METHOD FOR DETECTING CRACK GENERATION LIMIT STRAIN OF THIN FILM COATING

PURPOSE:To easily and accurately the limit strain of crack generation at low cost by placing a bending load on a metallic test-piece which is coated with a thin film and has a strain gauge stuck, and checking the coating surface. CONSTITUTION:A base material 1 is coated 2 and the strain gauge 3 is stuck on the surface to obtain the test-piece, which is strained by applying pressure at the positions of loading means 4 and 5. The strain is measured by the strain gauge 3 and recorded. The test-piece is checked through a microscope after the load is removed to find a range where a crack 7 exists and the minimum strain where the crack 7 exits. In this case, a% and a'% indicate the limit strain.