Plastic Strain - Concentration Factor of Cylindrical Bars With Circumferential Flat-Bottom Groove Under Static Tension
Geometrical irregularities affect stress and strain concentrations that are dominant and have been extensively
studied in recent years. The existence of geometrical irregularities such as grooves is a common reason for failures. The
elastic– plastic new Strain Concentration Factor (SNCF) for cylindrical bars with circumferential flat-bottom groove is
studied here using the Finite Element Method (FEM). Specifically, the effect of flatness length on the strain concentration
factor under elastic-plastic deformation and static tension is studied in this research. This new SNCF is defined under triaxial
stress state. The employed specimens have constant gross diameter (Do) of 16.7 mm and net section diameter (do) of 10.0
(mm). The flatness length (ao ) is varied form 0.0 ~12.5 (mm) to study the influence of the flatness length on the new SNCF.
Results showed that the elastic SNCF rapidly dropped from its maximum value at ao = 0.0 (circumferential U – notch). The
elastic SNCF reached a minimum value at ao = 3 (mm) and remained constant beyond ao = 3 (mm). At the groove root, the
value of tensile load at yielding is increased as the flatness length increase, which indicates that the range of elastic
deformation becomes larger with increasing flatness length. As the plastic deformation develops from the groove root; the
SNCF increases from elastic deformation to maximum value. The rate of increase in the SNCF augments with increasing
flatness length. The maximum value of the SNCF sharply decreases with increasing ao. This maximum SNCF reaches its
minimum at ao = 1 (mm) then increases with increases with ao. The maximum SNCF becomes nearly independent of ao after
ao = 4 (mm). As a results; the severity of the notch vanishes as the flatness length enlarged.