Establishment of SPM Nanofractographic Techique and Its Application to Investigation of Damage and Fracture Mechanisms of Materials

点击翻译按钮获取中文摘要

The research project focused on the application of scanning tunneling microscopy (STM), and atomic force microscopy (AFM), which are so called scanning probe microscopy (SPM), to investigate fracture mechanisms and strength evaluation of materials. In order to establish standard methods for observing fracture and damaged surfaces of materials, or nanofractography, round robin tests were conducted. The research group consisted of six institutes from five universities, one national institute, and two institutes from private companies. In order to perform round robin tests, standard SPM samples manufactured by micromachining were prepared and each institute measured the sample surface by using SPMs. The SPMs used for the round robin tests were STMs, contact mode AFMs, and tapping mode AFMs operating in air and/or ultra-high vacuum. The SPMs were manufactured by several leading SPM developers in Japan and the United States. Special attention was paid to shape of SPM tip, and therefore, the ultra-high resolution field emission type scanning electron microscope (SEM) images were taken before and after the observation. The research group investigated influences of tip shape on quantitative three dimensional shapes by SPM,the difference of vertical and horizontal length measured among the institutes, and among the SPM developers : the group discussed the affecting factors on SPM images. The group also discussed the application of SPM to analyze in situ nanoscopic observation of localized corrosion damage in a solution such as pitting corrosion, intergranular corrosion, and stress corrosion, as well as fatigue damage initiation and propagation of various kinds of materials in air : nanoscopic damage mechanisms of localized corrosion and fatigue were discussed. The research was also extended to the application of an atomic force microscope to measure nanoscopic hardness, and the development of measuring method of SPM tip radius in a nonmeter order.