2014 Volume 134 Issue 2 Pages 32-37
The stress-life characteristics of two groups of single-crystal silicon fatigue-test specimens were measured with each group having different etched sidewall surfaces. Specimens with vertical surface roughness exhibited S-N relationships with larger scattering shifted to the bottom-left side which indicates a shorter lifetime and lower strength. The experimental results were compared with stress distribution analyses and were explained adequately by the degree of stress concentration around the notch tip, which was caused by a reduction of the curve radius due to an additional small structure. Comparisons between the test results and crack growth propagation analyses suggested that direct adoption of roughness height as an initial crack was an inappropriate way to estimate the effects of roughness.