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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.