SA-08-4(095) In Situ Observation of Mesoscopic Fatigue Deformation Behavior of a Nodular Cast Iron(Flaw Progress & Failure Mechanism 1)
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概要
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The present study investigates mesoscopic fatigue deformation behavior of a nodular cast iron via the in-situ observation of multiple small cracks and other mesoscopic structures such as spheroidal graphite inclusions and grain boundaries. For this purpose, an in-situ observation system has been constructed by the use of an advanced CCD camera system. The camera system can zoom in on the fatigue-damaged specimen surface at a magnification of up to ×800. The observation revealed that the specimen surface was severely deformed at the first cycle of the applied load. The deformation reflected the mesoscopic structure of the material fatigued ; i. e., the surface roughness caused by the cyclic stress embossed the shapes of crystal grains. Most of the cracks observed were initiated at the separations of the matrix/graphite interfaces. Incipient cracks grew along gain boundaries; nevertheless, when they became larger, say, than 0.5 mm, they began to grow in the direction perpendicular to the applied load axis. Coalescence of multiple small cracks often caused the sudden fracture of the specimens. The mesoscopic strain distributions within the observation area were calculated from the change of the arbitrarily chosen points on each specimen surface by using the multi-dimensional spline interpolation technique. The result revealed the local strain concentration around cracks and other highly damaged regions of the specimen surface.
- 一般社団法人日本機械学会の論文
- 2001-06-03