FIGURE 1 Specimen.
To study the effect of micro scratches on fatigue life of TC17, rough specimens were prepared. The machining defect, mainly micro scratches, were not eliminated by fine grinding and polishing in last process step.
Because of the extremely small size at micron level, optical interferometer is the most suitable method of measuring the scratches. ZYGO 3D optical profiler instrument owns numerous advantages: high measurement precise, non-contact surface measurement, and nanoscale surface features. The surface topography of specimens, along with the essential geometric parameter such as depth and width of scratches can be observed and measured by ZYGO accurately.
As shown in Figs. 2A-D, micro scratches are the main morphological characteristics for the specimens. Table 1 gives the measurement results of actual micro scratch depth and width by ZYGO along with\(\sqrt{\text{area}}\) of each specimen. For each scratch, there cross-sections are measured and take the average value as the final depth and width. For each specimen with multiple scratches, only three largest scratches are observed and measured. Specific measurement methods and precautions are listed in Ref. [18].