Holes and notches raise local stress by a factor Kt.
Holes, notches, fillets and keyways raise local stress to σ_max=Kt·σ_nom. A circular hole in a wide plate has Kt=3. Reducing it: larger fillet radii, smooth transitions and stress-relief grooves. Critical for fatigue.
A shaft shoulder with a sharp corner may have Kt≈2.5; a generous radius cuts it to 1.5.
Holes, notches and fillets raise the local stress far above the nominal value, and this often starts cracks in real parts.
Holes and notches raise local stress by a factor Kt.
Holes, notches and fillets raise the local stress far above the nominal value, and this often starts cracks in real parts.
It is the ratio of peak local stress to nominal stress. Its value depends on the geometry, such as the ratio of hole diameter to plate width.
Use larger fillet radii, smooth transitions, and avoid sharp corners, which lowers the peak stress without adding much material.
Typical applications include designing a fillet radius on a shaft shoulder to reduce fatigue risk, checking the stress around a bolt hole in a plate and choosing the shape of a keyway to avoid high stress in a gear shaft.
Study "Strain energy" first (topic 66 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
Kt depends on geometry only. Fatigue notch factor Kf. Ductile materials redistribute at yield.
A shaft shoulder with a sharp corner may have Kt≈2.5; a generous radius cuts it to 1.5.
The next topic is "Fatigue", which builds directly on this one.
It is classed as Intermediate in Engineering Mechanics (topic 67 of 106). It is an intermediate topic. Work through the beginner topics in Engineering Mechanics first.
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