4. ENDURANCE LIMIT
Whenever a cyclic (repetitive) load is
applied on the material, If the
material shows no evidence of
fracture then this property of the
material is called, “Endurance Limit”
While if the material shows any
evidence of fracture during the
loading this property is called,
“Fatigue Limit”
5. ENDURANCE LIMIT
The conventional fatigue testing has
been concerned primarily with the
testing of specimens with smooth
surfaces under the conditions of
rotating-bending or uniaxial tension-
compression cycling.
The results of these tests are
presented in the form of plots of
stress verses the number N of stress
cycles required to cause the fracture.
6. ENDURANCE LIMIT
These plots are called δ-N diagrams, it
was suggested by “WhÖler”. These
diagrams are also called, “S-N
diagrams” in some literatures. It is
shown in the figure.
Usually in mild steel or certain other
steels, an endurance limit is observed.
7. ENDURANCE LIMIT
Actually when the cyclic load is applied on
the material stress decreases and once a
point is arrived where the stress becomes
constant, means there is no further
decrease in stress with the increase of N.
However many materials do not exhibit a
clear cut endurance limit, but δ-N curves
continues downward as N increases.
