22 D. Shiozawa et al. Fig. 1 Geometry of specimen 600 cycles. A microscope lens was attached to the infrared thermography camera to perform magnified measurements of the flat part. The spatial resolution at this time was approximately 20 µm/pixel. The flame rate was 300Hz, and the shooting time was 10s, and the dissipated energy, which is 2nd frequency components of the load frequency, was measured. A position correction process was performed to infrared thermography images using visible images to remove apparent temperature fluctuations that occur when the observation point moves due to deformation or displacement of the specimen [5]. In the position correction process, digital image correlation is performed on the visible images to measure the displacement of the specimen. Spot markers were painted on the test specimen. The displacement information obtained here was reflected in the infrared image and position correction process was performed. In the constant stress amplitude test, a fatigue test was performed under loading conditions of R=-1 and f =5Hz using a specimen without a flat surface, and an S-Ncurve was obtained. The runout number of cycles at which no fracture occurred was set to 107 cycles. Results Figure 2 shows the S-Ncurve obtained from the constant stress amplitude test. It was found from Fig. 2 that the fatigue limit of this specimenτw was between 300 MPa and 320 MPa, since no fracture occurred at τa=300MPa. Fig. 2 S-Ncurves
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