超高分子量ポリエチレンの衝撃圧縮特性に及ぼす低ガンマ線照射の影響と構成則の検討

概要

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The effects of low-gamma irradiation on the impact compressive properties of ultra high molecular weight polyethylene (UHMWPE) were investigated. Gamma irradiation was performed at 30kGy in nitrogen or at 29kGy in air without post-irradiation treatment. Impact compressive tests using the split-Hopkinson pressure-bar (SHPB) technique were performed to measure stress–strain relations up to a true strain of 8% at a strain rate of 260s<SUP>-1</SUP>. Gamma irradiation in air significantly increased the Young's modulus and the 0.5% yield stress, and gamma irradiation in N<SUB>2</SUB> significantly increased the 0.5% yield stress, as determined by impact compressive testing. The impact stress-strain behaviors of both unirradiated and gamma irradiated UHMWPE specimens were compared by the elasto-viscoplastic model proposed by Bergström [Biomaterials Vol.23 p.2329 (2002)]. We found that the elasto-viscoplastic model had a potential to predict the observed impact stress-strain responses.