Hokkaido University · Engineering
Professor Takashi Nakamura's research lab specializes in the mechanics of fatigue failure in advanced engineering materials, with a particular focus on very high cycle fatigue (VHCF) behavior in high-strength steels and titanium alloys. The lab employs advanced non-destructive evaluation techniques, such as synchrotron radiation microcomputed tomography (SR-μCT), to visualize and analyze the initiation and propagation of sub-surface and internal fatigue cracks at the micro- and nano-scale. A key research direction involves understanding the formation mechanisms of unique fracture features like ODA (originated from sub-surface damage) and the role of internal microstructural heterogeneities in crack nucleation. The lab also investigates the influence of environmental conditions on crack growth, contributing to improved life prediction and structural integrity assessment in high-performance engineering components.
Figures are computed from collected data and may differ slightly.
Very high cycle fatigue (VHCF) of high strength steel has become an important issue for mechanical engineers in recent years. In VHCF regime over 107 cycles, fatigue crack initiates not from surface but from sub-surface of materials. The sub-surface fractures even occur in a lower stress than surface-originating fractures; therefore, to clarify its mechanism is strongly needed for the safety use of high strength steel. In sub-surface fractures, a typical fracture surface with a fine concavo-conv
Abstract Small internal fatigue cracks initiated in Ti‐6Al‐4V in the very high cycle regime were detected by synchrotron radiation microcomputed tomography (SR‐μCT) at SPring‐8 in Japan. The initiation and growth behaviours of the cracks were nondestructively observed, and the da/dN ‐ ΔK relationship was measured and compared with that obtained in a high vacuum environment. SR‐μCT revealed that more than 20 cracks were initiated in one specimen. The crack initiation life varied widely from 20% t
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