Elliptical notch
<img src="https://eng-calculations.com/SVG/Peterson(and39)s_Stress_Concentration_Factors/Notches_and_grooves/Elliptical notch.svg" alt="Elliptical_notch" title="Elliptical_notch">
https://eng-calculations.com/SVG/Peterson(and39)s_Stress_Concentration_Factors/Notches_and_grooves/Elliptical notch.svg