Atomic force microscope image of a residual indent.

Researchers from the U.S. Army Research Laboratory have shown that early fatigue damage behavior in structures may be predicted through the study of the microscale mechanical behavior of the material. By understanding the behavior of the material prior to damage, it could lead to vehicle structures that act as sensors themselves, with the ability to report their health state and adapt to varying conditions.

To characterize the material behavior of the early stage damage, the researchers used Depth Sensing Indentation (DSI), or "nanoindentation," whereby a submicron probe is forced into the sample while the load and displacement are monitored. The DSI tests revealed that material had become more compliant in particular areas of a structure exposed to relatively high stress.