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Automatic restraint and visual detection of fatigue crack growth by applying an alumina paste
Author(s) -
TAKAHASHI I.,
USHIJIMA M.,
TAKAHASHI C.,
UEMATSU S.,
KOTANI N.
Publication year - 2007
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.2007.01156.x
Subject(s) - materials science , scanning electron microscope , composite material , wedge (geometry) , electron microprobe , optical microscope , joint (building) , diffractometer , aluminium , microscope , metallurgy , structural engineering , optics , engineering , physics
A paste comprising fine alumina particles was applied on surfaces of steel plate specimens and a welded joint specimen, and the effects of the paste on restraint and visual detection of fatigue crack growth were experimentally investigated by performing fatigue tests with in situ observations by a c harge c oupled d evice (CCD) microscope and through various kinds of fractographic observations and elemental analyses using an scanning electron microscope (SEM) and an electron probe microanalyser (EPMA). As a result, the crack growth rate in the plate specimen was drastically retarded by the wedge effect of the alumina particles, and a 311% increase in failure life was produced on an average. The restraint of crack opening displacement (COD) value by the wedge materials was estimated by elastic finite element (FE) analyses, and the results were compared with the experimental data. Similar crack growth restraint effects were also observed on the welded joint specimen, producing a 117% increase in failure life. In the fatigue tests of the specimens on which the alumina paste was applied, a remarkable black colour developed in the white alumina paste along the paths of crack propagation, facilitating the visual detection of the cracks. An analysis using an X‐ray diffractometer showed that the black matter in the paste consists of fine debris derived from the base metal.