Development and Evaluation of Alloys for the Electrodes for Functional Electrical Stimulation to Appropriate for the Long Term Implantation

开发并评价了用于FES（功能性电刺激）电极的合金，以适合长期植入。并取得了以下研究结果.新合金的开发：建立了合金设计数据库。并试制了几种高锰高氮奥氏体不锈钢铸锭。测试了这些合金的变形量与延伸率、断面收缩率的关系。结果表明，NAS106N（6mass%Mn，10mass%Ni，22mass%Cr，2mass%Mo，0.4mass%N）合金的综合性能最上级。用该合金制作了FES电极用细钢丝绳.新型合金制备的FES电极的评价：测量了新型合金NAS106N、不锈钢SUS316L和钴铬基合金NAS604PH制备的FES丝的磁化曲线。NAS106N和NAS604PH的非磁性性能优于SUS316L。采用双驱动弯扭疲劳试验，测试了NAS106N、NAS605PH和SUS316L电极在空气和0.9%NaCl盐水溶液中的疲劳寿命。NAS106N在空气中的所有实验条件下的疲劳寿命均高于SUS316L和NAS604PH，在盐溶液中的应力条件下的疲劳寿命也高于SUS316L和NAS604PH。在低应力条件下，SUS316L和NAS106的疲劳寿命均低于NAS604PH，NAS106N有望成为FES电极材料，但如何防止微动腐蚀仍是需要解决的问题。

Alloys for the electrodes for FES(Functional Electrical Stimulation)were developped and evaluated to appropriate for thelLong term implantation. And following results were obtained.1. Development of New Alloy : A database for alloy designing was created. And ingots of some high-manganese high-nitrogen austenitic stainless steels were producted experimentaly. Relation between reduction and elongation or reduction of area of these alloys were tested. And, it was confirmed that the alloy named NAS106N(6mass%Mn, 10mass%Ni, 22mass%Cr, 2mass%Mo, 0.4mass%N)shows the most superior properties. And thin wire rope for FES electrodes were made by this alloy.2. Evaluation of FES Electrodes made by New Alloy : Magunetization curves of FES wires made by newly developed alloy NAS106N, stainless steell SUS316L and cobalt-chromium based alloy NAS604PH were measured. NAS106N and NAS604PH shows the superior non-magnetic properties than SUS316L, Fatigue life of electrodes made by NAS106N, NAS605PH, SUS316L in air and 0.9%NaCl saline solution were also measured by dual-driven rotating-bending test. NAS106N has higher fatigue life than SUS316L and NAS604PH at all experimental condition in air and high at stress conditions in saline solution. On the other hand, fatigue lives of SUS316L and NAS106 were lower than NAS604PH at low stress condition in saline solution.Accordingly, NAS106N will be promising material for FES electrodes but to prevent the fretting corrosion should be the problem to be solved.