The Fatigue Behaviour of Circumferentially Notched Aluminium Alloy Specimens as Affected by Notching Tool Dwell Time

Cylindrical specimens with circumferential grooves have been used for many years to assess the fatigue notch sensitivity of materials, and have been extensively employed in investigations involving the four major types of fatigue loading conditions--axial, plane bending, rotating bending and torsion. By adopting different radii at the root of the notch the severity of the stress concentrating effect under load can be readily altered. Although parallel sided notches have been used in some instances, the majority of circumferentially notched specimens have incorporated a Vee-form with a flank angle of between about 45 degree and 90 degree. Because of the increasing requirement to use fatigue specimens which are more representative of actual design features, and also to cope with the greater current emphasis on the measurement of fatigue crack propagation rates--for which edge or centrally notched specimens in flat material are better suited--the use of circumferentially notched specimens to obtain axial load fatigue data for structural fatigue applications has declined. However, circumferential notches have particular applications in the case of shafts and axles subjected to torsional or rotating bending conditions. In addition, circumferentially notched specimens tested in relatively simple rotating bending fatigue machines, can provide useful information when making initial appraisals and comparisons of the fatigue behaviour of materials, processes, etc. (Author)