The shape of casting defects includes a variety of irregular shapes, but the effect on stress concentration can be attributed to the radius of curvature. The smaller the radius of curvature, the more serious the stress concentration caused by it. Taking the elliptical casting defect as an example, the stress concentration degree at the top of the elliptical long axis can be calculated according to the analytical solution formula of its stress distribution.

Taking the ratio of the long / short half axis of the ellipse as the representative of the curvature of the tip of the long half axis of the ellipse, the influence of the curvature radius of the casting defect on the stress concentration factor is shown in the figure.

It can be seen from the figure that with the decrease of the radius of curvature of casting defects, the shape of casting defects is closer to the crack tip, and the degree of stress concentration is also sharply increased.