth of MOCVD-hydride epitaxial heterostructures based on ternary solid solutions Al _x Ga_1?x As heavily doped with phosphorus and silicon has been studied using high-resolution X-ray diffraction and X-ray microanalysis. The prepared epitaxial films are five-component solid solutions (As _x Ga_1?x As _y P_{1 ? y} )_{1 ? z} Si _z .     

Small Scale Models Subjected to Buried Blast Loading Part II: Frame Accelerations with Hulls and Additional Mitigation Methods

Small scale models representing key vehicle structural elements, including bottom-mounted hulls and other relatively simple strategies for blast mitigation, have been manufactured and subjected to a range of buried blast loading conditions. By varying surface stand-off distance and depth of burial for several hull and structure configurations, the response of full-scale vehicle frames has been quantified through input-scaling. High speed stereo-vision and surface-mounted accelerometers are used to measure accelerations during the blast loading process. The maximum vertical acceleration and the Head Injury Criterion (HIC₁₅) at selected frame locations are quantified as metrics to assess the severity of the blast event. Results show that (a) inverted and standard V-shaped hulls provide essential blast mitigation capability, reducing the maximum frame accelerations over 100X, with similar reductions also measured for HIC₁₅, (b) stiffened frame structure locations experience substantially lower levels of acceleration and HIC₁₅ than measured previously on the floorboard at the expense of decreased damping of structural vibrations and (c) hull coating systems such as polyurea provide significant additional mitigation, though at the expense of increased overall weight.