Detection and Observation of Fatigue Damage in Metallic Thin Wires with an A.C. Potential Method and a Digital Microscopy
Yoshikazu NAKAI, Akihisa HASHIMOTO and Akihiko TAKETANI
Abstract:Fatigue tests of thin wires made of commercially pure iron or aluminum were conducted in air. The fatigue damage of the materials was successfully measured either an A.C. potential method or a digital microscope. For the A.C. potential method, constant current of 600 mA with 888 Hz was applied to the specimen. In pure iron, the value of electric potential was increased for a specimen whose diameter was 0.20 mm, however it was almost constant for a specimen of 0.60 mm in diameter. In pure aluminum, the value of potential was increased for every specimen diameter. In this material also the change of A.C. potential was larger for smaller specimens. The change of A.C. potential value was detected before the specimen deformation observed with the digital microscope. Two types of fracture morphology were observed with digital microscope. Those were with or without fatigue cracks. In the latter case, the specimen was necked at the final stage of fatigue process. Key Words:Metallic micro-materials, A.C. potential method, Fatigue damage, Fracture morphology