電子ビーム積層造形したTi-6Al-4V合金ラティス構造の圧縮－圧縮疲労特性と寸法効果

抄録

Compression-compression fatigue tests were conducted using Ti-6Al-4V lattice structures, which were additively manufactured by electron beam melting (EBM) method. The specimens with two different sizes were used to investigate the effect of lattice sizes on the fatigue properties. Fatigue cracks mainly initiated in the horizontal pillars during fatigue tests, which indicated that the initiated cracks were parallel to the compression loading direction. Strain measurement on the horizontal pillars revealed that tension stress occurred in the horizontal pillars under compression of lattice structure. Buckling of the vertical pillars under compression was suppressed by the horizontal pillars, which induced tension stress in the horizontal pillars and fatigue crack initiation parallel to the loading direction. That fatigue crack initiation mechanism was irrespective of the lattice sizes and applied load levels. However, fatigue strength was lower in the smaller samples. When the lattice size gets smaller, Euler buckling load becomes lower because of the decrease of area moment of inertia, which results in the lower fatigue strength of smaller lattice structure.