[B-5-5] Fundamental Study on Double-Layered Surface Formation by Electrical Discharge Machining 〇Yuki Ikeuchi1, Shun-Ichiro Tsuetani1, Ryoji Kitada2, Akira Okada1 (1.Okayama University, 2.Sojo University) Keywords:EDM/ECM/others、Double-layered surface、 Surface roughness