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The fracture toughness of the right femoral neck, femoral shaft, and tibial shaft of matched cadaveric bones, ages 50 to 90 years, was compared. Results of this study indicate that tensile (G(Ic)) and shear (G(IIc)) fracture toughness vary depending on bone location. The femoral neck has the greatest resistance to crack initiation for both tension and shear loading while the femoral shaft has the least. The relationship between age and the fracture toughness of the femoral neck and shaft was investigated. G(c) of the femoral shaft significantly decreased with age for mode I and was nearly significant for mode II. Fracture toughness of the femoral neck did not change with age for the later decades of life. Implications of these findings are discussed.

A series of 11 identical laser-based powder bed fusion (PBF) builds were completed with varying amounts of virgin and recycled nitrogen gas atomized S17-4 PH stainless steel powder following a specific powder recycling strategy that simulates industrial practice. Mechanical properties of parts were evaluated using tensile and hardness tests. Recycled powder properties, such as particle size distribution, flowability, chemical composition, and microstructure were evaluated. The recycled powder showed no significant changes in its particle size (PS), particle size distribution (PSD), and particle shape but apparent density and powder bed density increased while flow time improved. Recycling the powder in a nitrogen atmosphere caused a slight increase of the martensitic-ferritic phase in the predominately austenitic S17-4 PH powder. Laser-based PBF fabricated austeniticmartensitic-ferritic S17-4 PH showed a ratio of approximately 1:1 between austenitic and martensitic-ferritic phases. The specimens were heat treated for stress relief. Tensile tests on the specimens did not show dramatic change in the tensile properties with recycling up to 11 times. The fine dendritic austenitic-martensitic-ferritic microstructure of the heattreated S17-4-PH reached a 0.2 % offset yield strength (YS0.2) above 520 MPa, and an elongation after fracture (A) of 28 %. Mechanical and material properties from specimens fabricated from powder recycled up to 11 times were similar to specimens fabricated from virgin powder.

In laser powder bed fusion (LPBF) processes, the powder size characteristics, like particle shape, particle size (PS), particle size distribution (PSD), and the resulting powder bed density (PBD), are key influencing factors of the built material properties. To better understand the correlations between the powder size characteristics and the powder properties influencing the LPBF process, apparent density (AD), flowability, and PBD were measured corresponding to two commercial metal powders with different PS and PSD. The powder samples were taken from different locations on the build platform to also investigate the variations of these powder characteristics resulting from the spreading process by the stiff recoater blade. It was shown that the PS and PSD had a significant effect on the AD and the PBD. Powders with a wide PSD and with particle sizes in the range of the effective powder layer thickness, led to a higher PBD than powder with a high proportion of finer particles. No significant differences in PS and PSD were observed as powder was pushed across a build plate by the recoater blade. Key wordsadditive manufacturing; apparent density; metal powder; particle size distribution; powder bed density; powder bed fusion; powder layer; powder layer thickness; powder spreading; selective laser melting; selective laser sintering. iv This publication is available free of charge from: https://doi

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A wired sensor network was created to measure water-flow rate in a fire hose. An integrated electronic piezoelectric (IEPE) accelerometer was chosen as the sensor to measure the flow rate based on the vibrations generated by water flowing through a fire hose. These sensors are small, lightweight, and they can be attached to the outside of the hose, not obstructing the water's flow path. A relationship was determined between the flow rate of the water and vibration detected by the accelerometer for a range of flow rates. The raw acceleration signal was used to calculate two metrics: the dominant frequency and the standard deviation of acceleration. In a future study, the relationship between the dominant-frequency metric and the flow rate will be applied to a wireless accelerometer network. The relationship will be used to determine the real-time fire hose flow rate critical for improving situational awareness on the fireground.