How this calculator works
The stress ratio compares a local elastic peak with a consistent nominal stress. The elliptical-hole relation assumes an infinite isotropic plate loaded perpendicular to the a semi-axis. The orthotropic formula treats an infinite plate with a circular hole and material axes aligned with the load. E_x is along the load, E_y transverse, and nu_yx = nu_xy E_y/E_x. Finite edges, nearby holes and yielding change these ideal results.
Formula
Kt = sigma_max/sigma_nom; ellipse Kt = 1+2a/b; orthotropic circular hole Kt = 1 + sqrt(2[sqrt(Ex/Ey)-nu_xy]+Ex/Gxy).
Worked example
An elliptical hole with a = 20 mm and b = 10 mm gives Kt = 5 for the stated loading orientation. A circular hole has Kt = 3 in an infinite isotropic plate.
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Frequently asked questions
Is Kt the fatigue notch factor?
No. The fatigue notch factor also accounts for notch sensitivity and material response.
Does hole orientation matter?
Yes. Here a is transverse to remote loading. Rotating an ellipse changes the peak stress.
Can the ideal peak exceed yield?
Yes mathematically, but a linear elastic peak above yield does not describe the redistributed plastic stress field.