解析及び実験的手法による自己強化ポリ乳酸スクリューの力学的特性予測

抄録

Bone fracture treatments has been increasing with the number of bone fracture patients because of the aging society. Thus, bioabsorbable bone fixation devices are required to improve quality of life of patients. Poly(lactic acid) with higher biocompatibility has attracted much attention as a material of the device. However, applications of PLA bone fixation device are limited to low loaded region, because of their lower mechanical characteristics. As a method to improve mechanical properties of PLA, extrusion drawing has been developed. In this study, optimum molding conditions are investigated to improve mechanical properties of PLA. Deformation behavior of PLA rods during drawing was simulated through finite element calculation and pseudo-affine model. Orientation in the rods was estimated from plastic strain in axial direction caused during drawing. And, shear strength of drawn PLA screw was calculated by combining simulated orientation function and relationship of shear strength and orientation function which was obtained in experiment. As a result, the simulated shear strength at extrusion ratio 8 which obtained by extrapolation of experimental results showed good agreement with the experimental values. On the other hand, the simulated shear strengths at extrusion ratio 1 and 2 showed differential values with the experiment. This is due to accuracy of simulated orientation function and/or effect of other factor such as a morphology.