ABSTRACT
Specimens and machine components containing small cracks, defects and nonmetallic inclusions having the same value of the square root of projection area, √area, have the same fatigue strength regardless of different shapes, different stress concentration factors. The reason is explained on the basis of both microscopic observation and numerical analysis of cracking from small cracks, defects and inclusions.
The fatigue limit ow of components containing surface defects can be predicted by the equation, using two parameters, the geometrical parameter √area and the Vickers hardness Hv. https://www.w3.org/1998/Math/MathML"> σ w = 1.43 ( H v + 120 ) / ( √ area) 1 / 6 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203477021/be9e9212-91e2-414c-a3fd-3411e53b9ffb/content/math_169_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>
where the units are σw in MPa, Hv in kgf/mm2 and √area in μm. The above equation is valid over a range that is dependent on the material.
Applications based on fatigue strength prediction equation and quality control of materials based on statistics of extreme of material defects and inclusions are also outlined.
