Stress concentration occurs where there are irregularities or discontinuities in a material, like holes or grooves, and greatly increases stresses in these local areas, where fatigue failure often originates. Stress concentration factors quantify how much a discontinuity increases stresses but are not needed for ductile materials under static loads, as local yielding relieves these concentrations. Notch sensitivity values between 0 and 1 indicate a material's sensitivity to notches, with 1 being fully sensitive and 0 having no sensitivity. Geometric stress concentration factors estimate stress amplification near geometric features.

1. Presented by Onkar A. Powar

2. • The existence of irregularities or discontinuities, such as holes, grooves,
or notches, in a part increase the magnitude of stresses significantly in
the immediate vicinity of the discontinuity. Fatigue failure mostly
originates from such places.
• stress concentration factor need not be used with ductile materials when
they are subjected to only static loads, because (local) yielding will relieve
the stress concentration.
What is stress concentration

3. It is defined as
The values of q are between zero and unity. It is evident that if q=0, then Kf
=1, and the material has no sensitivity to notches at all. On the other hand if
q=1, then Kf = Kt, and the material has full notch sensitivity.
Notch Sensitivity q

4. Notch sensitivity of common materials

5. Notch Sensitivity q in bending

6. Notch Sensitivity q in torsion

7. Geometric stress concentration factors can be used to estimate the stress
amplification in the vicinity of a geometric discontinuity.
Geometric Stress Concentration

8. Stress concentration factor in tension

9. Stress concentration factor in tension

10. Stress concentration factor in bending

11. Stress concentration factor in bending

12. Stress concentration factor in torsion

13. Stress concentration factor in torsion