午夜剧场

From my student days until today, I have been conducting research on "fatigue." However, I am not referring to the "fatigue" of us humans, but rather the "fatigue" of metallic materials. Just as we humans get fatigued, metallic materials also experience "fatigue." The greater the load and the longer the duration of the load, the more damage from fatigue progresses. Humans and metals are the same in this regard. The only difference is whether recovery is possible. We humans know how to recover. Eating delicious food, getting plenty of sleep... the methods vary from person to person. In the case of metallic materials, it is extremely difficult to recover from fatigue damage; in most cases, fatigue simply continues to accumulate. Eventually, it leads to "fracture." At times, fracture accidents caused by metal fatigue lead to catastrophic results, causing not only economic and social losses but even the loss of human life. Unfortunately, with current technology, it is impossible to realize "fatigue-free metal = unbreakable metal." However, technology to create "break-resistant metals" is advancing steadily step by step. To achieve this, it is important to understand the mechanism of why things break. Driven by this motivation, I continue my daily exploration of metal fatigue.

To elucidate the mechanism of metal fatigue, it is important to observe the damage behavior that accumulates due to fatigue, but it is extremely difficult to accurately observe damage on the order of several microns occurring inside metallic materials. However, one day more than ten years ago, a student in my laboratory showed me a surprisingly beautiful three-dimensional image of internal damage. When I asked, they explained that it was an image created by polishing a cross-section near the damaged area, photographing the damage with a microscope, then polishing it by 0.01 mm and photographing the damage on the new cross-section. This process was repeated endlessly to obtain a vast number of two-dimensional images, which were then stitched together three-dimensionally. The progress of observation equipment in recent years has been remarkable, and we are in an era where we can observe things that were completely impossible to see a decade or so ago. However, every time I look at the three-dimensional image created by that student, I feel as though I am being taught that even without using such expensive, state-of-the-art equipment, one can sometimes obtain results that surpass those of the latest expensive observation devices by working steadily and sparing no effort.

The "fatigue" required to obtain this single image is immeasurable. I am glad that we humans have the ability to recover from fatigue.